Potential water recovery during lithium mining from high salinity brines

Area of Science:

• Geochemistry
• Environmental Engineering
• Chemical Engineering

Background:

• Traditional lithium extraction from continental brines relies on large-scale evaporation ponds, raising significant environmental concerns due to substantial water loss.
• Integrating desalination processes offers a potential solution for concentrating lithium brines while simultaneously recovering fresh water.

Purpose of the Study:

• To evaluate the feasibility of using advanced desalination techniques for lithium-rich brine concentration.
• To estimate the thermodynamic properties and energy requirements for desalination of various brines.
• To assess the impact of brine composition on the efficiency of desalination and lithium recovery.

Main Methods:

• Application of the Pitzer thermodynamic model with effective molality to estimate activity coefficients for native brines.
• Calculation of the least work of separation for hypothetical advanced desalination processes.
• Prediction of thermodynamic properties such as boiling point elevation, vapor pressure lowering, and osmotic pressure.

Main Results:

• Rational activity coefficients significantly deviate from unity for all tested brines.
• The least work of separation ranges from 18 to 42 kJ kg⁻¹ at zero recovery, increasing with higher recovery ratios.
• Brine chemical composition, particularly the concentration of divalent ions (Mg-Ca-SO₄²⁻), strongly influences separation work and thermodynamic properties, not just total dissolved solids.

Conclusions:

• Desalination presents a viable, integrated system for simultaneous fresh water and lithium mineral production.
• The Pitzer model provides accurate thermodynamic predictions crucial for optimizing brine processing.
• Specific brine chemistry dictates the energy requirements and efficiency of integrated lithium extraction and water recovery systems.