杂化电容去离子技术的构筑及高镁锂比盐湖卤水中锂的回收

Lithium is one of the most important elements in various fields including national defense, chemical engineering and energy storage industry, and demands for lithium are constantly increasing these days. Salt-lake brines in Qaidam basin, China have high Mg/Li concentration ratios, unlike brines in other countries, and it is very difficult to recover lithium from salt-lake brines in China using sedimentation and calcinations methods because of preferential magnesium extraction. This remains a big challenge. The project reports an electrochemical lithium recovery method based on a manganese oxide/activated carbon hybrid capacitive deionization system. In this system, lithium ions and counter anions are effectively captured at each electrode with low energy consumption in a salt solution containing various cationic species or simulated brine lake water. The relationship between the structure and properties of the precursor manganese oxide and the as-made manganese oxide using sol-gel method will be explored, which will help to optimize the preparation processes that will be capable of tuning the properties, microstructures of the manganese oxide phase. The dependence of the high capacity of the manganese oxide materials on the size, distance, functional groups and the microstructure will be examined, which will reveal the capacity mechanism governing desalination. Furthermore, we designed this system as a flow process for practical applications. By experimental analyses, we will confirm that this system has high selectivity and long-term stability, with its performance being retained even after repetitive captures and releases of lithium ions. This project will pave a new way for making novel CDI processes to solve the bottle-neck problems. The advantages achieved through this innovative work will lead to more efficient separation technologies across many sectors, such as desalination of saline, treatment of lithium ions in slat-lake brines in Qaidam basin.

锂作为一种重要的新型能源材料，已被广泛用于国防、化工、电子等领域，国内外市场对锂的需求量也日益增加。柴达木盆地盐湖卤水含有丰富的锂资源，然而卤水中镁锂比较高，现有技术在提取锂的过程中面临难以将镁锂有效分离的复杂难题。本项目通过锰氧化物/碳材料作为电极材料来构筑杂化电容去离子技术，利用电化学原理将锂离子与相反电荷的离子选择性的捕获到对应的电极上，具有选择性好、能耗低的优势。主要研究内容包括：（1）利用溶胶凝胶法制备结构和性能可控的纳米锰氧化物提锂离子筛；（2）诠释电极材料电化学性能、提锂性能与其微纳结构、孔隙结构、原子比等之间的构效关系；（3）构筑杂化电容去去离子提锂装置，进行基于高镁锂水体的提锂实验研究，揭示选择性提锂机制。项目的实施将丰富和发展电容去离子技术的内涵，为开发低耗高效的复杂水体中提锂技术奠定理论和技术基础，有重要的学术价值和广阔的应用前景。

锂及其化合物广泛应用于国民经济的各个领域，是一种重要的战略资源。盐湖卤水中含有大量的锂，但是大部分同时伴生有大量的镁，由于镁锂化学性质相似，离子半径和电荷相近，传统方法难以分离。本项目通过锰氧化物/碳材料作为电极材料来构筑杂化电容去离子技术，利用电化学原理将锂离子与相反电荷的离子选择性的捕获到对应的电极上，具有选择性好、能耗低的优势。主要研究内容及其重要结果、数据如下：（1）利用一步水热制备的纳米级的LiMn2O4，作为杂化电容去离子电极材料，最高吸附容量为23.6mgLi/g；（2）采用MnO2作为阳极，PVPD包覆的碳材料作为阴极组装的杂化电容去离子模块，在1.4V电压窗口下，获得了脱盐容量高达14.9mg/g的钠离子吸附容量，350次循环后电吸附容量保持率高达95.4%；（3）进行了整体式高介孔聚合物和提锂剂的复合研究；当锰酸锂/聚丙烯腈复合比例为1.2 g : 0.8 g 时，锂离子饱和吸附量达到了27.3 mg·g-1，同时表现出了良好的吸附动力学，在4 h内可以达到吸附平衡；此外，为了测试吸附剂的再生性能以及展示整体式材料易于分离的优势，采用固定床进行吸附再生研究，研究表明：吸附完成后用0.5 M HCl再生循环使用，循环吸附3次后吸附量可以维持在90%以上，展现了良好的再生性能。.项目的实施将丰富和发展电容去离子技术的内涵，为开发低耗高效的复杂水体中提锂技术及其脱盐技术奠定理论和技术基础，有重要的学术价值和广阔的应用前景。