Imidacloprid degradation activated by peroxydisulfate with NiCoAl layered metal oxide catalysts: The unique role of Al

Abstract

Improper use of neonicotinoid insecticides (NNIs) can cause serious harm to aquatic ecosystems and human health. Despite the demonstrated excellent reactivity of nonradical persulfate activation in complex aquatic environments, the relationship between defect engineering and catalytic activity, as well as the construction of nonradical directed activation systems, remains uncertain. In this study, we synthesized and characterized Al-doped NiCoAl-LDO layered metal oxide catalysts for the first time. These catalysts were then used to activate peroxydisulfate (PDS) for degrading imidacloprid (IMI) in wastewater. Through degradation experiments and characterization analysis, singlet oxygen (¹O₂) and electron transfer were identified as the primary mechanisms responsible for IMI removal. Under optimized conditions (0.5 g/L catalyst loading, 1 mM PDS dosage, pH = 7.0), the degradation rate of IMI reached 0.06 min⁻¹. The NiCo₂Al₁-LDO/PDS system exhibited efficient IMI degradation over a wide pH range (pH = 4–10) (> 73.6 %) and demonstrated excellent resistance against interference from anions such as Cl⁻, SO₄²⁻, HCO₃⁻, CO₃²⁻, as well as Humic acid (HA). Our findings confirm that Al doping induces lattice distortion and enhances interfacial electron transfer processes in the catalyst structure, thereby facilitating the transformation from radical to nonradical pathway during the degradation process. This study not only advances our fundamental understanding of metal oxide active site doping regulation, but also presents a novel defect engineering strategy for nonradical oxidation of IMI, offering valuable insights for future research and practical applications of persulfate.