Lead biosorption from industrial wastewater using Cladophora

Discharge of wastewater containing lead ions poses serious risks to plants, aquatic organisms, and human health. Conventional heavy metal removal methods, such as membrane filtration and activated carbon adsorption, are often costly and less effective at trace concentrations. This study investigates the biosorption potential of three adsorbents: the green alga Cladophora glomerata (CGM) collected from the Red Sea (Egypt), silicon dioxide (SiO₂) nanoparticles, and a hybrid composite of CGM with SiO₂ nanoparticles, for lead removal from industrial wastewater. The adsorbents were characterized using SEM and FTIR, and the effects of pH, adsorbent dose, and other operating parameters (temperature: 20 ± 2 °C, stirring speed: 300 rpm, contact time: 60 min, and initial lead concentration: 20 mgL^- 1) were investigated. CGM achieved 100% removal efficiency at pH 5.0 with a biomass dose of 1.3 g/L, while SiO₂ nanoparticles achieved the same efficiency at 0.5 g/L. The hybrid composite reached 97.79% efficiency at 0.7 g/L, suggesting possible competition for adsorption sites. Kinetic studies indicated that the biosorption followed the pseudo-second-order non-linear model with high correlation coefficients (R² = 0.998, 0.998, and 0.9998 for CGM, SiO₂, and the hybrid, respectively). These findings highlight the strong potential of algae-based, nanoparticle-based, and hybrid biosorbents as cost-effective and environmentally friendly solutions for surface water treatment and wastewater post-treatment.