Waste treats waste: the gold selective extraction from electronic waste utilizing coffee grounds

Achieving economically feasible and eco-friendly gold recovery from electronic waste (e-waste) remains a critical challenge in the field of resource circularity. Spent coffee grounds (SCGs), a globally abundant agricultural waste, are routinely discarded without effective utilization, resulting in resource waste and ecological burden. To address the dual resource waste issue of e-waste and SCGs, this study adopted SCGs as functional adsorbents for exceptional gold extraction capacity and enable eco-friendly recovery of gold from e-waste. SCGs exhibits an optimum adsorption capacity of 4.29 g of gold per gram of SCGs (4.29 g/g) at pH 1 and a high selectivity for Au(III) in the presence of competing ions. Such excellent adsorption performance is attributed to the aromatic structure of SCGs which act as active sites and key electron donors. These structures facilitate gold ion adsorption and simultaneously provide electrons for Au(III) reduction, enabling the spontaneous transformation of gold ions into metallic gold. Technoeconomic analysis verifies the outstanding economic viability of this strategy, with a high input-output ratio of 1386% and considerable net profit. Compared with conventional gold recovery technologies, the proposed approach achieves synergistic valorization of two types of waste, providing a cost-effective and environmentally sustainable solution for e-waste recycling and SCGs upcycling.