Abstract:

The preparation of nesquehonite (MgCO₃·3H₂O) and hydrogen chloride by MgCl₂ and CO₂ based on a coupled reaction-extraction-alcohol precipitation process is an effective way for the comprehensive utilization of brine. The effects of impurity ions Na⁺, K⁺ and Ca²⁺ in brine on the morphology of the solid product obtained in the coupled reaction-extraction-alcohol precipitation process are investigated systematically. The results indicate that Na⁺ and K⁺ have a similar influence on the coupled process. The products are rod-like high purity MgCO₃·3H₂O when Na⁺ and K⁺ are added. Moreover, Na⁺ and K⁺ can be selectively absorbed onto the axial face (101) of MgCO₃·3H₂O, that will hinder the growth along the (1 0 1) direction and resulting a decrease in the diameter of MgCO₃·3H₂O. Ca²⁺ shows a negative effect on the coupled process. The added impurity CaCl2 can react with CO₂ and form spherical amorphous nano Mg/Ca-carbonate, which will decrease the purity of the solid products.

Key words: brine, coupled reaction-extraction-alcohol precipitation process, nesquehonite, impurity ions, morphology

摘要：

通过反应-萃取-醇析耦合过程，将MgCl₂和CO₂制备成碳酸镁和氯化氢气体是盐湖老卤资源化利用的有效途径。系统地研究了老卤中Na⁺、K⁺、Ca²⁺对MgCl₂和CO₂反应-萃取-醇析耦合过程得到的固体产物晶型晶貌的影响。结果表明，Na⁺和K⁺对耦合过程的影响相似，固体产物均为高纯棒状三水碳酸镁（MgCO₃·3H₂O），且Na⁺和K⁺均能选择性吸附在MgCO₃·3H₂O晶体的轴面（101），阻碍该晶面的生长，使得棒状MgCO₃·3H₂O直径变小；Ca²⁺对反应-萃取-醇析耦合过程有不利的影响，由于CaCl2能参与反应，生成球状无定形纳米钙镁碳酸盐，使得三水碳酸镁纯度降低。

关键词: 盐湖老卤, 反应-萃取-醇析耦合, 三水碳酸镁, 杂质离子, 形貌