Amine-functionalized polymeric membrane for selective recovery of Au(III) ions from e-waste leachate: development and performance evaluation: development and performance evaluation

Selective gold recovery from waste printed circuit board (WPCB) leachates is hindered by competing metal ions, low acidity, and solution complexicity. In this study, we developed an amine-functionalized polymeric membrane (APM) incorporating polyethylenimine (PEI) in polyvinyl chloride (PVC) framework to enhance gold selectivity while ensuring chemical and mechanical stability in harsh leachate conditions. The high density of amine groups enables strong Au(III) interactions, enabling preferential adsorption. Characterization via FTIR, XPS, and EDS confirmed the successful amine functionalization, and mechanical testing verified membrane durability. Adsorption experiments with synthetic and real WPCB leachates revealed a q_max of 713.74 ± 6 mg/g at pH 2 and 28 °C, with minimal interference from competing ions. Increasing the temperature to 48 °C raised the q_max to 873.02 ± 8 mg/g. Kinetic analysis followed a pseudo-second-order model, while equilibrium data fit with the Langmuir isotherm. Mechanistic studies with XPS, FTIR, and XRD highlighted the dominance of electrostatic attraction and soft-soft interactions between Au(III) and amine groups. Notably, APM facilitates in-situ Au(III) reduction to Au⁰ without external reducing agents. The membrane retained high performance over multiple adsorption–desorption cycles, confirming reusability and scalability. By overcoming key limitations in gold recovery, this work offers a sustainable and practical approach for high-purity gold extraction from e-waste leachates, contributing to circular economy and resource-efficient recycling.