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

Abstract 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 Li 2 SO 4 ·H 2 O 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 Mg 2 + , and 10.0 mM Mn 2 + ), to a degree of concentration ( D con ) in excess of 13, produced high purity (97%) Li 2 SO 4 ·H 2 O crystals in 54% yield. The addition of ethanol to the eluate resulted in an increased yield of Li 2 SO 4 ·H 2 O 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 ·H 2 O crystals in 43% yield after the CaSO 4 ·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 Li 2 SO 4 ·H 2 O crystals in 83% yield and in 84% purity. This simple evaporation method can be applied to lithium extraction from salt lakes in arid areas.