Impact of Reaction Parameters and Water Matrices on the Removal of Organic Pollutants by TiO(2)/LED and ZnO/LED Heterogeneous Photocatalysis Using 365 and 398 nm Radiation

In this work, the application of high-power LED(365nm) and commercial, low-price LED(398nm) for heterogeneous photocatalysis with TiO(2) 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 LED(398nm) than for LED(365nm), but r(0)(7-HC)/r(0)(COU) ratio was significantly higher for LED(398nm). The COU mineralization rate was the same for both photocatalysts using LED(365nm), but a significant difference was observed using LED(398nm). The impact of matrices and their main inorganic components Cl(−) and HCO(3)(−) were significantly different for ZnO and TiO(2). The negative effect of HCO(3)(−) was evident, however, in the case of high-power LED(365nm) and TiO(2), and the formation of CO(3)(•−) almost doubled the r(0)(7-HC) and contributes to the conversion of neonicotinoids by altering the product distribution and mineralization rate.