Научная статья на тему 'Development of new smart metal nanomaterials based on titanium-dioxide for photocatalytic and antimicrobial activities'

Development of new smart metal nanomaterials based on titanium-dioxide for photocatalytic and antimicrobial activities Текст научной статьи по специальности «Химические науки»

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ДИОКСИД ТИТАНА / TIO2-НАНОЧАСТИЦЫ / TIO2 ЛЕГИРОВАННЫЕ LA3+ / FE3+ И V3+ / ПРОДОЛЖИТЕЛЬНОСТЬ ПРОКАЛИВАНИЯ / ШТАММЫ PSEUDOMONAS AERUGINOSA DV 2739 И ATCC 9023 / ФОТОКАТАЛИТИЧЕСКАЯ АКТИВНОСТЬ / АНТИМИКРОБНАЯ АКТИВНОСТЬ / TITANIUM-DIOXIDE / TIO2-NANOPARTICLES / TIO2 DOPED WITH LA3+ / FE3+ AND V3+ / CALCINATION DURATION / PSEUDOMONAS AERUGINOSA STRAINS DV 2739 AND ATCC 9023 / PHOTOCATALYTIC ACTIVITY / ANTIMICROBIAL ACTIVITY

Аннотация научной статьи по химическим наукам, автор научной работы — Kuburovic Natasa D., Golubovic Aleksandar V., Babincev Ljiljana M.

The subject of this study was the synthesis, characterization and testing of titanium (IV) oxide nanoparticles (TiO2-NPs) and their lanthanum (La 3+ ), iron (Fe 3+ ) and vanadium (V 3+ ) dopants for the photocatalytic and microbiological activity, as well as their comparison with the catalytic activity of the tested commercial TiO2 (Degussa P-25 ® and anatase nanoparticles, 99.9 %, Alfa Aesar Lancaster). The TiO2-NPs photocatalysts were synthetized and doped with different metal dopants concentrations for different calcination durations, such as: TiO2-NPs (anatase-NPs, calcination duration of 5 and 7 h), La 3+ (0.65, 1, 2, 3, 4, 5 and 6 wt. %, calcination duration of 7 h), Fe 3+ (1, 2.5, 3.0 and 5 wt. %, calcination duration of 7 and 24 h), and V 3+ (10 wt. %, calcination duration of 7 and 24 h). The Pseudomonas aeruginosa strains DV 2739 and ATCC 9023 were used as model microorganisms in the microbiological experiments performed in a microbiological cabinet. The photocatalytic and coupled photocatalytic-microbiological processes were performed in a slurry-catalyst bath circulation photoreactor in the presence of direct UV radiation simulated with a sodium lamp SONT UV400 in lab conditions. The study has demonstrated that the catalyst sample S28, an La-dopant with a concentration of 1wt. %, displays the best photocatalytic properties among all La-dopants, while the best photocatalytic activity among all catalysts was achieved in S111 sample, an Fe-dopant of titania (5 wt. %, calcination duration of 7 h). Our results also show different degradation rates for TiO2 doped with V 3+ of 10.0 wt. %, samples S93 and S96, synthetized with different duration times (7h and 24h, respectively) and calcination heating rates (66.7 and 135 C/h, respectively), which can be explained by anomalies in their behavior. Finally, the best antimicrobial activity is obtained in S24 sample, an Fe-dopant for which it was shown that 0.25 mg/L could be toxic for microorganisms. In accordance with our results of superior Fe-dopant characteristics and theoretical knowledge for TiO2 nanoparticles doped with Ag, Au and Fe, we get directions for further studies of their photocatalytic and antimicrobial activities, as well as for the development of TiO2-nanoparticles and nanotubes for enhancing antibiotics and their use in cancer treatment.

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РАЗРАБОТКА НОВЫХ УМНЫХ МЕТАЛЛИЧЕСКИХ НАНОМАТЕРИАЛОВ НА ОСНОВЕ ДИОКСИДА ТИТАНА ДЛЯ ФОТОКАТАЛИТИЧЕСКОЙ И АНТИМИКРОБНОЙ АКТИВНОСТЕЙ

Предметом данного исследования являются синтез, классификация и испытания наночастиц титана (IV) оксида (TiO2 НЧ-а) и легирования лантана (La3+), железа (Fe3+) и ванадия (V3+) для фотокаталитической и микробиологической активностей, а также сравнение с каталитическим активностима испытанными в коммерческих целях TiO2 (P25, Degussa® и наночастиц анатаза, чистоты 99,9%, компанией Alfa Aesar из Ланкастера). Наночастицы диоксида титана были синтезированы и легированы с различной концентрацией металлических допантов, при различной продолжительности процесса прокаливания: TiO2-НЧ (анатаз-НЧ, время процесса прокаливания 5 и 7 часов), La3+ (0.65, 1, 2, 3, 4, 5 и 6 вес. %, продолжительность прокаливания 7 часов), Fe3+ (1, 2,5, 3,0 и 5 вес. %, продолжительность прокаливания 7 и 24 часа) и V3+ (10 вес. %, продолжительность прокаливания 7 и 24 часа). Штамм „Pseudomonas aeruginosa DV 2739“ использован в качестве модели микроорганизмов в микробиологических экспериментах, проведенных в микробиологической лаборатории. Совместный процесс фотокаталических и микробиологических испытаний эксперимента проводился в катализаторной ванне при прямом концентрированном ультрафиолетовом излучении от натриевой лампы SONT UV 400, симулирующей солнечное излучение. Исследование показало, что образец катализатора С28, La-легирующей примеси с концентрацией 1 вес. %, обладает лучшими фотокаталитическими свойствами по сравнению с другими La-допантами, в то время, как лучшая фотокаталитическая активность была достигнута в образце S111, Fe-легирующей примеси диоксида титана (5 вес.%, продолжительность прокаливания составляет 7 часов). Результаты нашего исследования также показали различную степень деградации при применении V-допанта TiO2 с концентрацией 10 вес.% образцы С93 иС96 были синтезированы при различной продолжительности прокаливания (67.5 и 135 ᵒC/ч, поочередно), что можно считать аномалией в их поведении. И наконец лучшая антимикробная активность получена в образце СS24, Fe-легирующей примеси, которая показала, что 0,25 мг/л является токсичным для микроорганизмов. Результаты нашего исследования о преимущественных характеристиках Feлегирующей примеси и теоретические знания о наночастицах TiO2, легированных Ag, Au и Fe, безусловно облегчат исследователям дальнейшую работу в изучении фотокаталитической и антимикробной активностей, а также развития наночастиц TiO2 и нанотрубок, с целью усиления действия антибиотиков и их применения при лечении онкологических заболеваний.

Текст научной работы на тему «Development of new smart metal nanomaterials based on titanium-dioxide for photocatalytic and antimicrobial activities»

DEVELOPMENT OF NEW SMART METAL NANOMATERIALS BASED ON TITANIUM-DIOXIDE FOR PHOTOCATALYTIC AND ANTIMICROBIAL ACTIVITIES

Natasa D. Kuburovica, AleksandarV. Golubovicb,

Ljiljana M. Babincevc

a Eco Energy Engineering & Consulting, Belgrade, Republic of Serbia, e-mail: natasa.kuburovic@eeec.rs,

ORCID Ю: ©http://orcid.org/0000-0003-2565-6607 b University of Belgrade, Institute of Physics, Center for Solid State Physics and New Materials, Belgrade, Republic of Serbia, e-mail: golubovic@ipb.ac.rs,

ORCID iD: ©http://orcid.org/0000-0003-4618-424X c University of Pristina, Faculty of Technical Sciences,

Kosovska Mitrovica, Republic of Serbia

e-mail: ljiljana.babincev@pr.ac.rs

ORCID iD: ©http://orcid.org/0000-0001-6290-1902

DOI: 10.5937/vojtehg66-17261; https://doi.org/10.5937/vojtehg66-17261

FIELD: Chemical & Materials Engineering, Catalytic processes and Composite Materials

ARTICLE tYpE: Original Scientific Paper ARTICLE LANGUAGE: English

ACKNOWLEDGMENT: The first author would like to express her gratitude to Dr Suzana Dimitrijevic - Brankovic, full professor at the Faculty of Technology and Metallurgy, University of Belgrade, for her kind help in the preparation of microorganisms and their measurements during the experimental research, as well as for her useful suggestions. Also, the first author is especially grateful to colleague Dr Antonije Onjia, Ph. D. Sci Ch. Eng., Associate Professor at the Faculty of Technology and Metallurgy, University of Belgrade, owner and long lasting director of the Anahem Laboratory d.o.o., for his generous help and the opportunities to support necessary analyses during the first author's scientific research work done in his lab. The photocatalytic and coupled photocatalytic-microbiological experiments were carried out in the Laboratory of the Department for Organic Chemistry at the Faculty of Technology and Metallurgy, University of Belgrade, which the first author used for scientific research work during her PhD study in Inorganic Chemical Technology and Chemical Engineering. The microbiological activity experiments were carried out in the Laboratory of Biochemical Engineering and Biotechnology at the FTM BU. The synthesis and part of characterization of TiO2 nanoparticles were carried out in the Center for Solid State Physics and New Materials at the Institute of Physics, University of Belgrade. The GC-MS determinations were carried out in the Laboratory of the "Occupational Safety and Environmental Protection, Beograd doo''.

Kuburovic, N. et al, Development of new smart metal nanomaterials based on titanium-dioxide for photocatalytic and antimicrobial activities pp.771-835

VOJNOTEHNICKI GLASNIK / MILITARY TECHNICAL COURIER, 2018, Vol. 66, Issue 4

Abstract:

The subject of this study was the synthesis, characterization and testing of titanium (IV) oxide nanoparticles (TiO2-NPs) and their lanthanum (La2*), iron (Fe2*) and vanadium (V2*) dopants for the photocatalytic and microbiological activity, as well as theircomparison with the catalytic activity of the tested commercial TiO2 (Degussa P-25® and anatase nanoparticles, 99.9 %, Alfa Aesar Lancaster). The TiO2-NPs photocatalysts were synthetized and doped with different metal dopants concentrations for different calcination durations, such as: TiO2-NPs (anatase-NPs, calcination duration of 5 and 7 h), La2* (0.65, 1, 2, 2, 4, 5 and 6 wt. %, calcination duration of 7 h), Fe2* (l, 2.5, 2.0 and 5 wt. %, calcination duration of 7 and 24 h), and V2* (10 wt. %, calcination duration of 7 and 24 h). The Pseudomonas aeruginosa strains DV2729 and ATCC 9022 were used as model microorganisms in the microbiological experiments performed in a microbiological cabinet. The photocatalytic and coupled photocatalytic-microbiological processes were performed in a slurry-catalyst bath circulation photoreactor in the presence of direct UV radiation simulated with a sodium lamp SONT UV400 in lab conditions. The study has demonstrated that the catalyst sample S28, an La-dopant with a concentration of 1wt. %, displays the best photocatalytic properties among all La-dopants, while the best photocatalytic activity among all catalysts was achieved in S111 sample, an Fe-dopant of titania (5 wt. %, calcination duration of 7 h). Our results also show different degradation rates for TiO2 doped with V2* of10.0 wt. %, samples S92 and S96, synthetized with different duration times (7h and 24h, respectively) and calcination heating rates (66.7 and 125 °C/h, respectively), which can be explained by anomalies in their behavior. Finally, the best antimicrobial activity is obtained in S24 sample, an Fe-dopant for which it was shown that 0.25 mg/L could be toxic for microorganisms. In accordance with our results of superior Fe-dopant characteristics and theoretical knowledge for TiO2 nanoparticles doped with Ag, Au and Fe, we get directions for further studies of their photocatalytic and antimicrobial activities, as well as for the development of TiO2-nanoparticles and nanotubes for enhancing antibiotics and their use in cancer treatment.

Key words: titanium-dioxide, TiO2-nanoparticles, TiO2 doped with La2*, Fe2* and V2*, calcination duration, Pseudomonas aeruginosa strains DV 2729 and ATCC 9022, photocatalytic activity, antimicrobial activity.

Introduction

Titanium, the ninth most abundant element in the Earth’s crust, can be found in the form of minerals: ilmenite, rutile and titanium. In its most stable form as titanium (IV) oxide (TiO2), it can be found in three possible crystalline forms: brookite (orthorhombic), rutile (tetragonal) and anatase

(tetrarombic). From a photocatalytic point of view, only rutile and anatase are relevant, the latter having the highest photocatalytic activity, as reported by Fernandez-Ibanez et al (Fernandez-Ibanez et al, 2004). Among different options available in the market, Degussa P-25® is one of the most efficient and tested nanomaterials, in the form of powder with a particle size of around 25 nm, forming aggregates of several hundred nanometers to several micrometers in the aqueous solution with a surface of 50m2/g, consisting of 70% anatase and 30% rutile. It is well known that TiO2 with the anatase molecular structure was found to be a superior photocatalytic material for purification and disinfection of water and the air, as well as for the remediation of hazardous waste (Hoffmann et al, 1995), (Fujishima et al, 2000). Nanomaterials like TiO2 nanoparticles (TiO2-NPs), smaller than approximately 100 nm in diameter, have become a new generation of advanced materials due to their novel and interesting optical, dielectric, and photocatalytic properties from size quantization (Alivisatos, 1996). The challenge for the so-called nanotechnologies is to achieve perfect control of nanoscalerelated properties, which obviously requires correlating the parameters of the synthesis process, such as: self-assembly, microlithography, sol-gel, polymer curing, electrochemical deposition, laser ablation, etc. with the resulting nanostructure (Gouadec et al, 2007). Many efforts have been devoted to research, development and production of advanced TiO2-NPs with controlled size, shape, and porosity for use in thin films, nanowares and electrodes, catalysts, ceramics and composite materials. The effects of nanometer sizes are caused by the large surface-to-volume ratio, resulting in more atoms along the grained boundaries than in the bulk material, which can be explained by the fact that if many particles reduce their size, more attractive interactions between the particles become dominant so attractive forces lead them to aggregate or agglomerate, which results in nanoparticle aggregates (NPAs). The control of the particle size distribution and the aggregate structure is the key criterion for product quality considering that the desired product properties can vary with the particle size, as well as the degree of aggregation or aggregate structure. It has been accepted that NPs can exist in two states within a liquid: stable, i.e. particles separate, non-adhering and dispersed, and aggregated or flocculated, i.e. adherent and randomly clumped (Schwarzer & Peukert, 2005). This clumping can occur due to van der Waals attractive forces or may be caused by magnetic or other attractions imposed by externally imposed fields. For the calculation of the particle-particle interaction, the DLVO theory can be employed (Hunter, 2000). Hence, it is very important to realize that the NPs being

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used in experiments, especially in a suspension or colloid form, have the properties (e.g., size distribution) which are different from those specified by manufactures; in experimental processes such as sonication, autoclave, pH value, etc., the state or properties of the particles may be changed, so it is essential that the experiments are carried out with care (Sungkaworn et al, 2008). With the increasing use of NPs in commerce, to date few studies have investigated the toxicological and environmental effects of NPs. Exposure to nanoparticle substances can be an important risk factor for human health. The sub-micron size of NPs offers a number of distinct advantages over micro particles (MPs). NPs have in general relatively higher intracellular uptake rate compared to MPs, which was demonstrated in studies in which 100 nm size NPs showed 2.5 fold greater uptakes compared to 1 mm and 6 fold higher uptakes compared to 10 mm NPs in Caco-2 cell line, as reported by Waliszewski (Waliszewski, 1997). Similar results were obtained when these formulations of NPs and MPs were tested in a rat in situ intestinal loop model. The efficiency of uptake of 100 nm sized particles was 15-250 fold greater than larger sized (1 and 10 mm) MPs (Zhang & Sun, 2004). In this rat study, it was found that NPs were able to penetrate throughout the sub mucosal layers while the larger size MPs were predominantly localized in the epithelial lining. Also, TiO2 or titanium could be used as an alternative complement to conventional technology for biocides activity via photocatalysis. It is well known that photocatalytic events occur when the UVA/UVB with wavelengths of lower than 385nm (365 < wavelength < 385) illumination of TiO2 (band-gap energy of anatase, 3.2 eV; for rutile, 3.0 eV) and subsequent formation of electron/hole pairs are numerous and very complex; the following electron/hole separation, the two charge carriers migrate to the surface through diffusion and drift, in competition with a multitude of trapping and recombination events in the lattice bulk. The carriers are poised, at the surface, to initiate redox chemistry with suitable pre-adsorbed acceptor and donor molecules in competition with recombination events to yield radioactive and nonradioactive emissions, and/or trapping of the charge carriers into shallow traps at lattice sites (e.g., anion vacancies, Ti4+, and others). Thus, on absorption of UV light, titanium particles yield superoxide radical anions and hydroxyl radicals that can initiate oxidations (Hoffmann et al, 1995).

It is also well known that thinner nanowires (NWs) may further enhance the sensitivity of the devices owing to an increased surface-to-volume ratio, as Chueh et al. reported (Chueh et al, 2007). This study has shown the investigation of the RuO2/TiO2 core/shell structure

photoconductivity under the UV illumination of 256 nm (4.9 eV), which is strong enough to excite the electron-hole pair near the band edge, and their results suggest the potential application of NWs as interconnects and optoelectronic devices

Photocatalytic-biological inactivation is explained by the attack of oxygen-derived molecular species or reactive oxygen species (ROS), especially radicals photo generated at the surface of the TiO2 catalysts like O2", HO2' and Oh, although the mechanism of cell death or damage has not been understood yet (Maness et al, 1999). Also, oxygen-derived molecular species or reactive oxygen species (ROS) such as superoxide (O2") and hydrogen peroxide (H2O2) are produced in cells as a result of aerobic metabolism. Excess generation of these species can result in damage to macromolecules such as the DNA and lipids (Maness et al, 1999). Photocatalytic TiO2 nanoparticles, as showed by Xu et al. (Xu et al, 1998) in their experimental research, have features to kill malignant cells through a series of oxidized chain reactions and induce the malignant cells to be stressed by ROS. Then, the cells were stressed to death either through apoptosis or necrosis depending on the used dosage. Finaly, photocatalytic TiO2 nanoparticles can severely destruct the cellular membrane system and cause the cellular genetic macromolecules damage through the reactive oxygen species accumulation within the cells, and even induce cell death. The result of this research (Xu et al, 1998) also partly reveals the mechanism of cell death by photocatalytic TiO2 nanoparticles, which is very important for the direction of the research and development of photocatalytic TiO2 nanoparticles in biomedical application.

Anpo (Anpo, M. 2004) reported that the nanosized anatase TiO2, due to a large surface area and band-gap energy, showed better photo activity than their bulk phase. However, the nanosized anatase-TiO2 transforms to the rutile structure at temperatures about 600°C and this phase transformation of TiO2 greatly reduces surface areas of the particles (Zhang & Sun, 2004), which may result in the decrease in photocatalytic ability of TiO2. It was found that the stability temperature of the anatase-TiO2 can be increased by doping TiO2 with lanthanide ions; so it is believed that the development of high-temperature stabilized photocatalysts is important for immobilizing the photocatalyst on the working objects by chemically bonding, the process of which commonly requiresrelatively high temperatures. Zhang & Sun (Zhang & Sun, 2004) studied the microstructure and the photocatalytic properties of lanthanide doped TiO2 prepared by a sol-gel method and they reported that La, Eu, Gd or Yb dopants significantly inhibited the nanosized TiO2 phase

Kuburovic, N. et al, Development of new smart metal nanomaterials based on titanium-dioxide for photocatalytic and antimicrobial activities pp.771-835

VOJNOTEHNICKI GLASNIK / MILITARY TECHNICAL COURIER, 2018, Vol. 66, Issue 4

transformation of anatase-to-rutile. It was also found that transition metal oxides are extensively employed as catalysts, because they possess featured active centers to adsorb reaction molecules. Titania doped with iron ions shows superior activity due to its unique half-filled electronic configuration and shallow trapping compared to other metal dopants with closed shell electronic configuration, which can be more effective to influence the photo activity (Yan et al, 2015), (Liu & Zhang, 2013), (Ramli et al, 2015), (Su et al, 2015), (Dinesh et al, 2015), (Flak et al, 2015), (Su et al, 2012), (Wang et al, 2012). Theoretical and experimental studies show that Fe doping can effectively reduce the trapping density and charge recombination, resulting in drastically improved adsorption, reported Huang et al (Huang et al, 2016).

Many studies by the authors: Heller (Heller, 1995), Ollis et al (Ollis et al, 1991), Sitkiewitz & Heller (Sitkiewitz & Heller, 1996), Takeuchi et al (Takeuchi et al, 2003) and Uchida et al (Uchida et al, 1993); using TiO2 photodecomposition of pollutants with the aim of developing methods to purify water and the air have been carried out. For the bactericidal activity, several results have been reported using TiO2 powder (Cai et al, 1991), (Ireland et al, 1993), (Matsunaga & Okochi, 1995), (Watts et al, 1995) and (Wei et al, 1994), and TiO2-coated materials for this purpose (Kikuchi et al, 1997). However, few studies have investigated the impacts of TiO2 in cancer science or in the field of oncology, as reported by Minhua et al. (Minhua, X. et al. 1998). However, the actual factors that control the photo catalytic activity of specific TiO2 particles are still unknown, and the detailed studies of the effects of TiO2 on biological systems in dark condition have been very rare. Cancer has been a leading cause of human death in the world, but it is not too much known about the biological mechanisms leading to the establishment or the growth of malignant tumors. Many attempts have been made in recent decades to describe the basic biological mechanisms of tumor growth. Benign masses generally have smooth, circumscribed, and well-defined contours, whereas malignant tumors commonly have rough, speculated, and ill-defined contours (Sungkaworn et al, 2008). Also, Fe-doped TiO2 nanotubes (NTs) can be a potential photosensitizer for the near-visible light driven photodynamic therapy (PDT) against cervical cancer cells (HeLa). Fe-doped TiO2 nanoparticles exhibited none or lower dark cytotoxicity than un-doped TiO2 nanotubes, which confirms their superior biocompatibility. Under the near-visible light irradiation (~405 nm), Fe-doped TiO2 nanoparticles showed higher photo-cytotoxic efficacy than un-doped TiO2 nanoparticles, which was found to be dependent on the nanoparticles concentration, but not on the incubation time of the cells

after the near-visible light irradiation. The highest activity was observed in 0.70 and 1.40 wt. % Fe-TiO2 nanoparticles (Flak et al, 2015).

The aim of this study is finding the optimum synergetic effects of the synthetized type of smart TiO2-nanoparticles and their different metal dopant concentration on photocatalytic, microbiological and antimicrobial activities in aerobic conditions, which will give us further directions of the development of TiO2 nanoparticles for environmental and biomedical applications.

Background of the TiO2-Particle Synthesis

Many studies have been conducted on the synthesis of TiO2-nanoparticle catalysts that will have adequate nanometres-sized effects, as well as other relevant catalyst and electrochemical characteristics, which can give best performances for photocatalytic, photoelectrochemical and antimicrobial activities.

Nedeljkovic et al. (Nedeljkovic et al, 1997) performed a TiO2 nanoparticles ultrasonic spray pyrolysis using a colloidal solution of 10-2 M TiO2 at 800°C. The experimentally determined value of the mean diameter of TiO2 was 286 nm. It differed significantly from the expected theoretical values between 132 nm and 195 nm. Jokanovic et al. (Jokanovic et al, 2004) explained the design of nanostructured hollow sized particles during the ultrasonic spray pyrolysis method, which was in comparison between theoretically estimated and experimentally obtained ring thickness about 7-15 %. The mean sub particle size estimated by the theoretical model was 4.7 nm. Depending on the type of packing, the mean diameter of the hollow sphere was different: for hexagonal packing - 87 nm, for cubic packing - 95 nm, which is in accordance with the theoretical model developed by Jokanovic.

Backman et al. (Backman et al, 2004) produced nanosized TiO2 particles using flame reactors and aerosol pyrolysis. The measured median sizes of TiO2 prepared from titanium (IV) tetraisopropoxide Ti(OC3H7)4 were 13 nm at 600-1100°C reactor’s temperature and 22 nm at 1100°C, respectively. The fundamental problem was the presence of carbon in the product that is produced at 1100°C since the processes of coalescence agglomeration and sintering are dominant at higher reaction temperatures (1100°C), as opposed to 600°C. The desired crystalline anatase phase of TiO2 was formed at high temperature. The TEM and BET analyses of TiO2-nanoparticles confirmed that by changing the temperature values the surface area and phase content can be controlled.

Kuburovic, N. et al, Development of new smart metal nanomaterials based on titanium-dioxide for photocatalytic and antimicrobial activities pp.771-835

VOJNOTEHNICKI GLASNIK / MILITARY TECHNICAL COURIER, 2018, Vol. 66, Issue 4

Aruna et al reported a nanosized rutile TiO2 particle synthesis via a hydrothermal method without mineralizers, which contaminate the samples and induce undesirable characteristics (Aruna et al, 2000). It is also used for preparing two sets of titania colloids (with and without stirring) the similar procedure by hydrothermal synthesis of titanium (IV) isopropoxide and nitric acid with pH value of 0.5. Stirring that maintains homogeneity in the solution during the hydrothermal process was highly important when a homogeneous product was required. The rutile nanocrystals of titania prepared by the hydrothermal method with a particle size of about 20 nm have a large surface area and are relatively stable at high temperatures.

Ahonen et al (Ahonen et al, 1999) synthetized TiO2-powders in the aerosol pyrolysis process of the freshly-prepared and well-mixed 0.2 M solution of titanium (IV) n-butoxide in n-butanol at a temperature range between 200 and 580°C in the air and the nitrogen atmosphere. Anatase powder was formed at 500°C in nitrogen, and at 580°C in the air, while the anatase to rutile transformation appeared in thermal annealing in the air. Physico-chemical phenomena occurring during the formation of particles were described in this paper (Ahonen et al, 1999).

The methodology for the preparation of TiO2 films, based on the process of ultrasonic spray pyrolysis using TiO2 nanoparticles as a precursor was reported by Blesic et al (BlesiC et al, 2002). Blesic et al have shown an advantage of the usage of TiO2 colloids in the process of ultrasonic spray pyrolysis. In the methodology, the growth mechanism of the TiO2 films formation is explained layer-by-layer. The compact smooth film or a porous structure might be obtained by adjusting the substrate temperature, and the mean diameter of particles can be adjusted changing the concentration of the precursor and a frequency of aerosol.

Panic et al (Panic et al, 2003) sythetized titanium anodes with an active RuO2 coating of two different thicknesses from the oxide suspended in ethanol, as an "ink" method, while the oxide itself was synthesized by the hydrolysis of ruthenium ethoxide in an ethanolic solution (alkoxide route). The authors showed that the anodes prepared via the alkoxide route are more active in the chlorine evolution reaction than the anode prepared from the inorganic oxide sol, due to their larger real surface area; it was also shown that the coating mass on the anode does not influence significantly the anode activity in the chlorine and oxygen evolution reaction at low over potentials. It can be explained that more compact thick coating appears to be more active for the chlorine evolution at higher overpotentials, due to forced micro-convections in the pores (Panic et al, 2003).

The sol-gel chemistry has recently been involved in a general and powerful approach to preparing inorganic materials, as reported by Lakshmi et al (Lakshmi et al, 1996). The sol-gel method has been proven to be a very flexible and promising means in view of the controlled synthesis of Au, Ag and other metal nanoparticle embedded metal oxides, as well as relevant for photocatalytic applications, which includes the synthesis of anatase titanium dioxide, anatase titanium dioxide doped with La, Fe, V, Au, Ag and other photocatalytic systems. Metal nanoparticles dopants as Ag, Cu and Au demonstrate a strong absorption band in the visible or near IR spectrum due to plasmin resonance. The position of the plasmin resonance band depends on the size and shape of metallic NP, so the NP plasma resonance control can be adjusted for a useful spectral region, e.g. for the region of the biological tissue transparency (between ~ 650 nm - 1200 nm). In this region, tissues (blood, bones, skin) are transparent. The metal NP is inert in the biological media, so it can be excited by light ~ 650 nm - 1200 nm if it were injected in the body. It allows, as reported by Huang et al (Huang et al, 2006), carrying out the photo thermal therapy in the nearInfrared Region by using gold-nanorods.

The great interests for antimicrobial effect research of new materials based on the nanosized particles toward pathogens is explained by the increase of new microbiological strains resistant to antibiotics, as well as by the motivation to further study disinfection possibilities of new systems based on nanosized particles. Microbes resistant to silver occur pretty rarely in the nature, which is very important for the application of process of TiO2 photocatalysis using silver ions or silver colloids for disinfection of microbes; therefore, the application of metallic plasmin nanoparticles represents a promising approach to the photothermolysis of bacterial cell or cancer cells. New materials with hybrid nanoparticles made from metallic and wide band semiconductors TiO2 and ZrO2 are suggested for medical and their environmental applications. Further research and studies are aimed at the development of the preparation of hybrid nanoparticles (hNPs) comprised by metal-nanoparticles (La, Fe, V, Ag, Au, etc.) on the wide band gap semiconductors (TiO2) and the study of antimicrobial effects against gram-negative and gram-positive bacteria in dark, under excitation by the visible light and UV-A light. We expected different mechanisms of hNP’s action on bacteria under light activation. Effect of hNP’s disinfection in dark towards the bacterial films formation will be studied in detail. The hNP’s surface modification will be developed in vivo for biomedical applications. The administrated nanoparticles are eliminated from the circulation within seconds to minutes through the

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reticula-endothelial system without surface modifications. Oxide nanoparticles will be obtained by processes such as mechanic-chemical synthesis, hydrothermal method, pyrolysis, plasma-chemical method, sol-gel technology and precipitation methods. By using zirconium or titanium salt of different nature and different agent-precipitated and various dopants, one can control the structure and the surface state of oxide nanoparticles.

It is well known that the traditional disinfection methods such as chlorine-based technologies lead to the formation of chloroorganic disinfection by-products (DBPs) with carcinogenic and mutagenic effects on mammals (Richardson, 2003); so, it is important to develop advanced disinfection processes and applications for sustainable supply of drinking water. Marugan et al (Marugan et al, 2010) in their study are focused on the evaluation of analogies and differences found when comparing the TiO2 photocatalytic treatment for chemical oxidation and microorganism’s inactivation, using methylene blue and Escherichia coli as references, respectively. The activation of both processes is based on the same physicochemical phenomena and consequently a good correlation between them is observed when analyzing the effect of operational variables such as the catalyst concentration or the incident radiation flux. Both factors influence common stages such radiation absorption and generation of reactive oxygen species. However, different microbiological aspects, such as osmotic stress, repairing mechanism, regrowth, bacterial adhesion to the titania surface, etc. make disinfection kinetics significantly more complex than the first-order profiles usually observed for the oxidation of chemical pollutants (Marugan et al, 2010). This study has shown that bacterial inactivation reactions are found to be extremely sensitive to the composition of water and modifications of the catalysts in comparison with the decolorization of the dye solutions, showing opposite behaviors in the presence of chlorides, incorporation of silver to the catalysts or the use of different types of immobilized TiO2 systems. The complex structure of living cells, the existence of several mechanisms for cell regeneration, and the possibility of post-irradiation regrowth could be considered as drawbacks when microorganism inactivation is compared to the oxidation of chemical pollutants; it is, therefore, particularly difficult to model the microbiological aspects involved in the disinfection treatment process (Marugan et al, 2010).

In recent years, researchers in the field of photocatalysis have paid more attention to the study of hybrid nanoparticle systems such as Ag nanoparticles on the TiO2 surface, which use UV-A light for the excitation of photocatalysts. Photo induced bactericidal activity of nanostructured

TiO2, and the deposition effect of silver and bimetallic Ag/Ni nanoparticles on the pathophysiological properties of titanium films were investigated. The model of microorganisms for antimicrobial activity of films was evaluated against Pseudomonas fluorescents B-22 (gramnegative bacteria) and Lactococcus lactic ssp. lactate 411 (gram-positive bacteria). The silver-modified TiO2 film demonstrates the highest photo biocide efficiency, enhancing the bactericidal activity of UV light cca. 71 times, which results from the radical improvement of microorganism adsorption and suppression of recombination of photo produced charge carriers (Skorb, E.V. et al, 2008). Recently gold-doped TiO2 (Au/TiO2) nanocomposites have been investigated to enhance the photocatalytic efficiency of TiO2 in decomposing organic compounds and photo killing bacteria.

Photocatalytic systems based on hybrid nanoparticles with UV excitation are suggested for the production of new medical products. Ag/titanium dioxide (TiO2)-coated silicon catheters were easily fabricated with Ag nanoparticles deposition on both the inside wall and the outside wall of TiO2-coated catheters by the TiO2 photocatalysis. This is an application of the silicon catheters coated with TiO2 which possess a self-sterilizing and self-cleaning property combined with UV light illumination (Ohko et al, 2001). Yao et al (Yao et al, 2008) reported that similarly to 15 nmol cm-2 of Ag, 99% effective sterilization occurred in a very short time: 20 min for E. coli, 60 min for Pseudomonas aeruginosa, and 90 min for Staphylococcus aureus; the Ag/TiO2-coated catheters possessed a strong self-cleaning property. The photocatalytic decomposition rate of methylene blue dye using UV illumination representing the self-cleaning capability, on an Ag/TiO2 catheter which was loaded with 2 nmolcm-2 of Ag, was similarly 1.2 times higher (at maximum) than that on the TiO2 coating alone. Furthermore, Ag nanoparticles can be pre-eminently and uniformly deposited onto the TiO2 coating, and the amount of Ag was easily controllable from a few nanomoles per square centimeter to 70 nmolcm-2 by changing the UV illumination time for the TiO2 photocatalysis. This catheter type shows a great promise in lowering the incidence of catheter-related bacterial infections (Yao et al, 2008).

Experimental

Material

Methyl-tertiary-butyl-ether (MTBE, purity > 99.5 %), hydrogen peroxide (35%), methanol (99.8%), sodium carbonate (NaCO3), ammonium hydroxide (NH4OH) and ethanol (all three purity grades were

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99.9%), barium hydroxide octahydrate ([Ba(OH)2 + 8H2O], 98%), phenolphthalein, Tryptic Soy Broth (TSB) and Caseinhydrolysate Glucose Yeast extract Broth (Base) were obtained from Merck Millipore, hydrogen chloride (35%) from Lachema, and sodium hydroxide from Euro Hemija. Titanium dioxides were purchased from Alfa Aesar Lancaster (anatase nanopowder, 99.9%) and Degussa AG Frankfurt (TiO2 powder, P-25®), and used as such. The Pseudomonas aeruginosa strains ATCC 9023 and DV 2739 were used in the experiments researching microbial activity and inactivity. All other chemicals used in

the synthesis of catalyst, such as LaCl3- 7H2O, FeCl3- 6H2O, VCl3, and TiCl4 were obtained from Merck Millipore as the analytical grade.

Method

The experimental research in this study consists of the following components:

1. Preparation of catalysts;

2. Characterization of catalysts;

3. Research of photocatalytic activities:

I Experiments of photocatalytic activities; and

II Coupled photocatalytic-microbiological experiments;

4. Research of microbial activity and inactivity:

I Microbial activity and inactivity of coupled photocatalytic-microbiological experiments; and

II Experiments of antimicrobial activities.

The commercial TiO2 catalysts, as anatase nanopowder and Degussa P-25®, synthetized TiO2-nanoparticles catalysts (calcination duration of 5 and 7h), and synthetized TiO2 nanoparticles based catalysts doped with different concentrations of following metals: La3+ (0.65, 1, 2, 3, 4, 5 and 6 wt. %), Fe3+ (1, 2.5, 3.0 and 5 wt. %, with calcination duration of 7 and 24 h), and V3+ (10 wt. %, with calcination duration of 7 and 24 h); were tested in the photocatalytic, coupled photocatalytic-microbiological and antimicrobial activities for different concentrations of the MTBE water solution. These experiments were performed in a slurry-catalyst bath circulation photoreactor in the presence of direct ultraviolet (UV) radiation simulated with a sodium lamp SONT UV400 in lab conditions. Also, both commercial titania (Degussa P-25® and anatase powder, purity: 99.9 %), synthetized TiO2 nanoparticles (synthesized at 550 °C with a calcination duration of 5 h), TiO2 nanoparticles doped La3+ (5 wt. %, with a calcination duration of 7 h) and Fe3+ ions (2.5 wt. %, with a calcination duration of 7 h) were tested in the antimicrobial activity

experiments. TiO2-nanoparticles and their dopants catalysts were synthetized and characterized before our experiments. Pseudomonas aeruginosa strain ATCC 9023 was used as a model microorganism in the coupled photocatalytic-microbiological and first antimicrobial activity experiments, and Pseudomonas aeruginosa strain DV 2739 was used as a model microorganism in the second antimicrobial activity experiments. The antimicrobial activity experiments were performed in a microbiological cabinet. The experiments are very important for the determination of the microorganism toxicity point with TiO2 nanoparticle catalysts, i.e. the concentration at which the release of microorganisms occurrs.

Photoreactor

The photocatalytic and coupled photocatalytic-microbiological experiments in the MTBE water solution were tested in a bath slurry-catalyst circular photoreactor (Fig.1). The photoreactor consisted of a 92 cm long quartz tube (inner diameter 19 cm and outer diameter 21 cm), and slurry circulated through the system by the pump, from the storage tank through the control valve and the reactor, and back to the storage tank that is thermo stated at 30 °C. This set-up of the system provided uniform distribution of the photo catalyst. The storage tank has a volume of 2 liters, which is operational in full capacity for all experiments.

Figure 1 - Experimental apparatus for the photocatalytic and coupled photocatalytic-

microbiological experiments

Рис. 1 - Экспериментальная аппаратура для фотокаталитического и комбинационного фотокаталитично-микробиологического эксперимента Слика 1 - Експериментална апаратура за фотокаталитички и комбиновани фотокаталитичко-микробиолошки експеримент

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The ultraviolet radiation needed for the photoreaction in the experiments was provided by a sodium lamp, SON-T UV400. The lamp produced a photon flux of 960 ^molm-1s-2 in two different wavelength intervals: 380-518 nm and 540-800 nm, as well as at the local maximum at 333 nm. The distance between the reactor and the sodium lamp was 17 cm. The reactor was in a chamber with the reflecting aluminum foil inner walls in order to provide a uniform UV radiation pattern and intensity for the experiments.

MTBE as a model compound

Methyl-tertiary-butyl-ether (MTBE) has been used as a high constituent and as a replacement for the anti-knocking agent (tetra ethyl lead) of gasoline since the late 1970s. MTBE is a colorless, transparent and flammable liquid whose harmful effects on the environment and the ecosystem have been confirmed over time. It is one of the most dangerous pollutants for human health in the environment; it is frequently detected in wastewater, groundwater, watercourses, drinking water and the soil. The purification and bioremediation of MTBE polluted groundwater is very slow; it is particularly difficult to treat, due to high MTBE solubility in the water (48.000 ^.g/L) and its low volatility (The Merck index, 1996), (Shaffer & Uchrin, 1997). Also, The EPA characterized MTBE as a potential cancerogenic compound in the environment and suggested the concentration limit of 20-40 ^.g/L for the compound in drinking water (Squillace et al, 1996), (Pontius, 1998). Also, the California Department of Health Services has adopted 5 ^.g/L as the maximum MTBE concentration levels (California Code of Regulations, 1999).

Catalyst preparation

The sol-gel method was used for the synthesis of pure and doped anatase nanopowders with iron (Fe3+), lanthanum (La3+) and vanadium ion (V3+). Titanium (IV) chloride (TiCl4, 99.0% pure, Merck) was used as the precursor in the synthesis process. Hydrogel, titanium (IV) hydroxide Ti(OH)4, was obtained by the hydrolysis of TiCl4 at 0°C with a controlled addition of 2.5 wt. % aqueous ammonia into the aqueous solution of TiCl4 (0.3 moll/l) and a careful control of the solution’s pH value of 9.3 for pure TiO2 nanoparticles, as well as La, Fe and V-dopants of TiO2-nanoparticles (Golubovic et al, 2009a), (Grujic-Brojcin et al, 2014). TiCl4 is soluble in water but it experiences rigorous reaction at 20°C which can be very important when performing this reaction at a lower temperature. After aging in the mother liquor for 5h, the as-prepared hydrogel was

filtered and washed out with distilled water until complete removal of chlorine ions. The obtained Ti(OH)4 hydrogel was converted to its ethanol gel by repeated exchanges with anhydrous ethanol for several times (by repeated introduction of anhydrous ethanol). The obtained Alco gel represents the starting point for the production of TiO2 nanoparticles. Alco gel was placed in a vessel, dried at 280°C and calcined at a temperature of 550°C for 5, 7 and 24 h (depending of the sample types); after that, it was converted to nanoparticles. Dopants were in the form of

chloride (LaCl3- 7H2O and FeCl3- 6H2O and VCl3) and mixed with TiCl4 in the adequate ratio before hydrolysis.

The heating rate, duration of calcination for pure (S05, S06, S07, S08, S10, S11, S99 and S102), La-doped (S16, S18, S28, S38, S40a, S48, S52a and S64), Fe-doped (S24, S111-S112, S117-S120), V-doped (S93 and S96) and their different wt. % of TiO2 dopants samples are specified in Table 1 at the Result and Discussion Section: Synthesis conditions. All samples except S05, S06, S10, S99 and S102 samples were used to test photocatalytic, microbiological and antimicrobial activities, while these pure titania nanoparticles were used for a comparative analysis in accordance with their temperature profile.

Characterization of the catalysts

X-Ray Power Diffraction (XRPD) was used for the identification of the crystalline phases, the quantitative phase analysis and the estimation of the crystallite size and strains, as explained earlier (Golubovic et al, 2009a), (Grujic-Brojcin et al, 2014). The XRPD patterns for TiO2-nanoparticles for pure samples (S07, S08 and S10) and La-dopants with 0.65 and 1 moll % of lanthanum ions (S18 and S28 samples) have been collected on a Philips diffract meter (PW1710) employing Cu K^, in the scanning range of 20 between 20 and 80° with the step size of 0.06° and the counting time of 41 s/step. Higher La-dopants concentrations of titanium (IV) dioxide nanoparticle patterns, such as in S52a (4 wt. %) and S64 (6 wt. %) samples, have been collected in the same range by using a Stoe Stadi MP diffract meter (Cu Ka1 radiation, primary beam germanium monochromatic linear PSD detector, Bragg-Brentano geometry), at every 0.01°, with a counting time of 80 s/step. A full-prof computer program was used for the structure refinements, the quantitative phase analysis and the estimation of the average crystallite size and strains (Rodriguez-Carvajal, 2008). The instrumental resolution function for the size-strain analysis was obtained by parameterizing the

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profiles of the diffraction pattern of an LaB6 (NIST SRM660a) standard specimen.

The composition/quality of TiO2 nanoparticles patterns of the samples such as S06 and S11, as well as their following La-dopants patterns ofS18, S28, S40a and S64 samples was analysed on a SEM (JOEL JSM-6460LV, with the operating voltage of 20 keV) equipped with the EDS (INCAx-sight) detector and the ‘’INAx-stream’’ pulse processor (Oxford instruments).

An Atomic Force Microscope - AFM (Omicron B002645 SPM PROBE VT AFM 25) in the contact mode was used to create an image of the surface topology of the TiO2 nanoparticles doped: La-dopant as S18 pattern and Fe-dopant S111 patterns of the samples.

The porous structure of the catalysts has been evaluated from the adsorption/desorption isotherms of N2 measured on the TiO2 samples such as S05, S06, S11, S18, S28 and S40a at 136°C using the gravimetric McBain method. The main parameters of porosity such as the specific surface area and the pore volume have been estimated by the BET method and the as-plot, as reported by Kaneko et al (Kaneko et al, 1998) and the references therein. The pore size distributions have been estimated from the experimental nitrogen sorption data by the BJH and CPSM methods (Golubovic et al, 2013), (Barrett et al, 1951).

The Raman scattering measurements of the chosen TiO2-nanoparticles patterns of samples such as S11, S99 and S102 and their doped patterns of samples such as S48, S93 and S96 were performed in the backscattering geometry at room temperature in the air using a Jobin-Yvon T64000 triple spectrometer, equipped with a confocal microscope and a nitrogen-cooled charge coupled device detector. To avoid local heating due to laser irradiation, the spectra have been excited by a 514.5 nm line of Ar+/Kr+ ion laser with an output power of less than 5 mW.

Measurement of photocatalytic activities

The photocatalytic activities of TiO2 (commercial and synthetized nanoparticles) and their La3+, Fe3+ and V3+ dopants were evaluated by the degradation of the MTBE water solution. The photocatalytic degradation of the water polluted by MTBE in lab conditions was carried out as described in our previous research, as reported by Kuburovic et al (Kuburovic et al, 2005, 2007, 2009) and presented at a conference (Kuburovic & Orlovic, 2010) as a part of the Preliminary study of photocatalytic wastewater treatments conducted in lab conditions using water samples from the Belgrade sewage system.

The photocatalytic activity measurement was performed in two types of experiments: the photocatalytic experiments and the coupled photocatalytic-microbiological experiments. The photocatalytic experiments were carried out in the presence of TiO2 (commercial and synthetized nanoparticles) and their dopant catalysts.

The stock solution for the first experiment type (photocatalytic experiment) was prepared by stirring 2 ml of MTBE with 8 ml of ethanol (both Merck Millipore). The prepared stock solution was mixed with distilled water (2L volume) from which 10 ml of water was extracted for all photocatalytic experiments.

The stock solution for the second experiment type (coupled photocatalytic-microbiological experiments) was prepared by stirring 1 ml of MTBE with 9 ml of ethanol (both Merck Millipore). The prepared stock solution was mixed with distilled water (2L volume) from which 30 ml of water was extracted in two steps: in the first step, 10 ml of water was extracted, added to the stock solution and mixed; in the second step, 20 ml of water solution was extracted followed by the addition of 20 ml of the microorganism (MO) Pseudomonas aeruginosa strain ATCC 9023 in a concentration of 107 CFU mL-1.

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The resulting water solution (in both experiments, with the MO and without it) of MTBE was poured into the photoreactor and thus prepared for each experiment. Each experiment began with a circulation in the photoreactor and the burning of the UV lamp. When the photoreactor started to work in the uniform mode, 10 minutes after the beginning, the experiment was started with zero time. After the completion of the experiment, the reactor was thoroughly washed and sterilized, and after that prepared for the next experiment. The method of preparing the MO for the coupled photo catalytic-microbiological experiments was explained in the part entitled Measurements of the Microbiological Growth.

The GC-MS determinations in the photocatalytic activity experiments were carried out on an Agilent Technologies gas chromatographer equipped with a mass detector using the headspace (GC/MSD/Headspace - 7890A/5975C/G1888). Nitrogen was used as a carrier gas.

The total oxigen carbon (TOC) analysis was carried out by the Astro-Zellwenger LabToc-2100 as in the previous research the results of which are compared in the study.

The kinetics of CO2 evoultion during the photocatalytic activity experiment for titania nanopowders Fe-dopants consisted of flushing the CO2 produced by oxygen into a flask containing a 10-2 M of Ba(OH)2

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solution followed by titration with a 0.001 N HCl solution. Phenolphtalein was used as an indicator.

The quantification of the bacterial cultures from all tested solutions in microbiological activity and inactivity during the coupled photocatalytic-microbiological experiments was carried out on the Shimatzu Cary "UV 1700” UV-VIS spectrophotometer, and for the antimicrobial activity, the experiments were carried out on a calorimeter analog photo calorimeter, Labtronics, India.

Measurement of the microbiological growth

The research of microbial activity and inactivity can be conducted with the measurements of the microbiological growth using optical density. The methodology of both experiments is presented in the text below.

Microbial activity and inactivity of the coupled photocatalytic-microbiological experiments

Our research of the microorganism activity from the coupled photocatalytic-microbiological experiments was performed on the model microorganism (MO) Pseudomonas aeruginosa strain ATCC 9023 in the presence and without TiO2-nanoparticles and their La, Fe and V-dopants at the batch slurry-catalyst circular photoreactor.

The MO model was a fresh bacterial culture of around 109 CFU mL"1 of a stationary concentration prepared by the inoculation of 100 mL Tryptic Soy Broth (TSB) enriched with 0.6 % of Caseinhydrolysate Glucose Yeast extract Broth (Base) (both Merck Millipore) and aerobic incubation at 370C under rotary shaking for 24 h. We thus obtained an TSB enriched substrate for the experiment and the zero control samples (k0). After that, the TSB enriched base substrate in a volume of 20 mL was additionally enriched with a 0.5 p,l/ml of the MTBE stock solution (as the first control sample - k1) and centrifuged for each experiments and rinsed twice with sterile ultrapure water (Milli-Q, 18.2 MQ cm) before diluting 20 mL of the resultant bacterial suspension to 2 L to prepare the reacting suspensions, with an initial concentration of viable bacteria around 107 CFU mL-1.

The experiment started 10 minutes (contact time) after mixing the water solution of MTBE with the 20 mL prepared MO, Pseudomonas strain ATCC 9023 (107 CFU mL-1), testing catalysts, at the batch slurry-catalyst circular photoreactor and switching the recirculation pump. The photocatalytic experiments were followed during 150 minutes, depending

on the experiment. The contact time was necessary for the habituation of the MO on the MTBE solution and the catalyst, as well as for preparing the uniform sodium lamp to work.

The quantification of Pseudomonas aeruginosa strain ATCC 9023 from all tested solutions has been determined on the Shimatzu Cary "UV 1700” UV-VIS spectrophotometer at 550 nm. Optical density was also measured when each component (MTBE water solution, mO, catalyst) was added to the MTBE water solution after mixing in the photoreactor. In this experiment, an increase in the absorption of the solution to 648 nm was observed, as a measure of increase of the MO growth and its microbiological activity.

Experiments of the antimicrobial activities

Pseudomonas aeruginosa strains ATCC 9023 and DV 2739 were used as model microorganisms for the experiments on antimicrobial activities, performed in a microbiological cabinet. Namely, Pseudomonas aeruginosa strain ATCC 9023 was used earlier for our preliminary research, the results of which were presented as an oral presentation by Kuburovic (Kuburovic & Dimitrijevic-Brankovic, 2006) at the EMEC7 Conference, but they have not been published yet. After our preliminary study, Pseudomonas aeruginosa strain DV 2739 was used in all other experiments on antimicrobial activities.

A fresh bacterial culture of around 109 CFU mL-1 of a stationary concentration was prepared for both experiments, by the inoculation of 50 mL Triptyc Soy Broth (TSB) enriched with 0.6 % Casein hydro lysate Glucose Yeast extract Broth (Base) (both Merck Millipore) and aerobic incubation at 37°C under rotary shaking for 24 h. We thus obtained an TSB enriched base substrate for the experiments and the zero control samples (k0), which was seeded individually on the following samples:

I Premilinary research: The volume of 2.0 ml of the TSB enriched base substrate for each of five samples was seeded with different concentrations of the MTBE stock solution of 0.15; 0.25; 0.5; 1.0 and 2.0 jLil/ml, respectively. Also, the volume of 2.0 ml of the TSB enriched base substrate was seeded for three new samples with the 0.5 pl/ml of MTBE stock solution with 0.1 g/L TiO2 (anatase TiO2 nanoparticles, 99.9 %, Alfa Aesar Lancaster), FeCl3 in a concentration of 5 pl/ml and the catalyst-reagent system TiO2 and FeCl3 in the ratio of 1:1 in the concentration of 5 pl/ml, respectively. All such prepared samples were centrifuged for each experiment and rinsed twice with sterile ultrapure water (Milli-Q,

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18.2 MQ cm) before diluting 2 mL of the resultant bacterial suspension to prepare the initial concentration of viable bacteria of around 107 CFU mL-1. We also prepared two following control samples for each experiment: the TSB enriched base substrate (without anything else) and the TSB enriched base substrate that was seeded with an initial concentration of 0.50 p,l/ml of the MTBE stock solution;

II Antimicrobial activity research: The volume of 2.0 ml of the TSB enriched base substrate was seeded for twenty-four samples (6 samples in 4 different concentrations) with 0.5 p,l/ml of the MTBE stock solution with different concentrations of TiO2 nanoparticle catalysts such as: comercial TiO2 (anatase, 99.9 %, Alfa Aesar Lancaster) and P-25 (Degussa P-25®), synthetized as pure S11 sample and doped TiO2 nanoparticles sample, S16 (La-dopant) and S24 (Fe-dopant), as well as the catalyst-reagent system of TiO2 and FeCl3 in the ratio of 1:1 in the concentration of 5 p,l/ml, respectively; each in several concentrations: 0.05, 0.10, 0.20 and 0.25 mg/L. All such prepared samples were centrifuged for each experiment and rinsed twice with sterile ultrapure water (Milli-Q,

18.2 MQ cm) before diluting 2 mL of the resultant bacterial suspension to prepare the initial concentration of viable bacteria of around 107 CFU mL-1. We also prepared two following control samples for each experiment: the tSb enriched base substrate (without anything else) and the TSB enriched base substrate that was seeded with the initial concentration of 0.50 p,l/ml of the MTBE stock solution;

The MTBE stock solution for both experiment types was prepared by stirring 1 ml of MTBE (Merck Millipore) with 9 ml of ultrapure water (Milli-Q, 18.2 MQ cm) without ethanol, which gave the MTBE concentration of 0.50 p,l/ml. The photo activity of the catalysts on Pseudomonas aeruginosa strains ATCC 9023 and DV 2739 in both experiments was investigated in a microbiological chamber illuminated sample with an UV-A lamp at 366 nm.

The quantification of Pseudomonas aeruginosa strains ATCC 9023 and DV 2739 from all tested solutions has been performed on an analog photocolorimeter (Labtronics, India) at 550 nm. In this experiment, a reduction in the absorption of the solution to 648 nm was observed, as a measure of decrease of the MO growth and their antimicrobial activity.

Results and Discussion Synthesis conditions

The properties of the synthetized pure and doped titanium (IV) oxide nanoparticles by the sol-gel method synthesis determined the main of the following parameters: the pH value in the hydrolysis process, the precursor type, the temperature and the duration of hydrolysis (aging) and drying, and Alco gel. The most important are the ones of the calcination process parameters: heating rate, temperature, calcination cooling and duration rate. Titanium (IV) chloride (TiCl4), as a cheap compound, is the primary starting material for the commercial production of titanium powders. The sol-gel method synthesis entails the hydrolysis of a precursor molecule solution aiming to obtain first a suspension of colloidal particles - the sol and then a gel composed of aggregated sol particles, which is in the further processing thermally treated yielding to the desired nanoparticles material. The process takes the following direction:

TiCl4 ^ Ti(OH)4 ^ Alco gel (1)

This reaction can be written in a chemical way as

TiCl4 + 4NH4OH ^ Ti(OH)4| + 4NH4Cl (2)

Ti(OH)4 ^ TiO2 + 2H2O (3)

The pH value of the precursor solution is a decisive factor in controlling the final particle size and shape, the crystal phase and the agglomeration (Zhang & Sun, 2004) due to its crucial influence on the relative rates of hydrolysis and polycondensation. Aruna et al (Aruna, et al, 2000) have found that the main hydrolysate in this reaction is [Ti(OH)n(H2O)6-n](4"n)+, where the amount of water varies with the relative rates of hydrolysis and polycondensation.

The titanium monomers formed during the reaction in the precursor solution play a significant role in the condensation process (Sun, J., et al. 2002) and in the formation of the final gel structure containing precursor molecules (Dlaz-Dlez, M.A., et al, 2003). Since the intention was to obtain TiO2 nanoparticles in the anatase form, the pH value of the solution during the hydrolysis process was chosen to be 9.3 which is in accordance with the pH value of 9.4 used by Venz et al (Venz, P.A. et al. 2000) for the same sol state and tetra isopropyl titanate used as a precursor. The pH value is several pH-units above the pH value where

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the zeta-potential is zero (isoelectric point), as shown by Venz et al (Venz, P.A. et al. 2000). This is suitable for obtaining the stable sol with the maximum reduction of particle aggregation.

Aging is a process during which the gel properties can be changed as a result of polymerization, coarsening and phase transformation as reported by Wang et al (Wang et al, 2012). The nano crystallite growth presents the coalescence of small neighboring crystallites that become oriented due to the atomic diffusion or discrete orientation attachment. The aging conditions were the same in all experiments, with the temperature of 0°C and the process duration of 5 h. This is in accordance with the literature data (He, D. et al. 2007; Hari-Bala, G.Y., et al. 2006). The influence of aging on the properties of synthetized anatase nanoparticles was thus eliminated.

Titanium hydroxide was dried and calcined at high temperature, in order to obtain crystalline TiO2-nanoparticles by the sol-gel method synthesis. In our experiment, as shown by Golubovic et al (Golubovic et al, 2009a), the drying temperature was always 280°C, while the process duration was 4 h. The influence of the calcination parameters on the physical-chemical properties of anatase nanopowders and their dopants was examined by changing the heating rates (55, 67.5 and 135°C/h) and their influence of three different calcination durations (5, 7 and 24) with the constant of the calcination temperature (550°C) and their cooling rate (37.42°C/h). Only S07 sample was synthesized with a little different value of the calcination temperature and the cooling rate from all other samples, at 500°C and 37.42°C/h respectively, which can be seen in Table 2.

Some of the sol-gel synthesis parameters for the chosen TiO2 samples (pure and doped), which are the subject of this paper are listed in Table 1.

The temperature profiles for pure TiO2-nanoparticles of S05, S06, S07, S08, S10, S11, S99 and S102 samples (Table 2) were obtained, investigated and reported earlier (S07, S08 and S10, as A2, A3 and A6 profile samples; S05 and S06, S99 and S102 with a calcination duration of 5, 7 and 24 h, respectively): Golubovic et al (Golubovic et al, 2009a), (Golubovic et al, 2013) and Scepanovic et al (Scepanovic et al, 2010) without S11 sample that is here for the comparison purposes.

During the sol-gel synthesis, we prepared pure and doped TiO2-nanoparticles. Based on the presented synthesis data in Tables 1 and 2, the models of the sample temperature profiles for pure TiO2-NPs, S05, S06, S07, S08, S10 and S99 and their dopants are shown in the text bellow.

Table 1 - Selected parameters for pure TiO2-NPs and their La3+, Fe3+ and V3+ dopants Таблица 1 - Выбранные праметры чистых TiO2-H4 и их La3+, Fe3+ и V3+ допантов Табела 1 - Одабрани параметри за чисте TiO2-H4-e и њихове La3+, Fe3+ и V3+

допанте

Pure TiO2-NPs La-doped TiO2-NPs Fe-doped TiO2-NPs V-doped TiO2-NPs wt. % dopant Calcination

Heating rate [°C/h] T [°C] t [h]

S05 55 550 5

S06 55 550 7

S07 55 500 7

S08 55 550 7

S10 135 550 7

S11 55 550 5

S16 5.0 67.5 550 7

S18 0.65 67.5 550 7

S24 2.5 135 550 7

S28 1.0 135 550 7

S38 5.0 135 550 7

S40a 2.0 135 550 7

S48 3.0 135 550 7

S52a 4.0 135 550 7

S64 6.0 135 550 7

S93 10 67.5 550 7

S96 10 135 550 24

S99 67.5 550 7

S102 135 550 24

S111 5.0 135 550 7

S112 5.0 135 550 24

S117 1.0 135 550 7

S118 1.0 135 550 24

S119 3.0 135 550 7

S120 3.0 135 550 24

Pure and dopants of the model of the S07 sample temperature profile: These samples were not doped, they were synthesized as S05, S06, S07 and S11 samples, all four with this temperature profile; the only differences between the samples are that S11 sample has a shorter calcination duration of 5 hours (than the calcinatin duration of 7 h for the other three samples), and that only S07 sample has a lower cooling temperature (500°C, and for the other three is 550°C)

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Table 2 - The parameters of the sol-gel process for the same TiO2-NPs samples (Golubovic et al, 2009a), (Golubovic et al, 2013) and (Scepanovic et al, 2010). Only S11 sample has not been reported earlier

Таблица 2 - Параметры золь-гель процесса по тем же образцам ТЮ2-НЧ (Golubovic et al, 2009a), (Golubovic et al, 2013) и (Scepanovic et al, 2010). Не был опубликован только образец С11

Табела 2 - Параметри сол-гел процеса за исте узорке ТЮ2-НЧ-а (Golubovic et al, 2009a), (Golubovic et al, 2013) и (Scepanovic et al, 2010). Само узорак С11 није

објављен раније

Sam- ple Aging Drying Calcination

t [h] T [°C] Duration [h] T [°C] t [h] Heat. rate [°C/h] T [°C] t [h] Cooling rate [°C/h]

S05 5 0 2 280 4 55 550 5 37.42

S06 5 0 2 280 4 55 550 7 37.42

S07 5 0 2 280 4 55 500 7 36.46

S08 5 0 2 280 4 55 550 7 37.42

S10 5 0 2 280 4 135 550 7 37.42

S11 5 0 2 280 4 55 550 5 37.42

S99 5 0 2 280 4 67.5 550 7 37.42

S102 5 0 2 280 4 135 550 24 37.42

Pure and dopants of the model of the S08 sample temperature profile:

• Dopants of lanthanum: S16 (wt. 5.0 %) and S18 (wt. 0.65 %) samples;

• Dopants vanadium: S93 (wt. 10 %) sample.

Pure and dopants of the model of the S10 sample temperature profile:

• Dopants of lanthanum: S28 (wt. 1.0 %), S38 (wt. 5.0 %), S40a (wt. 2.0 %), S48 (wt. 3.0 %), S52a (wt. 4.0 %) and S64 (wt. 6.0 %) samples;

• Dopant of iron: S24 (wt. 2,5 %), S111-S112 (wt. 5.0 %), S117-S118 (wt. 1.0 %) and S119-S120 (wt. 3.0 %) samples. The samples of S112, S118 and S120 had a longer calcination duration of 24 h (calcination duration of 7 h, for S111, S117 and S119 samples);

Pure and dopants of the model of the S99 sample temperature profile:

• Dopants vanadium: S93 (wt. 10 %) sample;

Pure and dopants of the model of the S102 sample temperature profile: • Dopant of vanadium: S96 (wt. 10%) sample.

The results ofXRD and XRPD diffractions

The XRPD and XRD patterns of pure and some La-doped TiO2 nanopowders are shown from Figure 2 to Figure 4. The most intensive diffraction picks can be ascribed to the anatase crystal structure (JCPDS card 78-2486). Structure refinements have been performed by the Rietveld method: the lattice parameters, the unit cell volume, the average crystallite size and the average strain in the anatase and brookite phase, and the results of the quantitative phase analysis for brookite (brookite content) are summarized in Table 3, as partially reported earlier by (Golubovic et al, 2009a), (Golubovic et al, 2013), (Grujic-Brojcin et al, 2014) and (Scepanovic et al, 2010). The value of the anatase a parameter for the chosen tested samples considered and compared in Table 3 varies around its reference value (a0 = 0.378479(3) nm), whereas the value of the c parameter is slightly lower than the reference one (c0 = 0.951237(1) nm), as reported by Grujic-Brojcin (Grujic-Brojcin et al, 2014) earlier; except for the sample labeled as S96. The unit cell volume of all samples of La-doped TiO2 is also lower in comparison with the reference value, except for the pure TiO2. The structural refinement has revealed that the anatase crystallite size of the doped samples is decreased from 15.0 to 17.5 nm in the pure TiO2 (S06, S05 and S11, respectively) to 12 nm in the La-doped samples. The pure TiO2-nanoparticles strain is slightly increased with doping (Table 3). The brookite phase is highly disordered in all samples, which is indicated with a large value of the average strain in brookite crystallite.

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The chosen XRD diffract grams of the chosen pure TiO2-nanoparticles patterns labeled as S07, S08 and S10 are presented in Figure 2, which has been reported earlier by Golubovic et al (Golubovic et al, 2009a).

The XPRD patterns labeled as S28, S52a and S64 of anatase TiO2-NPs doped with different wt. concentration of lanthanum (1 wt. %, 4 wt. % and 6 wt. %, respectively) are presented from Figure 3 to Figure 5, respectively. Figure 4 has been reported earlier by Golubovic et al (Golubovic et al, 2009b) as a conference poster.

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Table 3 - The results of the Rietveld analyses of the samples (the unit cell parameters and the unit volume of anatase, the average crystallite size and the average strain in the anatase and brookite mineral forms and the content of brookite form) for pure and La and Fe-doped TiO2-NPs (the values in the paretheses represent the estimated standard deviations) (Golubovic et al, 2009a), (Golubovic et al, 2013), (Scepanovic et al, 2010),

(Grujic-Brojcin et al, 2014)

Таблица 3 - Результаты проведенного по методу Ритвельда анализа образцов (параметры элементарной ячейки анатаза, в том числе ее объема, средний размер кристаллитов и средняя твердость анатаза и брукита и состав форм брукита) чистых и La и Fe легированных ТиО2-НЧ-e (значения в скобках представляют допустимые отклонения) (Golubovic et al, 2009a), (Golubovic et al, 2013), (Scepanovic et al, 2010), (Grujic-Brojcin et al, 2014)

Табела 3 - Резултати Ритвалдове анализе узорака (параметри јединичне ћелије и јединичне зепремине анатаса, просечна величина кристалита и просечна сила у минералној форми анатаса и брукита и садржај брукитне форме) за чисте и La и Fe допиране ТиО2-НЧ-а (вредности у заградама представљају процењена стандардна одступања) (Golubovic et al, 2009a), (Golubovic et al, 2013), (Scepanovic et al, 2010), (Grujic-Brojcin et al, 2014)

Sam- ple Dopant wt. % Anatase Brookite

a (nm) c (nm) V (10-3 nm3) Cryst .size (nm) Strain (x10-3) Content (%) Cryst. size (nm) Strain (x 10-3)

S05 0.0 0.37873(0) 0.9496(4) 136.21(4) 15.4

S06 0.0 0.37852(0) 0.9484(1) 17.5

S07 0.0 0.37844(1) 0.94838(4) 12 4.5 17 12 16.9

S08 0.0 0.37856(1) 0.94860(4) 12 4.2 16 35 19.6

S10 0.0 0.37884(1) 0.94980(3) 10 3.4 10 58 16.8

S11 0.0 0.37884(1) 0.94980(5) 136.31(1) 15 3 10(2) 58 17

S18 0.65 0.37895(2) 0.9485(1) 136.21(2) 12 4 42(5) 2 29

S28 1.0 0.37880(2) 0.94780(1) 136.01(2) 10 5 24(3) 26 22

S40a 2.0 0.37853(2) 0.94908(9) 135.99(2) 12 8 21(1) 12 8

S48 3.0 0.37823(6) 0.9471(3) 135.49(5) 12 8 21(4) 12 8

S16 5.0 0.37874(3) 0.9485(1) 136.06(2) 12 8 22(2) 12 8

S96 10.0 0.37719 0.95266

Reference value: a0 = 0.378479(3) nm, c0 = 0.951237(1) nm, and V0 = 136.26(1) (10-3 nm3)

Figure 2 - XRD diffract grams of the chosen temperature profiles of TiO2 samples

(Golubovic et al, 2009a)

Рис. 2 - XRD-дифрактограммы, выбранных температурных профилей образцов

TiO2 (Golubovic et al, 2009a)

Слика 2 - XRD дифрактограми одабраних температурних профила ТиО2 узорака

(Golubovic et al, 2009a)

Figure 3 - XPRD diffract gram for S28 sample Рис. 3 - XPRD-дифрактограмма образца С28 Слика 3 - XPRD дифрактограм за узорак С28

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Figure 4 - XPRD diffract gram for S52a sample (Golubovic et al, 2009b) Рис. 4 - XPRD-дифрактограмма образца С52а (Golubovic et al, 2009b) Слика 4 - XPRD дифрактограм за узорак С52а (Golubovic et al, 2009b)

Figure 5 - XPRD diffract gram for S64 sample Рис. 5 - XPRD-дифрактограмма образца С64 Слика 5 - XPRD дифрактограм за узорак С64

The results of the Raman spectroscopy

In the Raman mode of synthesized pure La and V-doped TiO2-NPs, which are the subject of this paper, the anatase Raman mode dominates (Ohsaka et al, 1978), (Scepanovic etal, 2007): Eg(1) (~143 cm-1), Eg(2) (~198 cm-1), B1g (~398 cm-1), A1g+B1g (~518 cm-1), and Eg(3) (~639 cm-1), as reported by Golubovic et al (Golubovic et al, 2009a), (Golubovic et al, 2013), Grujic-Brojcin et al (Grujic-Brojcinetal, 2014) and Scepanovic et al (Scepanovic etal, 2010). The Raman spectra of the chosen pure and some La3+ and V3+ doped TiO2 nanoparticles were measured at room temperature. Some of these spectra are shown in Figure 6 and Figure 7, as the samples labeled as S11 (pure TiO2-NP) and S48 (3 wt. %):

Figure 6 - Raman scattering spectra for S11 sample (Golubovic et al, 2009b)

Рис. 6 - Рамановская спектроскопия образца С11 (Golubovic et al, 2009b) Слика 6 - Раманов расејани спектри за узорак С11 (Golubovic et al, 2009b)

On the poster at the conference presented earlier in Figures 6 and 7, Golubovic et al (Golubovic, A. et al. 2009b) reported that the heating of pure TiO2-nanoparticles (S11 sample) to 800°C causes redshift and narrowing of anatase Eg(1). The Raman mode as well as the appearance of new Raman modes were assigned to the rutile phase. After the same heating treatment, there are neither a drastic change of Eg(1) Raman mode in the spectra of La-doped sample labeled as S48 nor the appearance of additional modes. Therefore, it can be concluded that doping with La3+ ions stabilizes the TiO2 nanostructure in the anatase phase at high temperature. The frequencies of the anatase modes in V-doped TiO2-nanoparticles shift more with different synthesis conditions, in comparison to their counterparts, as it can been seen from the data listed in Table 4, reported earlier (Scepanovic et al, 2010).

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Figure 7 - Raman scattering spectra for S48 sample (Golubovic et al, 2009b) Рис. 7 - Рамановская спектроскопия образца С48 (Golubovic et al, 2009b) Слика 7 - Раманови расејани спектри за узорак С48 (Golubovic et al, 2009b)

Table 4 - Frequencies of the anatase Raman modes in the pure and V-doped T1O2

nanoparticle samples

Таблица 4 - Частота Рамановского режима для атаназа чистых и V-легированных образцов наночастиц T1O2 Табела 4 - Фреквенције Раманових режима за анатас у чистим и V-допираним

ТиО2 наночестицама

Sample Raman frequencies of anatase modes (cm-1)

Eg(1) Eg(2) B1g(1) A1g(1)+B1g(2) Eg(3)

S93 145.3 198.4 397.0 516.5 637.7

S96 148.9 201.9 394.6 514.2 633.4

S99 143.7 197.7 396.8 518.7 639.6

S102 143.8 197.8 397.0 518.8 639.7

The Raman mode of TiO2-nanoparticles for the chosen pure and V-doped samples, labeled as S99, S93 and S96, respectively, feature twelve well-resolved bands at about 101, 143, 284, 305, 406, 478, 531, 699, 810, 926, 996 and 1020 cm-1, as reported by Scepanovic et al (Scepanovic et al, 2010). The frequencies of these additional Raman modes, which can be related to the presence of vanadium, are listed in Table 5.

Table 5 - Frequencies of the V-related Raman modes in the V-doped anatase TiO2-NPs Таблица 5 - Частоты V-связанных в Рамановском режиме в V-легированных

фазах анатаза TiO2-N4

Табела 5 - Фреквенције за V-повезане Раманове режиме у V-допираној фази

анатас Ti'02-НЧ-а

Sample Raman frequencies (cm-1)

1 2 3 4 5 6 7 8 9 10 11 12

V2O5 100 143 283 303 407 477 526 696 - - 995 -

S93 101 143 284 305 406 479 532 700 808 924 996 1017

S96 - 143 284 308 - - - 699 810 934 996 1027

The measured values of the data from Table 4 and Table 5 have been reported earlier by Scepanovic et al (Scepanovic et al, 2010); it has been reported earlier that the presence of the additional Raman mode in the spectra of doped samples unambiguously shows that vanadium ions formed vanadium oxides (mostly V2O5) and some other vanadate structures in V-doped nanopowders. This confirms that a higher concentration of V in TiO2 tends to stabilize V in the 5+ state predominantly, as reported by Bhattacharyya et al (Bhattacharyya et al, 2010). However, the change in pure TiO2-nanoparticles of the Raman modes in those samples reveals that a certain amount of vanadium ions is introduced into the TiO2 crystal lattice, which strongly depends on the conditions of the synthesis, such as the calcination heating rate and its duration.

The Results of the ESM

For TiO2, La and Fe dopants nanoparticles, the particle size distributions were obtained by the elastic sphere model (ESM) and presented in Figures 8 and 11, respectively. In Figure 8, we can see that the mean particle size was around 12 nm for the La-dopant TiO2-nanoparticles samples up to 4 wt. % of lanthanum ions, compared to pure anatase. The value of the mean particle size is increased for a higher lanthanum ion concentration.

The mean particle size was around 15.5 nm for S111 sample of Fe-dopant of TiO2 nanoparticles in a concentration of 5 wt. %, synthetized at the calcination duration of 7 h, as shown in Figure 11, compared to the same concentration of the La-dopant (Figure 8).

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Figure 8 - Particle size distributions in the pure and La-doped TiO2 samples such as S11, S28, S48 and S16 (Golubovic et al, 2009b)

Рис. 8 - Распределение частиц по размерам в чистых и легированных La образцах TiO2, таких как С11, С28, С48 и С16 (Golubovic et al, 2009b)

Слика 8 - Дистрибуција величине честица у чистим и La-допираним ТиО2 узорцима, као С11, С28, С48 и С16 (Golubovic et al, 2009b)

The results of the Atomic Force Microscopy Measurements

The surface of the lanthanum and iron doped TiO2 nanoparticles sample labeled as S18 (0.65 wt. %) and S111 (5.0 wt. %) recorded by the AFM in the non-contact mode is shown in Figures 9 (Golubovic et al, 2009b), 10 and 12, respectively. These images are recorded on doped La and Fe-doped TiO2-nanoparticles, previously dispersed in ethanol, deposited on freshly cleaved highly oriented prolific graphite (HOPG). From these images, we can observe that sample S18 consists of very small nanocrystals of 12 nm and greater agglomerated particles. Also, sample S111 consists of several larger nanocrystals, with a large number of agglomerates arranged as it can be seen on its particle histogram in Figure 11.

Figure 9 - AFMimage of S18 sample (anatase doped with 0.65 wt. % La3+)

(1000 x 1000 nm)

Рис. 9 - AFM изображение С18 образца (анатаз легированный с 0.65 вес. % La3+)

(1000 x 1000 nm)

Слика 9 - AFM слика С18 узорка (анатас допиран са 0.65 теж.% La3+)

(1000 x 1000 nm)

Figure 10 - AFM image of an S111 anatase nanoparticle sample doped with 5 wt. % Fe3+ and a calcination duration of 7 h (1000 x 1000 nm)

Рис. 10 - AFM изображение С111 образца наночастиц атаназа легированных с 5 вес. % Fe3+ и временем прокаливания - 7 ч. (1000 x 1000 nm)

Слика 10 - AFM слика С111 узорка анатас наночестице допиране са 5 теж. % Fe3+ и време трајања калцинације од 7 ч (1000 x 1000 nm)

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Figure 11 - Particle histogram for the Fe-doped TiO2-NP of S111 sample Рис. 11 - Гистограмма частиц образца С111 (Fe-допант TiC>2-H4) Слика 11 - Хистограм честица за узорак С111 (Fe-допант ТиО2-НЧ-а)

Figure 12 - AFM image of S111 sample - display at an angle Рис. 12 - AFM изображение образца С111 - вид под наклоном Слика 12 - AFM слика узорка С111 - приказ под углом

The chemical compositions of pure and some chosen La-doped TiO2-nanoparticles have been estimated by the EDS method, and summarized in Table 6, which was partially reported earlier (Golubovic et al, 2013), (Grujic-Brojcin et al, 2014).

Table 6 - EDS results for pure and some chosen La-doped TiO2-NPs Таблица 6 - EDS результаты по чистым и некоторым La легированным TiO2-H4 Табела 6 - EDS резултати за чисте и неке изабране La допиране Ti02-НЧ-а

La (wt. %) EDS data

O (wt. %) Ti (wt. %) Na (wt.%) Cl (wt.%) La (wt.%) Total (wt. %)

S06 0.0 32.72 64.54 1.84 0.90 0.0 100

S11 0.0 39.46 60.54 - - 0.0 100

S18 0.65 42.91 57.09 - - 0.0 100

S28 1.0 49.71 49.44 - - 0.85 100

S40a 2.0 44.59 53.45 - - 1.96 100

S64 6.0 41.71 52.39 - - 5.91 100

The EDS data (shown in Table 6) and the spectra of pure and La-doped of TiO2-nanoparticles patterns of samples have been reported earlier by Golubovic et al. (Golubovic et al, 2013), for S06 sample and Grujic-Brojcin et al (Grujic-Brojcin et al, 2014), for S11, S18, S28, S40a and S64 samples). These analyzes have shown that only S06 sample synthesized with a calcination duration of 7 h consists of sodium (Na+) and chlorine (Cl-) ions, which has not been detected in the other observed samples, as we can see in Table 6. Golubovic et al (Golubovic et al, 2013) have reported earlier that short duration of calcination may also be the reason for a relatively high concentration of sodium (Na+) and chlorine (Cl-) ions in the sample with a calcination duration of 1 h. We can see, in Table 6, that the oxygen weight percent in the pure TiO2-nanoparticle sample is close to stoichiometric TiO2 (40.0 wt. %), and that the percent of oxygen is higher in the La-doped samples. Based on the data obtained from the EDS measurement method, the final molar La/Ti ratio is lower than at the beginning of the synthesis process; which is estimated at around 63 % of the starting value, except in the case of the sample doped with 0.65 wt. % of La. Finally, the results also show that a low content of La (0.65 wt. %) could not be detected in S18 sample by the EDS method.

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The porous properties of the TiO2-nanoparticles samples such as P25, S05, S06, S11, S18, S28 and S40a have been estimated by the BET, BJH and CPMS methods and summarized in Table 7 which has been partially reported earlier (Golubovic et al, 2013), (Grujic-Brojcin et al, 2014).

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Table 7 - Porous properties of the chosen ТЮ2 samples (P-25, S05, S06, S11, S18, S28 & S40a): specific surface area (Sbet, Smeso, Smc & Sbjh), pore volume (Vp & Vmic), mean pore diameters obtained from different methods (Dbet, Dbjh & Dcpsm), CPMS fitting parameter (Ns) and the predicted tortuosity factor (t)

Таблица 7 - Характеристики пористой структуры, выбранных образцов Т1Ю2 (P25, S05, S06, S11, Sl8, S28 и S40a): Удельная поверхность (SBET, Smeso, Smic & SBJH), объем пор (Vp и Vmic) различные методы (DBET, DBJH & DCPSM), CPMS параметры настройки (Ns) и коэффициент извилистости (т)

Табела 7 - Порозна својства одабраних узорака ТЮ2 (P-25, S05, S06, S11, S18, S28 и S40a): специфична површина (Sbet, Smeso, Smc & Sbjh), запремина порa (Vp и Vmic) Средњи пречници пора добијени различитим методама (Dbet, Dbjh & Dcpsm), CPMS параметар за подешавање (Ns) и процењени фактор тортуозности (т)

Parameters Sample

P-25 P 0 0 СЛ S06 (0.0) S11 (0.0) S18 (0.65) S28 (10) S40a (2.0)

Sbet (m2g 1) 13 17 51 58 79 84 78

Smeso (m g ) 13 17 51 -

Smic (m g ) - - - -

Sbjh (mV) - - 58.2 79.4 83.8 78.1

Vp (cmV) 0.024 0.030 0.088 0.160 0.185 0.258 0.215

Vmic (cmV) - - - -

Dbet (nm) 7.5 7.1 6.9 7.1 6.0 7.9 7.1

Dbjh (nm) 7.4 6.7 6.8 7.1 6.3 7.7 7.5

Dcpsm (nm) 7.7 7.4 7.1 8.1 6.9 7.7 7.5

Ns 5.5 8 4 8 13 12 11

т 3.0 4.0 2.7 4.1 5.3 4.4 4.6

In order to investigate the effect of the chosen TiO2 nanoparticles and their lanthanum doped catalysts on the pore structure and the adsorption ability, the nitrogen sorption isotherm measurements have been carried out. The specific surface area (SBET) and the pore volume (Vp) obtained by the BET method, and the mesopore diameter calculated from both the BET and the BJH (DBET, DBJH, respectively) for the chosen samples can be seen in Table 7, the data of which have been shown earlier by Golubovic et al (Golubovic et al, 2013) for P-25, S05 and S06

patterns of samples and by Grujic-Brojcin et al (Grujic-Brojcin et al, 2014), for S11, S18, S28 and S40a patterns of samples, respectively.

Based on the porosity parameters obtained from the standard nitrogen adsorption isotherms determined from the ac plot (Kaneko et al, 1998), we can also establish that the chosen TiO2 samples are completely mesoporous nanoparticles. The value of SBET in the La-doped samples, S18 and S28: 79 and 84 m2g-1, respectively, are higher than those in the pure TiO2 nanoparticles samples, S05, S06 and S11: 17, 51 and 58 m2g-1 respectively. Also, the values of SBET for the synthesis of TiO2 nanoparticles, in the range of 17-58 m2g-1 are greater than SBET of Degussa P-25® in the value of13 m2g-1. The mean pore diameters, obtained from the BET results (%DBET • 4Vp = SBET) were in good agreement with the diameters obtained by the BJH method. The most commonly used method entitled as the BJH method for the determination of the pore size distribution (PSD) listed in Table 7, as reported by Barrett (Barrett et al, 1951), is estimated from the desorption branch of the hysteresis isotherm loops. Also, the CPSM method (Salmas & Androutsopoulos, 2001), (Androutsopoulos & Salmas, 2000) for the PSD evaluation has been applied. In this method, the pore structure is considered as a statistically large number of independent, non-intersected corrugated pores, made of a series of NS cylindrical segments of equal length, with randomly distributed diameters of mesopores nanoparticles (Golubovic et al, 2013), (Salmas & Androutsopoulos, 2001), (Androutsopoulos & Salmas, 2000). The CPSM fitting parameter NS, mentioned above, is also listed in Table 7: higher values of NS have been obtained for the doped samples, which can be associated with a more complex pore structure in the doped samples (Salmas & Androutsopoulos, 2001). As a result of the CpSm, the pore tortuosity factor т is also estimated and listed in Table 7, as a measure of diffusion through porous media based on the nitrogen sorption hysteresis data (Golubovic et al, 2013), (Salmas & Androutsopoulos, 2001). The dependence of the tortuosity factor on the La-content in the doped samples shows the same tendency as NS (Grujic-Brojcin et al, 2014); higher values of т are obtained for the doped samples, with the maximum in S18 sample with т = 5.3. This points to the most complex pore structure consisting of interconnected pore segments with different diameters in this sample.

Finally, we expect that the best catalytic properties of the chosen TiO2-NPs samples are found in S11 as pure and in S28 dopant sample that doped TiO2 nanoparticles in a concentration of 1.0 mole % of La3+ ions, based on the value of the SBET in Table 7. If we compare the

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properties of S05 samples synthesized with the calcination duration of 5 h and S06 and S11 samples, whose calcination duration was 7 h, we can determine that the catalysts calcined for 7 h have better properties. The best properties found in S11 sample for pure TiO2 nanoparticles, as seen in Table 7, led us to choose this pure TiO2 sample for photocatalytic research and testing in our study.

Result of the photocatalytic activities

The photocatalytic activity was measured in four experiments: three experiments of photocatalytic activities and one coupled photocatalytic-microbiological experiment. All experiments were carried out in a bath slurry-catalyst circular photoreactor, in dark and under direct ultraviolet radiation simulated with a sodium SONT UV400 lamp, with the initial concentrations of 1.00 ml/L and 0.50 ml/L MTBE in the water solution, respectively, depending on the types of experiments.

Results of the experiments of the photocatalytic activities

The experimental investigation of the photocatalytic degradation of MTBE was performed in three different experiments. The initial concentration in all these experiments was 1.00 ml/L and the solutions were thermo-stated at 30°C. All solutions were tested for 60 minutes in the bath slurry-catalyst circular photoreactor in aerobic conditions and their degradation rate was measured in 15-minute intervals.

The first experiment was carried out under direct UV radiation simulated with the sodium SONT UV400 lamp in the photoreactor with the initial concentration of 0.50 ml/L of the MTBE water solution and different types of synthetized TiO2 nanoparticles, using the following samples of TiO2 nanoparticles: S07 (pure TiO2 nanoparticles), S18, S28, S38, S40a, S48, S52a and S64 (TiO2 nanoparticles doped with La3+ in the following concentration: 0.65; 1.0; 2.0; 3.0; 4.0; 5.0 and 6.0 wt. %, respectively) and one commercial TiO2 nanoparticles catalyst (Degussa P-25®). The concentration of all catalysts used in the experiment was 0.1 g/L. The results of the measurements of the detected reduction of the MTBE concentration during all experiments at the GC/MSD/Headspace are shown In Table 8.

Our results in the experiment show that the best photocatalytic efficiency was obtained in TiO2 doped with La3+ of 1 wt. %, but the fastest drop in the polluted MTBE concentration in the water solution was achieved in TiO2 doped with La3+ of 3 wt. %.

Table 8 - Photocatalytic degradation of the MTBE initial concentration of 1.00 ml/L with different concentrations of La-doping of TiO2-NPs and pure TiO2-NPs (synthetized and commercial Degussa P-25®) in a concentration of 0.1 g/L Таблица 8 - Фотокаталитическая деградация МТБЭ начальной концентрации 1,00 ml/L с различной концентрацией La - легированных ЋО2-НЧ и чистых ЋО2-НЧ (синтезировано в коммерческих целях Degussa P-25®) с концентрацией 0,1 g/L Табела 8 - Фотокаталитичка деградација МТБЕ почетне концентрације од 1,00 ml/L са различитом концентрацијом La -допинта Ti'02-НЧ-а и чистих Ti'02-НЧ-а (синтетизованог и комерцијалног Degussa P-25®) у концентрацији од 0,1 g/L

Time UV (min) S07 P-25 Samples TiO2 doped with different wt. % La3+

S18 (0.65) S28 (1.0) S40a (2.0) S48 (3.0) S52a (4.0) S38 (5,0) S64 (6.0)

0 1.000 1.000 1.000 1.000 1.000 1.000 1.000 1.000 1.000

15 - - 0.797 - - 0.184 0.678 0.671

30 0.659 - 0.188 0.180 0.198 - 0.132 0.410

45 0.095 0.062 - - 0.225 0.239

60 0.093 0.488 - - 0.122 0.178 0.052 - -

The second experiment was carried out under direct ultraviolet radiation simulated with the SONT UV400 lamp in the photoreactor with the initial concentration of 1.00 ml/L of the MTBE water solution in presence of the catalyst synthetized TiO2-nanoparticles doped with different concentrations of Fe3+ ions and their two calcination durations of 7 and 24 h. We tested the photocatalytic activities catalysts and their dependence on the calcination duration of the following samples: S111 -S112 (5 wt. %, calcination duration of 7 and 24h, respectively), S117 -S118 (1 wt. %, calcination duration of 7 and 24h, respectively), and S119 - S120 (3 wt. %, calcination duration of 7 and 24h, respectively), as a photocatalytic degradation degree of MTBE in the water solution. The carbon-dioxide evolution during the experiment is shown in Table 9 in comparison with pure TiO2-nanoparticles: synthetized S07 catalyst sample and commercial catalyst - Degussa P-25®, determined at the GC/MSD/Headspace (as shown In Table 8). The concentration of all catalysts used in the experiment was 0.1 g/L.

Our results in the second experiment show that the best photocatalytic efficiency was found in TiO2 doped with the highest concentration of Fe3+ ions dopant, 5 wt. % and the calcination duration time of 7 h. The greatest difference in the degradation degree versus the calcination duration is the highest concentration catalyst, and the smallest concentration is 3 wt. % of the Fe-doped TiO2 nanoparticle catalyst.

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Table 9 - Photocatalytic degradation of MTBE as the percentage of the total CO2 yield, the initial concentration of 1.00 ml/L MTBE in the water solution with different concentrations of Fe-doping of TiO2-NPs and pure TiO2-NPs (synthetized and commercial Degussa P-25®) in a concentration of 0.1 g/L

Таблица 9 - Фотокаталитическая деградация МТБЭ как процент общего выброса CO2, с начальной концентрацией 1,00 ml/L МТБЭ в водном растворе с различной концентрацией Fe- легированных ЋО2-НЧ и чистых ЋО2-НЧ (синтезировано в коммерческих целях Degussa P-25®) с концентрацией 0,1 g/L

Табела 9 - Фотокаталитичка деградација МТБЕ-а као проценат укупног приноса CO2, почетне концентрације од 1,00 ml/L МТБЕ у воденом раствору са различитом концентрациям Fe-допинга од ТиО2-НЧ-а и чистих ТиО2-НЧ-а (синтетизованог и комерцијалног Degussa P-25®) у концентрацији од 0,1 g/L

Time UV (min) S07 P-25 Samples TiO2 doped with different wt. % Fe3+

S111 (5.0) S112 (5.0) S117 (10) S118 (10) S119 (3.0) S120 (3.0)

0 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000

15 - - 0.273 0.258 - 0.180 0.323 -

30 0.341 0.550 0.486 0.442 0.402 - 0.494

45 0.845 - 0.765 0.702 0.827 0.664

60 0.907 0.512 0.976 0.931 0.905 0.899 0.928 0.922

The third experiment was carried out under direct UV light exposure simulated with the SONT UV400 lamp in the photoreactor with the initial concentration of 1.00 ml/L of the MTBE water solution in the presence of different catalyst types of synthetized TiO2 nanoparticles, using the following samples of TiO2 nanoparticles: S07 (pure TiO2-NP), S93 and S96 (TiO2-NPs doped with 10 wt. % V3+), S28 (TiO2-NPs doped with 1.0 wt. % La3+), and commercial TiO2 nanoparticles (Degussa P-25®). The results of the measurement of the detected reduction of the MTBE concentration during the experiments were determined at the GC/MSD/Headspace. The results of the photocatalytic degradation of MTBE (Table 9) for the samples such as S117, S119 and S111 (TiO2-NPs doped with 1.0, 3.0 and 5.0 wt. % Fe3+, respectively, with the duration time of 7 h for all samples) are shown for comparison in Table 10. The concentration of all catalysts used in the experiment was 0.1 g/L.

Table 10 - Photocatalytic degradation of the MTBE initial concentration of 1.00 ml/L with La, Fe and V-doping of TiO2-NPs and pure TiO2-NPs (synthetized and commercial Degussa P-25®) in a concentration of 0.1 g/L Таблица 10 - Фотокаталитическая деградация МТБЭ начальной концентрации

1.00 ml/L с La Fe и V - легированных TO2-H4 и чистых ЋО2-НЧ (синтезировано в

коммерческих целях Degussa P-25®) с концентрацией 0,1 g/L Табела 10 - Фотокаталитичка деградација МТБЕ-а почетне концентрације од

1.00 ml/L са La, Fe и V-допингом ТиО2-НЧ-а и чисто ТиО2-НЧ-а (синтетизованог и

комерцијалног Degussa P-25®) у концентрацији од 0,1 g/L

Time UV (min) S07 P-25 Samples TiO2 doped with different wt. % V3+ La3+, wt % Fe3+, wt. %

S93 (10.0) S96 (10.0) S28 (1.0) S117 (1.0) S119 (3.0) S111 (5.0)

0 1.000 1.000 1.000 1.000 1.000 1.000 1.000 1.000

15 - - 0.345 - - 0.777 0.727

30 0.659 - - 0.650 0.180 0.558 - 0.450

45 - - 0.152 - 0.062 0.235 0.173 0.155

60 0.093 0.488 - - - 0.095 0.072 0.024

Our results in the experiment show that the best photocatalytic efficiency was found in TiO2 doped with La3+ of 1.0 wt. % (S28 sample) for 45 minutes, but the fastest drop in the polluted MTBE concentration in the water solution was in TiO2 doped with V3+ of 10.0 wt. % (sample S93). Also, our results show different degradation rates for TiO2 doped with V3+ of 10.0 wt. %, S93 and S96 samples, synthetized with different duration times (7 and 24 h, respectively). This can be explained by a different nanomaterial structure. If we compare the results in Table 10, we can see that the best degree of the total MTBE degradation in 60 minutes is achieved in S111 and S119 catalysts, which were doped with 3.0 and 5.0 wt. % of Fe, respectively, but their total MTBE degradation is smaller for 45 minutes compared to the case when we used the La-dopant of TiO2-NPs as a catalyst (S28 sample).

Results of the coupled photocatalytic-microbiological experiment

The experimental investigation of the coupled photocatalytic-microbiological degradation of MTBE was performed in one experiment. The initial concentration in the experiment was 0.50 ml/L, and the solutions were thermo-stated at 30°C.

The experiment was carried out under direct ultraviolet light exposure simulated with the UV lamp in the batch slurry-catalyst circular photoreactor in the presence of the microorganism (MO) Pseudomonas aeruginosa strain ATCC 9023 with the initial concentration of 107 CFU

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mL-1 (as explained in the following experimental part: Microbial activity and inactivity of the coupled photocatalytic-microbiological experiment) and with different concentrations (0.25, 0.50, 0.75 and 1.0 g/L) of commercial TiO2 nanoparticles - Degussa P-25 (Degussa P-25®, AG Frankfurt), and without a catalyst. The results of this research are shown in Table 11. All solutions were tested for 150 minutes in the photoreactor and gas chromatography with a mass detector using the headspace (GC/MSD/Headspace) has been applied in 15-minute intervals, and we presented only three time intervals (0, 60 and 150 minutes).

Table 11 - Photocatalytic activity of the coupled photocatalytic-microbiological processes

in the first experiment

Таблица 11 - Фотокаталитическая активность комбинационного фотокаталично-микробиологического процесса первого эксперимента Табела 11 - Фотокаталитичка активност комбинованих фотокаталитичко-микробиолошких процеса у првом експерименту

Serial No. Time (min) I sol. (% ) II sol. (% ) III sol. (% ) IV sol. (% ) V sol. (% ) VI sol. (% )

1 0.00 1.000 1.000 1.000 1.000 1.000 1.000

2 60.0 0.371 0.308 0.512 0.664 0.325 0.172

3 150.0 0.144 0.144 0.199 0.344 0.119 0.030

Legend (MTBE w. sol. (c=500 ml/L) + MO (c=107 CFU mL'1)):

I sol: UV lamp without TiO2; II sol: UV lamp + TiO2 (1.0 g/L); III sol: Dark experiment (without UV lamp); IV sol: UV lamp + TiO2 (0.50 g/L); V sol: UV lamp + TiO2 (0.25 g/L); VI sol: UV lamp + TiO2 (0.75 g/L).

The results in Table 11 show that the best degradation degree of MTBE was obtained in the VI solution, when we used direct UV radiation simulated with the sodium lamp - sOnT UV400 and 0.75 g/L of TiO2 powder Degussa P-25® for 60 and 150 minutes. The results of the I and II solutions show that the TiO2 catalyst in a concentration of 1.0 g/L achieved the detoxification effect on the MO after 60 minutes of the coupled process of the MTBE degradation; a better result was also achieved when we used the lamp and TiO2 powder Degussa P-25® in the concentration of 0.25 g/L. Also, the IV solution presented that the dark experiment (without the UV lamp and the catalyst) resulted in a higher MTBE degradation degree than in the I, II and IV solutions, especially in the highest concentration as well as in the effect of aeration condition in all experiments. These results show that TiO2 and direct ultraviolet radiation simulated with the sodium lamp - SONT UV400 inactivate and kill microorganisms. The optical density results have proven this assertion by measuring the microbial activity and inactivity in the coupled

photocatalytic-microbiological experiment, which is shown in the text bellow.

Results of the microbiological growth

The measurements of the microbiological growth for the selected Pseudomonas aeruginosa strains (ATCC 9023 and DV 2739) were studied in three experiments, one as the microbial activity and inactivity in the coupled photocatalytic-microbiological experiment and two in the experiments on antimicrobial activities. The coupled photocatalytic-microbiological experiment was performed in the batch slurry-catalyst circular photoreactor, in dark and under direct ultraviolet radiation simulated with the SONT UV400 lamp. The experiments on antimicrobial activities were carried out in the microbiological cabinet. The text below gives the optical density values, measured during these experiments.

Results of the microbial activity and inactivity of the coupled photocatalytic-microbiological experiment

The microbial activity and inactivity of the coupled photocatalytic-microbiological experiment are determined by the optical density measurement for the MTBE solutions in the colorimeter, at 550 nm. The results are shown in Table 12.

Our results show the following characteristics of the coupled photocatalytic-microbiological experiment:

• I solution: This experimental result shows that there has been a

linear increase in the growth of microorganisms, with the reduction of concentration of MTBE in the water solution at 90 and 150 minutes. The reduction of the concentration of MTBE is actually achieved owing to the combined influence of UV radiation simulated by the sodium lamp and the MO in aerobic conditions, which is shown in the coupled photo catalytic-microbiological degradation of MTBE (Tab. 11) and the MO activity (Tab. 12);

• II solution: The experiment with direct ultraviolet radiation

simulated with the sodium lamp and the TiO2 catalyst at a concentration of 1.0 g / L in the presence of MO showed an increase in the MO growth (30.0 min.); constant values (30.0 to 45.0) and low (45.0 to 75.0), after which a low drop in the MO growth occurred. Also, a somewhat greater decrease in the MTBE concentration was achieved than in the I solution at the end of the experiment (t = 150 min); the MTBE degradation

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degree was identical in both experiments (Tab. 11); also, a slightly lower MTBE concentration was achieved, as in accordance with the I solution, but at the end of the experiment (t = 150 min), the identical MTBE degradation rates in both experiments are achieved, as shown in Table 11;

• III solution: Our result in the dark condition experiment showed

that there has been a decrease in the MO growth to 135.0 minute, after which the MO growth increased. The effect in the last 15-20 minutes is possible to be explained by the aerobic conditions which caused the degradation degree of MTBE in the water solution at the end of the experiment.

• IV and V solution: The results of both experiments showed a very

similar profile of the catalyst influence (inactivity of activity) with direct artificial irradiation of the lamp on the MO in the aerobic conditions, and a reduced MO growth at the end of both experiments. A high degradation degree of MTBE in the water solution was obtained in the V solution compared to the IV solution due to a greater MO number and the catalyst concentration, as shown in Tables 11 and 12, respectively.

• VI solution: Our experiment results showed that there was an

increase in the MO growth at the 30th minute, followed by the MO growth reduction until the end of the experiment. This phenomenon can be explained in the following way: in the first 15 minutes, a high concentration of the catalyst inactivated the MO; after that, the MO accommodated to this condition and grew in the next 15 minutes due to the feeding with MTBE in aeration conditions. At the moment of a large decomposition of MTBE, which is formed in the coupled process, the detoxification of the microorganisms occurs.

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By comparing the results of the I to VI solution experiments, we have found out that the best results are achieved in the VI solution experiment due to the excessive concentration of the catalyst, which has a large inactivating effect on the MO. It has negatively affected the coupled photocatalytic-microbiological processes. Therefore, the best property of the coupled photocatalytic-microbiological experiment is achieved with the initial concentration of 0.75 g/L Degussa P-25® TiO2 nanopowder as the maximally effective photo catalyst for our experimental conditions.

Table 12 - Microbial growth for Pseudomonas aeruginosa strain ATCC 9023, with the initial concentration of 107 CFU mL-1 at 0.50 ml/L of the MTBE water solution Таблица 12 - Рост микроорганизмов штамма бактерий Pseudomonas aeruginosa ATCC 9023 с начальной концентрацией 107 CFU mL-1 на 0,50 ml/L водного

раствора МТБЭ

Табела 12 - Микробни раст за сој бактерије Pseudomonas aeruginosa ATCC 9023 почетне концентрације од 107 CFU mL-1 у воденом раствору МТБЕ-а концентрације од 0,50 ml/L

Serial No. Time (min) I sol. II sol. III sol. IV sol. V sol. VI sol.

1 0.00 0.039 2.395 0.043 1.380 1.428 1.852

2 15.0 0.050 2.436 0.040 1.256 1.461 1.642

3 30.0 0.052 2.659 0.042 1.173 1.403 2.051

4 45.0 0.041 2.659 0.036 1.438 1.364 1.623

5 60.0 0.080 2.334 0.032 1.452 1.432 1.577

6 75.0 0.098 2.683 0.046 1.350 1.375 1.595

7 90.0 0.089 2.290 0.035 1.286 1.395 1.621

8 105.0 0.099 2.232 0.026 1.387 1.360 1.502

9 120.0 0.103 2.280 0.029 1.314 1.323 1.670

10 135.0 0.129 2.232 0.074 1.256 1.265 1.565

11 150.0 0.104 - 0.076 1.199 1.297 1.481

Legend (MTBE w. sol. (c=0.50 ml/L) + MO (c=107 CFU mL-1):

I sol: UV lamp without TiO2; II sol: UV lamp + TiO2 (1.0 g/L); III sol: Dark experiment (without UV lamp); IV sol: UV lamp + TiO2 (0.50 g/L); V sol: UV lamp + TiO2 (0.25 g/L); VI sol: UV lamp + TiO2 (0.75 g/L).

Results of the experiments of antimicrobial activities

The antimicrobial activities are examined by the measurement of the optical density for the MTBE solutions of Pseudomonas aeruginosa strains ATCC 9023 as the model microorganism (MO) for the first experiment. We investigated the effect of different concentrations of MTBE (0.15, 0.25, 0.50 and 1.5 ml/L), as well as a commercial titania catalyst (anatase, purity 99.9 %, Alfa Aesar Lancaster, c=0.1 g/L) and the catalyst-reagent system TiO2 and FeCl3 (TiO2:FeCl3 = 1:1, c=0. 1 g/L) on the growing of the MO. The results were obtained by measuring the optical density in the colorimeter, at 550 nm, and presented in Figure 13.

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Figure 13 - The effect of different concentrations of MTBE, catalysts and reagens on the growth of Pseudomonas aeruginosa strain ATCC 9023 Рис. 13 - Влияние различных концентраций МТБЭ, катализатора и реагента на рост штамма бактерий Pseudomonas aeruginosa ATCc 9023 Слика 13 - Утицај различите концентрације МТБЕ-а, катализатора и реагенса на раст соја бактерије Pseudomonas aerugenosa ATCC 9023

Our results showed that the highest Pseudomonas aeruginosa strain ATCC 9023 growth was obtained with a high MTBE concentration of 1.5 ml/L. The Fenton reagent and the catalyst-reagent system of TiO2 and FeCl3 in the ratio of 1:1 have a stimulation effect on the growth of microorganisms. Finally, the best microbiological growth was achieved with the catalyst-reagent system TiO2 and FeCl3 in the ratio of 1:1, which can be explained with a coupled stimulation influence of the Fenton reagent in a combination with anatase titania nanopowder in equal portions. It is the best nutrition for bacteria and their growth in our experiment.

In the second experiment, we measured the effect of different types and concentrations of catalysts on antimicrobial activities of Pseudomonas aeruginosa strain DV 2739, as a model microorganism. We studied six different catalysts, such as titania nanopower catalysts: commercial titania anatase nanopowder (A), titania power Degussa P25®, the catalyst-reagent system of anatase TiO2 and FeCl3 in the ratio of 1:1 (A-Fe), synthetised nanopower TiO2 (S11 sample), synthetised nanopower TiO2 doped with 2.5 wt. % of Fe3+ (S24 sample, duration time

of 7h) and synthetised nanopower TiO2 doped with 5.0 wt. % of La3+ (S16 sample, duration time of 7 h), all in four concentrations of 0.05, 0.1, 0.2 and 0.25 mg/L. The quantified results of the measurements on the colorimeter are shown in the following Tables (Tab. 13 to Tab. 16).

Table 13 - The effect of c=0.05 mg/L of different catalyst types on the microbial (growth for Pseudomonas aeruginosa strain DV 2739, with the initial concentration of 107 CFU mL-1 at 1.00 ml/L of the MTBE water solution

Таблица 13 - Влияние c=0.05 mg/L различных типов катализаторов на рост штамма бактерий Pseudomonas Aeruginosa DV 2739, с начальной концентрацией 107 CFU mL-1 на 1.00 ml/L водного раствора МТБЭ

Табела 13 - Утицајразличитих типова катализатора концентрације од 0.05 mg/L на микробни раст за сој бактерије Pseudomonas aerugenouse DV 2739, почетне концентрације од 107 CFU mL-1 у воденом раствору МТБЕ-а концентрације од 1,00 ml/L

Time (h) 0.05 mg/L catalysts

A P-25 S11 S24 S16 A-Fe K (only TSB base) K1 (TSB base + MTBE)

0 0.025 0.110 0.000 - - 0.040 0.000 0.005

1 0.060 0.115 0.010 0.010 0.045 0.060 0.000 0.020

2 0.045 0.115 0.015 0.015 0.055 0.065 0.000 0.005

3 0.045 0.125 0.018 0.015 0.050 0.072 0.000 0.010

After 20 h, we added Pseudomonas aeruginosa strain DV2739 (MO)

Time (h) 0.05 mg/L titania powder and titania based catalysts

A P-25 S11 S24 S16 A-Fe K (only TSB base) K1 (TSB base + MTBE)

20 0.062 0.125 0.020 0.027 0.045 0.065 0.010 0.020

24 0.290 0.360 0.275 0.280 0.310 0.335 0.270 0.280

25 0.315 0.380 0.270 0.280 0.310 0.320 0.270 0.280

26 0.310 0.370 0.270 0.280 0.320 0.330 0.280 0.290

27 0.310 0.360 0.270 0.280 0.310 0.330 0.290 0.295

44 0.300 0.360 0.250 0.275 0.300 0.330 0.260 0.270

47 0.280 0.360 0.260 0.265 0.310 0.325 0.250 0.265

49 0.280 0.360 0.240 0.270 0.290 0.320 0.250 0.260

51 0.280 0.360 0.255 0.255 0.300 0.320 0.255 0.260

grow 0.255 0.250 0.255 0.255 0.255 0.280 0.255 0.255

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Table 14 - The effect of c=0.10 mg/L of different catalyst types on the microbial growth for Pseudomonas aeruginosa strain DV 2739, with the initial concentration of 107 CFU mL-1 at 1.00 ml/L of the MTBE water solution

Таблица 14 - Влияние c=0.10 mg/L различных типов катализаторов на рост штамма бактерий Pseudomonas Aeruginosa DV 2739, с начальной концентрацией 107 CFU mL'1 на 1.00 ml/L водного раствора МТБЭ

Табела 14 - Утицај различитих типова катализатора концентрације од 0.10 mg/L на микробни раст за сој бактерије Pseudomonas aerugenouse DV 2739, почетне концентрације од 107 CFU mL-1 у воденом раствору МТБЕ-а концентрације од 1,00 ml/L

Time (h) 0.10 mg/L catalysts

A P-25 S11 S24 S16 A-Fe K (only TSB base) K1 (TSB base + MTBE)

0 0.155 0.190 0.032 0.015 0.030 0.175 0.000 0.005

1 0.175 0.200 0.040 0.030 0.055 0.207 0.000 0.020

2 0.200 0.195 0.055 0.040 0.055 0.210 0.000 0.005

3 0.210 0.200 0.055 0.035 0.060 0.220 0.000 0.010

After 20 h, we added Pseudomonas aeruginosa strain DV 2739 (MO)

Time (h) 0.10 mg/L titania powder and titania based catalysts

A P-25 S11 S24 S16 A-Fe K (only TSB base) K1 (TSB base + MTBE)

20 0.200 0.200 0.055 0.033 0.040 0.195 0.010 0.020

24 0.430 0.430 0.320 0.300 0.315 0.440 0.270 0.280

25 0.440 0.420 0.310 0.280 0.310 0.430 0.270 0.280

26 0.440 0.420 0.320 0.290 0.310 0.460 0.280 0.290

27 0.440 0.420 0.310 0.310 0.310 0.450 0.290 0.295

44 0.420 0.420 0.310 0.280 0.310 0.470 0.260 0.270

47 0.410 0.410 0.300 0.275 0.300 0.430 0.250 0.265

49 0.410 0.410 0.290 0.285 0.300 0.440 0.250 0.260

51 0.410 0.420 0.310 0.290 0.305 0.440 0.255 0.260

grow 0.255 0.230 0.278 0.275 0.275 0.265 0.255 0.255

Table 15 - The effect of c=0.20 mg/Lof different catalyst types on the microbial growth for Pseudomonas aeruginosa strain DV2739, with the initial concentration of 107 CFU mL-1 at 1.00 ml/L of the MTBE water solution

Таблица 15 - Влияние c=0.20 mg/L различных типов катализаторов на рост штамма бактерий Pseudomonas Aeruginosa DV 2739, с начальной концентрацией 107 CFU mL-1 на 1.00 ml/L водного раствора МТБЭ

Табела 15 - Утицај различитих типова катализатора концентрације од 0.20 mg/L на микробни раст за сој бактерије Pseudomonas aerugenouse DV 2739, почетне концентрације од 107 CFU mL-1 у воденом раствору МТБЕ-а концентрације од 1,00 ml/L

Time (h) 0.20 mg/L catalysts

An at P-25 S11 S24 S16 A-Fe K (only TSB base) K1 (TSB base + MTBE)

0 0.190 0.275 0.053 0.046 0.085 0.160 0.000 0.005

1 0.210 0.300 0.072 0.080 0.125 0.207 0.000 0.020

2 0.250 0.300 0.080 0.080 0.125 0.210 0.000 0.005

3 0.240 0.300 0.083 0.080 0.116 0.260 0.000 0.010

After 20 h, we added Pseudomonas aeruginosa strain DV 2739 (MO)

Time (h) 0.20 mg/L titania powder and titania based catalysts

A P-25 S11 S24 S16 A-Fe K (only TSB base) K1 (TSB base + MTBE)

20 0.240 0.310 0.080 0.086 0.105 0.220 0.010 0.020

24 0.460 0.480 0.330 0.340 0.345 0.450 0.270 0.280

25 0.470 0.500 0.320 0.350 0.355 0.460 0.270 0.280

26 0.470 0.490 0.320 0.350 0.350 0.460 0.280 0.290

27 0.465 0.490 0.330 0.350 0.350 0.440 0.290 0.295

44 0.440 0.490 0.320 0.360 0.350 0.460 0.260 0.270

47 0.430 0.480 0.320 0.340 0.350 0.460 0.250 0.265

49 0.435 0.475 0.310 0.340 0.340 0.450 0.250 0.260

51 0.430 0.490 0.325 0.350 0.350 0.470 0.255 0.260

grow. 0.240 0.215 0.272 0.304 0.265 0.310 o.255 0.255

Kuburovic, N. et al, Development of new smart metal nanomaterials based on titanium-dioxide for photocatalytic and antimicrobial activities pp.771-835

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Table 16 - The effect of c=0.25 mg/L of different catalyst types on the microbial growth for Pseudomonas aeruginosa strain DV 2739, with the initial concentration of 107 CFU mL-1 at 1.00 ml/L of the MTBE water solution Таблица 16 - Влияние c=0.25 mg/L различных типов катализаторов на рост штамма бактерий Pseudomonas Aeruginosa DV 2739, с начальной концентрацией 107 CFU mL-1 на 1.00 ml/L водного раствора МТБЭ Табела 16 - Утицај различитих типова катализатора концентрације од 0.25 mg/L на микробни раст за сој бактерије Pseudomonas aerugenouse DV 2739, почетне концентрације од 107 CFU mL-1 у воденом раствору МТБЕ-а концентрације од 1,00 ml/L

Time (h) 0.25 mg/L catalysts

A P-25 S11 S24 S16 A-Fe K (only TSB base) K1 (TSB base + MTBE)

0 0.380 0.620 0.060 0.110 0.175 0.540 0.000 0.005

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1 0.410 0.640 0.090 0.130 0.210 0.560 0.000 0.020

2 0.420 0.640 0.100 0.130 0.210 0.570 0.000 0.005

3 0.440 0.640 0.095 0.125 0.202 0.560 0.000 0.010

After 20 h, we added Pseudomonas aeruginosa strain DV2739 (MO)

Time (h) 0.25 mg/L titania powder and titania based catalysts

A P-25 S11 S24 S16 A-Fe K (only TSB base) K1 (TSB base + MTBE)

20 0.430 0.650 0.100 0.127 0.185 0.520 0.010 0.020

24 0.630 0.750 0.290 0.380 0.445 0.690 0.270 0.280

25 0.640 0.740 0.330 0.380 0.455 0.675 0.270 0.280

26 0.640 0.740 0.350 0.370 0.460 0.680 0.280 0.290

27 0.630 0.740 0.330 0.380 0.450 0.690 0.290 0.295

44 0.620 0.775 0.340 0.400 0.460 0.700 0.260 0.270

47 0.620 0.750 0.340 0.380 0.460 0.710 0.250 0.265

49 0.620 0.760 0.340 0.390 0.450 0.700 0.250 0.260

51 0.620 0.760 0.330 0.380 0.460 0.720 0.255 0.260

grow. 0.240 0.140 0.270 0.270 0.285 0.180 0.255 0.255

The results of our experimental research of the influence of the types and different concentrations of catalysts on the increase of the MO growth showed the following:

1. Catalyst concentration of 0.05: The best MO growth at the lowest catalyst concentration is obtained for the samples in this order: S24 & S11 (identical values), then A (titania powder anatase), P-25 (Degussa P-25®) and A-Fe (catalyst system titania powder anatase - FeCl3);

2. Catalyst concentration of 0.10: The best MO growth at the catalyst concentration of 0.10 g/L is obtained for the samples in this order: S24 (titania doped Fe3+), then S11 (titania nanopower), S16 (titania doped La3+), A, A-Fe and P-25;

3. Catalyst concentration of 0.20: The best MO growth at the catalyst concentration of 0.20 g/L is obtained for the samples in this order: S24, then S16, S11, A-Fe, A, and P-25;

4. Catalyst concentration of 0.25: The best MO growth at the catalyst concentration of 0.25 g/L is obtained for the samples in this order: S11, then S24, S16, A, A-Fe, and P-25.

Based on these results from Table 13 to Table 16, it can be concluded that the optical density drops between 26 and 27 hours after the start of the experiment, i.e. between 6 and 7 after adding the MO for all concentrations, there was a decrease in optical density in all samples. Nevertheless, S11, S16 and S24 samples showed tendencies for growth after this fall, which suggests that these samples represent suitable catalysts for the coupled photocatalytic-microbiological experiment. The catalyst-reagent system of TiO2-FeCl3 in the ratio of 1:1 achieved very similar results for the 0.20 mg/L catalyst concentration. The best mO growth was obtained in S16 for the 0.25 mg/L catalyst concentration.

Also, S11, S16 and S24 samples showed the same tendency in contrast to the other catalysts used in which optical density increased during the entire experiment of 0.25 mg /L. Therefore, the best antimicrobial activity is obtained in S24 sample; it has also been shown that 0.25 mg/L could be toxic for microorganisms, and our subsequent research using more sophisticated instrumental techniques can confirm it.

Correlation between the results

Correlating the parameters of the sol-gel synthesis process with the resulting properties of nanostructure systems is necessary for the understanding and systematic control of the nanomaterial properties and their quality. Namely, the control of particle size distribution and aggregate structure is the key criterion for product quality. This section describes the influence of the variation of some synthesis parameters on the change in the structural properties of the obtained anatase nanoparticles, examined by XRD, Raman spectroscopy and the BET analysis of their photocatalytic and microbiological activity. Both XRD and Raman spectroscopy could enable more precise determination of the average particle size, compared to AFM measurements (Golubovic et al,

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2009a). In the obtained AFM images, it was not possible to detect subtle variations in the particle size, of the order of few nanometers.

The presented results and the results reported earlier by Golubovic et al (Golubovic et al, 2009a) have shown that the properties of TiO2 nanoparticles depend on a few parameters of the sol-gel synthesis process. The nanoparticles size and content of brookite in the produced nanoparticles are the result of a subtle interplay between many synthesis parameters such as the type of the precursor, the temperature and the heating rate of the calcination process and the pH value of the hydrothermal solution. It is important to be able to investigate partial influence of the parameters on the efficiency of catalysts.

The influence of the calcination temperature on the anatase nanoparticles size, as reported by Gouadec et al (Gouadec et al, 2007), Bersani et al (Bersani et al, 1998) and Golubovic et al (Golubovic et al, 2009a), shows a tendency of the particle size to increase with an increase in calcination temperature. When all other synthesis parameters are fixed, a higher calcination temperature leads to the formation of larger nanoparticles, as shown by Golubovic et al. (Golubovic et al, 2009a). This is confirmed by our results shown in Table 3 and Table 7.

The pH value shown can influence significantly the polymorphous structure of TiO2 nanopowders: low and neutral pH values result in the production of TiO2 nanopowders containing brookite and sometimes rutile, while the alkali solution with a high pH value leads to the formation of anatase nanoparticles with high stability during calcination (Ovenstone & Yanagisawa, 1999). The pH value was set to 9.3 for the synthesis of titania nanoparticles, pure and dopants. Based on the data shown in Table 3, It seems that the alkali pH value is not high enough to avoid the formation of brookite from the TiCl4 precursor although the literature suggested (Pottier, a. et al. 2001) that brookite phase was observed only in acidic solutions.

Therefore, we fixed the parameters, such as the pH value at 9.3, in order to obtain a single-digit result of the influence of the key parameters on the catalytic efficiency and the microbial activity and inactivity, i.e. its dependence on the dopant concentration, calcination duration, calcination temperature and their free surface of the mesoporous catalyst (SBET). Our results showed that the values of SBET in the La-doped samples (S18 and S28), 79 and 84 m2g-1, respectively, are higher than those in pure TiO2 nanoparticle samples (S05, S06 and S11), 17, 51 and 58 m2g-1, respectively. It explains the best photocatalytic activity of S28 sample in Table 8. It explains that the particle size and its free surface are the key factor for photocatalytic and antimicrobial activities. The best

performance of S111 sample in all experiments is shown from Figure 9 to Figure 12, as a comparison between S18 and S111 samples. When we compare S93 and S96 samples (Table 10) synthetized using different duration times (7 and 24 h, respectively), our results show different degradation rate forthe TiO2 doped with V3+ of 10.0 wt. %, which can be explained by the anomalies in the behavior of the photocatalyst synthetized at higher calcination temperature. We expected that S96 sample would have higher activity than S93 sample due to its heating rates during the calcination process (135 and 67.5°C/h, respectively). If we compare our results from the preliminary study reported earlier (Kuburovic et al, 2009) with the results from Table 8 to Table 10, a higher degradation rate with a lower catalyst concentration loading can be explained with a synergetic influence of the aerobic condition effect and a

slightly higher temperature (ЛГ = 5° C) in the photocatalytic activity experiments. In addition, the photocatalytic and photothermolytic effects on the degradation of MTBE in water should be considered at elevated temperatures in aerobic conditions. The further detailed research will explain the impact of values of the parameters of different processes in order to obtain the optimum values for the parameters for photocatalytic, microbiological and their antimicrobial activities.

Conclusion

Mesoporous pure as well as La, Fe and V-doped titanium (IV) oxide nanoparticle photo catalysts prepared by the sol-gel method have been extensively characterized by various sophisticated techniques and their photocatalytic and antimicrobial activities tested. The photocatalytic activity, microbiological activity and inactivity in the bath slurry-catalyst circular photoreactor were researched in detail and gave us the directions for a further study of titania-based catalysts.

We investigated the photocatalytic activity of titania doped with different concentrations of lanthanum. It was shown that the best photocatalytic efficiency was obtained with TiO2 doped with La3+ of 1 wt. % for 45 minutes, but the fastest drop in the polluted MTBE concentration in the water solution was achieved by TiO2 doped with La3+ of 3 wt. %. These results also showed the fastest drop during the photocatalytic degradation of MTBE in the water solution in S93 sample (TiO2 doped with V3+ of 10.0 wt. %), and then in 28 sample (TiO2 doped with La3+ of 1.0 wt. %) for 45 minutes. Our results also show different degradation rates for TiO2 doped with V3+ of 10.0 wt. %, S93 and S96 samples synthetized with different duration times (7 and 24 h, respectively) and

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calcination heating rates (66.7 and 135°C/h, respectively), which can explain their anomalous behavior. The best photocatalytic efficiency is achieved with S111 sample, which can be explained by its drastically improved adsorption and superior activity of the Fe-dopant of titania nanoparticles owing to its unique half-filled electronic configuration and shallow trapping compared to other metal dopants tested in our study.

Our results showed that the best coupled photocatalytic-microbiological properties are achieved when we use direct ultraviolet radiation simulated with the sodium lamp SONT UV400 with the initial concentration of 0.75 g/L Degussa P-25®TiO2 nanopowder for 60 and 150 minutes. These results show that TiO2 and direct ultraviolet radiation simulated with the sodium lamp SONT UV400 in lab conditions and titania in the concentration of 1.0 g/L have the effect of inactivating and killing microorganisms. The optical density results have proven this assertion by measuring the microbial activity and inactivity in the coupled photocatalytic-microbiological experiment. We also studied the antimicrobial activity of Pseudomonas aeruginosa strain DV 2739 which was seeded with different concentrations of MTBE and catalysts. The biggest Pseudomonas aeruginosa strain DV 2739 growth was obtained with a high MTBE concentration of 1.5 ml/L. The Fenton reagent and the catalyst-reagent system of TiO2 and FeCl3 in the ratio of 1:1 have a stimulation effect on the growth of microorganisms. Finally, the best microbiological growth was achieved with the catalyst-reagent system of TiO2 and FeCl3 in the ratio of 1:1, which can be explained by the coupled stimulation influence of the Fenton reagent and anatase titania nanopowder in equal portions. It is the best nutrition for bacteria and their growth in our experiment. In accordance with the results in the previous experiment, we expected that the TiO2 nanoparticles doped with Fe3+ can give the best growth of microorganisms. It was the reason for the research and testing different concentrations of TiO2 nanoparticle catalysts carried out in another experiment in order to obtain the optimum concentration and type of catalyst for antimicrobial activity, as well as the limits which microorganisms can reach to give them the best performance for the coupled photocatalytic-microbiological experiments. Based on these results, it can be determined that the optical density drops between 26 and 27 hours after the start of the experiment, i.e. between 6 and 7 after adding the MO. For all concentrations, there was a decrease in optical density in all samples. Nevertheless, S11, S16 and S24 samples showed tendencies for growth after this fall, which suggests that these samples represent suitable catalysts for coupled photocatalytic-microbiological experiments. The catalyst-reagent system

of TiO2-FeCl3 in the ratio of 1:1 achieved very similar results for the catalyst concentration of 0.20 mg/L. The best mO growth was obtained in S16 for 0.25 mg/L catalyst concentration. So, the best antimicrobial activity was obtained in S24 sample; it was also shown that 0.25 mg/L could be toxic for microorganisms, and our subsequent research using more sophisticated instrumental techniques can confirm it. The results showed that the effect of the optical density concentration and the MO growth is in a direct correlation with the structure of TiO2 nanoparticle catalyst and the doper metal type.

Our results of the superior Fe-dopant characteristics together with the theoretical knowledge on TiO2 nanoparticles doped with Ag (van Grieken et al, 2009), (Menesi et al, 2009), Au (Huang et al, 2006) and Fe (Flak et al, 2015) give us directions for further studies of their photocatalytic and antimicrobial activities, as well as for the development of TiO2-nanoparticles and nanotubes for enhancing antibiotics and their use in the cancer treatment. Finally, in our further studies, we will research in detail the impact of different values of the parameters of different processes such as irradiance wavelength, light penetration and irradiance intensity, Influence of temperature, substrate concentration and chemical characteristics, retention time, flow, temperature and pH value, initial concentration of the compound and the catalyst, dissolved oxygen, optimal areas of wavelength radiation for individual phases decomposition process, absorption and selective absorption, etc. in order to obtain the optimum values for the parameters for photocatalytic, microbiological and antimicrobial activities, as well as their synergetic effects for their environmental and biomedical applications in real conditions. All this will ultimately explain the mechanisms of these processes.

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РАЗРАБОТКА НОВЫХ УМНЫХ МЕТАЛЛИЧЕСКИХ НАНОМАТЕРИАЛОВ НА ОСНОВЕ ДИОКСИДА ТИТАНА ДЛЯ ФОТОКАТАЛИТИЧЕСКОЙ И АНТИМИКРОБНОЙ АКТИВНОСТЕЙ

Наташа Д. Кубуровича, Александр В. Голубович* б,

Лиляна М. Бабинчевв

a Eco Energy Engineering & Consulting, г. Белград, Республика Сербия

б Белградский университет, Институт физических исследований, Отделение физики твердого тела и новых материалов, г. Белград, Республика Сербия в Университет в г. Приштина, Факультет технических наук, г.Косовска Митровица, Республика Сербия

ОБЛАСТЬ: химическая инженерия и материаловедение,

каталитические процессы и композиционные материалы ВИД СТАТЬИ: оригинальная научная статья ЯЗЫК СТАТЬИ: английский

Резюме:

Предметом данного исследования являются синтез, классификация и испытания наночастиц титана (IV) оксида (TiO2-НЧ-а) и легирования лантана (La3+), железа (Fe3+) и ванадия (V3+) для фотокаталитической и микробиологической активностей, а также сравнение с каталитическим активностима испытанными в коммерческих целях TiO2 (P25, Degussa® и наночастиц анатаза, чистоты 99,9%, компанией Alfa Aesar из Ланкастера).

Наночастицы диоксида титана были синтезированы и легированы с различной концентрацией металлических допантов, при различной продолжительности процесса прокаливания: TiO2-НЧ

(анатаз-НЧ, время процесса прокаливания 5 и 7 часов), La3+ (0.65, 1, 2, 3, 4, 5 и 6 вес. %, продолжительность прокаливания 7 часов), Fe3+ (1, 2,5, 3,0 и 5 вес. %, продолжительность прокаливания 7 и 24 часа) и V3+ (10 вес. %, продолжительность прокаливания 7 и 24 часа). Штамм „Pseudomonas aeruginosa DV 2739“ использован в качестве модели микроорганизмов в микробиологических экспериментах, проведенных в микробиологической лаборатории. Совместный процесс фотокаталических и микробиологических испытаний эксперимента проводился в катализаторной ванне при прямом концентрированном ультрафиолетовом излучении от натриевой лампы SONT UV 400, симулирующей солнечное излучение. Исследование показало, что образец катализатора С28, La-легирующей примеси с концентрацией 1 вес. %, обладает лучшими фотокаталитическими свойствами по сравнению с другими La-допантами, в то время, как лучшая фотокаталитическая активность была достигнута в образце S111, Fe-легирующей примеси диоксида титана (5 вес.%, продолжительность прокаливания составляет 7 часов).

Результаты нашего исследования также показали различную степень деградации при применении V-допанта TiO2 с концентрацией 10 вес.% образцы С93 и С96 были синтезированы при различной продолжительности прокаливания (67.5 и 135 C/ч, поочередно), что можно считать аномалией в их поведении. И наконец лучшая антимикробная активность получена в образце CS24, Fe-легирующей примеси, которая показала, что 0,25 мг/л является токсичным для микроорганизмов. Результаты нашего исследования о преимущественных характеристиках Fe-легирующей примеси и теоретические знания о наночастицах TiO2, легированных Ag, Au и Fe, безусловно облегчат исследователям дальнейшую работу в изучении

фотокаталитической и антимикробной активностей, а также развития наночастиц TiO2 и нанотрубок, с целью усиления действия антибиотиков и их применения при лечении онкологических заболеваний.

Ключевые слова: диоксид титана, 1Ю2-наночастицы, TiO2

легированные La3+, Fe3+ и V+, продолжительность прокаливания, штаммы Pseudomonas aeruginosa DV 2739 и ATCC 9023, фотокаталитическая активность, антимикробная

активность.

KuburoviC, N. et al, Development of new smart metal nanomaterials based on titanium-dioxide for photocatalytic and antimicrobial activities pp.771-835

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РАЗВОЈ НОВИХ ПАМЕТНИХ МЕТАЛНИХ НАНОМАТЕРИЈАЛА НА БАЗИ ТИТАНИЈУМ-ДИОКСИДА ЗА ФОТОКАТАЛИТИЧКУ И АНТИМИКРОБНУ АКТИВНОСТ

Наташа Д. Кубуровића, Александар В. Голубовић6,

Љиљана М. Бабинчевв

a Eco Energy Engineering & Consulting, Београд, Република Србија б Универзитет у Београду, Институт за физику, Центар за физику чврстог стања и нове материјале, Београд, Република Србија в Универзитет у Приштини, Факултет техничких наука,

Косовска Митровица, Република Србија

ОБЛАСТ: хемијско инжењерство и инжењерство материјала, каталитички процеси и композитни материјали ВРСТА ЧЛАНКА: оригинални научни чланак ЈЕЗИК ЧЛАНКА: енглески

Сажетак:

Предмет ове студије била је синтеза, карактеризација и тестирање наночестица титанијум (IV) оксида (Т102-НЧ-а) и њихових допаната лантана (La3+), гвожђа (Fe3+) и ванадијума (V3+) за фотокаталитичку и микробиолошку активност, као и њихово поређење са каталитичким активностима тестираних комерцијалних Ti02 (Дегуса П-25® и наночестица анатаса, чистоће 99,9%, Алфа Аесар из Ланкестера). Титанијум-диоксид наночестице су синтетизоване и допиране различитим концентрацијама металних допаната, током различитог трајања калцинације, као што су: Л02-НПс (анатас-НПс, време трајања калцинације од 5 и 7 h), La3+ (0.65, 1, 2, 3, 4, 5 и 6 тежинских %, са трајањем калцинације од 7 h), Fe3+ (1, 2,5, 3,0 и 5 тежинских %, са трајањем калцинације од 7 i 24 h) и V3+ (10 тежинских %, са трајањем калцинације од 7 и 24 h). Сојеви „Pseudomonas aeruginosa DV 2739 и ATCC 9023” коришћени су као модел микроорганизама у микробиолошком делу експеримената који су изведени у микробиолошком кабинету. Заједнички фотокаталитички и микробиолошки процеси изведени су у циркуларном фотореактору са емулгованим катализатором у присуству директног УВ зрачења симулираног натријумовом лампом „SONT UV400”. Студија је показала да узорак катализатора С28, Ла-допанта са концентрациям од једног тежинског %, показује најбоље фотокаталитичке особине од свих La-допаната, али најбољу фотокаталитичку активност од свих катализатора постигнут је код С111 узорка, Fe-допанта (5 тежинских %, трајанје калцинације од 7 h). Наши резултати такође показују различити степен деградације када је коришћен V-допант Ti02 у концентрацији од 10 тежинских %, узорци С93 и С96, синтетисани са различитим трајањем калцинације (7 и 24 h) и брзином загревања током

калцинације (67,5 i 135 °C/h, редом), што се може објаснити аномалијом у њиховом понашању. Коначно, најбоља антимикробна активност добијена је коришћењем узорка S24, Fe-допанта, који је показао да концентрација од 0,25 mg/L може бити токсична за микроорганизме. У складу са нашим резултатима супериорних карактеристика Fe-допанта и теоријских знања за наночестице TiO2 допираних Ag, Au и Fe, дошло се до смерница за даља истраживања њихове фотокаталитичке и антимикробне активности, као и за развој титанијум-диоксид наночестица и нанотуба за унапређење антибиотика и њихову употребу у лечењу рака.

Кључне речи: титанијум-диоксид, TiO2-наночестице, TiO2 допиран са La3+, Fe3+ и V3+, трајање калцинације, Сојеви Pseudomonas aeruginosa DV 2739 и ATCC 9023, фотокаталитичка активност, антимикробна активност.

Paper received on / Дата получения работы / Датум пријема чланка: 24.04.2018. Manuscript corrections submitted on / Дата получения исправленной версии работы / Датум достављања исправки рукописа: 04.07.2018.

Paper accepted for publishing on / Дата окончательного согласования работы / Датум коначног прихватања чланка за објављивање: 06.07.2018.

© 2018 The Authors. Published by Vojnotehnicki glasnik / Military Technical Courier (www.vtg.mod.gov.rs, втг.мо.упр.срб). This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution license (http://creativecommons.org/licenses/by/3.0/rs/).

© 2018 Авторы. Опубликовано в «Военно-технический вестник / Vojnotehnicki glasnik / Military Technical Courier» (www.vtg.mod.gov.rs, втг.мо.упр.срб). Данная статья в открытом доступе и распространяется в соответствии с лицензией «Creative Commons» (http://creativecommons.org/licenses/by/3.0/rs/).

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Kuburovic, N. et al, Development of new smart metal nanomaterials based on titanium-dioxide for photocatalytic and antimicrobial activities pp.771-835

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