Rapid removal of vanadium-chromium ions from solution by titanium-based microspheres photocatalytic deposition

Titanium-based microspheres exhibit exceptional adsorption properties and remarkable photocatalytic reduction capabilities. With a bandgap of 3.14 eV a conduction band potential of −0.23 eV, these microspheres can effectively reduce V5+ to V2+ and Cr6+ to Cr3+. A mixed V5+-Cr6+ solution at a total concentration of 400 mg/L can be treated to meet national emission standard within 60 min. The microspheres demonstrate deposition capacity of 278.65 mg/g for V5+ and 479.30 mg/g for Cr6+. In the photocatalytic process, photogenerated electrons facilitate the reduction and deposition of vanadium and chromium ions onto the catalyst surface without destroying the functional groups. Under acid and alkaline conditions, selective elution enables the recovery of vanadium (263.3 mg/L, 99.82 % purity) and chromium (143.4 mg/L, 99.73 % purity). By integrating adsorption and photocatalysis, novel ion-imprinted materials can be developed for selective adsorption of V5+, purity of ∼99.50 % V5+ solution can be achieved over five cycles. Additionally, the titanium-based microspheres demonstrate effective utilization of natural light and can effectively treat actual vanadium-chromium wastewater.