Reviewing Recent Advances in Nanofiltration Membranes for Efficient Lithium and Magnesium Separation from Salt Lake Brines

Abstract

In recent years, with the rapid development of the new energy industry, electric vehicles and electronic wearable devices, the consumption of elemental lithium is increasing rapidly, and the demand for lithium resources is challenging to fulfil. Salt lake brine is rich in lithium. However, the high ratio of magnesium to lithium in salt lake brine makes the separation of lithium and magnesium from salt lake brine very challenging. Compared with extraction, adsorption, electrochemistry, reaction coupling and other methods, nanofiltration has attracted much attention as an environmentally friendly, energy-efficient and low-cost process which can effectively separate lithium and magnesium and enrich lithium to facilitate its further purification. This review analyzes nanofiltration membrane preparation methods and evaluates the effects of temperature, pressure, pH and salinity on the performance of the membranes, which prefer low pH and salinity environments. In addition, the ability of nanofiltration to reduce the Mg/Li ratio, as well as its stability, was analyzed in terms of monomer optimiza­tion, post-modification and process improvement.