基于盐湖尾卤溶液结构变化的镁锂分离研究

Separation of Magnesium and Lithium Based on the Structure Change of Tail Brine

中文关键词:  硫酸镁  尾卤  红外  锂镁分离  溶液结构

英文关键词:Magnesium sulfate  Tail halogen  Infrared  Lithium magnesium separation  Solution structure

中文摘要:

      盐湖卤水提锂工艺的难点之一在于卤水中镁锂比过高。采用红外光谱对非平衡动态降温过程中溶液结构变化进行分析,测定不同类型单盐溶液和卤水的结构变化,并基于此规律强化盐湖尾卤的镁锂分离。结果表明,MgSO4 溶液在40 ℃及以上时, 984 cm-1 处的特征峰显示可能出现接触式离子对结构(Mg²⁺-SO₄2-)；1 280 cm-1处出现溶剂共享型离子对结构( Mg²⁺-H₂O-SO₄2-)；Li₂SO₄溶液中出现溶剂共享型离子对结构的可能性低,镁锂之间会出现结构差异。基于如上溶液结构的变化,通过非平衡动态降温过程,实现盐湖尾卤中的镁锂分离,镁锂质量比值可由最初的40降至20左右,Mg²⁺以MgSO₄·nH₂O型混合结晶产品的形式从卤水中析出,而液相中Li⁺的损失率可低至5.01%以下,以此达到了脱镁及锂富集的效果。

英文摘要:

      One of the difficulties of lithium extraction from salt lake brine is the high magnesium to lithium ratio in salt lake. The structural changes of different types of single salt solutions and brines were analyzed by infrared spectroscopy in the process of non-equilibrium cooling,and the separation of magnesium and lithium of salt lake tail halides was strengthened based on this rule. The results show that the characteristic peak at 984 cm-1 of MgSO₄ solution at 40 ℃ and above shows that the contact ion pair structure (Mg²⁺-SO₄2-) may appear; Solvent shared ion pair structure (Mg²⁺-H₂O-SO₄2-) appeared at 1 280 cm-1. The possibility of solvent sharing ion pair structure in Li₂SO₄ solution is low,and there will be structural differences between magnesium and lithium. Based on the above solution structure changes,through the non-equilibrium dynamic temperature change process,the magnesium and lithium in the brine tail halide can be separated,the magnesium and lithium mass ratio can be reduced from the initial 40 to about 20,Mg²⁺ is precipitated from the brine in the form of MgSO₄·nH₂O type mixed crystallization product,and the loss rate of Li⁺ in the liquid phase can be as low as 5.01%. In this way,the effect of magnesium removal and lithium enrichment is achieved,and the separation of magnesium and lithium is realized.