Process for obtaining monohydrated lithium sulfate from natural brines

A process for obtaining monohydrated lithium sulfate from brines from natural salt deposits which comprises the following steps:

• a) evaporating two samples of the brines by solar evaporation in order to obtain a first brine which is saturated or substantially saturated with silvinite (NaCl, KCl), monohydrated lithium sulfate (Li2SO4.H2O), and carnallite (KCl MgCl2.6H2O) and which has a lithium content of 0.8-1.2% by weight, 4.7-6% magnesium, and 1.2-4.0% total sulfate, and a second brine that is saturated or substantially saturated with carnallite (KCl MgCl2.6H2O), monohydrated lithium sulfate, and bischofite (MgCl2.6H2O), and which has a lithium content of 2.5-6% by weight, less than 6% magnesium, and less than 0.2% total sulfate;
• b) independently heating the first and second brines at a temperature of between 0 and 100° C.;
• c) mixing the first and second brines in order to produce a third brine with lithium content equal to or greater than 2% by weight, whereby the saturation value of monohydrated lithium sulfate in the brine mixture is exceeded;
• d) crystallizing the monohydrated lithium sulfate from the resulting third brine in a crystallizer;
• e) separating the third brine by recovering fine monohydrated lithium sulfate crystals from overflow of the cyrstallizer in a sedimenter and separating the monohydrated lithium sulfate crystals from the overflow of the crystallizer from overflow of the sedimenter in a solid-state separation device;
• f) filtering and washing the monohydrated lithium sulfate crystals on a filter with water or a filtrate solution from a second filtration and washing of step (h) of the monohydrated lithium sulfate crystals;
• g) re-pulping the monohydrated lithium sulfate crystals with water or a filtrate solution from the second filtration and washing of step (h) of the monohydrated lithium sulfate crystals;
• h) filtering and washing with water the monohydrated lithium sulfate crystals, whereby the filtrate solution is recycled to the previous re-pulping of step (g) and to the first filtration and washing of step (f) of the monohydrated lithium sulfate crystals;
• i) drying the monohydrated lithium sulfate crystals of step (h) with air or hot gas;
• j) re-circulating separated third brine from the solid-state separation device of step (e) with overflow from the sedimenter of step (e) and the wash water from the first filtration of step (f) for solar evaporation and recycling the evaporated brine back to the process in order thereby to increase the overall recovery of lithium from the brines.