Mechanism for Photopromoted Release of Vanadium from Vanadium Titano-Magnetite

The release of V from vanadium titano-magnetite, a predominant natural source of V, was studied under light irradiation. The release rate of V from vanadium titano-magnetite was accelerated by light irradiation, and the oxidation of V was detected. The essence of the photopromoted release of V is that the immobile low valence V is transformed to the mobile V(V) by photoinduced active species generated from the photocatalysis process of magnetite. Among the photoinduced active species, •OH and H 2 O 2 were recognized as the most important oxidizing agents. Not only can they directly convert the immobile low-valence V to the mobile V(V) but also initiate the Fenton reaction, which produces more •OH and then further promotes the oxidation of low-valence V. In addition, a conceptual model of the photo promoted release of V was proposed. This study, as part of a broader study of the release behavior of V, can improve the understanding of the pollution problem about V, as well as the fate and environmental geochemistry cycling of V in the natural environment.