Solvothermal synthesis of nonmetals-modified SnO2 nanoparticles with high visible-light-activated photocatalytic activity in the reduction of aqueous Cr(VI)

•Nonmetals-modified SnO2 was synthesized by a HNO3-involved solvothermal method.•High specific surface area and excellent visible-light-absorbing ability.•High photocatalytic activity in the reduction of aqueous Cr(VI) under visible-light.•Photocatalyst dosage and Cr(VI) concentration affect the reduction rate of Cr(VI).

This work took the initiative to conduct the synthesis and evaluation of visible-light-active nonmetals (N, C and Cl)-modified SnO2 nanoparticles for photocatalytic reduction of aqueous Cr(VI). Using inexpensive SnCl4⋅5H2O, absolute ethanol and concentrated (65–68 mass%) nitric acid as the starting materials, a one-step low temperature (180 °C) solvothermal method was developed for the synthesis of nonmetals (N, C and Cl)-modified SnO2 nanoparticles (which was abbreviated as SnO2–HNO3). The composition, structure, BET specific surface area and optical property of SnO2–HNO3 were characterized by powder X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, N2 adsorption and UV–vis diffuse reflectance spectroscopy. The photocatalytic activity of SnO2–HNO3 was tested in the reduction of aqueous Cr(VI) under visible-light (λ > 420 nm) irradiation, and compared with that of SnO2–NH3 (which denoted the product synthesized when 65–68 mass% HNO3 was replaced by 25–28 mass% NH3⋅H2O). It was observed that SnO2–HNO3 exhibited high photocatalytic activity, whereas SnO2–NH3 exhibited no photocatalytic activity in the reduction of aqueous Cr(VI) under visible-light (λ > 420 nm) irradiation. Besides, the dosage of SnO2–HNO3 and the initial concentration of Cr(VI) aqueous solution had great effects on the photocatalytic reduction rate of Cr(VI). This work suggests that SnO2–HNO3 is a new promising visible-light-activated photocatalyst in efficient utilization of solar energy for treating Cr(VI) wastewater.