Innovative lithium recovery technique from seawater by using world-first dialysis with a lithium ionic superconductor

• New method for Li recovery from seawater is proposed using the world-first dialysis. • Li ionic superconductor as the Li separation membrane (LISM) was used. • Only Li ions can permeate the LISM. • The Li recovery ratios to approximately 7% after 72 h with no electrical supply. • Li separation process generates electricity, requiring no external power source.

Carbon felt Fig. 5. Overview of the world-first dialysis system with LISMs. seawater is approximately 4.25 mg. After 30 days of dialysis, the amount of Li in recovery solution was approximately 2.1 mg, and Li recovery ratio was 49.4%. 3.3. Fabrication of Li2CO3 Li carbonate (Li2CO3) is used as the raw material for Li ion batteries and similar products, and Li2CO3 is known to be easily handled. Thus, it is preferable to recover Li in the form of Li2CO3; however, in the world-first dialysis proposed in this study, Li2CO3 precipitates when it is generated in the HCl recovery solution. Because the circulation of HCl is necessary in this method, it is preferable that Li2CO3 is not formed in HCl solution. Li2CO3 can be easily generated by the following reaction: LiCl ðaqÞ þ Na2 CO3 ðaqÞ→Li2 CO3 ðprecipitationÞ þ NaCl ðaqÞ: ð2Þ In other words, Li2CO3 and sodium chloride (NaCl) are generated by allowing Li chloride (LiCl) to react with sodium carbonate (Na2CO3; Fig. 7). It is desirable that LiCl be in the aqueous form in which it exists as Li and Cl ions. Accordingly, by forming the recovery HCl solution after treatment as a Li chloride aqueous solution, the above reaction (2) can be initiated by the addition of Na2CO3 aqueous solution; in this manner, Li2CO3 can be extracted as a precipitate from this aqueous solution. In this study, the recovery HCl solution was transferred to another container for heat treatment and the aqueous Na2CO3 solution was added after the Li concentration reached 10%.