Surface Hydroxyl-Promoted Visible-Light Activation of Peroxymonosulfate by ZnAl-LDH for Water Purification: Mechanistic Insights and Ecological Assessment

Zinc aluminium hydrotalcite (ZnAl-LDH) based photocatalytic advanced oxidation processes show considerable promise for pollutant degradation. Yet, the specific role of surface hydroxyl groups in the reaction mechanism—particularly with regard to environmental and ecological risk control—remains inadequately understood. This study systematically explores the function of surface hydroxyl groups on ZnAl-LDH in the photoactivation of peroxymonosulfate (PMS). A surface-hydroxyl-rich ZnAl-LDH was synthesized using a simple and scalable coprecipitation approach. The material demonstrated exceptional PMS activation performance and a distinctive non-radical pathway, enabling complete photocatalytic degradation of nitenpyram (NTP) within 5 minutes under low PMS concentrations. Surface hydroxyls were found to be crucial in the activation process, acting as both adsorption sites for PMS and catalytic centers for its activation. Notably, the developed oxidation system exhibited marked environmental and ecological benefits, representing a green and low-carbon technology. Zebrafish assays, wheatgrass growth tests, and full life-cycle assessments consistently confirmed its eco-friendly efficacy. Ultimately, this work underscores the dual advantage of surface hydroxyl groups as active sites in catalytic oxidation: they facilitate the activation process while ensuring minimal environmental impact.