Recovery of lithium from salt-brine eluates by direct crystallization as lithium sulfate

Brine from natural salt lakes (salt brine) is an important source of lithium; consequently the recovery of lithium from brine eluates prepared through Li+ adsorption-desorption is economically important. The present paper describes a study on the direct crystallization of LiSO4 center dot H2O from synthetic and real salt-brine eluates. Thermal evaporation of a sulfate-type synthetic eluate (1400 mM Li+, 61 mM Na+, 6.7 mM K+, 16.7 mM Mg2(+), and 10.0 mM Mn2+), to a degree of concentration (D-con) in excess of 13, produced high purity (97%) Li2SO4 center dot H2O crystals in 54% yield. The addition of ethanol to the eluate resulted in an increased yield of Li2SO4 center dot H2O crystals, but these crystals were of lower purity due to the co-precipitation of other metal sulfates. Two types of eluate were prepared by the batchwise adsorption of Li+ from brine followed by desorption with 2 M sulfuric acid. Evaporation of an eluate with a Li+ concentration of 1370 mM to a D-con of 8.6 at 323 K produced high-purity (97%) Li(2)SO(4)4 center dot H2O crystals in 43% yield after the CaSO4 center dot 2H(2)O had been removed at a D-con, of around 3. The evaporation of the eluate to dryness at 323 K followed by rinsing with water afforded LiSO4 center dot H2O crystals in 83% yield and in 84% purity. This simple evaporation method can be applied to lithium extraction from salt lakes in arid areas.