The visible-light-driven photocatalytic reduction of Cr⁶⁺ using BiVO₄: assessing the effect of Au deposition and the reaction parameters

In this work, fern-leaf-like BiVO4 was used to photocatalytically reduce Cr6+ in water. Nanosized BiVO4 displayed bandgap energy and specific surface area of 2.49 eV and 5.65 m(2) g(-1), respectively. Metallic Au nanoparticles were deposited on the BiVO4 to increase the photocatalytic performance. To optimize the reaction conditions, the sacrificial agents methanol, ethanol, formic acid, dimethyl sulfoxide, and KI were tested, while different catalyst dosages and Au loadings were assessed. The best sacrificial agent was formic acid, which was used at an optimal concentration of 0.01 mol L-1. The complete removal of Cr6+ was attained after 90 min of visible light irradiation using a catalyst dosage of 1.5 g L-1. Depositing metallic Au nanoparticles barely improved the photocatalytic performance, thus unmodified BiVO4 was used to remove Cr6+ in tap water. The matrix effect slowed the photocatalytic process, and the complete removal of Cr6+ was achieved in 120 min. Cr3+ and Cr6+ species were precipitated on the catalyst surface at the end of the photocatalytic process; still, BiVO4 displayed high stability after three reaction cycles.