Hydrothermal synthesis of SnO2/ZnS nanocomposite as a photocatalyst for degradation of Rhodamine B under simulated and natural sunlight

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A novel nanocomposite, SnO2/ZnS, was successfully synthesized via a one-step hydrothermal method. The composite was characterized by several techniques such as XRD, SEM, TEM, XPS and UV–vis spectrum, and utilized for photocatalytic degradation of refractory dye Rhodamine B (RhB) under simulated and natural sunlight. It was found that the composite prepared at the molar ratio of n(SnCl4·5H2O)/n(Zn(NO3)2·6H2O)=1.5 and hydrothermal temperature of 180°C showed the highest photocatalytic activity. The photocatalytic degradation of RhB reached the maximum of 95% at the 1g/L SnO2/ZnS dosage, 10mg/L initial RhB concentration, 4.59 initial solution pH and 23°C. The RhB photocatalytic degradation fitted well to the first-order kinetics model, and the increased SnO2/ZnS dosage, decreased initial RhB concentration and optimal initial solution pH were responsible for the increase of RhB photocatalytic degradation rate. The composite also displayed stable performance during 5 runs of reuse. Quenching tests demonstrated that the dominant active species generated in SnO2/ZnS-RhB-H2O-simulated sunlight system was O2−; nevertheless, h+ and OH also contributed to RhB degradation. The formation mechanism of the SnO2/ZnS nanosphere and RhB photocatalytic degradation mechanism were proposed. Moreover, the composite has proved to have the high efficiency for the degradation of RhB under natural sunlight irradiation.