Enhanced photocatalytic degradation of chlorpyrifos in wastewater using a TiO2/chitosan/Ag2CO3 nanocomposite: synthesis, characterization, and optimization

The persistence of the pesticide Chlorpyrifos (CPS) in agricultural wastewater poses serious environmental challenges, necessitating effective remediation strategies. In this study, a TiO₂/Chitosan/Ag₂CO₂ (TiO₂/CS/Ag₂CO₂) nanocomposite was synthesised and evaluated for photocatalytic CPS degradation under both UV and visible light. Structural and optical characterization (XRD, BET, SEM, TEM, PL, FT-IR, DLS, UV-Vis, and DRS) confirmed the successful incorporation of Ag₂CO₂ nanoparticles into the TiO₂/CS matrix and demonstrated a reduced band gap with enhanced light absorption across the UV-visible spectrum. Photocatalytic experiments revealed that the nanocomposite exhibited markedly higher activity than pure TiO₂, achieving 5.35-fold improvement under UV and 1.96-fold under visible light. Optimization of key parameters showed maximum degradation efficiency (91.52%) for 100 ppm CPS at pH 4, using 0.146 mg catalyst after 60 min of irradiation. Mechanistic investigations indicated that hydroxyl radicals (•OH) and photogenerated holes (h⁺) were the dominant reactive species responsible for degradation. These results demonstrate that TiO₂/CS/Ag₂CO₂ is a stable, efficient, and environmentally friendly photocatalyst with strong potential for removing persistent organic pollutants from wastewater.