Kinetic studies on the sulfathiazole degradation by activated persulfate with ascorbic acid and cysteine

Abstract

In this study, ascorbic acid (AA) and cysteine (Cys) were used as homogeneous potassium persulfate (S₂O₈²⁻) activators. The efficiency of the S₂O₈²⁻/AA and S₂O₈²⁻/Cys systems was investigated to generate sulfate radicals (SO₄^−•) for the oxidation of sulfathiazole (STZ). The presence of AA and Cys displayed a promoting effect on the activation of S₂O₈²⁻. The results indicated that the STZ/S₂O₈²⁻ redox reaction followed pseudo-first order kinetics with respect to STZ concentrations. The oxidative degradation of STZ is accelerated by temperature, dose of S₂O₈²⁻, AA, Cys, and pH with S₂O₈²⁻/AA and/or S₂O₈²⁻/Cys systems. The degradation rates of STZ followed the order S₂O₈²⁻/AA > S₂O₈²⁻/Cys > S₂O₈²⁻ under similar experimental conditions. The presence of SO₄^−• and HO^• were tested with two radical scavengers, tertiary butanol (TBA) and ethanol, in which HO^• was mainly responsible for STZ degradation at higher pH. In summary, S₂O₈²⁻/AA and S₂O₈²⁻/Cys systems might provide a potentially useful technique for remediation of water contaminants.