Role of surfactants on Fe2+ mediated oxidative decolorization of Acid Red 13 by peroxydisulfate

Abstract

Over the past few years, environmental concerns regarding dye contamination have grown. Removing dye from wastewater from industry is crucial for environmental sustainability. The removal of Acid Red 13 (AR13) dye was achieved through its oxidative degradation utilizing peroxydisulfate. While there are few reports on the Fe2+-mediated oxidation of azo dyes by peroxydisulfate, further investigation is needed to understand the effect of surfactants on their degradation. The present study focuses on investigating the influence of cationic, anionic, and neutral surfactants on the decolorization of Acid Red 13 (AR13) in aqueous solutions using peroxydisulfate. The decolorization kinetics of AR13 in the peroxydisulfate process adhered to the principles of second-order reaction kinetics, with a rate constant of 2.96 × 10−4 M−1 min−1 at 4.0 mM S2O8 2− concentration. A decolorization efficiency of 92.9 ± 3.6% was achieved in 120 min under optimal reaction conditions. The rate constants of 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 AR13 decolorization. At higher pH, sulfate-free radical production decreases, limiting AR13 decolorization. Recent findings show that CTAB (cetyltrimethylammonium bromide) and SDS (sodium dodecyl sulfate) retard Fe2+-catalyzed S2O8 2− activation, whereas no discernible impact on S2O8 2− activation was observed in the case of TX-100 (triton X-100). Peroxydisulfate decolorized AR13 with a low activation energy of 45.10 ± 1.71 kJ mol−1 at 2.0 mM starting concentration. The positive ΔG value indicates the non-spontaneity of the decolorization process.