Supercritical CO2 extraction of critical and strategic metals: a review of mechanisms, factors and application

With the rapid development of new energy and manufacturing industries, the demand for critical and strategic metals such as rare earths, lithium, cobalt, nickel, manganese, palladium, copper, and uranium has increased significantly. In the context of a low-carbon economy, the green and efficient recovery of these essential resources has received growing attention. Supercritical carbon dioxide (scCO₂) is regarded as a highly selective, environmentally friendly, and promising extraction technology. It is considered effective for addressing the environmental and energy challenges present in conventional extraction processes. In this paper, a detailed overview of the extraction principles and equipment related to scCO₂ is provided. Recent progress in the extraction of strategic metals using scCO₂ is systematically summarized. Key factors influencing extraction efficiency, including process conditions and additives, are reviewed along with their underlying mechanisms. Finally, the prospects for further development of scCO₂ extraction are discussed from the perspectives of extraction mechanisms, extractant design, and equipment optimization. Through this review, new insights are offered for the green and efficient utilization of critical and strategic metal resources.