Lithium extraction from carbonate-rich Salt Lake brine using HBTA/TBP system

Abstract

China's salt lakes hold significant lithium reserves, yet the development of low-concentration lithium resources from the carbonate brines in Tibet is a pressing matter. Alkyl β-diketones extractants are capable of efficiently extracting lithium from alkaline solutions using an extraction method, but its optimized extraction prerequisite is an extreme alkaline solution with higher pH. This research introduces a process for the effective extraction and separation of lithium and sodium from the carbonate brine of Jieze Caka Salt Lake, utilizing trifluorinated β-biketone HBTA (4,4,4-trifluoro-1-phenyl-1,3-butanedione)–TBP (tributyl phosphate)/kerosene system. A three-stage extraction yielded 98.06% of Li⁺ and 1.69% of Na⁺ from the initial brine with a lower pH of 8.961 and a separation factor (β_Li/Na) of 2948. The simplified process was then implemented using organic direct recycling without regeneration and scrubbing raffinate reflux for a total of 23 cycles, thereby demonstrating the exceptional effectiveness and stability of this system. The resulting lithium-rich stripping solution, with the Li/Na mass ratio amplified by 747 times, underwent further magnesium removal and precipitation using sodium carbonate to yield a high-purity lithium carbonate product of 99.50%. This study offers a novel approach and technology for the efficient separation of lithium ion directly from a partial-neutral carbonate salt lake with a high Na/Li ratio and low lithium concentration.

Graphical abstract