Photo fenton like process Fe3+/(NH4)2 S2O8/UV for the degradation of Di azo dye congo red using low iron concentration

Abstract

Degradation of Congo Red (CR) a di azo dye in aqueous solution is investigated by a Photo Fenton like process using Fe3+ ions as the catalyst and peroxy disulfate as the oxidant. The influence of various reaction parameters like, concentration of Fe3+ ions, concentration of the dye, concentration of ammonium persulfate, pH of the solution and the presence of hydroxyl radical scavenger are studied and optimal conditions are reported. The degradation rate decreased at higher dye concentration and at higher pH. The rate constant (k), catalytic efficiency (kc) and process efficiency (φ) are evaluated for different concentration of Fe3+ ions. The degradation of CR by the photo Fenton like process leads to the formation of 4-Amino, 3-azo naphthalene sulphonic acid, dihydroxy substituted naphthalene, dihydroxy substituted biphenyl, phenol, quinol etc., as intermediates, based on which probable degradation mechanism is proposed. These results show that a photo Fenton like process could be useful technology for the mineralization of di azo dyes under lower concentration of iron in acidic conditions. The present process is advantageous as it lowers the sludge production resulting from the iron comple. © Versita Warsaw and Springer-Verlag Berlin Heidelberg 2009.