盐湖锂资源现状及提锂技术研究进展

Present situation of salt-lake lithium resources and research progress of lithium extraction technology

  • 摘要: 锂广泛应用于新能源汽车、电子产品、储能等诸多领域,在能源结构转型中是一种关键战略资源. 从盐湖卤水中提取和分离锂,具备资源储量大、成本低等特点,引起了世界范围内的广泛关注. 中国盐湖资源丰富,主要分布于青海和西藏等地,但存在锂浓度较低、镁锂比高和分离难度较大的问题. 同时,不同地区盐湖成分差异大,技术通用性差,阻碍了我国盐湖提锂的发展. 本文从盐湖锂资源的分布、禀赋特征和提取方法以及发展方向等方面,综述了盐湖卤水提锂的主要研究进展. 重点介绍了沉淀法、溶剂萃取、吸附法、膜分离和电化学提锂的基本原理、操作和发展趋势,分析了不同提取方法的优缺点、分离效果和适用条件. 传统的沉淀法和萃取法均存在药剂用量大,环境污染严重的问题;吸附法用水量大,吸附剂易溶损,导致其生产应用受限. 而新兴的膜分离和电化学方法具有分离效果好、药剂添加需求少、产生废物少、适用性广等优点,在分离Mg/Li或Na/Li方面表现出优异的性能,展现出较好的工业应用潜力. 最后对盐湖提锂技术未来的发展方向和研究重点进行了展望.

     

    Abstract: Motivated by the electric vehicle revolution, the demand for lithium (Li) has significantly increased during the last decade. Li is the key strategic resource in energy structure transformation to be extensively employed in several fields, such as new energy vehicles, electronic products, and energy storage. For sustainable Li supply, developing cost-effective and green methods to extract Li from various sources is urgently needed. Due to the abundant reserves and low cost, the recovery of Li from salt-lake brines has garnered immense attention globally. China is rich in salt-lake resources; among them, brine Li resources are mainly distributed in Qinghai and Xizang, but the separation is difficult because of low concentration and high Mg/Li ratio. Moreover, the composition of salt lakes in different regions varies, and the poor technical universality restricts the development of Li extraction from salt lakes in China. This review summarizes the major developments in Li recovery from brines. An overview of the Li distribution, endowment characteristics, extraction methods, and development direction is presented, concentrating on the mechanisms, operation and development of precipitation, solvent extraction, adsorption, membrane separation, and electrochemical Li extraction. The advantages and disadvantages, separation effects, and applicable conditions of the extraction methods are examined. Although the prevalent precipitation, extraction, and adsorption methods are appropriate for the mass extraction of Li from brine sources with low Mg/Li ratios, they are not ecofriendly and typically show low Li recovery. For example, precipitation and extraction methods have issues with large dosages of chemicals and severe environmental effects; meanwhile, adsorption methods have drawbacks of intensive water use and easy dissolution of adsorbents, greatly limiting industrial application. The emerging membrane separation and electrochemical methods have good separation effects, limited requirements for additional chemicals, minimal waste production, wide applicability, and outstanding performance in Mg/Li or Na/Li separation, thereby demonstrating broad application prospects. However, these methods are limited by the poor technical maturity for large-scale lithium recovery. We underscore the most pressing challenges that these technologies encounter, including limited electrode capacity, poor electrode stability, and limited Li selectivity between homovalent ions. Then, potentially effective strategies are systematically described to overcome these challenges. Finally, future development directions and research focus on Li extraction technology from salt-lake brines are prospected.

     

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