A comparison of visible-light photocatalysts for solar photoelectrocatalysis coupled to solar photoelectro-Fenton: Application to the degradation of the pesticide simazine.

Three different visible-light photocatalysts (hematite (α-FeO), bismuth vanadate (BiVO) and Mo-doped bismuth vanadate (BiMoVO)) deposited on transparent fluorine-doped SnO (FTO) were evaluated for the solar-driven photoelectrocatalytic treatment of emerging pollutants. BiMoVO was found to be the most effective photoanode, yielding the fastest degradation rate constant and highest mineralization efficiency using phenol as the oxidation probe. The BiMoVO photoanode was then used to degrade the herbicide simazine in a photoelectrolytic cell combining photoelectrocatalysis (PEC) with photoelectron-Fenton (PEF) under solar light (SPEC-SPEC). Total simazine removal was achieved within 1 min of treatment (k = 4.21 min) at the optimum electrode potential of 2.5 V vs Ag/AgCl, with complete TOC removal in 2 h. The analysis of anionic species in solution during treatment showed that most of the nitrogen heteroatoms in the simazine structure were converted into NO following OH addition to organic N. This innovative process combining BiMoVO-PEC with PEF using solar light as a sustainable source of energy (SPEC-SPEF) achieved the highest degradation/mineralization efficiency ever reported for simazine treatment. Besides, this is the first work reporting the photo(electrochemical) degradation of this toxic herbicide.