A novel magnetic ZnFe₂O₄ aerogel photocatalyst for visible light reduction of Cr(VI) at high concentrations: Facile synthesis, enhanced activity and photocatalytic mechanism, combined with first-principles calculations

Herein, we prepared a novel magnetic ZnFe₂O₄ aerogel capable of visible light reduction of Cr(VI) via the sol-gel method. The influences of different heat treatment temperatures on the physical phase, structure, and properties of the catalysts were systematically investigated. Photocatalytic experiments revealed that the 400 °C heat-treated ZnFe₂O₄ aerogel exhibited the optimal photocatalytic performance. To attenuate the influence of catalyst adsorption on the photocatalytic experiments, the concentration of Cr(VI) solution was as high as 100 mg/L. The reduction rate of Cr(VI) was significantly higher than that of some previously reported ZnFe₂O₄ photocatalysts after visible light irradiation for 120 min. A plausible photocatalytic reaction mechanism was deduced based on the first-principles DFT calculations and photoelectrochemical experiments. In addition, the 400 °C heat-treated ZnFe₂O₄ aerogel possessed a high specific surface area of 115.31 m²/g and a saturation magnetization intensity of 10.6 emu/g, which allowed for recovery by magnetic separation.