Visible-light-assisted photodegradation of an azo dye, Reactive Red 180 (RR180), in the presence of nitrogen-doped TiO2 (N-TiO2) has been studied. The photodegradation of RR180 is evaluated through decolorization studies and total organic carbon analysis. The efficacy of hydrogen peroxide (H2O2), potassium peroxomonosulfate (oxone or PMS), and potassium peroxodisulfate (PDS) in improving the photodegradation of the dye in the N-TiO2-RR180 system is also examined. The effect of combining photo-Fenton-like reaction with N-TiO2-mediated photodegradation of RR180 under visible light has been investigated. The photoactivity of N-TiO2-RR180-Fe3+/Cu2+-oxidant systems is compared with the individual techniques of photocatalysis and photo-Fenton-like reactions. The coupled system possesses superior photomineralization ability towards the abatement of RR180. 1. Introduction Now a days, combining several oxidation systems for the degradation and mineralization of organic pollutants has become a common practice, for the reason that a single process usually cannot reach a desirable effectiveness in the degradation and mineralization of organic pollutants. Heterogeneous photocatalysis using titania photocatalyst has been established as a principal advanced oxidation process (AOP) for wastewater treatment. For a century, photo-Fenton reactions were also considered widely for the removal of organic pollutants [1–7]. The combination of heterogeneous photocatalysis with another AOP can be cost-effective as long as this combination produces a synergic effect. In the earlier efforts to increase the photodegradation efficiency through combined systems, photocatalysis coupled with ultrasonic treatment [8], integrating photocatalysis with membrane filtration [9], or combinations of photo-electro-Fenton [10], sono-Fenton [11], and electro-Fenton [12] processes were carried out, and better performances were observed. Not many attempts were made in pairing photocatalysis and photo-Fenton-like reactions for wastewater treatment. In general, the rate of photodegradation of pollutants is proportional to the efficiency of reactive radical formation. In photocatalysis- and photo-Fenton-coupled systems, two independent sources of hydroxyl radicals exist: (a) occurrence of hydroxyl radicals in photocatalytic reactions on titanium dioxide and (b) Fe(III) aqua complexes are independent and are more efficient sources of hydroxyl radicals through the photoredox reaction [13]. But the efficiency of photocatalytic process is limited by the recombination of photogenerated electrons and holes
References
[1]
C. Walling, “Fenton's reagent revisited,” Accounts of Chemical Research, vol. 8, no. 4, pp. 125–131, 1975.
[2]
G. Ruppert, R. Bauer, and G. Heisler, “The photo-Fenton reaction: an effective photochemical wastewater treatment process,” Journal of Photochemistry and Photobiology A, vol. 73, no. 1, pp. 75–78, 1993.
[3]
K. Wu, Y. Xie, J. Zhao, and H. Hidaka, “Photo-Fenton degradation of a dye under visible light irradiation,” Journal of Molecular Catalysis A, vol. 144, no. 1, pp. 77–84, 1999.
[4]
H. Park and W. Choi, “Visible light and Fe(III)-mediated degradation of Acid Orange 7 in the absence of H2O2,” Journal of Photochemistry and Photobiology A, vol. 159, no. 3, pp. 241–247, 2003.
[5]
J. Farias, G. H. Rossetti, E. D. Albizzati, and O. M. Alfano, “Solar degradation of formic acid: temperature effects on the Photo-Fenton reaction,” Industrial and Engineering Chemistry Research, vol. 46, no. 23, pp. 7580–7586, 2007.
[6]
N. Masomboon, C. Ratanatamskul, and M. C. Lu, “Chemical oxidation of 2,6-dimethylaniline in the fenton process,” Environmental Science and Technology, vol. 43, no. 22, pp. 8629–8634, 2009.
[7]
A. O. Ifelebuegu and C. P. Ezenwa, “Removal of endocrine disrupting chemicals in wastewater treatment by fenton-like oxidation,” Water, Air, and Soil Pollution, vol. 217, no. 1–4, pp. 213–220, 2011.
[8]
J. Madhavan, F. Grieser, and M. Ashokkumar, “Degradation of orange-G by advanced oxidation processes,” Ultrasonics Sonochemistry, vol. 17, no. 2, pp. 338–343, 2010.
[9]
S. Mozia, A. W. Morawski, M. Toyoda, and T. Tsumura, “Integration of photocatalysis and membrane distillation for removal of mono- and poly-azo dyes from water,” Desalination, vol. 250, no. 2, pp. 666–672, 2010.
[10]
J. Ramírez, L. A. Godínez, M. Méndez, Y. Meas, and F. J. Rodríguez, “Heterogeneous photo-electro-Fenton process using different iron supporting materials,” Journal of Applied Electrochemistry, vol. 40, no. 10, pp. 1729–1736, 2010.
[11]
P. J. D. Ranjit, K. Palanivelu, and C. S. Lee, “Degradation of 2,4-dichlorophenol in aqueous solution by sono-Fenton method,” Korean Journal of Chemical Engineering, vol. 25, no. 1, pp. 112–117, 2008.
[12]
A. Lahkimi, M. A. Oturan, N. Oturan, and M. Chaouch, “Removal of textile dyes from water by the electro-Fenton process,” Environmental Chemistry Letters, vol. 5, no. 1, pp. 35–39, 2007.
[13]
H. Mestankova, G. Mailhot, J. Jirkovsky, J. Krysa, and M. Bolte, “Effect of iron speciation on the photodegradation of Monuron in combined photocatalytic systems with immobilized or suspended TiO2,” Environmental Chemistry Letters, vol. 7, no. 2, pp. 127–132, 2009.
[14]
H. Sun, Y. Bai, W. Jin, and N. Xu, “Visible-light-driven TiO2 catalysts doped with low-concentration nitrogen species,” Solar Energy Materials and Solar Cells, vol. 92, no. 1, pp. 76–83, 2008.
[15]
W. L. Kostedt, A. A. Ismail, and D. W. Mazyc, “Impact of heat treatment and composition of ZnO-TiO2 nanoparticles for photocatalytic oxidation of an azo dye,” Industrial and Engineering Chemistry Research, vol. 47, no. 5, pp. 1483–1487, 2008.
[16]
J. Yang, H. Bai, and X. Tan, “IR and XPS investigation of visible-light photocatalysis-Nitrogen-carbon-doped TiO2 film,” Applied Surface Science, vol. 253, no. 4, pp. 1988–1994, 2006.
[17]
M. R. Dhananjeyan, V. Kandavelu, and R. Renganathan, “An investigation of the effects of Cu2+ and heat treatment on TiO2 photooxidation of certain pyrimidines,” Journal of Molecular Catalysis A, vol. 158, no. 2, pp. 577–582, 2000.
[18]
P. Bouras, E. Stathatos, and P. Lianos, “Pure versus metal-ion-doped nanocrystalline titania for photocatalysis,” Applied Catalysis B, vol. 73, no. 1-2, pp. 51–59, 2007.
[19]
G. Li, X. S. Zhao, and M. B. Ray, “Advanced oxidation of orange II using TiO2 supported on porous adsorbents: the role of pH, H2O2 and O3,” Separation and Purification Technology, vol. 55, no. 1, pp. 91–97, 2007.
[20]
L. G. Devi, S. G. Kumar, and K. M. Reddy, “Photo fenton like process Fe3+/(NH4)2 S2O8/UV for the degradation of Di azo dye congo red using low iron concentration,” Central European Journal of Chemistry, vol. 7, no. 3, pp. 468–477, 2009.
[21]
S. K. Kuriechen, S. Murugesan, S. P. Raj, and P. Maruthamuthu, “Visible light assisted photocatalytic mineralization of Reactive Red 180 using colloidal TiO2 and oxone,” Chemical Engineering Journal, vol. 174, no. 2-3, pp. 530–538, 2011.
[22]
P. Maruthamuthu and P. Neta, “Radiolytic chain decomposition of peroxomonophosphoric and peroxomonosulfuric acids,” Journal of Physical Chemistry, vol. 81, no. 10, pp. 937–940, 1977.
[23]
M. Muruganandham and M. Swaminathan, “Photocatalytic decolourisation and degradation of Reactive Orange 4 by TiO2-UV process,” Dyes and Pigments, vol. 68, no. 2-3, pp. 133–142, 2006.
