Selective Recovery of Gold from E-Wastewater Using Poly-<i>m</i>-phenylenediamine Nanoparticles and Assembled Membranes

Abstract

The economic value of recovering gold from electronic waste (e-waste) has generated significant interest, but selective capture of gold from complex acidic electronic leaching solutions remains challenging. Here, we synthesized Poly-m-phenylenediamine (PmPD) nanoparticles with a positively charged surface and amino functional groups, resulting in an adsorption capacity of 2063 mg/g for Au(Ⅲ) in acidic solutions, superior to most traditional adsorbents. Electrostatic adsorption and reduction were identified as the adsorption mechanism for Au(Ⅲ) by zeta potential, XRD, TEM, FT-IR, and XPS analyses. To enable adsorbent recycle, PmPD nanoparticles were assembled into adsorptive membranes and used for gold recovery from e-wastewater via a continuous-flow membrane separation process. The PmPD membrane achieved a dynamic gold recovery capacity of approximately 530 mg/g and could be effectively regenerated after washing with a mixture of thiourea and HCl. We demonstrated the practical application of the adsorptive membranes by recovering about 100% of gold from the leaching solution of waste printed circuit boards of computers. Finally, the recovered gold nanoparticles on PmPD membrane were used to catalyze the degradation of p-nitrophenol, showcasing the catalytic property of gold. The Au@PmPD membrane loaded with 4 mg gold exhibited a high catalytic reduction performance with an apparent rate constant of 0.59 min−1 , one of the highest catalytic degradation rate constants of p-nitrophenol reported to date. Our study presents an effective and economical approach for recovering gold from e-waste, providing a prototype of resource recovery and reuse.