Conductive polymer–natural clay nanocomposites for efficient heavy metal removal from aqueous solutions

Water pollution caused by heavy metals such as zinc (Zn(II)), copper (Cu(II)), and cadmium (Cd(II)) poses significant environmental and health risks due to their persistence and toxicity. This study investigates the synthesis and characterization of novel conductive polymer (polypyrrole and polyaniline) montmorillonite nanocomposites (PPy@Mont and PAni@Mont) as efficient adsorbents for heavy metal removal from aqueous solutions. The composites were prepared via intercalation of the polymers into sodium-exchanged montmorillonite using in situ polymerization, yielding materials with enhanced adsorption properties. Comprehensive characterization was performed using XRD, FTIR, TGA, SEM, and EDX spectroscopic and microscopic techniques to confirm successful polymer incorporation and evaluate structural and thermal stability. Batch adsorption experiments assessed the effects of pH, contact time, adsorbent dosage, initial metal concentration, and temperature on the adsorption performance. Both composites exhibited optimal adsorption at pH 7.5 and equilibrium at 110 minutes. PPy@Mont demonstrated higher adsorption capacities for Zn(II) and Cu(II), while PAni@Mont showed superior performance for Cd(II). Adsorption isotherms and kinetic studies revealed that the process aligns with Langmuir and pseudo-second-order models, indicating chemisorption as the dominant mechanism. These findings highlight the potential of PPy@Mont and PAni@Mont as cost-effective, efficient, and reusable adsorbents for heavy metal remediation.