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

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, X-ray diffraction, transmission electron microscope, Fourier transform infrared, and X-ray photoelectron spectroscopy analyses. To enable adsorbent recycling, 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 the 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.