Oxidative decolorization of a malachite green oxalate dye through the Photochemical Advanced Oxidation Processes

This report was aimed at an investigation of efficiency for Photochemical Advanced Oxidation Processes (UV photolysis, UV/H2O2, UV/TiO2, UV/H2O2/TiO2 and UV/H2O2/Fe2+ processes) to decolorize Malachite Green Oxalate (MGO) dye. Experimental runs were performed using laboratory scale photochemical reactor. About 98% decolorization was obtained with initial 100 ppm MGO dye in Photo-Fenton process under optimal conditions (60 ppm Fe2+ concentration, 12 mM of oxidant concentration, at pH 3.0 for 60 min). 97% decolorization was obtained using UV/H2O2/TiO2 process having [TiO2]o of 0.6 gm/L for similar reaction conditions. The percentage decolorization of MGO was in range of 94-95% for both UV/TiO2 and UV/H2O2 processes. Concentration of ferrous salt (60 ppm) was considered as an optimal value to carry out the UV/H2O2/Fe2+ process for MGO decolorization. Influence of oxidant (H2O2) and Fe2+ ions for oxidation of MGO was studied in Photo-Fenton process. Sulphate radical based AOPs was proved to be more effective in treating MGO dye with irradiation. Results indicate that decolorization efficiency by Photochemical AOPs for MGO dye in photochemical reactor were more efficient. Pseudo-first-order model of kinetics was noticed to be the best model fit to explain the decolorization of MGO dye solution.