A critical review on membrane extraction with improved stability: Potential application for recycling metals from city mine

Abstract

Mining from the city is one of the future directions for sustainable resource management. The separation of highly dispersed, low concentration valuable metals requires highly efficient extraction technology, where membrane extraction has shown significant advantages owing to its potentially high selectivity and low footprint. This review summarizes the recent progress in membrane extraction with respect to the development of membrane materials and the process configurations with special focus on preventing the loss of the organic extractant and/or degradation of the membrane materials. Prior research work was reviewed first on the development of various membrane materials for extending the membrane performance. Further developments on membrane configuration and process are presented on ion exchange membranes and membrane contactors, and composite hollow fiber membranes where the advantages and problems are stressed. Hydrophilic/hydrophobic blend polymers and block co-polymers have shown much more extended lifetime, which is a potential development direction. In summary, this review provides not only the recent development on membrane materials but also the application process/scheme that can help to improve the performance of membrane extraction, which might be beneficial for a broad audience ranging from academic scientists and industrial engineers who are looking for pioneering alternative solutions for city mining.