Optimization of the degradation of imazalil by photocatalysis: Comparison between commercial and lab-made photocatalysts

• The efficiency of photocatalysis in the elimination of imazalil was proved.
• Commercial and several home-made photocatalysts were studied.
• The fastest degradation of imazalil was obtained with a home-made photocatalyst.
• The degradation pathway was proposed and five by-products were confirmed by LC–MS.
• The degradation pathway was confirmed by FTIR studies and ion chromatography.

The elimination and mineralization of the fungicide imazalil and its by-products has been studied by means of heterogeneous photocatalysis. The activity of different photocatalysts, including the commercial TiO2 benchmark photocatalyst (Evonik P25) and several TiO2-based lab-made catalysts, is compared. The best results were achieved with the new lab-made photocatalyst synthesized by using sulphuric acid in the sol–gel process and calcined at a high temperature (EST-1023t). The apparent initial rate constant was up to 2 times faster for EST-1023t when compared to that obtained with Evonik P25. The effect of different operating parameters (pH, photocatalyst load and initial imazalil concentration) on the photocatalytic process were studied for these two photocatalysts and a degradation pathway was proposed considering data obtained from ion chromatography, LC–MS and FTIR studies. The formation of imidazole acetic acids was confirmed, as well as complete mineralization and release of stoichiometric nitrogen (as ammonium and nitrate) and chloride ions.

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