Upcycling PVC and styrofoam waste into adsorptive PVC/SPS composite membranes for efficient Pb(II) and Cr(III) removal

Plastic waste accumulation and heavy-metal contamination of water are two pressing environmental problems. In this work, polyvinyl chloride (PVC) and Styrofoam waste were upcycled into three types of adsorptive composite membranes (ACMs) — PVC, PVC/polystyrene (PVC/PS), and PVC/sulfonated polystyrene (PVC/SPS) — through a simple solution-casting technique and applied for the removal of Pb²⁺ and Cr³⁺ from contaminated water. The fabricated ACMs were characterized by FTIR, XPS, FE-SEM, TGA/DSC, and XRD, and their density, porosity, water uptake, and ion-exchange capacity were evaluated. Adsorption was monitored by atomic absorption spectrometry as a function of contact time, initial metal concentration, temperature, and pH. The adsorptive PVC/SPS membrane achieved the highest removal efficiency, reaching 94.0 ± 0.67% for Pb²⁺ and 91.5 ± 1.30% for Cr³⁺, with sorption capacities following the order PVC 0, and ΔS° > 0) confirmed a spontaneous, endothermic process. The ACMs also exhibited high selectivity against competing cations and retained >90% of their initial activity over five regeneration cycles. These findings demonstrate that PVC/SPS composite membranes offer an economical route for upcycling plastic waste into efficient adsorbents for polluted water treatment.