Electropositive carbon sites and sulfur vacancies in SnS2/g-C3N4 for achieving adsorption and photocatalytic degradation of As(III) in stages by pH regulation

In this work, a high content of pyrrole nitrogen carbon nitride (HPCN)-SnS 2 has been successfully constructed with −C═Sn− chemical bond as the interface framework. The charge state of Sn species was adjusted by β particles to obtain controllable sulfur defects onto the HPCN-SnS 2 through electron beam irradiation (EBI). The composites exhibited excellent photocatalytic oxidation capacity of As(Ⅲ) and adsorption capacity of As(Ⅴ). It is confirmed that the optimized HPCN-SnS 1.38 can remove the total As concentrations below 0.40 mg/L within 80 min. Additionally, the effect of various conditions (pH value and type of anions) was evaluated using degradation experiments, and HPCN-SnS 1.38 could be reused at least 5 times without an obvious reduction in the photocatalysis and adsorption performances. Based on the experimental results, the photocatalytic mechanism of As(Ⅲ) by HPCN-SnS 2 after electron beam irradiation was studied. Free radical quenching experiments and electron paramagnetic resonance (EPR) showed that the oxidation of As(III) under visible light is mainly controlled by •O 2 − and •OH, and •OH is converted from •O 2 − under acidic conditions.