基于碳酸化溶液结构研究的盐湖卤水镁锂分离

The Mg-Li Separation of Salt Lake Brine Based on the Investigation of Carbonated Solution Structure

中文关键词:  盐湖卤水  镁锂分离  碳酸化  溶液结构  红外光谱

英文关键词:Salt lake brine  Magnesium-lithium separation  Carbonated method  Aqueous solution structure  Infrared spectroscopy

中文摘要:

      针对盐湖卤水中镁锂性质相似难以分离的问题，基于CO₂溶入卤水后生成的CO32-浓度稳定、CO32-和Mg2+在亚稳状态下易于发生沉淀反应的假设，采用碳酸化反应方法进行镁锂分离研究。通过红外光谱研究了三种不同盐体系的溶液结构，结果表明在氨水调碱后的MgCl2-NH₃·H2O-CO₂体系中，1?520 cm-1和1?012 cm-1处产生CO32-的伸缩振动峰，CO32-与Mg2+发生沉淀反应后促使Mg2+以固相形式析出；LiCl-NH₃·H2O-CO₂体系中，在1?012cm-1处产生的信号较弱的CO32-振动峰，由于CO32-与Li+发生的反应不强烈，因此Li+主要还以溶解态形式存在；在MgCl2-LiCl-NH₃·H2O-CO₂反应体系中，Mg2+影响了1?520 cm-1处的CO32-伸缩振动峰，说明二者易于发生结晶反应，从而促使Mg2+和Li+分别以固液形式富集在两相中，实现了镁锂分离。镁锂溶剂化结构的不同致使碳酸化反应中的发生反应振动的峰值不同，分离实验表明与传统的碳酸盐沉淀法相比，氨水和CO₂分离工艺更易于得到高纯度的镁盐产品。

英文摘要:

      Aiming at the problem that magnesium-lithium properties are similar and difficult to separate in salt lake brine， the separation mechanism of magnesium-lithium is studied by carbonation reaction by taking advantage of the differential properties of magnesium-lithium in the structure of the hydration layer. The solution structure of three different salt systems was studied by infrared spectroscopy， and the microscopic mechanism in the separation process of magnesium and lithium was explored. The results show that MgCl2-NH₃·H2O-CO₂ system generates a telescopic vibration peak of CO32- at 1?520cm-1 and 1?012cm-1. After the precipitation reaction between CO32- and Mg2+， Mg2+ exists mainly in solid phase. CO32-vibration peak with a weak signal generates at 1?012cm-1 in the LiCl-NH₃·H2O-CO₂ system. The reaction between CO32- and Li+ is not strong， and Li+ mainly exists in liquid form. In MgCl2-LiCl-NH₃·H2O-CO₂ reaction system， a telescopic vibration peak of CO32- is generated at 1?520cm-1 and 1?012cm-1. The telescopic vibration peak of CO32- vibrates with Mg2+， the solution structure changes， most of the lithium ions remain in the liquid phase， and magnesium ions are enriched in the solid phase， which can realize the magnesium-lithium separation. The different solvation structure of magnesium and lithium leads to different signals of reaction vibration in carbonation reaction， which provides a new idea for magnesium-lithium separation. Compared with traditional carbonate precipitation methods， the separation process using ammonia-CO₂ assisted reaction method makes it easier to obtain high-purity magnesium salt products.