The transition of tetragonal to monoclinic phase in BiVO coupled with peroxymonosulfate for photocatalytic degradation of tetracycline hydrochloride.

At present, the mechanism difference between tetragonal BiVO (t-BiVO) and monoclinic BiVO (m-BiVO) coupled peroxymonosulfate (PMS) to realize photocatalysis is still unclear. In this study, m-BiVO and t-BiVO were obtained by adjusting the bismuth-vanadium ratio in the precursor solution (Bi:V = 3:1; 1:1; 1:2 and 1:3). The results of photocatalytic experiments showed that both t-BiVO and m-BiVO had certain activation effects on PMS, and the prepared monoclinic B1V2 has the strongest photocatalytic performance. Using 20 mg B1V2 to activate 4 mmol L PMS in 30 min, the degradation rate of tetracycline hydrochloride (TCH) reached 92.8%. The free radical quenching experiment and EPR test showed that when m-BiVO coupled PMS degraded TCH, the contribution of active species was SO>•OH>•O > h. Compared with m-BiVO, the wide band gap of t-BiVO makes the photogenerated carrier recombination. When t-BiVO coupling PMS, the contribution of active species is •O > SO>•OH>h. In addition, the intermediate products of TCH degradation were analyzed by LC-MS, and three possible degradation paths of TCH were proposed.