Enhanced Photodegradation of Imidacloprid Using ZnO@Ca-Alginate Composites: Optimization of pH and pHzcp for Effective Water Treatment

This research focused on the photodegradation of the insecticide imidacloprid (IM) via a ZnO@Ca-Alginate composite catalyst to address water contamination issues, particularly in agricultural areas such as Palestine. The composite was synthesized and characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray (EDX), thermogravimetric analysis (TGA), and Fourier transform infrared (FT-IR) spectroscopy, confirming the presence of ZnO. Photocatalytic experiments under simulated solar light revealed significant IM degradation, with a 50 % reduction in 40 minutes, an 80 % reduction in 2 hours, and up to 94 % in 3 hours. The degradation efficiency was influenced by the point of zero charge (pHzcp) and solution pH, with optimal performance under neutral to slightly basic conditions. UV-visible spectrophotometry, high-performance liquid chromatography (HPLC), and total organic carbon (TOC) analyses verified complete IM mineralization, yielding CO₂, Cl⁻, and NO₃⁻ after 3 hours. The ZnO@Ca-Alginate composite demonstrated high reusability, highlighting its potential for treating pesticide-contaminated water. This study emphasizes the need for efficient pollutant removal technologies in regions where agricultural pollutants are prevalent.