Continuous multicolumn ion exchange process for spent lithium-ion battery leachate: Recovery and purification of a Li+Ni+Co mixture

Abstract

A continuously operated ion exchange process scheme for the recovery and purification of valuable metals from acid leachates of spent Lithium-ion battery cathodes was developed. The aim is to provide a versatile and industrially feasible alternative for liquid-liquid extraction and precipitation for recycling of spent Li-ion batteries. A chelating resin with aminomethylphosphonic acid functional group (Lewatit® MDS TP 260) was used in a laboratory-scale multicolumn configuration that combined counter-current and cross-current operations. The process was operated at 60°C with a synthetic leachate with pH 1.8 as the feed. A two-step desorption procedure (1.0 M sulfuric acid (H2SO4) followed by 0.4 M potassium oxalate (K2C2O4)) was found to prevent accumulation of strongly bound metals in the resin. 1 M H2SO4 was found sufficient for regeneration. Pure raffinate containing Li, Ni, and Co was successfully separated from impurity metals (Mn, Cu, Al, and Fe). In steady state operation, no loss of ion exchange capacity was observed. The process was optimized experimentally with focus on the effect of fresh feed and eluent flow rates to increase the productivity and improve the recovery rates of the target metals while maintaining a raffinate purity of 100 %. Increasing the amount of leachate processed per switch was found to enhance the recovery of Co, Li and Ni due to the displacement effect. Very high recovery yields (96.97 % for Co, 99.15 % for Ni, and 100 % for Li) were achieved. The laboratory scale unit could process 1.64 L (L·h)-1 of leachate to yield 34.04 g (L·h)-1 of Li+Ni+Co mixture in the raffinate. Moreover, Cu+Mn and Al+Fe rich extract streams with 84.74 % and 97.46 % purities were obtained as by-products. With respect to the recovery rates, the continuous ion exchange process is superior to batchwise operation of ion exchange columns, conventional solvent extraction and not to mention precipitation processes making it a viable alternative in hydrometallurgical LIB recycling.