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Electrodialysis of a Lithium Sulphate Solution: An Experimental Investigation


 In the hydrometallurgical recycling of spent lithium-ion batteries, a lithium sulphate solution (Li2SO4) can be obtained as a by-product. Electrodialysis (ED) was employed in this study to split Li2SO4 into lithium hydroxide (LiOH) and sulfuric acid (H2SO4) solutions, which can be reused in the recycling process to create a closed-loop process. A three-compartment ED cell with a dilute channel filled with a Li2SO4 solution and two concentrate channels separately filled with LiOH and H2SO4 solutions was developed. The dilute and concentrate channels were separated by cation-exchange and anion-exchange membranes, respectively. High ion recovery ratios of Li+ and SO42- of 94.3 and 87.5%, respectively, were achieved at a current density of 833 A·m-2. The effects of the current density, inlet concentrations, and initial fluid volume on the overall efficiency of the cell were studied. Electro-osmosis played an important role during ED, particularly on the functioning of the cation-exchange membrane. Increasing the initial solution volume in the concentrated compartments can enhance current efficiency and ion recovery. In conclusion, the present study provides insights into the transport of coupled species through an ED cell, and the findings may guide future designs and operations of ED cells for optimal efficiency.