Investigation on mechanism of photocatalytic reduction of Cr(Ⅵ) by ZnFe2O4

The leaching residue of ZnFe2O4 produced in the process of traditional zinc hydrometallurgy was used as raw material for photocatalytic reduction of Cr(Ⅵ) after pretreatment. The sample was characterized by XRD, FT-IR, SEM and XPS etc, and its photocatalytic performance was also studied. The effects of reaction time, EDTA dosage, solid-liquid ratio, initial solution concentration and pH on the photocatalytic reduction of Cr(Ⅵ) were investigated. The results show that ZnFe2O4 is a n-type semiconductor with a band gap of 1.71 eV and a conduction band edge(vs.RHE) of 0.01 V, which can theoretically reduce Cr(Ⅵ). Because EDTA can consume holes and form [Cr-EDTA]3+ complex, the effective separation of photogenerated electron hole pairs has greatly improved the performance of ZnFe2O4 in photocatalytic reduction of Cr(Ⅵ). Under the optimal conditions of 0.1 mL EDTA, solid-liquid ratio 1 g/L, and initial solution concentration 20 mg/L, pH=3, the reduction rate of Cr(Ⅵ) by ZnFe2O4 reaches 97.95% within 120 min. © 2023 Central South University of Technology. All rights reserved.