In this work, the application of high-power LED365nm and commercial, low-price LED398nm for heterogeneous photocatalysis with TiO2 and ZnO photocatalysts are studied and compared, focusing on the effect of light intensity, photon energy, quantum yield, electrical energy consumption, and effect of matrices and inorganic components on radical formation. Coumarin (COU) and its hydroxylated product (7-HC) were used to investigate operating parameters on the •OH formation rate. In addition to COU, two neonicotinoids, imidacloprid and thiacloprid, were also used to study the effect of various LEDs, matrices, and inorganic ions. The transformation of COU was slower for LED398nm than for LED365nm, but r07-HC/r0COU ratio was significantly higher for LED398nm. The COU mineralization rate was the same for both photocatalysts using LED365nm, but a significant difference was observed using LED398nm. The impact of matrices and their main inorganic components Cl- and HCO3- were significantly different for ZnO and TiO2. The negative effect of HCO3- was evident, however, in the case of high-power LED365nm and TiO2, and the formation of CO3•- almost doubled the r07-HC and contributes to the conversion of neonicotinoids by altering the product distribution and mineralization rate.
Keywords: carbonate radical; coumarin; hydroxyl radical; matrix effect; neonicotinoid.