Recovery of lithium from Uyuni salar brine

A hydrometallurgical process was developed to recover lithium from a brine collected from Salar de Uyuni, Bolivia, which contains saturated levels of Na, Cl and sulphate, low Li (0.7-0.9 g/L Li) and high Mg (15-18 g/L Mg). Unlike other commercial salar brines currently being processed, the high levels of magnesium and sulphate in Uyuni brine would create difficulties during processing if conventional techniques were used. A two-stage precipitation was therefore first adopted in the process using lime to remove Mg and sulphate as Mg(OH)(2) and gypsum (CaSO4 center dot 2H(2)O). Boron (at 0.8 g/L in the raw brine), a valuable metal yet deleterious impurity in lithium products, could also be mostly recovered from the brine by adsorption at a pH lower than pH11.3 in this first stage. The residual Mg and Ca (including that added from lime) which were subsequently precipitated as Ca-Mg oxalate could be roasted to make dolime (CaO.MgO) for re-use in the first stage of precipitation. Evaporation of the treated brine up to 30 folds would produce 20 g/L Li liquors. The salt produced during evaporation was a mixture of NaCl and KCl, containing acceptable levels of sulphate, Mg, Ca, etc. The final precipitation of lithium at 80-90 degrees C produced a high purity (99.55%) and well crystalline lithium carbonate. (C) 2012 Elsevier B.V. All rights reserved.