High-performance pure and Fe³⁺-ion doped ZnS quantum dots as green nanophotocatalysts for the removal of malachite green under UV-light irradiation

The heterogeneous photocatalysis using UV-radiation and quantum dots (QDs) is an interesting method for the treatment of water polluted with the organic substances. In this study, ZnS QDs, as a pure and doped with Fe³⁺, were prepared for photodecolorization of malachite green (MG) as a model dye. The synthesis of QDs was carried out using a chemical precipitation method in aqueous solution, in the presence of 2-mercaptoethanol as a capping agent. The XRD patterns indicated that the doped nanoparticles are crystalline, with cubic zinc blend structure. The effects of dopant content, pH, nanophotocatalyst amount, irradiation time, and initial dye concentration on the removal efficiency of MG were studied. Results showed that the QDs presented high MG decolorization efficiency, and doping with Fe³⁺ promoted the dye removal. The maximum removal of dyes was obtained at 80mg/L of photocatalyst as an optimum value for the dosage of photocatalyst in pH of 8.0.