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'ВестЛик, ИГ Коми НЦ УрО РАН, Январь, 2016 г., № 1
УДК 547.992.3 DOI: 10.19110/2221-1381-2016-1-34-36
HYDROTHERMAL SYNTHESIS OF TiO2 NANOTUBES FROM CONCENTRATE OF TITANIUM ORE OF PIZHEMSKOE DEPOSIT (RUSSIA)
O. B. Kotova1, A. V. Ponaryadov1, L. A. Gomze2
1 Institute of Geology of Komi SC UB RAS, Russia, [email protected] 2 University of Miskolc, Hungary, [email protected]
A high cost of TiO2 nanoparticles and their demand in industry determine the timeliness of the hydrothermal method of synthesis of titanium dioxide nanotubes from the low-cost natural mineral raw materials. The starting material (non-magnetic fraction of gravity concentrate of titanium ore of Pizhemskoe deposit) and synthesized samples were characterized by scanning electron microscopy, X-ray diffraction and X-ray fluorescence methods.
Keywords: TiO2 nanotubes, hydrothermal method, titanium ore, Pizhemskoe deposit.
ГИДРОТЕРМИЧЕСКИЙ СИНТЕЗ НАНОТРУБОК ДИОКСИДА ТИТАНА ИЗ КОНЦЕНТРАТА ТИТАНОВОЙ РУДЫ ПИЖЕМСКОГО МЕСТОРОЖДЕНИЯ
(РОССИЯ)
О. Б. Котова1, А. В. Понарядов1, Л. А. Гёмзе2
1 Институт геологии Коми НЦ УрО РАН, Сыктывкар 2 Университет Мишкольца, Венгрия
Высокая стоимость наночастиц TiO2 и их востребованность в промышленности определяют актуальность синтеза нанотрубок диоксида титана гидротермическим методом из недорогого минерального сырья. Исходный материал (немагнитная фракция гравитационного концентрата титановой руды Пижемского месторождения) и синтезированные образцы были исследованы с помощью сканирующей электронной микроскопии, рентгенодифракции, состав определен рентгенофлуоресцентным методом.
Ключевые слова: нанотрубки TiO2, гидротермический синтез, титановая руда, Пижемское месторождение.
Introduction The aim of this article: the development of scientific
Titanium is one of the strategic metals of modern basics of synthesis of titanium dioxide nanotubes based
industry. The demand for titanium has been steadily on the mineral raw materials using a simple hydrothermal
increasing, and this trend will obviously continue. In Russia method. there are mainly undeveloped deposits, titanium concentrate is not produced. On the territory of Komi Republic the
prospects of mining industry are associated with the Titanium nanotubes can be obtained by several
largest deposits of titanium (Yaregckoe and Pizhemskoe). methods, such as sol-gel, electrospinning, template
New applications of titanium ore based on its mineralogical synthesis, chemical vapor deposition (CVD), etc. Each
and processing characteristics have a real commercial method has its advantages and disadvantages depending
interest: the list of commodity products is expanding (and on the implementation. After the pioneer works by
consequently the prospects for production), energy costs are T. Kasuga et al. [6] the hydrothermal method became
reducing, environmental risks are decreasing, efficiency of one of the most applied methods for the production of
sustainable development of region is increasing. One of the one-dimensional (1D) nanostructured TiO2 products.
promising directions of solution of this problem can be the The authors previously published a number of works on
synthesis of titanium dioxide nanotubes from mineral raw the synthesis of TiO2 nanotubes from synthetic analogs of
materials (for example from titanium ore of Pizhemskoe titanium minerals and their application [7—9].
deposit). TiO2 nanotubes were produced by a simple
In recent decades one-dimensional nanostructure hydrothermal method. The procedure for the preparation of
materials, derived from titanium dioxide, have been widely nanostructures from synthetic TiO2 is described elsewhere
used in photocatalysis, as a base for catalysts, implants, [7, 9]. In this work this procedure is adapted for the non-
reagents enhancing blood coagulability, batteries etc. magnetic fraction of gravity concentrate of titanium ore of
[1—5]. Pizhemskoe deposit.
Due to a high cost of commercially available TiO2 In a typical preparation 0.8 g of starting ore (reduced
nanoparticles their synthesis from cheap natural raw size) was placed in 100 ml autoclave, where 80 ml of 10 M
materials by hydrothermal method becomes very important. NaOH solution were added. The autoclave was kept at 110 °C
Experimental Procedure
Vestnùk IG Komi SC UB RAS, January, 2016, № 1
Fig. 1. Diffraction pattern of the starting material (Q — quartz, R — rutile) Рис. 1. Дифрактограмма исходного сырья (Q — кварц, R — рутил)
Fig. 2. Diffraction pattern of synthesized sample (Q — quartz, T — sodium titanate) Рис. 2. Дифрактограмма синтезированного образца (Q — кварц, T — титанат натрия)
during 24 h (temperature sensor was mounted on the stove, not inside the autoclave). After the hydrothermal reaction the autoclave was cooled to room temperature, and the resulting flaky precipitate was washed successively by distilled water and solution of hydrochloric acid (0.1 M) until neutral pH (6.5-7). The washed samples were dried in the oven at 90 °C for 12 hours.
The shape and size of the starting ore and synthesized samples were obtained by scanning electron microscopy (TESCAN Vega 3). The crystalline structures of the initial ore and synthesized samples were analyzed by diffractometer (Shimadzu XRD-6000), the material composition was studied by X-ray fluorescence (XRF Shimadzu-1800).
Results and Discussion
Until recently the starting material for TiO2 nanotubes synthesis was only high-purity synthetic analogs [1—5, 7]. In 2011 a group of scientists published a paper [10], which provided data on the production of titanium dioxide nanotubes by the hydrothermal method from Thai leucoxene. According to those data, Thai leucoxene was
enriched. The starting material for nanotubes was a rutile concentrate with a TiO2 content more than 93 %.
Mineral and chemical composition ofbulk concentrates of titanium ore of Pizhemskoe deposit is given in [11]. Beside leucoxene pseudorutile, Fe-ilmenite, ilmenite and siderite were found. Chemical composition (wt. %): TiO2 — 50.07, SiO2 - 30.52, Fe2O3 - 13.37, MnO - 0.26, CaO -0.04, MgO - 0.17, Al2O3 - 2.16, K2O - 0.77, Na2O - 0.02, P2O5 - 0.16, ZrO2 - 0.10, S - 0.09, CO2 - 1.90, H2O+ -0.39.
In comparison with bulk concentrates of titanium ore of Pizhemskoe deposit characterized in [11] the used starting material - non-magnetic fraction of gravity concentrate of titanium ore of Pizhemskoe deposit - the content of Fe2O3 and TiO2 is lower, while content of SiO2 and Al2O3 -higher. Chemical composition (wt. %): TiO2 - 42.12, SiO2 - 46.57, Fe2O3 - 1.04, Al2O3 - 7.57, K2O - 1.61, MnO -0.06, CaO - 0.13, MgO - 0.37, SO3 - 0.06, P2O5 - 0.17, ZrO2 - 0.05, NbO - 0.11. The average particle size after grinding - 20-40 |im.
The X-ray diffraction pattern (Fig. 1) indicates that the starting ore is mainly a mixture of two phases: rutile and quartz. The peaks are clear, that testifies to a high crystallinity of these phases. The weak reflections of clay minerals, ilmenite and anatase are present.
The synthesized sample (Fig. 2) is a mixture of two phases: quartz and hydrogen titanate (NaxH2-xTi3O7), which is consistent with the results of[1-3]. Chemical composition (wt. %): TiO2 - 74.68, SiO2 - 12.64, Fe2O3 - 5.44, Al2O3 -4.71, Na2O - 0.14, K2O - 0.93, MnO - 0.64, CaO - 0.12, MgO - 0.25, P2O5 - 0.09, ZrO2 - 0.08, NbO - 0.14.
The formation of titanium dioxide nanotubes takes place in several stages: the slow dissolution of raw is accompanied by the epitaxial growth of layered sodium titanate nanosheets ^ exfoliation of nanosheets ^ folding of nanosheets into tubes ^ growth of nanotubes along X axis ^ exchange of sodium ions by protons during washing and separating of nanotubes from each other. The crystalline lattice of initial rutile is converted into amorphous product
Fig. 3. Titanium dioxide nanotubes Рис. 3. Нанотрубки диоксида титана
ÂccmAèc ИГ Коми НЦ УрО РАН, Январь, 2016 г., № 1
at alkali processing, after treatment with distilled water and solution of hydrochloric acid the titanium dioxide nanotubes are formed. According to [7], the nanotubes consist of layers of titanate, which composition depends on such synthesis conditions as temperature and duration of treatment, ratio of solid and liquid phases.
Fig. 3 shows SEM image of synthesized TiO2 nanotubes. The channels inside the produced nanotubes are clearly visible. The resolution of scanning electron microscope allows evaluating their outside diameter (70100 nm) and length (up to 4500 nm). The synthesized TiO2 nanotubes have a large surface area, which is, according to [7], by orders higher than the specific surface of the starting raw, which provides high sorption properties.
Conclusion
TiO2 nanotubes were obtained using simple
The
hydrothermal method in Laboratory of mineral raw technology in Institute of Geology Komi SC UB RAS. An inexpensive natural raw material - non-magnetic fraction of gravity concentrate of titanium ore of Pizhemskoe deposit - was used as a starting material. The synthesized titanium dioxide nanotubes have outer diameter 70-100 nm and length up to 4500 nm. The synthesized TiO2 nanotubes have a large surface area that results in a good sorbent material.
8. Kotova O. B., Ponaryadov A. V., Vayon J. Nanostructured mineral surface: sorption properties // Vestnik of Institute of Geology of Komi SC UB RAS, 2007. No. 10. P. 8-10. (in Russian)
9. Ponaryadov A., Kotova O. Leucoxene and TiO2 pho-tocatalysts for water purification // Materials Science and Engineering, 2013. Vol. 47. P. 198-202.
10. Aphairaja D., Wirunmongkol T., Pavasupree S., Limsuwan P. Synthesis of Titanate Nanotubes from Thai Leucoxene Mineral // Procedia Engineering, 2012. Vol. 32. P. 1068-1072.
11. Makeev A. B., Lyutoev V. P. Spectroscopy in technological mineralogy, mineral composition of concentrates of titanium ore from Pizhemskoy deposit (Middle Timan) // Obogashchenie rud, 2015. No. 5. P. 33-41. (in Russian)
Acknowledgements
The authors express gratitude to the common use center Geonauka for their help in analytical work. This work was supported by the Program of UB RAS (project 15-18-5-33).
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