Advanced water treatment using Cu-doped ZnO: reactive oxygen species generation and photocatalytic performance toward pesticides in drinking water and synthetic sewage

The presence of Contaminants of Emerging Concern (CECs) in aquatic environments demands advanced treatment technologies capable of operating under complex matrix conditions. In this study, the photocatalytic performance of ZnO doped with 5% copper (ZnO-Cu) was evaluated for the degradation of pesticides (2,4-D, alachlor, atrazine, carbendazim, diuron, fipronil, pendimethalin, pyraclostrobin, simazine, and λ-cyhalothrin) in drinking water and synthetic sewage, via heterogeneous photocatalysis, under conditions relevant to tertiary treatment. Initially, mechanistic investigations combining scavenger experiments and EPR spectroscopy were performed to assess the influence of Cu doping on the photocatalytic mechanism. The results indicated that photogenerated h + and ●OH are the main oxidizing species in pristine ZnO. For ZnO-Cu, ●OH remained dominant; however, a greater contribution of reactive oxygen species derived from molecular oxygen, such as O 2 ● − , H 2 O 2 , and 1 O 2 , was observed, associated with a more efficient generation of reactive species. The photocatalytic assays showed high degradation efficiencies in both matrices, with reduced performance in synthetic sewage due to matrix effects. The significant decrease in TOC confirmed the effective oxidation of organic matter, especially in drinking water. The results demonstrate the potential of ZnO-Cu for applications in advanced treatment of contaminated waters and provide mechanistic insights into the effect of doping on the photocatalytic process.