Mechanism and process for the extraction of lithium from the high magnesium brine with N,N-bis(2-ethylhexyl)-2-methoxyacetamide in kerosene and FeCl3

The degradation of TBP has become a stumbling block to the industrial continuous production of lithium chloride extraction from brines with high Mg/Li ratio by solvent extraction. To develop a more stable and more efficient extraction system, a novel amide system, containing newly synthesized extractant N,N-bis(2-ethylhexyl)-2-methoxyacetamide (NBEHMOA), FeCl3 6H2O and sulfonated kerosene, was proposed in this work. Compared with TBP and N523, NBEHMOA extracted Li+ and H+ in the sequence of TBP ˃ NBEHMOA ˃ N523 and N523 ˃ TBP ˃ NBEHMOA respectively. The solution containing 5.5 mol/L LiCl and 0.5 mol/L HCl was used as the eluent in the scrubbing process. A Li+ extraction efficiency of 96.7% and 22.31 g/L Li+ in the stripping solution were achieved by the whole process with counter-current twelve stages. The extraction mechanism investigated via FT-IR spectroscopy illustrated that the metal ions Fe3+ and Li+ were mainly coordinated by the carbonyl C = O in NBEHMOA. This novel amide system can successfully achieve the cascade extraction effect for lithium, Li/Mg separation and avoid the generation of phase interface objects through counter-current extraction of lithium from brine at a lower acidity. This work provided a novel extraction system to recover lithium from the higher magnesium/lithium ratio brines.