Visible-light-active chitosan-Cu/ZnO photocatalyst for the removal of organic pollutants from aqueous solutions

Developing sustainable solar-driven catalysts for degrading hazardous organic pollutants is of paramount importance. Herein, a visible-light-active chitosan-supported Cu/ZnO nanocomposite (CS–Cu/ZnO) was synthesized via a green route for the individual degradation of methyl red (MR) and phenol. CS acted as an eco-friendly biopolymeric matrix, stabilizing the Cu/ZnO nanoparticles. Structural and optical characterizations (including XRD, TEM, HR-TEM, FE-SEM, BET, FT-IR, UV–Vis, and zeta potential analysis) verified the uniform anchoring of Cu/ZnO within the CS framework, affording a specific surface area of 71.83 m 2 ⋅g −1 and a pore volume of 0.571 cm 3 ⋅g −1 . Optimal degradation was achieved using 0.004 g of catalyst at pH 6 for MR, and 0.005 g at pH 7 for phenol. In the presence of co-existing inorganic anions (Cl − , S O 2 − 4 , N O − 3 , and H C O − 3 ), the nanocomposite retained over 80% of its catalytic efficiency, demonstrating good ionic tolerance. Furthermore, the catalyst exhibited reliable reusability over five consecutive cycles with robust structural retention and negligible metal leaching (<0.05 mg⋅L −1 ). Radical scavenging assays identified photogenerated holes (h + ) and hydroxyl radicals (•OH) as the primary reactive species. This work highlights a practical approach for fabricating biopolymer-supported photocatalysts targeting dye and phenolic wastewater remediation.