A hydrometallurgical process for the separation of aluminum, cobalt, copper and lithium in acidic sulfate media

Abstract

Acid leach liquors from spent lithium-ion batteries that use lithium cobalt dioxide (LiCoO2) as a cathode active material contain valuable metals such as cobalt and lithium, as well as common metals such as aluminum and copper. The objective of this study was to develop a hydrometallurgical process that provides a degree of high selectivity between aluminum, cobalt, copper, and lithium from acidic sulfate media.The results from batch experiments showed that a selective hydroxide precipitation approach was not suitable because a significant amount of cobalt was coprecipitated with aluminum and/or copper hydroxides. In contrast, batch experiments and the subsequent data analysis indicated that the sequence of solvent extraction circuits using PC-88A, Acorga M5640, and tri-n-octylamine (TOA) extractants effectively separates four metals of interest. In the first circuit of the proposed process, copper was selectively extracted by Acorga M5640 at pH 1.5–2.0. Aluminum, cobalt, and lithium remained in the aqueous phase. In the second circuit, aluminum was selectively extracted by PC-88A at pH 2.5–3.0. For separation of the remaining cobalt and lithium, Acorga M5640 provided higher cobalt selectivity (separation factor could not be accurately obtained due to negligible lithium extraction) compared to PC-88A (βCo, 90%/Li=350 at pH 4.5) and PC-88A/TOA (βCo, 90%/Li=1,170 at pH 5.4). However, the stripping efficiency of cobalt from the Acorga M5640 organic phase was found to be low (less than 10%). Therefore, the PC-88A/TOA mixed extractant rather than Acorga M5640 is a suitable choice for the separation of cobalt and lithium.