Gold recovery at Ultra-high Purity from Electronic Waste Using Selective Polymeric Film

Abstract

We propose a sustainable Au recovery technology from e-waste with high purity and probe recyclability, which is established on a selective coordination-based colorimetric probe immobilized on the surface of a quartz substrate to form a thin polymeric film (F1). In particular, the N,N'-dimethylacrylamide (DMA), (E)-2-(methyl(4-(phenyldiazenyl)phenyl)amino)ethyl acrylate (M1), and N-(4-benzoylphenyl)acrylamide (BPAm) are copolymerized by free radical copolymerization to yield the polymeric probe [p(DMA-co-M1-co-BPAm)] (designated as P1). M1 contains a selective 1:1 Au binding site. P1 exhibited sensitive and selective colorimetric responses toward Au(III) in aqueous media with naked-eye detectability via a color change from yellow to brick-red. The immobilized film, F1, was able to determine the presence of Au(III) in various e-waste samples via the color changes, which is in turn used to decide if further Au recovery is lucrative. Thereafter, trace amounts of Au at ultra-high purity (23.97 K) with Au(III) extraction capacity up to 0.40 g Au(III)/g F1 are rapidly recovered (10 min) even in the presence of an approximately 100-fold excess of other metal ions (copper and nickel) commonly found in e-waste without the use of harsh acids, bases, or toxic methods. Au(III)-liberated F1 can be used to further recover Au(III), and this process was repeated for multiple cycles.