Potential water recovery during lithium mining from high salinity brines

BASPINEIRO, CELSO F.; FRANCO, JUDITH; FLEXER, VICTORIA

THE SCIENCE OF TOTAL ENVIRONMENT

ELSEVIER

Año: 2020 vol. 720 p. 1 - 13

0048-9697

Lithiumextraction fromcontinental brines involves the evaporation of large amounts of water in open air ponds, in order to concentrate the brine. The evaporitic technology implies the evaporation of largewater volumes, raisingenvironmental concerns. Ifwe envision the use of desalination processes for the concentration of lithium-rich brines, then fresh water production/recovery becomes a processwell integratedwith lithiumextraction.Herewe apply the Pitzer thermodynamicmodelwith effectivemolality to estimate activity coefficients for 8 different native brines, and for the resulting concentrated solutions produced by a hypothetical advanced desalinization technique. In all cases, rational activity coefficients deviate considerably from unity.We calculate next the least work of separation for a hypothetical desalination process for the 8 different brines. Because of the large total salinity, the calculation shows that the least work of separation ranges from18 until 42 kJ kg−1 at nil recovery ratio,and escalating from those numbers as more water is recovered.We can also predict the boiling point elevation, the vapour pressure lowering, and the osmotic pressure. Our calculations show that results are not strictly proportional to the total dissolved solids. Results are strongly dependent with the specific chemical composition of each brine, with the amount of divalent ions (Mg-Ca-SO4 2−) in particular strongly influencing calculations.Fresh water and lithium minerals production could be part of a single integrated production system.