Kinetic studies on visible light-assisted degradation of acid red 88 in presence of metal-ion coupled oxone reagent

Visible light-assisted photo-Fenton-like oxidation of a mono-azo textile dye, acid red 88 (AR88), has been carried out in presence of Cu2+ or Fe3+ ions as the catalyst and oxone as the oxidant. The optimal concentrations of metal-ion (Cu2+ or Fe3+) and oxidant (oxone) for the abatement of the azo dye were determined. Decolorization of AR88 in Cu2+/oxone system was found to follow zero-order kinetics with respect to the dye and first-order kinetics when Fe3+/oxone system was employed. In both the cases, the decolorization of AR88 was found to be accelerated with increasing concentrations of metal-ions in solution. Almost 95% decolorization was attained in 2 h with Cu2+ ion and within 14 min with Fe3+ at each metal-ion concentration of 0.075 mM. Mineralization studies were also carried out by monitoring the reduction of total organic carbon (TOC) content during the course of the reaction. A suitable mechanism has been proposed to explain the observed kinetics of decolorization of AR88 in both the Fe3+/oxone and Cu2+/oxone systems.