Abstract
The preparation of Li2CO3 from brine with a high mass ratio of Mg/Li is a worldwide technology problem. Membrane separation is considered as a green and efficient method. In this paper, a comprehensive Li2CO3 preparation process, which involves electrochemical intercalation-deintercalation, nanofiltration, reverse osmosis, evaporation, and precipitation, was constructed. Concretely, the electrochemical intercalation-deintercalation method shows excellent separation performance of lithium and magnesium, and the mass ratio of Mg/Li decreased from the initial 58.5 in the brine to 0.93 in the obtained lithium-containing anolyte. Subsequently, the purification and concentration are performed based on nanofiltration and reverse osmosis technologies, which remove mass magnesium and enrich lithium, respectively. After further evaporation and purification, industrial-grade Li2CO3 can be prepared directly. The direct recovery of lithium from the high Mg/Li brine to the production of Li2CO3 can reach 68.7%, considering that most of the solutions are cycled in the system, the total recovery of lithium will be greater than 85%. In general, this new integrated lithium extraction system provides a new perspective for preparing lithium carbonate from high Mg/Li brine.
Highlights
The fast development of electric vehicles, storage devices, and hand-held electronic devices has dramatically increased the demands for lithium [1,2,3,4]
We have proved that the electrochemical intercalation-deintercalation (EID) method shows an excellent lithium extraction properties from the high mass ratio of brine [20,21,33]; the mass ratio of brine can be decreased from the initial 58.5 in the brine to 0.93 in the obtained anolyte
The above results are attributed to the fact that the lithium concentration in the second cycle is lower than that in the first cycle, which leads to more serious polarization of lithium extraction in the second cycle
Summary
The fast development of electric vehicles, storage devices, and hand-held electronic devices has dramatically increased the demands for lithium [1,2,3,4]. Global lithium (Li) demand has reached 180,000 tons of lithium carbonate equivalent in 2015, with forecasts as high as 1.6 M tons by 2030 [6,7]. Most lithium resources in continental brines are found in a small region in South America, often referred to as the “Lithium Triangle” [9,10]. A notable feature of brines in the “Lithium Triangle” region is the low mass ratio of Mg/Li. In contrast, the grade of brine in other regions is much worse. A typical feature of magnesium sulfate subtype brines is the mass ratio of Mg/Li, which has a long span (from tens to hundreds, even more than 1000) [13]. How to effectively realize the separation of magnesium and lithium is the key to produce Li2 CO3 from high Mg/Li brines
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