Recent advances in the recovery of precious metals (Au, Ag, Pd) from acidic and WEEE solutions by solvent extraction and polymer inclusion membrane processes-a mini-review

The growing demand for precious metals, such as gold, silver and palladium, and the depletion of primary metallic resources contribute to the search for new solutions that enable the recovery of these valuable materials from waste electrical and electronic equipment (WEEE), which is now treated as their secondary source. Conventional methods based on high-temperature pyrometallurgical routes are now giving way to hydrometallurgical processes due to their greater accuracy, ease of control and the possibility of planning the metal recovery processes at various scales. Scientists are particularly interested in the precious metal recovery methods based on the utilization of solvent extraction (SE) and polymer inclusion membranes (PIMs) processes, mainly because of their high efficiency and the possibility of using various chemical compounds as extractants and carriers. The article reviews the latest achievements in the applications of SE and PIMs for the recovery of Au(III), Ag(I) and Pd(II) from acidic solutions, including those obtained as a result of leaching WEEE. The limitations and advantages of SE and PIMs processes based on the use of both commercial and non-commercial chemicals are described.