High value-added resource utilization of solid waste: Review of prospects for supercritical CO2 extraction of valuable metals

With the reduction of available minerals, rare and precious metals recovered from waste are gradually becoming an effective alternative to the circular economy. Supercritical CO2 extraction is a novel, promising, and environmentally friendly method that can be used to address environmental issues brought by conventional metal extraction methods. This paper reports the role of rare and precious metals, reviews the pathways to recover valuable metals from “secondary resources”, discusses the key technical and environmental challenges of common approaches in the recovery of valuable metals by taking smelting soot as an example, and then highlights the potential of supercritical CO2 technology to extract valuable metals from solid waste. Furthermore, the research progresses of supercritical CO2 extraction technology are summarized, and the prospects for developing a green supercritical CO2 extraction technology are discussed from multiple perspectives, including process, device, influencing factors, mechanism, and application. By analyzing valuable metal extraction from solid waste and supercritical CO2 technology in detail, this paper provides useful theoretical support for effectively utilizing the resources in solid waste and developing potential resources in rare and precious metals.