Efficient Gold Recovery from E-Waste via a Chelate-Containing Porous Aromatic Framework

Extracting gold from wastes of electronic equipment (e-waste) is a sustainable strategy for the recovery of the precious metal, reducing environmental pollution, and addressing the growing demands for gold resources. In this work, we synthesized a thiourea-modified porous aromatic framework (PAF-1-thiourea) with exceptional gold-extraction ability. The optimum adsorption capacity for PAF-1-thiourea to gold reaches up to 2629.87 mg g-1. The adsorption process can be well fitted according to the pseudo-second-order kinetic model and Langmuir model, featuring strong affinity caused by strong soft-soft interactions between Au(III) and the S and N donor atoms of the modified PAF and the electrostatic interactions between protonated amino groups and AuCl4-. PAF-1-thiourea was especially capable of extracting gold rapidly and efficiently (capturing 98.73% of gold within 5 min) from a central processing unit (CPU) in extremely acidic conditions. It is found that PAF-1-thiourea captures gold ions and simultaneously converts it to a Au(0) solid, obtaining gold with purity up to 23.5 karat. PAF-1-thiourea with its high acid resistance and anti-interference against cheap metals in the recovery process presents a practical means to extract gold from e-waste.