Extraction of lithium from salt lake brine containing boron using multistage centrifuge extractors

Lithium extraction process from salt lake brine containing H3BO3 was investigated in this paper. The extraction, scrubbing, stripping and regeneration processes were studied respectively, using N, N-bi-(2-ethylhexyl) acetamide (N523) and tri-butyl phosphate (TBP) as the extractant, kerosene as diluent and FeCl3 as co-extractant. H3BO3 present in the brine could be extracted by TBP in the extraction stage. The presence of H3BO3 had no significant effect on lithium extraction efficiency and separation effect between lithium and magnesium. The main portion of the extracted H3BO3 could be scrubbed in the scrubbing stage, magnesium could be nearly scrubbed completely. The whole extraction process experiment and magnified experiment were conducted on separating funnels and centrifugal extractors, respectively, and no third phase appeared. The lithium extraction rate reached 96%. The Mg/Li mass ratio changed from 48 in salt lake brine to 0.0015 in the stripping liquor, meanwhile, H3BO3/Li mass ratio changed from 5.6 to 0.018. The stripping liquors contained 28 g/L Li+ with small amounts of H3BO3, and other impurity ions. This study indicated that the presence of H3BO3 in salt lake brine had no significant influence on lithium extraction and quality of stripping liquors. Furthermore, it was shown that centrifugal extractors were effective in the lithium extraction process.