Separation and utilization of lithium, magnesium, and boron resources from salt lakes through Ionic liquid extraction and CO2 mineralization

Salt lakes are abundant in three crucial resources − lithium(Li), magnesium(Mg), and boron(B). The separation efficiency of these resources is low, the excessive use of acid and the environmental harm caused by the accumulation of magnesium source after Li + extraction still exist. In this work, a new process of step-by-step extraction of B-Li and Mg mineralisation is proposed to separate the three resources. Boron was extracted using 2-ethyl-1,3-hexanediol (EHD) + kerosene, and it was found that the addition of FeCl 3 could significantly improve the boron extraction rate(E). In the R(O:A) = 1:3, 40 %EHD + 60 %kerosene, adding 0.15 mol/L FeCl 3 , after three-stage countercurrent extraction, the E(B 3+ ) reached 99 %, E(Fe 3+ ), E(Li + ) and E(Mg 2+ ) less than 4 %. Tributyl Phosphate (TBP)-Ionic Liquids (ILs)-kerosene-FeCl 3 system was used to extract Li + , the ILs and FeCl 3 existed in the extraction process with a competitive behaviour. The extraction efficiency of lithium was improved by cationic [C 4 mim + ] exchange reaction. Under the conditions of R(O:A) = 1:1, 5 %ILs + 65 %TBP + 30 %kerosene, and three-stage extraction, the E(Li + ) was reached 91 %. (NH 4 ) 2 CO 3 was used to mineralise the magnesium resources. At a reaction temperature of 40 °C, the product was magnesium carbonate trihydrate(MgCO 3 ·3H 2 O) with a smooth surface and rod-like structure, and the conversion rate reached 85 %. At 75 °C, the product was an irregular spheroidal basic magnesium carbonate(4MgCO 3 ·Mg(OH) 2 ·5H 2 O) with a magnesium conversion of 91.7 %.