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.

In order to recover lithium from brine with a high Mg²⁺/Li⁺ ratio, a positively charged nanofiltration (NF) membrane was prepared by depositing polydopamine (PDA)-coated graphitic carbon nitride (g-C₃N₄) as the interlayer (PDA-g-C₃N₄) and the interfacial polymerization (IP) of polyethyleneimine (PEI) and trimesoyl chloride (TMC) was carried out. Under optimal conditions, the water contact angle of the composite membrane is only 55.5° and the isoelectric point (IEP) is 6.01. The final positively charged NF membrane (M5) exhibits high permeance (10.19 L·m⁻²·h⁻¹·bar⁻¹) and high rejection of Mg²⁺ (98.20%) but low rejection of Li⁺ (13.33%). The separation factor (SF) is up to 48.08, and the Mg²⁺/Li⁺ ratio of the permeate is 0.036 in the simulated brine. In conclusion, the M5 membrane shows a good separation performance for salt lake brine (SF = 12.79 and Mg²⁺/Li⁺ ratio of the permeate = 1.43) and good fouling resistance. Therefore, the positively charged M5 membrane with PDA-g-C₃N₄ as the interlayer has the potential to be used for the recovery of lithium from brine.

Maleic anhydride-modified homopolymerized polypropylene (PP-g-MAH) and maleic anhydride-modified polyolefin elastomer (POE-g-MAH) were used as bulking agents to improve the poor processing and mechanical properties of highly filled composites due to high filler content. In this study, a series of linear low-density polyethylene (LLDPE)/magnesium hydroxide (MH) composites were prepared by the melt blending method, and the effects of the compatibilizer on the mechanical properties, flame retardancy, and rheological behavior of the composites were investigated. The addition of the compatibilizer decreased the limiting oxygen index (LOI) values of the composites, but they were all greater than 30.00%, which belonged to the flame retardant grade. Mechanical property tests showed that the addition of the compatibilizer significantly increased the tensile and impact strengths of the LLDPE/60MH (MH addition of 60 wt%) composites. Specifically, the addition of 5 wt% POE-g-MAH increased 154.07% and 415.47% compared to the LLDPE/60MH composites, respectively. The rotational rheology test showed that the addition of the compatibilizer could effectively improve the processing flow properties of the composites. However, due to the hydrocarbon structure of the compatibilizer, its flame retardant properties were adversely affected. This study provides a strategy that can improve the processing and mechanical properties of highly filled composites.