Lithium Separation and Up-concentration from Battery Recycling Effluent by Synergistic Solvent Extraction

Abstract

Exponential growth in the electric vehicle (EV) market warrants a stable supply of certain materials including lithium (Li). Due to its criticality and environmental concern, Li recycling from spent batteries is justified. Although there are several industrially established schemes for end-of-life battery recycling, major drawbacks are still encountered regarding Li recovery. In most recycling schemes, Li stands to be the last element that is recovered. This causes major loss of Li during the process and high energy is consumed to recover it from the final effluent i.e. evaporation, rendering Li recovery economically unattractive. Evaporation is generally applied to up-concentrate Li in the effluent to attain the minimum concentration required to induce precipitation and crystallization in Li salt production. In this research, solvent extraction is being proposed as a low energy alternative in Li up-concentration and separation from recycling effluent. The synergistic effect between 2-thenoyl trifluoro acetone (HTTA) and trioctylphosphine oxide (TOPO) as extractants in kerosene as diluent has been tested in batch studies to increase Li concentration in the final solution. Optimal extraction conditions reported include HTTA/TOPO mol ratio 1, shaking speed 250 rpm, extraction time 10 min, aqueous/organic volume ratio 1 and pH 10.1 (Li extraction rate 55.6 %). The maximum loading capacity of organic phase for Li was 1.2 g/L and complete stripping of Li could be achieved using 0.5 M sulfuric acid. It was demonstrated that the solvent extraction scheme can increase Li concentration in the effluent from 0.23 g/L to 10.06 g/L, which is suitable concentration for Li salt production by further precipitation or crystallization.