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

针对盐湖卤水中镁锂性质相似难以分离的问题,基于CO_(2)溶入卤水后生成的CO_(3)^(2-)浓度稳定、CO_(3)^(2-)和Mg^(2+)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MgCl_(2)-NH_(3)·H_(2)O-CO_(2)体系中,1 520 cm^(-1)和1 012 cm^(-1)处产生CO_(3)^(2-)的伸缩振动峰,CO_(3)^(2-)与Mg^(2+)发生沉淀反应后促使Mg^(2+)以固相形式析出;LiCl-NH_(3)·H_(2)O-CO_(2)体系中,在1 012cm^(-1)处产生的信号较弱的CO_(3)2-振动峰,由于CO_(3)2-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MgCl_(2)-LiCl-NH_(3)·H_(2)O-CO_(2)反应体系中,Mg^(2+)影响了1 520 cm^(-1)处的CO_(3)^(2-)伸缩振动峰,说明二者易于发生结晶反应,从而促使Mg^(2+)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CO_(2)分离工艺更易于得到高纯度的镁盐产品。

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 MgCl_(2)-NH_(3)·H_(2)O-CO_(2) system generates a telescopic vibration peak of CO_(3)^(2-) at 1520cm^(-1) and 1012cm^(-1).After the precipitation reaction between CO_(3)^(2-) and Mg^(2+),Mg^(2+)exists mainly in solid phase.CO_(3)^(2-) vibration peak with a weak signal generates at 1012cm^(-1) in the LiCl-NH_(3)·H_(2)O-CO_(2) system.The reaction between CO_(3)^(2-) and Li^(+) is not strong,and Li^(+) mainly exists in liquid form.In MgCl_(2)-LiCl-NH_(3)·H_(2)O-CO_(2) reaction system,a telescopic vibration peak of CO_(3)2-is generated at 1520cm^(-1) and 1012cm^(-1).The telescopic vibration peak of CO_(3)^(2-) vibrates with Mg^(2+),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-CO_(2) assisted reaction method makes it easier to obtain high-purity magnesium salt products.