In this study, the photolytic and photocatalytic removal of the herbicide paraquat is investigated under UV-C (254 nm). For photocatalytic experiments, SiC foams were used with P25-TiO2 nanoparticles deposited by dip-coating. The foams were characterized by scanning electron microscopy and paraquat’s degradation under UV-C photolysis or photocatalysis, followed by UV–vis spectroscopy, total organic carbon analyzer, LC–MS and ion chromatography. After 3 h of reactions by photolysis and photocatalysis, 4% and 91% of TOC removal were observed. An analysis of degradation by-products showed a similar degradation pathway with pyridinium ions observed by LC/MS and carboxylic acids (succinate, acetate, oxalate and formate) detected by ion chromatography. In conclusion, these two different photo-degradation processes are able to remove paraquat and produce similar by-products. However, the kinetics of degradation is rather slow during photolysis and it is recommended to combine the UV-C lightning with a TiO2 photocatalyst to improve the mineralization rate.
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Marien et al. (2018) studied this question.
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