Effectiveness of photocatalytic degradation of phenol in aqueous solution using semiconductor oxides (SO) prepared by a sol-gel method was examined. The physical and chemical properties of synthesized catalysts were investigated by X-ray diffraction (XRD), diffuse reflectance UV-Vis spectroscopy (DRS), and N2-adsorption measurements. The optimal conditions of the photocatalytic degradation of phenol using prepared titanium dioxide sample were defined. 1. Introduction Heterogeneous photocatalysis on the semiconductors allows achieving complete mineralization of the various classes toxic and biorefractory organic substances [1, 2]. Recently, the photocatalytic degradation of toxicants became one of the most promising directions of “green chemistry” [3]. The use of nanosized SO presents a great interest due to their outstanding optical, magnetic, catalytic, and sensing properties [4, 5]. The phenolic compounds contained in the wastewater of chemical, petrochemical, and pharmaceutical industries are hazardous carcinogenic and mutagenic pollutants [6, 7]. Furthermore, the oxidation of these substances in water bodies leads to decrease in dissolved oxygen required for normal functioning of animals and plants. Finding effective methods for the protection of water systems from phenols contamination is an important aim to ensure environmental safety [8, 9]. Among SO photocatalysts (PC) high activity have Fe2O3, WO3, ZnO and TiO2. Iron oxide polymorphs of hematite (α-Fe2O3) are nontoxic, cheap, and stable to photocorrosion material intensively absorbs radiation in the range from 295 to 600？nm. The semiconductor properties of α-Fe2O3 are the same as WO3, which can be seen in the position of band gaps relative to the standard hydrogen electrode. WO3 has chemical stability in acidic medium and electrolyte solutions as well as photoactivity in the near ultraviolet and blue regions of solar spectrum [10]. According to Daneshvar et al. nanosized ZnO is a suitable alternative to TiO2 due to the band gap energy. Dinda and Icli found that ZnO was as reactive as TiO2 for the photocatalytic degradation of phenol under concentrated sunlight [11]. Figure 1 shows a scheme of the energy levels of the studied semiconductor oxides relative to the standard hydrogen potential [12]. Several authors have associated the efficiency of semiconductor photocatalysts with electronic, structural, and morphological properties of the material such as band gap energy, crystalline structure, surface area, particle size [13]. Figure 1: Energy band gap of investigated semiconductor oxides. The
References
[1]
U. I. Gaya and A. H. Abdullah, “Heterogeneous photocatalytic degradation of organic contaminants over titanium dioxide: a review of fundamentals, progress and problems,” Journal of Photochemistry and Photobiology C, vol. 9, no. 1, pp. 1–12, 2008.
[2]
V. V. Goncharuk, Environmental Aspects of Modern Technologies Protect the Aquatic Environment, Naukova dumka, Kiev, Ukraine, 2005.
[3]
M. Anpo, “Utilization of TiO2 photocatalysts in green chemistry,” Pure and Applied Chemistry, vol. 72, no. 7, pp. 1265–1270, 2000.
[4]
D. Chen and L. Gao, “A facile route for high-throughput formation of single-crystal α-Fe2O3 nanodisks in aqueous solutions of Tween 80 and triblock copolymer,” Chemical Physics Letters, vol. 395, no. 4-6, pp. 316–320, 2004.
[5]
V. V. Goncharuk, “Photocatalytic destructive oxidation of organic compounds in aqueous media,” Chemistry for Sustainable Development, vol. 5, pp. 345–355, 1997.
[6]
S. K. Pardeshi and A. B. Patil, “A simple route for photocatalytic degradation of phenol in aqueous zinc oxide suspension using solar energy,” Solar Energy, vol. 82, no. 8, pp. 700–705, 2008.
[7]
N. M. Soboleva, A. A. Nosovich, and V. V. Goncharuk, “The heterogenic photocatalysis in water treatment processes,” Journal of Water Chemistry and Technology, vol. 29, no. 2, pp. 72–89, 2007.
[8]
L. E. Sheinkman and D. V. Dergunov, “Protection of surface and groundwater from phenols pollution in underground coal mining,” in Proceedings of the International Scientific and Practical Conference Science and Technology in the Modern World, 2011.
[9]
A. O. Samsoni-Todorov, E. A. Rolya, V. M. Kochkodan, and V. V. Goncharuk, “Photocatalytic destruction of phenol in water in the presence of cerium hydroperoxide,” Journal of Water Chemistry and Technology, vol. 30, no. 3, pp. 151–156, 2008.
[10]
A. Memar, W. R. W. Daud, S. Hosseini, E. Eftekhari, and L. J. Minggu, “Study on photocurrent of bilayers photoanodes using different combination of WO3 and Fe2O3,” Solar Energy, vol. 84, no. 8, pp. 1538–1544, 2010.
[11]
Y. J. Jang, C. Simer, and T. Ohm, “Comparison of zinc oxide nanoparticles and its nano-crystalline particles on the photocatalytic degradation of methylene blue,” Materials Research Bulletin, vol. 41, no. 1, pp. 67–77, 2006.
[12]
M. Gr？tzel, “Photoelectrochemical cells,” Nature, vol. 414, no. 6861, pp. 338–344, 2001.
[13]
A. Martínez-de la Cruz, D. S. Martínez, and E. L. Cuéllar, “Synthesis and characterization of WO3 nanoparticles prepared by the precipitation method: evaluation of photocatalytic activity under vis-irradiation,” Solid State Sciences, vol. 12, no. 1, pp. 88–94, 2010.
[14]
M. Cri？an, A. Brǎileanu, M. Rǎileanu et al., “Sol-gel S-doped TiO2 materials for environmental protection,” Journal of Non-Crystalline Solids, vol. 354, no. 2-9, pp. 705–711, 2008.
[15]
W. Yan, H. Fan, Y. Zhai, C. Yang, P. Ren, and L. Huang, “Low temperature solution-based synthesis of porous flower-like α-Fe2O3 superstructures and their excellent gas-sensing properties,” Sensors and Actuators B, vol. 160, no. 1, pp. 1372–1379, 2011.
[16]
D. Li and H. Haneda, “Morphologies of zinc oxide particles and their effects on photocatalysis,” Chemosphere, vol. 51, no. 2, pp. 129–137, 2003.
[17]
K. I. Gnanasekar, V. Subramanian, J. Robinson, J. C. Jiang, F. E. Posey, and B. Rambabu, “Direct conversion of TiO2 sol to nanocrystalline anatase at 85°C,” Journal of Materials Research, vol. 17, no. 6, pp. 1507–1512, 2002.
[18]
V. V. Goncharuk, M. V. Sychev, I. V. Stolyarova, R. V. Prihod'ko, I. O. Ledenev, and A. V. Lozovski, “MPK 7 B01 J21/00, 23/48, C 01 F1/70, The catalyst for water purification from nitrate ions, the method of its preparation and water purification,” Patent of Ukraine 7, Bulletin, 2006.
[19]
A. V. Tarasov, Metallurgy of Titanium, Akademkniga, Moscow, Russia, 2003.
[20]
A. Zecchina, G. Spoto, S. Bordiga et al., “Framework and extraframework Ti in Titanium-Silicalite: investigation by means of physical methods,” Studies in Surface Science and Catalysis, vol. 69, pp. 251–258, 1991.
[21]
T. Sreethawong, Y. Suzuki, and S. Yoshikawa, “Synthesis, characterization, and photocatalytic activity for hydrogen evolution of nanocrystalline mesoporous titania prepared by surfactant-assisted templating sol-gel process,” Journal of Solid State Chemistry, vol. 178, no. 1, pp. 329–338, 2005.
[22]
G. R. Bamwenda and H. Arakawa, “The visible light induced photocatalytic activity of tungsten trioxide powders,” Applied Catalysis A, vol. 210, no. 1-2, pp. 181–191, 2001.
[23]
M. Yan, F. Chen, J. Zhang, and M. Anpo, “Preparation of controllable crystalline titania and study on the photocatalytic properties,” Journal of Physical Chemistry B, vol. 109, no. 18, pp. 8673–8678, 2005.
[24]
Y. I. Gerasimov, “Course of Physical Chemistry,” Chemistry, vol. 2, article 289, 1973.
[25]
M. I. Litter, “Heterogeneous photocatalysis: transition metal ions in photocatalytic systems,” Applied Catalysis B, vol. 23, no. 2-3, pp. 89–114, 1999.
[26]
S. Ahmed, M. G. Rasul, W. N. Martens, R. Brown, and M. A. Hashib, “Heterogeneous photocatalytic degradation of phenols in wastewater: a review on current status and developments,” Desalination, vol. 261, no. 1-2, pp. 3–18, 2010.
[27]
N. Kashif and F. Ouyang, “Parameters effect on heterogeneous photocatalysed degradation of phenol in aqueous dispersion of TiO2,” Journal of Environmental Sciences, vol. 21, no. 4, pp. 527–533, 2009.
[28]
V. V. Goncharuk, Kyiv Pump Room. The Quality of Artesian Water, vol. 55, Geoprint, 2003.
