Photocatalyst production from modified Scenedesmus algae with zinc oxide nanoparticles for the removal of heavy metals (lead and cadmium) from aqueous solution

Heavy metal pollution poses a severe global threat, demanding sustainable remediation techniques. This study synthesized a novel eco-friendly photocatalyst by incorporating ZnO nanoparticles into modified Scenedesmus algae for efficient Pb²⁺ and Cd²⁺ removal from water via combined adsorption–photocatalytic processes. Performance was evaluated using Central Composite Design (CCD) across ranges of pH (5.0–8.0), photocatalyst dosage (50–150 mg), pollutant concentration (10–50 mg/L) and contact time (60–120 min). Statistical analysis revealed photocatalyst dosage and contact time significantly enhanced removal efficiency, while higher pollutant concentrations decreased it due to active site saturation. Optimal removal occurred near neutral pH (~ 6.5). Under optimal conditions, the ZnO-algal photocatalyst achieved remarkable removal efficiencies of 97% for Pb and 98% for Cd. FESEM imaging confirmed uniform ZnO distribution on the algal surface and an enlarged surface area, crucial for enhanced charge transfer and increased active sites. These results emphasized the significant catalytic improvement by ZnO modification, providing a green, stable, cost-effective and reusable material. This work demonstrated the promising potential of bio-based photocatalysts for sustainable heavy metal remediation and clean water production.