Synergistic activation of persulfate by natural chalcocite and ferrous ions by promoting the cycling of Fe3+/Fe2+ couple for degradation of organic pollutants

Abstract

Natural chalcocite (NCC) was chosen as a co-catalyst for activation of persulfate (PS) to degrade organic contaminants in this study. A synergistic effect between NCC and ferrous ions (Fe²⁺) was found in catalyzing PS for degradation of orange G (OG). The main role of NCC in the NCC/Fe²⁺/PS system was to facilitate Fe³⁺ reduction back to Fe²⁺ and thus improve the stoichiometric efficiency of PS. The results of scavenging experiments and electron paramagnetic resonance tests proved that both sulfate and hydroxyl radicals were the primary reactive oxidants in the NCC/Fe²⁺/PS system. Twelve potential intermediate products of OG were identified, and the degradation pathway was proposed. Experiment parameters, such as NCC dose, Fe²⁺ concentration, initial pH, and the presence of anions (H₂PO₄^‒ and Cl^‒), all had important impacts on OG degradation. NCC had good reusability in synergistic activation of PS with Fe²⁺ for OG degradation for five cycles. This study demonstrated a natural sulfide mineral as an efficient co-catalyst towards PS activation for destruction of organic contaminants in water.

Keywords: Co-catalyst; Degradation pathway; Fe(2+) regeneration; Sulfide mineral; Synergistic effect.