Selective Separation of Metal Ions via Bipolar Membrane Electrodialysis Coupled with Chelation

提出了一种从溶液中分离金属的新工艺，并将其应用于锂钴混合溶液中，如废旧锂离子电池的回收。当在锂离子和钴离子的混合液中加入螯合剂乙二胺四乙酸(EDTA)时，几乎所有的钴离子都被EDTA络合形成阴离子，而锂离子几乎不被络合，在pH=4时。料液的电渗析采用三室式电渗析系统，由两个离子交换膜和一个双极膜组成。利用外加电场，锂被输送到锂回收电池，钴被输送到钴回收电池。回收槽中各金属的选择性约为99%。将该分离体系应用于Li-Co-Mn和In-Al系，研究了该体系的分离性能。

A new type of process for separating metals in solution is proposed, and applied to a mixed solution of lithium and cobalt, as in the recycling of waste lithium-ion batteries. When a chelating agent, ethylenediaminetetraacetic acid (EDTA), was added to a mixed solution of lithium ions and cobalt ions, almost all the cobalt ions were chelated by EDTA to form anions, whereas lithium ions were hardly chelated, at pH > 4. Electrodialysis of the feed solution was conducted using a three-cell-type electrodialysis system, with a unit consisting of two ion-exchange membranes and a bipolar membrane. Lithium was transported to the lithium recovery cell and cobalt was transported to the cobalt recovery cell, using an applied electric field. The selectivity for each metal in the recovery cell was about 99%. The separation system was also applied to Li-Co-Mn and In-Al systems, and its separation performance was studied.e