【Frontiers in HaiChuan Chemical Technology】New breakthrough achieved in key lithium extraction technologies from salt lakes at the Qinghai Salt Lake Research Institute, Chinese Academy of Sciences
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On November 12, reporters learned from the Qinghai Provincial Department of Science and Technology that the Qinghai Salt Lake Institute of the Chinese Academy of Sciences, building on research into the optimization of atom-economical and environment-friendly lithium extractants, has independently designed and synthesized new green extractants through innovations in molecular structure and improvements in performance. It has uncovered the extraction mechanism at the molecular level, determined the structure of the extraction complexes for the first time, and systematically addressed the various challenges associated with environmental impact, safety, and cost control in traditional extraction systems. It is reported that the recovery of lithium-rich mother liquor is a key step in lithium extraction from salt lakes, as it affects economic benefits and resource utilization efficiency. Applying extraction methods to the recovery of lithium-precipitation mother liquor can significantly reduce the consumption of chemical reagents and improve the lithium extraction yield, providing a viable approach for the recovery and clean utilization of such mother liquor. This extraction process successfully achieved a Li+ concentration in the lithium-enriched solution of over 37 g/L, a Na+ concentration of less than 1.0 g/L, and an organic matter content in the raffinate of less than 10 mg/L. It also resulted in a comprehensive set of technical solutions that include customized formulations for the extraction system, modular design for the processes, and intelligent integration of equipment – thereby laying a solid technical foundation for large-scale industrial application. Furthermore, by partnering with Qinghai Qingyuan Lithium Industry Technology Co., Ltd., the world’s first industrial demonstration line for the extraction of lithium from lithium-rich brine at a rate of 6,000 tons per year to produce battery-grade lithium carbonate was established at Qinghai CITIC Guoan Technology Development Co., Ltd. This facility has achieved full operational capacity and meets all specified standards; the lithium recovery rate on this extraction line is over 98%, and it has generated an additional economic value of more than 300 million yuan. It provides key technical support for the high-quality development of lithium resources derived from salt lakes in China.
To address the scientific challenge of structural collapse and instability in high-capacity organic small-molecule electrodes caused by volume expansion due to ion intercalation, the research team innovatively proposed a new approach to constructing stable crystal structures based on molecular interaction networks. Using phenazine as a model system, studies have shown that an orthogonally perpendicular molecular stacking arrangement can lead to the formation of a strong intermolecular force network and ion-selective nanochannels. This structure not only effectively suppresses mechanical failure caused by volume expansion, but also the lithium-loving pores it generates exhibit preferential transport and selectivity for monovalent metal ions (Li) at the atomic scale, with a selective lithium extraction capacity as high as 109 mg/g. This work originally reveals the underlying physicochemical relationships between molecular stacking microstructures and the macroscopic electrochemical stability and ion selectivity of electrode materials, providing an important theoretical foundation for designing a new generation of organic electrochemical ion capture materials with high stability, high selectivity, and high throughput. During the electrochemical extraction of halite resources, the principle of electrical neutrality must be taken into account; therefore, it is equally important to efficiently extract the associated anions. Polyaniline (PANI) is widely used in fields such as energy storage, environmental purification, and ion separation, thanks to its excellent electrical conductivity and reversible doping properties. However, traditional PANI is limited in its application for high-performance electrochemical desalination due to issues such as low utilization of nitrogen active sites and an unclear micro-macro structure-property relationship. The research team creatively discovered that the polymerization potential is a key parameter for regulating its microstructure (such as degree of polymerization, chain structure, and defect types). Through methods such as in-situ electrochemical spectroscopy, it was demonstrated that adopting a \"low potential\" strategy can effectively suppress coupling side reactions, enabling the preparation of low-degree linear polyaniline with nanoscale tips. This unique structure significantly enhances the exposure efficiency and accessibility of nitrogen-containing sites, enabling breakthrough high-capacity adsorption of chloride ions (a capacity of 339 mg/g) and sodium ions (142 mg/g). This work has significantly advanced the design of structurally controllable polymers and their application in electrochemical separation.
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