Photocatalytic degradation of a triazole pesticide, cyproconazole, in water

The degradation of a pesticide, cyproconazole, by UV/TiO2 photocatalysis in water using industrial titanium dioxide coated non-woven paper was studied for the first time. The influence of parameters such as initial concentration and dissolved oxygen were investigated. The analysis of the first organic by-products suggests that a hydroxyl radical attack occurs on the phenyl ring, the methyl groups and the carbon C1 of the cyproconazole. The fate of heteroatoms has been investigated. The nitrogen atoms in the triazole moiety of the molecule are partially transformed into NH4+ and NO3−. The potential formation of N2 and cyanuric acid could explain the lack of stoichiometric nitrogen balance. The chlorine atoms were completely released as chloride ions. The oxidative and reductive pathways are both involved in the chlorine release mechanism. The study of the influence of the oxygen concentration showed the importance of the oxygen mass transfer when designing an industrial photocatalytic reactor. For the second time, an original calculation process was carried out to evaluate the adsorption constant of oxygen over the whole photocatalysis period and confirmed the validity of the method for cyproconazole pesticide.