浓海水提镁过程中碳酸钠法除钙研究

Calcium removal from concentrated seawater by sodium carbonate in process of magnesium extraction

在利用浓海水提取浆状氢氧化镁的过程中，钙离子的存在是影响氢氧化镁产品纯度的重要因素。主要对浓海水提镁过程中的碳酸钠法除钙进行了研究，考察了分离方式、碳酸钠加入量、搅拌速度、陈化时间和反应时间对钙离子去除率和镁离子损失率的影响。确定了适宜操作条件：反应温度为20～25℃，碳酸钠加入量为理论量的1．3倍，反应时间为4h，陈化时间为48h，搅拌速度为200r／min，分离方式为抽滤。在此条件下钙离子的去除率在60％以上，有效解决了用浓海水制备浆状氢氧化镁产品中钙含量过高的问题。

In the process of magnesium extraction from concentrated seawater, Ca2＋ is the main factor affecting purity and quality of magnesium hydroxide. Ca2＋ removal by sodium carbonate method was studied in pretreatment process of magnesium extraction. Effects of operation conditions including separation method, addition amount of sodium carbonate, stirring speed,aging time, and reaction time on removal efficiency of Ca2＋ and on loss rate of Mg2＋ were investigated. Optimum operation conditions were confirmed as follows ： reaction temperature was 20 - 25 ℃ , addition amount of sodium carbonate was 1.3 times of theoretical value, reaction time was 4 h, aging time was 48 h, stirring speed was 200 r/min, and separation method was suction filtration. Under above conditions, removal rate of Ca2＋ was more than 60% and this method effectively solved the problem that the over-high content of calcium in magnesium hydroxide paste product prepared with concentrated seawater.