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.
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