Carbon-oxygen dual-defect engineered ZnAl-LDH nanosheets with floatable properties for superior photodegradation of emerging pollutants: Mechanistic insights into aluminum's role and comprehensive toxicity evaluation

This study presents the successful development of a novel floatable photocatalyst, EPLDH, exhibiting exceptional enrichment and degradation capabilities for nitenpyram (NTP) under visible light irradiation. Structural characterization via EPR confirmed that the carbon-oxygen dual-defect electronic defect zones in EPLDH significantly enhance photogenerated charge carrier separation efficiency. Crucially, the reduction of surface-coordination-induced negative charge was identified as the key factor driving the superior catalytic performance of the optimized EPLDH0.2 sample. Degradation kinetic experiments demonstrated that the EPLDH0.2/Vis system achieved complete NTP removal within 40 minutes–1.6 times higher than control systems (EP/Vis: 62 %; ZnAl-LDH/Vis: 67 %). This remarkable performance stems from synergistic effects: (1) morphology regulation and defect engineering, (2) efficient Z-scheme heterojunction charge transfer, and (3) interfacial enrichment enabled by the catalyst's floatability, collectively boosting reactive oxygen species (ROS) generation and utilization. EPLDH0.2 exhibited broad-spectrum degradation capability, efficiently removing 22 emerging contaminants (ECs), underscoring its anti-interference capacity and universal applicability. Practical validation in an immobilized dual continuous-flow system under natural sunlight confirmed high removal efficiency for NTP, bisphenol A, and ciprofloxacin, offering a cost-effective solution for aquatic micropollutant remediation. Mechanistic studies identified 1 O 2 , •O 2 − , and h + as dominant active species through quenching experiments and ESR analysis. Degradation pathways of NTP, including alkyl chain cleavage, nucleophilic ring-opening, and decarboxylation, were proposed based on intermediate analysis, Fukui index calculations, and electrostatic potential distribution. Ecological toxicity assessments confirmed significant reduction after mineralization, ensuring environmental safety.