Oxidative decolorization of Mordant Black 17 by peroxydisulfate facilitated by Fe2+

Abstract

The present study focuses on investigating the decolorization of Mordant Black 17 (MB17) in aqueous solutions using peroxydisulfate. The impact of the initial dye concentration, as well as the concentrations of peroxydisulfate and Fe²⁺, temperature, and pH on the decolorization of MB17 was investigated. The experimental data were examined employing kinetics of both first and second order. The decolorization kinetics of MB17 in the peroxydisulfate process adhered to the principles of second-order reaction kinetics, with a rate constant of 2.75 × 10^-4 M^-1 min^-1 at 3.0 mM S₂O₈^2-concentration.  Decolorization efficiency above 93 % was achieved in 120 minutes under optimal reaction conditions. The rate constants pertaining to the second-order chemical process demonstrated a positive association with both S₂O₈^2- concentration and temperature. Fe²⁺ activates S₂O₈^2- to generate sulfate radical ion, amplifying MB17 decolorization. At higher pH, sulfate-free radical production decreases, limiting MB17 decolorization. Peroxydisulfate decolorized MB17 with a low activation energy of 45.36 kJ mol^-1 at 3.0 mM starting concentration. The positive ΔG value indicates the non-spontaneity of the decolorization process.