Kinetic Evaluation of Fe²⁺ Catalyzed Oxidative Degradation of Ponceau 4R Using Proxydisufate

The present study focuses on investigating the decolorization of Ponceau 4R 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 Ponceau 4R was investigated. The experimental data were examined employing kinetics of both first and second order. The decolorization kinetics of Ponceau 4R in the peroxydisulfate process adhered to the principles of second-order reaction kinetics, with a rate constant of 1.47 × 10^–4 M^–1 min^–1 at 2.5 mM S₂O \(_{8}^{{2 - }}\) concentration. Decolorization efficiency above 90% was achieved in 120 min under optimal reaction conditions. The rate constants pertaining to the second-order chemical process demonstrated a positive association with both S₂O \(_{8}^{{2 - }}\) concentration and temperature. Fe²⁺ activates S₂O \(_{8}^{{2 - }}\) to generate sulfate radical ion, amplifying Ponceau 4R decolorization. At higher pH, sulfate-free radical production decreases, limiting Ponceau 4R decolorization. Peroxydisulfate decolorized Ponceau 4R with a low activation energy of 42.8 ± 0.23 kJ mol^–1 at 2.5 mM starting concentration. The positive ΔG value indicates the non-spontaneity of the decolorization process.