Removal of calcium and magnesium from lithium brine concentrate via continuous counter-current solvent extraction

The effect of the operating parameters (pH, temperature, phase ratio, and residence time) were studied in a bench-scale two-stage continuous counter-current setup with both reagents. The overall performance was good, yielding ppm impurity levels in terms of Ca and Mg and, typically, 3-5% Li co-extraction. While the Mg extraction could be increased by increasing the pH in the mixers and decreasing the A/O phase ratio, the Li co-extraction would also be increased. A compromise must be made between purity and Li yield. Decreasing the temperature or residence time did not have a significant effect on performance. It was demonstrated that a high throughput can be achieved because a mixer residence time of 2 min or even less can be used.