H2O2 activation over Co substitution in Fe1-xS for tetracycline degradation: Effect of Co substitution

In this work, the effect of Co substitution in the Fe1-xS (CSP) on the activation of H2O2 to degrade tetracycline (TC) is investigated. A series of CSP samples with different Co content are synthesized via a high-temperature sulfidation method and characterized by XRD, XPS, SEM, and electrochemical analysis. The result showed that low Co content (<= 1%) promotes the catalytic activity of Fe1-xS, while excessive Co (1%?x <= 3%) inhibits its catalytic activity. The investigation of Behnajady-Modirshahla-Ghanbery kinetic model (BMG) showed that the maximum initial degradation rate of TC over 1.0% CSP/H2O2 was 1.6 times than that of in CSP/H2O2 system. The Box-Behnken with Response Surface Methodology was employed to verify optimum condition for TC degradation. The quenching experiments and ESR determined that .OH, .O-2(-) and O-1(2) were involved in TC degradation with the treatment of 1.0% CSP/H2O2 system. Electrochemical analysis, .OH quantification, and metal ion concentrations measure reveal that Co substitution accelerates electron transfer efficiency and Fe2+ regeneration. Furthermore, nine intermediates are identified and the possible degradation pathway of TC is proposed. The unique effect of Co provides novel insight and efficient strategies for improving the reactivity of iron sulfide.