Mineral salts removal and lithium traces determination in highly concentrated solutions and natural brines.

The usual methods, of lithium traces determination, refer in particular to the aqueous solutions whose dry residues do not exceed 7gL(-1). Flame spectrometry or atomic absorption is used for the determination of the considered element. In the case of natural brines, the total dissolved salt ranges from 250 to 350gL(-1). Consequently the determination of lithium traces in this kind of solutions, by the above mentioned spectroscopic methods, may be disturbed due to interferences phenomena. So, a preparatory processing step of the samples is needed. In order to prevent the mentioned phenomena, the total or partial removal of mineral salts, by adding appropriate organic solvent, is carried out. Accordingly, it is significant to make sure that the total quantity of lithium remains in the solution. Therefore, the experimental conditions (sulfate ion removal, solvent ratio and solid-liquid contact time) are optimized. After that the different experimental steps are arranged to make sure the lithium determination, by flame spectrometry, practicable. Finally, the established method is applied firstly to determine Li(+) in some natural brines and secondly to estimate the lithium reserves in the Tunisian natural brines deposits.