Abstract
This research work delved into the photocatalytic degradation of monoazo dye (methyl orange) and diazo dye (congo red) in aqueous solution using Fe3+/C/S-doped TiO2 nanocomposites. The nanocomposites were synthesised through sol-gel method and characterized using XRD, FTIR, SEM, TEM, EDX, BET and UV-Vis. Photocatalytic degradation of the dyes was monitored under simulated visible light using pristine TiO2, C/S/doped-TiO2 and Fe3+/C/S doped-TiO2 with varying concentrations of Fe3+. The influence of catalyst doping, solution pH, and light intensity were also examined. Doping TiO2 with Fe3+/C/S caused reduction in its band gap value with the resultant improvement in its visible light activity. The photocatalytic efficiency of the catalysts is given as follows: TiO2 < C/S/TiO2 < Fe3+/C/S-TiO2 with Fe3+/C/S-TiO2 (0.3% Fe3+) as the best performing photocatalyst. The monoazo dye experienced higher degradation efficiency than the diazo dye. Degradation of the azo dyes was observed to decrease with increasing pH from 2 to 12. Increased visible light intensity enhanced the photodegradation efficiency of the dye. Dye decolourization was observed to be faster than its mineralization.
Highlights
The release of dye polluted wastewater by textile industries into surface water is causing serious environmental challenges
These factors possibly resulted in improved utilization of visible light instead of UV light, charge carrier transfer efficiency, enhanced adsorption of dye molecules and subsequent photodegradation due to large surface area and retardation of electronhole recombination emanating from acceptance of electrons from the conduction band by the dopant ions
The visible light active hetero-elements doped TiO2 was successfully synthesized through sol-gel method, confirmed by Fourier transform infrared (FTIR), X-ray diffraction (XRD), energy dispersed x-ray (EDX) AND UV-Vis analyses
Summary
The release of dye polluted wastewater by textile industries into surface water is causing serious environmental challenges. There has been several reports on the use of TiO2 to degrade organic compounds in wastewater,[9,10] due to its numerous advantages including high optical, electronic and photocatalytic properties, chemical stability, non-toxicity and low cost.[11] In spite of these advantages, the practical application of TiO2 as an efficient photocatalyst for complete photodegradation of organic pollutants in wastewater is hampered by some inherent problems associated with TiO2 as a photocatalyst These problems include its relatively high band gap of 3.2 eV which limits its ability to work in the visible light range, and its sensitivity to recombination of photogenerated electrons and hole, which decrease its photocatalytic activity.[12]. The influence of factors such as catalyst modification, pH and visible light intensity on the photocatalytic degradation of the dyes, as well as the degree of mineralization of the dyes was studied using the catalyst with the best photodegradation potential
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