High-efficiency gold recovery from electronic waste with 2D silicon nanosheets†

Electronic waste (e-waste) has become one of the fastest-growing solid waste streams globally, with most e-waste containing significant quantities of high-value yet environmentally hazardous substances, particularly noble metals exemplified by gold (Au). These elements not only pose a potential threat to the environment and human health but also carry substantial economic value. Thus, the efficient and eco-friendly recovery of noble metals from e-waste can simultaneously mitigate environmental pollution and generate significant economic benefits. In this work, silicon—the second most abundant and cost-effective element in the Earth's crust—was utilized to synthesize two-dimensional silicon nanosheets (SiNSs) capable of highly efficient gold ion extraction. The SiNSs demonstrated exceptional extraction capacities (as high as 1500 mg Au per gram of SiNSs) at low concentrations (10 ppm). The redox-mediated mechanism governing Au extraction exhibited a lower energy barrier than traditional chemisorption. Furthermore, a continuous-flow extraction device was engineered, in which SiNS membranes maintained remarkable extraction performance even for ultralow-concentration Au ions (100 ppb).