离子液体体系用于盐湖卤水提取锂

doi:10.11949/j.issn.0438-1157.20141834

摘要/Abstract

摘要：

3种咪唑类离子液体:1-丁基-3-甲基咪唑六氟磷酸盐([C₄mim][PF₆])、1-己基-3-甲基咪唑六氟磷酸盐([C₆mim][PF₆])、1-辛基-3-甲基咪唑六氟磷酸盐([C₈mim][PF₆])被作为绿色溶剂用于盐湖卤水分离镁锂, 建立了以离子液体(ILs)、磷酸三丁酯(TBP)分别为萃取介质和萃取剂的盐湖卤水锂萃取体系, 并与使用传统有机溶剂磺化煤油和氯仿的萃取效果进行了对比。研究发现, 该离子液体体系较使用传统挥发性有机溶剂的萃取体系有更高的萃取率。锂的萃取率随离子液体中烷基碳原子数的减小而增加。详细考察了溶液pH、离子液体浓度、相比对萃取效率的影响, 获得了离子液体体系萃取的最优条件。在最佳萃取条件下, 3种离子液体体系对锂的单级萃取效率均高于80%, 分离系数最高达到100以上。机理研究表明:离子液体体系是以阳离子交换实现对锂的萃取, Li⁺与TBP形成[Li·2TBP]⁺络合物进入有机相。

关键词: 离子液体, 萃取, 分离, 锂, 磷酸三丁酯

Abstract:

Lithium is known as the energy metal and it's a key raw material for preparing lithium isotopes which have important applications in nuclear energy source. The amount of lithium resources in salt lakes occupies over 69% of its industrial reserves in the world, so the hot point in lithium industry is to exploit lithium resources in salt lakes. It is well known that many salt lakes exhibit characteristically high Mg to Li ratios, which render the efficient extraction of lithium very difficult. In this paper, the ionic liquids(ILs), [C₄mim][PF₆], [C₆mim][PF₆] and [C₈mim][PF₆], are used as a kind of green solvent to study liquid/liquid extraction of lithium ion from salt lake brine. A new extraction system had been established in this paper. In this new system, the tributyl phosphate (TBP) was used as the extractant and the ionic liquids were used as extraction medium. It was found that the TBP in conjunction with the present ionic liquids provided extraordinary extraction of lithium ion. The close relationship between the extraction efficiency and the length of the alkyl chain is obvious. With decreasing number of carbon atom of alkyl group in the ionic liquids, the extraction efficiency of lithium increased. The effects of phase ratio, RTILs volume in TBP and solution pH on extraction efficiencies of metal ions had been investigated in detail and the optimal extraction conditions of these systems were obtained. The extraction efficiencies of these ionic liquids systems were all higher than 80%, and the highest the separation factor was over 100 when the experiments were conducted under the optimal conditions. Study on the mechanism revealed that the use of ionic liquids increased the extraction yield of lithium through cation exchange in these systems. The plots of [lgD_Li+lg[C_nmim]⁺_aq-lg[C_nmim]⁺_org] versus lg[TBP] produce a straight line with a slope near to 2. According to the slope analysis, the lithium ion was extracted into the organic phase by forming a complex of [Li·2TBP]⁺.

Key words: ionic liquids, extraction, separation, lithium, tributyl phosphate

中图分类号:

TQ028.8

石成龙, 景燕, 肖江, 邱方龙, 贾永忠. 离子液体体系用于盐湖卤水提取锂[J]. 化工学报, 2015, 66(S1): 265-271.

SHI Chenglong, JING Yan, XIAO Jiang, QIU Fanglong, JIA Yongzhong. Application of ionic liquids for extraction of lithium from salt lake brine[J]. CIESC Journal, 2015, 66(S1): 265-271.

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