Abstract:

With the rapid development of new energy and other industries, the demand for lithium has increased dramatically. Nanofiltration membranes are receiving more and more attention as a method of lithium extraction from salt lakes with the advantages of low energy consumption, low cost and green environment protection. This method can reduce the magnesium-lithium ratio in the brine and reduce the difficulty of subsequent lithium extraction, which has great potential in the salt lake lithium extraction industry. However, due to the late development, the theoretical system was not yet perfect and the process of promoting industrial applications was slow. This paper analyzed the modification methods used to enhance the performance of nanofiltration membranes for magnesium-lithium separation in recent years by starting from the separation mechanism, including five methods of surface grafting modification, two-phase solution additives, new monomer design, base membrane modification and optimization of interfacial polymerization (IP) process. The effects of the various modification methods on the structure and properties of nanofiltration membranes were also described. The analysis showed that the surface modification methods can change the membrane surface charge but cannot precisely regulate the membrane pore size. The additives can reduce the water transport resistance but the membrane tolerance needed to be investigated. The monomer design and base membrane modification can effectively improve selectivity and permeability, and the process optimization was more complex and industrial scale-up was difficult. Overall, the development of nanofiltration membranes in the salt lake lithium extraction industry was very promising. It can achieve green and efficient lithium extraction with other lithium extraction processes.

Key words: separation of magnesium and lithium, nanofiltration membrane, modification method, selective, permeability

摘要：

随着新能源等行业的快速发展，锂的需求量急剧增加。纳滤膜分离作为一种具有能耗低、成本低、绿色环保等优点的盐湖提锂方法，受到越来越广泛的关注。该方法能够减小卤水中的镁锂比，降低后续提锂难度，在盐湖提锂行业拥有巨大的潜力。但由于发展较晚，理论体系尚不完善，推动工业应用的进程缓慢。本文从分离机理入手，分析了近年来用于提升镁锂分离纳滤膜性能的改性方法，包括表面接枝改性、两相溶液添加剂、新单体设计、基膜改性和界面聚合（IP）工艺优化五种方法。同时，阐述了各种改性方法对纳滤膜结构和性质的影响。分析表明：表面改性的方法可以改变膜表面电荷但无法精确调控膜的孔径；添加剂可以减小水传输阻力但膜的耐受性有待考察；单体设计和基膜改性能够有效地提升选择性和渗透性；工艺优化较为复杂，进行工业放大有一定难度。总的来说，纳滤膜在盐湖提锂行业的发展十分具有前景，配合其他提锂工艺，以期实现绿色提锂、高效提锂。

关键词: 镁锂分离, 纳滤膜, 改性方法, 选择性, 渗透性