Chitosan–PVA composite reinforced with Cu-decorated ZnO nanoparticles for photocatalytic dye degradation

This study presents a chitosan–polyvinyl alcohol (PVA) composite reinforced with copper-decorated zinc oxide (ZnO–Cu) nanoparticles for wastewater treatment. ZnO–Cu was synthesised via photocatalytic reduction using Cu(NO₃)₂ and CuSO₄·5H₂O salts and incorporated (0.1–0.5 wt%) into a grafted chitosan–PVA matrix. Characterisation (DLS, FT-IR, SEM-EDX, TEM, XRD, thermal analysis) confirmed uniform nanoparticle decoration, crystalline stability, and homogeneous dispersion within the polymer. Photocatalytic activity was assessed by Rhodamine B (RhB) degradation under UVA and visible light. Optimal conditions (pH 5, 2.0 g/L catalyst) achieved 72.1% RhB removal within 90 min, following pseudo-first-order kinetics (k = 0.0125 min⁻¹, R² = 0.9843), nearly double the rate of pure ZnO–Cu (0.0060 min⁻¹). The composite showed good recyclability, retaining over 80% activity after five cycles. Antioxidant assays revealed strong DPPH radical scavenging (85% at 100 µg/mL). Antimicrobial tests indicated moderate antifungal effects against Fusarium oxysporum but limited antibacterial activity, likely due to nanoparticle encapsulation. Overall, the ZnO–Cu/chitosan–PVA composite combines efficient photocatalysis, reusability, and antioxidant activity with a biodegradable support, offering a cost-effective and scalable strategy for dye and organic pollutant removal in wastewater remediation.