Photo-Fenton oxidation of Orange G azo dye: process optimization and mineralization mechanism

Textile effluents containing synthetic dyes areone of the most important sources of water pollution. Several dyes are toxic to the aquatic life and indirectly to humans, and therefore should be treated before rejection to natural water streams. As conventional wastewater treatment systems remain inefficient for treatment of these recalcitrant pollutants, the use of advanced oxidation processed is required. The degradation of the OrangeGdye wasstudied using thephoto-Fenton process. Results showed that the use of experimental kinetics rate constants to optimize the ratio R=[H2O2]/[Fe3+] constitutes a suitable way to minimize the occurrence of side reactions. An optimal molar ratio Rof13.8 was found allowing complete degradation of Orange G in 4min and 93.41% total organic carbon (TOC) removal in180min. Based on detected intermediates and end-products, a plausible degradation mechanism of Orange G dye is proposed. Therefore, we demonstrated that the photo-Fenton process can be applied efficiently to the removal of toxic/persistent organic pollutants such as synthetic dyes from water.