CC BY
13
ISSN 2522-1841 (Online) ISSN 0005-2531 (Print)
UDC 66.081: 546.57
EFFICIENCY OF GRAPHITE CARBON NITRIDE IN THE SORPTION OF IRON (Fe2+) AND COPPER (Cu2+) IONS FROM AQUEOUS SOLUTION
A.A.Guliyeva, S.S.Abbasov, N.A.Agayeva, H.K.Nurullaev, N.I.Abbasova,
A.A.Heydarov, V.M.Ahmedov
M.Nagiyev Institute of Catalysis and Inorganic Chemistry, Ministry of Science and Education of the
Republic of Azerbaijan advesv@gmail.com Received 12.01.2023 Accepted 25.02.2023
In the present work, freshly prepared from urea powders of graphite carbon nitride were subjected to ultrasonic exfoliation and were used to evaluate their adsorption efficiency for iron and copper ions from an aqueous solution. It has been established that the sorption efficiency is significantly affected by the pH of the medium, the contact time, and the initial concentration of metal ions. It is shown that the Fe2+ sorption isotherm by carbon nitride can be well modeled by both the Langmuir and Freundlich adsorption isotherms based on correlation coefficients.
Keywords: carbon nitrides, adsorption, iron, copper, sorption capacity, isotherms.
doi.org/10.32737/0005-2531-2023-2-123-130
Introduction
The technologies used in the processing industry do not ensure the complete extraction of metals from raw materials and in many cases become a source of industrial pollution. Waste-water discharged from industrial plants, including chemical production [1], mining [2] and batteries [3], mainly contain pollutants containing heavy metal ions. As a rule, processing waste and wastewater from their washing contain a significant amount of metals such as Al, Ca, Fe, Si, Co, Cu, Zn, Mn, V, Ga, etc., which are the most common environmental pollution. The extraction of valuable components from processing waste is not only of economic interest, but is also necessary to prevent the migration of metals into the environment under the influence of atmospheric factors. They have a negative effect on living beings [4].
To solve this universal environmental problem, various methods have been studied for the removal of heavy metal ions, including biosorption [5], precipitation [6], ion exchange [7], reverse osmosis [8], and adsorption [9]. Many of the available methods are inefficient in terms of high energy and chemical reactivity requirements, high operating costs, and inefficiency at low contaminant concentrations. Numerous studies in this area show that the removal of heavy
metal ions from wastewater by simple and inexpensive adsorption is more practical and cost-effective [10]. A number of adsorbents such as activated carbon [11], clays [12], polymers [13], bio-sorbents [14] and zeolites [15] have been proposed and studied for the treatment of various wastewater sources. However, due to the low efficiency of some of these materials and the difficulty of synthesizing others, their use for commercial purposes has not been developed. For this reason, the synthesis and study of easily available effective adsorbents is now of great practical importance.
Recently, due to the unique properties of fullerene, graphene, carbon nanotubes and gra-phene oxides, new forms of carbon nano-materials, there have been revolutionary changes in various areas of nanotechnology: electronics, optics, medicine, chemical synthesis and catalysis. These materials also show notable properties including high sorption capacity properties [1619].
Graphitic carbon nitride (g-C3N4) is one of the most promising among two-dimensional carbon-based nanomaterials [20-22]. The interaction of functional groups such as -NH-, NH2-, N-C=N and C=C on the surface creates basic and n-donor-acceptor properties in carbon nitride, which make it a unique non-metallic or-
ganic catalyst in electrophilic and nucleophilic type reactions. In addition to its use as a heterogeneous catalyst, the presence of a large number of different nitrogen-containing functional groups also allows carbon nitride to be able to efficiently coordinate various metal ions. Thus, the multifunctional properties g-C3N4 provides grounds for designing more efficient adsorbents. However, conventional methods for the synthesis of g-C3N4 by thermolysis of nitrogen-rich inexpensive precursors (cyanamide, dicyandi-amide, urea, melamine, etc.) afford to obtain non-porous materials of dense morphology, characterized by a small specific surface area limiting their efficiency in sorption process of metal ions. Therefore, it is important to modify the texture of g-C3N4. It has been established that ultrasonic exfoliation easily transforms freshly prepared powders of graphite carbon nitride into a layered structure of g-C3N4 sheets. This results in a significant increase in surface area [21-25].
The initial analysis showed that a significant amount of iron, copper, cobalt, manganese, zinc, etc. remains in the wash waters of the waste from the Dashkesan iron ore deposits in Azerbaijan [16]. These wastes are potential raw materials for the extraction of remains valuable metals. Therefore, we are conducting systematic research in order to efficiently extract these metals from wash waters. in this work, the sorption characteristics and uptake of iron (Fe2+) and copper (Cu2+) ions from aqueous solutions using g-C3N4 adsorbents were studied. Various parameters affecting the adsorption process, such as pH, contact time, and concentrations of initial metal ions, has been investigated.
Experimental part
Materials
Solvents and reagents of analytical or chemical purity grade were used, and if necessary they were purified by standard methods prior to use.
Synthesis g-C3N4 samples
In this work, the synthesis of carbon nitride samples was carried out by thermolysis of urea in the temperature range of 490-5 500C, followed by ultrasonic treatment. In a typical synthesis: 40 g of urea powder was placed in an aluminum crucible with a lid and then heated slowly in a muffle fur-
nace to the desired temperature over 4 hours. The resulting yellow powders of g-C3N4 samples were dispersed in distilled water and subjected to ultrasonic exfoliation for 1 hour.
Characterization of obtained g-C3N4 samples
The structure identity and phase composition of the g-C3N4 samples before and after exfoliation were evaluated by X-ray powder diffraction on a D2 PHASER diffractometer (Bruker). The specific surface area of the SBET samples (Brunauer-Emmett-Teller method) was determined from nitrogen adsorption-desorption data at 77 K using a ThermoFisher Scientific automatic gas analyzer. Fourier transform infrared spectra (FT-IR) were used to study the surface functional groups of g-C3N4 adsorbents. The spectra were recorded on a Varian 3600 IR Fourier spectrometer (Varian, Inc) in the frequency range 400-4000 cm-1 in KBr pellets.
Batch adsorption experiments
Iron (Fe2+) and copper (Cu2+) ions were selected to investigate the adsorption properties of prepared samples under static conditions. Experiments were carried out to study the effect of solution pH, initial concentrations of Fe2+ and Cu2+, sorption duration, and the possibility of reuse on the adsorption capacity of the adsorbent. The adsorption experiments were performed by batch equilibration technique. To do this, solutions of FeSO4.7H2O and CuSO4.5H2O were prepared with a concentration of 1000 mg/l (pH=3-4) in deionized water and a sorbent was added to a certain volume of the mother solution, then the mixture was subjected to ultrasonic treatment for 1060 minutes at room temperature. All the experiments were conducted in triplicate, and the averages of the results were used in the data analysis. FEK-spectrophotometric and titration methods were used to determine the efficiency of the sorption process under normal conditions. The equilibrium adsorption capacity (Qe, mg g_1) and the adsorption degree (R, %) were calculated from the following equations:
Qe = (C0 - Ce) xV /m (1)
R (%) = (C0 - Ce) / C0)x 100% (2)
where C0 and Ce (mg L_1) are the initial and equilibrium concentrations of iron and copper in solution, respectively, V(mL) is the volume of solution and m (g) is the mass of the adsorbent.
Results and discussion
Analysis of synthesized g-C3N4 samples The diverse syntheses of carbon nitride materials cover a broad set of varied carbon- and nitrogen-rich starting compounds and the detail characterization data can be found in the literature [20-22]. The phase composition of the adsorbent samples synthesized from urea was analyzed on the basis of X-ray diffractometry, which confirmed the formation of graphite-like structures. The synthesized samples of carbon nitride contain two peaks: a weak diffraction peak at 13.1° indexed in the (100) plane, which corresponds to a planar structural stacking of tri-s-triazine units with a period of 6.91 A and a strong reflection at an angle of 27.4°, indexed in the (002) plane, fixing the interlayer packing of conjugated aromatic systems and corresponding to the interlayer distance d = 3.26 A. After soni-cation, the intensity of the (002) peak is significantly reduced due to delamination of the freshly prepared carbon nitride. These data are in good agreement with accepted standards for graphite structures (JCPDS card no. 87-1526) and literature data [26].
The results of BET analysis obtained from nitrogen adsorption-desorption data at 77 K showed that the specific surface area of freshly prepared carbon nitride samples synthesized from urea is 16-18 m2g-1. As a result of ultrasonic exfoliation for 60 minutes. the specific surface area of the g-C3N4 samples increased to 76-78 m2g-1.
Information about the structure of the synthesized samples of carbon nitride was obtained using FT-IR spectroscopy in the range of 400-4000 cm-1 (Figure 1). The spectra in the range 1460-1750 cm-1 contain strong bands at 1637, 1570, 1541, and 1458 cm-1, which are related to stretching vibrations of conjugated C-N bonds in the heterocycle. Absorption at 809.7 cm-1 is characteristic of out-of-plane bending vibrations of C-N heterocycles in the triazine block [27]. The characteristic absorption bands at 1405.6, 1315.6, 1235.2 cm-1 refer to CN(-C)-C or C-NH-C stretching g vibrations [28, 29].
Sorption study
The experiments were carried out by sonicating a certain volume of FeSO47H2O and CuSO45H2O solutions in the presence of g-C3N4 for 5-60 min in order to determine the degree of adsorption. All prepared sorbent samples showed high sorption activity with respect to iron ions, among which the g-C3N4 sample prepared at 4900C turned out to be the most effective, where the degree of Fe2+ sorption reached 80-81% at 250C.
Fig. 1. FT-IR spectrum of g-C3N4 recorded between 400 and 4000 cm-1. AZERBAIJAN CHEMICAL JOURNAL № 2 2023
At the same time, under test conditions, the degree of sorption of copper ions was at the level of 43-44%. For this reason, the influence of various parameters on the sorption activity of this sample was chosen for further studies. The effect of solution pH, initial metal concentration, and equilibrium time was studied.
The value of adsorption of metal ions is significantly affected by the pH of the medium, since the degree of electrolytic dissociation of molecules depends on the pH value. Therefore, the effect of pH on the adsorption capacity of g-C3N4 was studied in the pH range of 1.0-5.0 in order to avoid precipitation of iron and copper. It has been found that Fe2+ adsorption capacity of the sorbent increases from 270 to 488 mg/g as the pH increases from 1 to 3, and then decreases to 355 mg/g at pH 5.0. (Figure 2 (1)). The same changes were observed in the case of Cu2+: the adsorption capacity increases from 120 to 250 mg/g as the pH increases from 1 to 3, and then decreases to 190 mg/g at pH 5.0 (Figure 2 (2)). Apparently, as pH values increase, the negative charge of the adsorbent increases and creates an electrostatic attraction
favorable for Fe2+ and Cu2+.
The contact time is considered as an important parameter characterizing the efficiency of extracting metal ions from waste. The main data necessary for modeling adsorption isotherms are the time of establishment of the equilibrium concentration of metal ions (Ce) in the solution and the amount of cation adsorbed per
unit (Qe) of a fixed mass of the sorbent, at the corresponding values of Ce. The influence of contact time on the adsorption capacity of g-C3N4 towards Fe2+ ions is shown in Figure 3. The Fe2+ adsorption rate reached equilibrium after about 30 minutes. at room temperature when the initial concentration of metal ions was 1000 mg.l-1 at pH=3-4 and the adsorbent dose was 0.1 g. The adsorption rate was high in the initial period of adsorption, when the adsorption capacity increased approximately four times from 5 to 30 min. These results can be associated with the presence of a large number of free centers in the initial period of adsorption, which become saturated with time.
The equilibrium Fe2+ sorption process was studied using known sorption isotherms underlying sorption systems (Figure 4). The equilibrium sorption capacity of g-C3N4 increases with an increase in the initial concentration of Fe2+ ions from 10 mg/L to 120 mg/L, which may be due to the strong interaction of Fe2+ ions with the surface of the sorbent. The results obtained also demonstrate a tendency to decrease in the degree of sorption with an increase in the initial concentration of Fe2+ ions. At low concentrations, all metal ions present in the sorption medium can interact with the active centers of the sorbent, which leads to an increase in the degree of sorption. On the contrary, at high initial concentrations of sorbate ions, the degree of sorption decreased due to the saturation of sorption centers.
600
500
400
)
)g t 300
(m e 200
a
100
3
pH
Fig. 2. Influence of the medium pH on the adsorption capacity of g-C3N4 with respect to Fe + (1) and Cu + (2) ions (pH 1-5, Time = 60 min, 250C).
0
0
1
2
4
5
600
500
400
/g
g/m 300
e 200
a
100
20
40
Time (min)
60
80
Fig. 3. Effect of contact time on the adsorption capacity of g-C3N4 with respect to Fe2+ ions (g-C3N4 = 0.1g, V= 30 ml).
0
0
Ce (mg/ L)
Fig. 4. Adsorption isotherm of Fe + on g-C3N4
To describe the adsorption process of Fe2+ the isotherm was analyzed using the Langmuir and Freindlich isotherm models [16, 30]. The Langmuir model is valid for monolay-er sorption on a surface with a certain number of identical reaction centers and is described by the following equation:
Ce/Qe = 1/bQm + Ce/Qm ,
where b (mg-1) is the Langmuir constant, Ce (mg. l-1) is the equilibrium concentration, Qe (mg. g-1) is the amount adsorbed at equilibrium, and Qm (mg. g-1) is the capacity monolayer.
A plot of Ce/Qe versus Ce gives a straight line with a slope of 1/Qm and an intersection point of 1/bQm (Figure 5).
Model of the Freundlich isotherm on the adsorbent. g-C3N4 can be expressed as:
lnQe = lnKp + (1/n) lnCe,
where KF (mg/g) and n are the Freundlich constants characterizing the adsorption capacity and adsorption intensity, respectively. The Freundlich equation can be represented in linear form as a result of logarithms, and the constants can be determined graphically (Figure 6).
Fe2+ adsorption isotherm constants on g-C3N4 are shown in Table. The R2 values suggest that both models can describe well the adsorption isotherms of Fe2+ on g-C3N4. The results of the Langmuir isotherm model show that the theoretical saturated capacity of the adsorbent is 588.2 mg.g-1, and the KL value is 0.0425, i.e. g-C3N4 has a high adsorption capacity. The results of the Freundlich isotherm model show that the value 1/n =1.12, i.e. more, indicating a high level of adsorption of iron ions. From the obtained results, we can conclude that the adsorption of Fe2+ g-C3N4 ions follows the Langmuir and Freundlich adsorption models.
Ce (mg/ L)
Fig. 5. Fe2+ Adsorption Isotherms on g-C3N4: Langmuir Isotherm Line Plot.
LnCe
Fig. 6. Adsorption isotherms of Fe2+ on g-C3N4: Freundlich isotherm line graph.
Fe2+ adsorption isotherm constants on g-C3N4
Kinetic model Parameters
Qm (mg.g-1) 588.2
Langmuir isotherm model Kl (lmg-1 ) 0.0425
R2 0.997
1/n 1.12
Freundlich isotherm model Kf 3.21
R2 0.966
Desorption and reuse of g-C3N4 The desorption characteristics of g-C3N4 were determined to eval uate the reverse desorption of iron and copper ions. To measure the desorption of the adsorbent preliminarily loaded with metal, the samples were prepared, as indicated in the adsorption experiment, with an initial concentration of metal ion solutions of 1000 mg/l. After adsorption, desorption of iron and copper ions adsorbed on g-C3N4 was carried out with 1 M HCl solution at pH3. The g-C3N4
suspension was separated by centrifugation and thoroughly washed with distilled water. After drying in a vacuum oven at a temperature of 500C, the obtained sample was reused for the adsorption of metal ions. As shown in Figure 7, the adsorption capacity of g-C3N4 for Fe2+ (1) and Cu2+ (2) ions decreased by approximately 6% after five cycles of regeneration experiments. These results show that g-C3N4 synthesized from urea has good chemical stability and recyclability.
m
<D
a
600 500 400 300 200 100
12345 Round
Fig. 7. Adsorption efficiency of Fe2+ (1) and Cu2+ (2) ions on reused g-C3N4 samples.
Conclusions
Freshly prepared samples of graphite carbon nitride from carbamide after sonication were studied in the process of adsorption of iron and copper ions from an aqueous solution. It has been established that the sorption efficiency of g-C3N4 is significantly affected by the pH of the medium, the contact time, and the initial concentration of ions. Adsorption of Fe2+ was confirmed by the Langmuir model with a maximum adsorption capacity of 588.2 mg.g-1 for carbon nitride at 250C and pH 3.0. The obtained results show that g-C3N4 synthesized from urea has good chemical stability and reusability.
References
1. Tang S., Zhang H., Lee H.K. Advances in sample extraction. Anal. Chem. 2015. V. 88. P. 228-249.
2. Miller J.R. Forensic Assessment of Metal Contaminated Rivers in the 21st Century Using Ge-ochemical and Isotopic Tracers. Minerals. 2013. V. 3. No 2. P. 192-246.
3. Gottesfeld P., Cherry C.R. Lead emissions from solar photovoltaic energy systems. Energy Policy, P. Gottesfeld, C.R. Cherry / Energy Policy. 2011. V. 39. P. 4939-4946.
4. Mushak P. Gastro-intestinal absorption of lead in children and adults: Overview of biological and biophysico-chemical aspects. Chem Spec Bioavailab. 1991. 3(3-4):87-104.
5. Barquilha C. , Cossicha E. , Tavaresa C. , Sil-vac E., Biosorption of nickel and copper ions from synthetic solution and electroplating effluent using fixed bed column of immobilized
brown algae. Journal of Water Process Engineering, 2019, V.32, p.1-10
6. Han Y., Xu Z., Gao C. Ultrathin graphene nano-filtration membrane for water purification Adv. Funct. Mater. 2013. V. 23. P. 3693-3700.
7. Fu F.L., Wang Q.J. Environ. Manage. Removal of heavy metal ions from wastewaters. 2011. V. 92. P. 407-418.
8. Cheng Z, Wu C., Yang W., Xu. T. Preparation of bromomethylated poly(2,6-dimethyl 1,4-phenylene oxide) hollow fiber cation-exchange membranes and immobilization of cellulose thereon. J. Membrane Science. 2010. V. 358. P. 93-100.
9. Ning R.Y. Desalination. Arsenic removal by reverse osmosis. 2002. V. 143. P. 237-241.
10. Jia W. & Lu S. Few-layered graphene oxides as superior adsorbents for the removal of Pb(II) ions from aqueous solutions. Korean J. Chem. Engineering. 2014. V. 31. P. 1265-1270.
11. D^browski A. Adsorption - from theory to practice, Adv. Colloid Interface Sci. 2001. V. 93. P. 135-224.
12. Mouzdahir Y. El., Elmchaouri A., Mahboub R., et al. Interaction of stevensite with Cd2+ and Pb2+ in aqueous dispersions. Appl. Clay Sci. 2007. V. 35. P. 47-58.
13. Ovejero G. et al. Bentonite as an Alternative Adsorbent for the Purification of Styrene. Monomer Adsorption Science & Technology. 2010. V. 28. P. 101-123.
14. Pan B.J., et al. Development of polymeric and polymer-based hybrid adsorbents for pollutants removal from waters. Chem. Eng. J. 2009. V. 151. P. 19-29.
15. Ekmekyapar F., Aslan A. Biosorption of Pb(II) by Nonliving Lichen Biomass of Cladonia rangi-formis Hoffm J. Hazard. Mater. 2006. P. 137-293.
16. Gulieva A.A., Geidarov A.A. et al. Sorption recovery of cobalt, copper, zinc, and Manganese ions from technical solutions by modified natu-
1
0
ral zeolites, Russian Metallurgy (Metally).
2018. V. 7. P. 605-613.
17. Ren X.M.. Carbon nanotubes as adsorbents in environmental pollution management. Chem. Eng. J. 2011. V. 170. P. 395-410.
18. Penny S. M., Judy S. A., Cathy E. A. Phosphine functionalised multiwalled carbon nanotubes. J. Enviromental Science. 2012. V. 24. P. 1133-1141.
19. Smith S.C., Rodrigues D.F. Carbon-based na-nomaterials for removal of chemical and biological contaminants from water: a review of mechanisms and applications. Carbon. 2015. V. 91. P. 122-143.
20. Hashemi1 B. & Rezania Sh. Carbon-based sorbents and their nanocomposites for the enrichment of heavy metal ions, Microchim Acta.
2019. V. 186. No 578. P. 1-20.
21. Thomas A. Graphitic carbon nitride materials: variation of structure and morphology and their use as metal-free catalysts. J. Mater. Chem. 2008. V. 18. P. 4893-4908.
22. Akhmedov V.M., Melnikova N.E., Akhmedov I.D. Synthesis, properties, and application of polymeric carbon nitrides. Russ. Chem. Bull. Int. Ed. 2017. I. D. V. 66. P. 782-807.
23. Dehkharghani A.A., Exfoliated Graphitic Carbon Nitride for the Fast Adsorption of Metal Ions from Acid Mine Drainage: A Case Study from the Sungun Copper Mine, Mine Water and the Environment. https://doi.org/10.1007/s 10230-018-0561-x.
24. Liu J.H. Simple pyrolysis of urea into graphitic carbon nitride with recyclable adsorption and photocatalytic activity. J. Mater. Chem. 2011. P. 14398-14401.
25. Jun J.S. From Melamine-Cyanuric Acid Sup-ramolecular Aggregates to Carbon Nitride Hollow Spheres. Adv. Funct. Mater. 2013. V. 23. P. 1-7.
26. Dang Y., Hu Q., He P., Ren T. Tailoring the ratio of ammonium chloride and graphitic carbon nitride for high photocatalytic activity, J. Molecular Structure. 2020. V. 1209. P. 127-961.
27. Ge L. Synthesis and photocatalytic performance of novel metal-free g-C3N4 photocatalysts, Mater. Lett. 65(17-18) 2011. P. 2652-2654.
28. Shalom M., Inal S., Fettkenhauer C., Neher D., Antonietti M. Improving Carbon Nitride Photo-catalysis by supramolecular Preorganization of Monomers. J. Am. Chem. Soc., 2013. V. 135. P. 7118-7121.
29. Liu J.H., Zhang T.K., Wang Z.C., Dawson G. and Chen W. Simple pyrolysis of urea into graphitic carbon nitride with recyclable adsorption and pho-tocatalytic activity, J. Mater. Chem. 2011. V. 21. P.14398-14401.
30. Akhmedov V.M., Maharramov A.M., Azizov A.A., Alosmanov R.M., Bunyad-Zadeh I.A. and Aliyeva S.B. Equilibrium, kinetic, and thermo-dynamic studies on the sorption of some heavy metal ions by the phosphorus-containing polymer sorbent; Russian Chemical Bulletin. Int. Ed. 2019. V. 68. P. 514-520.
KARBON NÍTRÍD ÜZORÍNDO DOMÍR (Fe2+) va MÍS (Cu2+) ÍONLARININ SULU MOHLULDAN
sorbsíyasi
A.A.Quliyeva, S.S.Abbasova, N.O.Agayeva, H.K.Nurullayev, N.Í.Abbasova, A.A.Heyd3rov,V.M.Ohmadov
Bu içda karbamiddan hazirlanmiç qrafit karbon nitrid nümynalari ultrasas vasbtasila eкsfолиаsиya olunmuç va onlann sulu mahluldan damir (Fe2+) va mis (Cu2+) ionlarini adsorbsiya etma effektivliyi tadqiq edilmiçdir. Müayyan edilmiçdir ki, mühitin pH, adsorbsiya müddati va metal ionlannin ilkin qatiligi sorbsiyanin samaraliliyina mühüm tasir göstarir. Karbon nitrid ila Fe2+ sorbsiya prosesini Langmuir va Freundlix adsorbsiya izotermlari vasitasila modellaçdirmak olar. Fe2+-nin adsorbsiyasi 250C va pH 3.0-da karbon nitrid ûçûn maksimum 588.2 mg.g-1 oldugu Langmuir modeli ila tasdiqlanmiçdir. Alinan naticalar göstarir ki, karbamiddan sintez edilan g-C3N4 yüksak kimyavi dayaniqliga va takrar istifadaya yararlidir.
Açar sözlzr: karbon nitrid, adsorbsiya, d3mir, mis, sorbsiya qabiliyyati, izotermbr.
ЭФФЕКТИВНОСТЬ ГРАФИТОВОГО НИТРИДА УГЛЕРОДА ПРИ СОРБЦИИ ИОНОВ ЖЕЛЕЗА (Fe2+)
И МЕДИ (Cu2+) ИЗ ВОДНОГО РАСТВОРА
А.А.Гулиева, СХ.Аббасова, НААгаева, Х.К.Нуруллаев, Н.И.Аббасова, А.А.Гейдаров, В.М.Ахмедов
В настоящей работе свежеприготовленные порошки графитового нитрида углерода из карбамида подвергались ультразвуковой эксфолиации и были использованы для оценки их адсорбционной эффективности для ионов железа (Fe2+) и меди (Cu2) из водного раствора. Установлено, что на эффективность сорбции существенное влияние оказывают рН среды, время контакта и начальная концентрация ионов металлов. Показано, что изотерма сорбции Fe2+ нитридом углерода может быть хорошо смоделирована как изотермой адсорбции Ленгмюра, так и изотермой адсорбции Фрейндлиха на основе коэффициентов корреляции. Адсорбция Fe2+ подтверждена моделью Ленгмюра с максимальной адсорбционной емкостью 588.2 мг.г-1 для нитрида углерода при 25 С и значении рН 3.0. Полученные результаты показывают, что g-C3N4 синтезированной из карбамида обладает высокой химической стабильностью и возможностью повторного использования.
Ключевые слова: нитриды углерода, адсорбция, железо, медь, сорбционная емкость, изотермы.
