Study on the recovery of lithium from high Mg²⁺/Li⁺ ratio brine by nanofiltration

An experiment to recover lithium from high Mg²⁺/Li⁺ ratio brine by nanofiltration (NF) was carried out. The combination of Donnan exclusion, dielectric exclusion and steric hindrance governed the mass transport inside the NF membrane. Experimental results showed that NF is an efficient technique to recycle Li⁺ and reduce Mg²⁺/Li⁺ ratio from high Mg²⁺/Li⁺ ratio brine. When content reached 6.0 g/L, operating pressure reached 0.8 MPa and Mg²⁺/Li⁺ ratio in feed was 40, the rejection of magnesium (R(Mg²⁺)) and the separation factor (SF) were 0.96 and 42, respectively. The Mg²⁺/Li⁺ ratio in permeate could be reduced to 0.9, and Li⁺ recovery ratio was 85%. Adding potassium (K⁺) or sodium (Na⁺) to solution can reduce R(Mg²⁺) and SF.