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 FeCl3 could significantly improve the boron extraction rate(E). In the R(O:A) = 1:3, 40 %EHD + 60 %kerosene, adding 0.15 mol/L FeCl3, after three-stage countercurrent extraction, the E(B3+) reached 99 %, E(Fe3+), E(Li+) and E(Mg2+) less than 4 %. Tributyl Phosphate (TBP)-Ionic Liquids (ILs)-kerosene-FeCl3 system was used to extract Li+, the ILs and FeCl3 existed in the extraction process with a competitive behaviour. The extraction efficiency of lithium was improved by cationic [C4mim+] 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 %. (NH4)2CO3 was used to mineralise the magnesium resources. At a reaction temperature of 40 degrees C, the product was magnesium carbonate trihydrate (MgCO3 center dot 3H2O) with a smooth surface and rod-like structure, and the conversion rate reached 85 %. At 75 degrees C, the product was an irregular spheroidal basic magnesium carbonate(4MgCO3 center dot Mg(OH)2 center dot 5H2O) with a magnesium conversion of 91.7 %.