Rapid capture of trace precious metals by amyloid-like protein membrane with high adsorption capacity and selectivity

Abstract

Current technologies for recovering precious metals suffer from high energy consumption, poor adsorption selectivity, slow adsorption kinetics, poor recyclability and expensively complex recovery processes. Thus, there is an urgent need to develop an ecofriendly system to recover precious metals from resources (e.g., ores, waste electrical components or wastewater) with high capacity and low cost. Here, we report a protein-based bilayer membrane made from the one-step aqueous self-assembly of phase-transitioned lysozyme that can efficiently sequester gold ions from dilute aqueous solutions (0.1 to 400 ppm). Notably, this membrane, with a special design of top microparticles and bottom nanomembrane layers, has a cost comparable to that of activated carbon, and exhibits an adsorption capacity for gold of 1034.4 mg g⁻¹, which is 3–15 times higher than those of the most-utilized industrial adsorbents, such as activated carbon and ion exchange resins. The high adsorption capacity for gold could be further extended to other primary precious metals, and high selectivity towards precious metals was simultaneously maintained when extracting precious metals at <1 ppm from ores or waste electrical leachate solutions containing a large amount of competing metal ions. Without the extra addition of any reductants, the membrane could be further directly used to reduce the adsorbed gold ions, affording gold with a final purity of 23 K (95.8 wt%) after pyrolysis.