Sustainable Approach for Spent V₂O₅–WO₃/TiO₂ Catalysts Management: Selective Recovery of Heavy Metal Vanadium and Production of Value-Added WO₃–TiO₂ Photocatalysts

In order to control nitrogen oxides emissions, V₂O₅–WO₃/TiO₂ catalysts are widely applied in coal-fired power plants. Consequently, a large number of V₂O₅–WO₃/TiO₂ catalysts are spent annually because of their short operating life. Although these spent catalysts contain amounts of heavy metals, they have also been regarded as a potential secondary resource for the recovery of valuable elements titanium, tungsten, and vanadium. Therefore, this study developed an efficient method for selective leaching of heavy metal vanadium with an “H₂SO₄ + Na₂SO₃” acid reduction system. The use of this leaching solution achieved nearly 100% efficiency in vanadium removal, and the effects of the leaching parameters on the vanadium leaching efficiencies were investigated. Subsequently, the titanium-enriched residue obtained from the leaching process was used to produce high-performance WO₃–TiO₂ photocatalysts with dominant {001} facets via a hydrothermal treatment. The influence of the amount of hydrogen fluoride on the morphology and percentage exposure of the {001} facets of the photocatalysts was studied systematically. The method proposed in this study constitutes a novel and sustainable approach for the disposal of spent V₂O₅–WO₃/TiO₂ catalysts.