Photoredox catalysis of As(III) by constructed CSnS bonds: Using biomass as templates leads to bio‑carbon/SnS2 nanosheets capable of the efficient photocatalytic conversion of As(III) and calcium arsenate capture.

In this paper, a new interface design strategy for bio‑carbon/SnS2 nanosheets equipped with CSnS bonds was proposed by using biomass as a template for the efficient photocatalytic conversion of As(III). The characterization results illustrated that the CSnS bonds could effectively prevent the agglomeration of SnS2, expand the photoresponse range and improve the hydrophilicity of the bio‑carbon/SnS2 composites while reducing their transfer resistance. Therefore, the construction of CSnS bonds could more efficiently promote the photoredox catalysis of As(III) to As(V) compared with pure SnS2, attributing to the polarization and conjugation effects of the CSn bonds. Meanwhile, CaSO4·nH2O (n = 0, 0.5, 2) could rapidly convert AsO43- into Ca3(AsO4)2 precipitates to eliminate arsenic from the aqueous solution in one step. In particular, 7500 μg/L As(III) could not only be photocatalyzed into As(V) but also be converted to Ca3(AsO4)2 to achieve the removal of arsenic within only 55 min in the coexistence of CaSO4. In addition, the electron transfer path in the photocatalytic oxidation system on arsenite was proposed according to the Mott-Schottky (MS) plots of SnS2 and graphitic carbon. The electron paramagnetic resonance (EPR) results implied that O2- and h+ were the main active substances in the photooxidation arsenic system and the effect of OH could be negligible. Thus, the possible mechanism of the photocatalytic conversion of As(III) was discussed.