Selective and Sequential Precipitation for Critical Mineral Extraction from Electronic Waste

The recycling of critical materials from electronic waste (e-waste) shows a great potential for urban mining. However, convectional separation methods are often chemical- and energy-intensive as they mainly rely on organic ligands, ionic liquids, and ion-selective membranes and/or electrodes. The sustainable production of valuable critical elements from e-waste requires a paradigm shift away from currently used resource-intensive processes. We present a novel approach based on the coupling of ion diffusion and precipitation kinetics. Simply by placing a mixed salt solution on top of a hydrogel loaded with a precipitating agent, we obtained spatially separated precipitates along the reactor. Our proof-of-concept has been demonstrated for sequentially precipitating transition metals with modeled feedstocks representative of lithium-ion battery cathodes and rare earth elements from NdFeB permanent magnets. We expect this approach to be broadly relevant to chemical separations from complex feed streams and diverse chemistries—enabling more sustainable materials extraction and processing.