Deep eutectic solvent assisted electrodialysis towards selective resource recovery from model spent batteries effluents

Critical minerals will remain major active ingredients to most battery technologies for decades and innovation to improve extractive operations during spent battery effluent recycling must be carried out. Although the recovery of metal-ions in aqueous solutions has been demonstrated with membrane systems, including electrodialysis, process intensification to increase the diffusion rate at the membrane/liquid interface must be achieved to improve recovery efficiency. This manuscript presents a unique approach to increase the rate of recovery and transfer of Li+ and Co2+ ions from a membrane bulk phase to an organic liquid phase by applying deep eutectic solvent (DES) instead of an aqueous solution as the permeate stream during electrodialysis. The DES, based on choline chloride and urea at a molar ratio of 1:2, is considered green and relatively non-toxic valuable for solvent extraction purpose. Here, electrodialysis tests were conducted with this solvent on the permeate side using commercial Neosepta and laboratory-made cobalt selective membranes. The DES significantly affected cobalt transport across the membranes and separation factor which increased from 247 to 516, leading to cobalt recovery as high as 66 %. Furthermore, the use of DES on the permeate side greatly improved the energy efficiency increasing the amount of recovered cobalt per Joule of energy by over 20 %.