Photoreduction of 4-nitrophenol and Cr (VI) using ZnS/ZnO-tubes synthesized with hexamethylenediamine

The presence of toxic substances constitutes an environmental problem and even affects health. To evaluate the photoreduction of 4-nitrophenol (4-NF) and Cr(VI), both highly polluting substances, two Zn materials synthesized by the precipitation method; ZnS (Zinc Sulfide) and ZnS/ZnO-tubes (Zinc Sulfide deposited on Zinc Oxide tubes) have been used. The ZnS/ZnO-tubes assisted photoreduction of 4-NP to 4-aminophenol (4-AP) exhibits pseudo-first order kinetics with a rate constant of 0.1476 min⁻¹ and a yield of 90% at 15 min, while the ZnS material exhibits zero-order kinetics with a rate constant of 0.07859 mg/L*min and a reducing yield of 30% at 15 min. However, for the Cr(VI) to Cr(III) photoreduction reaction they exhibit pseudo-second-order kinetics with a rate constant of 2.711 L/mg*min accompanied by a 90% reducing yield at 15 min in the presence of ZnS/ZnO tubes, and pseudo-zero-order kinetics with a rate constant of 0.518 mg/L*min and a 30% reducing yield at 15 min for the ZnS material. In both cases, the hybrid ZnS/ZnO-tubes material exhibits exceptional catalytic performance. The photocatalytic efficiency of the ZnS/ZnO-tubes material is cooperatively attributed to its morphological and chemical properties. The average particle size of ZnS/ZnO-tubes is 150 nm, while that of ZnS particles is 450 nm.