Research Progress on Charged Nanofiltration Membranes for Separation of Magnesium and Lithium in Salt Lakes
In recent years,new energy electric vehicles powered by lithium secondary batteries have developed rapidly,and the rapid growth of lithium demand indicates that lithium resources have become an important strategic resource for China's development.Lithium resources are abundant in salt lakes in China,but the high mass ratio of magnesium/lithium makes it difficult to extract lithium from salt lakes.Nanofiltration(NF)is an emerging low-pressure driven membrane separation technology that has a certain interception effect on multivalent ions,allowing only monovalent ions and water molecules to pass through,and can be used for the separation of Mg2+/Li+.This article reviews the research progress on the preparation process of negatively charged and positively charged NF membranes for Mg2+/Li+separation.It is believed that commercial NF membranes and negative NF composite membranes have certain operability for Mg2+/Li+separation,but negative charge on the surface of NF membranes are not conducive to Mg2+/Li+separation.In addition,the extraction of lithium from salt lakes using positive NF membranes on the surface has advantages such as environmental protection,economy,and efficiency.Mg2+/Li+can be efficiently separated by adjusting the structure and performance parameters of the NF membrane.In the future,it is necessary to increase research investment by reducing the thickness of the polyamide layer in the NF membrane,focusing on the separation effect of Mg2+/Li+when the middle layer and lower surface layer are negative charge.It is hoped that this article can provide valuable reference for the research of lithium extraction from salt lakes.
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