Mechanism of metal sulfides accelerating the REDOX cycle of Fe(II)/Fe(III) and promoting the degradation of As(III) by oxalate

In this study, a matrix composite material of CdZnS and α-FeOOH on carbon cloth (CZS@FeOOH@CC) was prepared by a hydrothermal method, and was used for the degradation of As(III). The composite material has good photocatalytic activity of removing As(III) in the presence of oxalate. CZS@FeOOH@CC can completely degrade 10 mg/L As(III) within 10 min under visible light irradiation. The influence factors of CZS@FeOOH@CC composite material on catalytic oxidation of As(III) were also studied in the oxalate system. The photocatalytic oxidation efficiency of As(III) is affected by the oxalate concentration in the reaction system, and the atmosphere plays a major role in the degradation of As(III). Under visible light, oxalate first combines with Fe(III) on the surface of iron oxide to form Fe(III)-oxalate complex, and then the Fe(III)-oxalate composite is activated to produce·C2O4−. In the presence of oxygen, Fe(II) readily reacts with O2 and oxidizes to Fe(III). The introduction of CdZnS promoted the separation of interfacial electron holes, and accelerated the REDOX cycle of Fe(II)/Fe(III). This study provides a feasible and simple method for accelerating the catalytic removal of heavy metals from wastewater by iron-based materials.