Kinetics of decolorization and mineralization of the azo dye Reactive Black 5 by hydrogen peroxide and UV light

C.I. Reactive Black 5 is one of the most used reactive dyes for textile fin ishing. It is a diazo dye, which can be decolorized by facultative anaerobi c bacteria, sulfate reducing bacteria and aerobic white rot fungi. Minerali zation by microorganisms has proven difficult. Advanced oxidation processes are promising alternatives for the decolorization and mineralization of Re active Black 5, alone and in combination with aerobic biodegradation. The k inetics of the decolorization of Reactive Black 5 using a combination of hy drogen peroxide and UV radiation have been investigated. The rate of decolo rization is first order with respect to dye concentration. It is enhanced w ith increasing hydrogen peroxide concentrations up to an optimum value. In our model we have correlated an empirical reaction rate expression which co nsiders the contribution of both hydrogen peroxide and UV flux radiation ba sed on the reaction kinetics. This empirical correlation agrees well with t he experimental data for these conditions. Complete decolorization correspo nded with 40-50% mineralization of the dye. Further mineralization can be a chieved with extended radiation time.