Treatment of aqueous solution containing mixed binary reactive dyes via integrated advanced oxidation processes involving activation of mixed binary oxidants

Abstract

A systematic procedure for the removal of color and chemical oxygen demand (COD) of an aqueous solutions comprising initial mixed binary azo reactive dyes (Corafix Red ME4B and Corazol Black BX), present in any proportions of initial concentrations, has been developed. It utilizes a Fenton-like advanced oxidation process (AOP) involving the activation of mixed binary oxidants as a pretreatment and a hybrid process, consisting of US cavitation and O3 based AOPs, as a post-treatment method. For the red dye, the optimum values of activator concentration, initial oxidant-ratio, initial oxidant-dosage, initial pH of initial H2O2 solution have been determined to be 100 g L−1, 3 wt% mM−1, 18:6 wt% mM−1, and 5 respectively; while, the US cavitation or O3 has been determined to be an optimum post-treatment. Similarly, for the black dye these optimum values and process are identified to be 100 g L−1, 3 wt% mM−1, 30:10 wt% mM−1, 3, and hybrid process respectively. The common optimum values of various parameters of pretreatment and a common optimum post-treatment method have been derived and experimentally demonstrated for the treatment of mixed binary dye solutions. The mechanisms responsible for decolorization and COD removal have been identified via hydroxyl and superoxide radical-trapping experiments.