Photochemical dissolution of bismuth vanadate and formation of volatile bismuth species: Effects of low-molecular-weight organic acids and chloride ions

Bismuth vanadate (BiVO 4 ), a widely employed functional material in pigments and photocatalysts, is susceptible to environmental release during manufacturing and application. Previous researches showed that the dissolution of BiVO 4 could be induced by light irradiation, releasing Bi(III) and V(V) ions. Besides, Bi(III) can be converted into volatile and toxic species under UV irradiation in the presence of low molecular weight organic acids (LMWOAs). However, the influence of LMWOAs on the photodissolution of BiVO 4 and the subsequent transformation of the dissolved Bi(III) remains unclear. In this study, it was found that under UV irradiation, BiVO 4 was dissolved and then further transformed into volatile Bi in media such as formic acid (FA), acetic acid (AA), oxalic acid (OA), and citric acid (CA). The generation efficiency of volatile Bi was enhanced by the co-existing Cl − ions through the consumption of hydroxyl radicals (•OH). The recombination of electron-hole pairs on the surface of BiVO 4 could be inhibited by LMWOAs acting as electron donors, and the dissolution was thereby promoted. In addition, the dissolved Bi(III) could be converted into volatile substances by the radicals generated from the photolysis of LMWOAs. (CH 3 ) 3 Bi was speculated to be formed from BiVO 4 in the AA medium, while BiH 3 was released in the FA, OA, and CA media. Transmission electron microscopy characterization showed a lightening of the color of the edges of BiVO 4 particles after light exposure, confirming the dissolution of BiVO 4 . The research results provide a scientific basis for evaluating the environmental migration and transformation risks of BiVO 4 .