Solar light induced photocatalytic process for reduction of hexavalent chromium and degradation of tetracycline and methylene blue by heterostructures made of SnS2 nanoplates surface modified by ZnWO4 nanorods

Residual emerging and conventional pollutants in water bodies, including drinking water, has led to developing strategies for their removal. Here we report a very efficient method of removing Cr(VI) by photocatalytic reduction, and removing of tetracycline (TC) antibiotics and methylene blue (MB) dyes by photocatalytic degradation in aqueous medium using type-II heterojunction based ZnWO4/SnS2 solar photocatalyst. The photocatalytic activity of hydrothermally synthesized ZnWO4/SnS2 is corroborated by structural, compositional, morphological and optical properties. Under sunlight exposure, more than 99.9% photocatalytic reduction of Cr(VI) is achieved within 65 min at a reaction rate of 0.061 min−1. Similarly, photocatalytic degradations of TC (95%) and MB (99.6%) degradation are achieved in 90 min and 75 min, at a degradation rate of 0.023 min−1 and 0.055 min−1, respectively. The photocatalytic degradation is attributed to in-situ generation of reactive oxygen species (ROS), e.g., superoxide radicals and hydroxyl radicals. The role of ROS towards photocatalytic degradation is confirmed from ROS scavenging studies. The degradation mechanism has been discussed by analyzing intermediates of the degradation products by ultra-performance liquid chromatography coupled to quadrupole time-of-flight mass spectrometry (UPLC-Q-Tof-MS).