乙醇结晶法提取硼铁矿酸浸液中的硫酸镁

摘要

提出一种通过乙醇结晶提取硼铁矿酸浸液中硫酸镁的新方法,并计算硫酸镁分别在水溶剂和水-乙醇混合溶剂中的溶剂化能以及溶解过程的焓变(△Hs)和吉布斯自由能变(△Gs),从理论上验证该方法的可行性.考察溶液pH、乙醇加入量、结晶温度和初始硫酸镁浓度对硫酸镁在水-乙醇相中结晶析出的影响.研究结果表明硫酸镁在水-乙醇混合溶液中结晶析出的最佳条件为:溶液pH在1.5～2.0之间,乙醇加入体积为溶液体积的1.5倍,结晶温度为常温(l0～30℃),硫酸镁的初始浓度在1.5 mol/L以上.在此条件下,硫酸镁的析出率达到97.73％,通过XRD和TG测试分析验证结晶析出产品为七水硫酸镁,测定其纯度为99.10％,达到七水硫酸镁的国家化工行业标准HG/T2680-2009中的Ⅰ类一等品的要求.%A new method that magnesium sulfate crystal extracted from acid-leaching solution of ludwigite using ethanol was proposed,and the feasibility of this method was discussed by calculating the enthalpy change (△Hs) and Gibbs free energy change (△Gs) of dissolving process and the solvation energy of magnesium sulfate both in water and water-ethanol.The effects of pH,crystallization temperature,the amount of ethanol and the initial concentration of magnesium sulfate on the crystallization rate of magnesium sulfate in ethanol-water were also discussed.The results show that the optimum processing parameters of magnesium sulfate crystallization in water-ethanol mixture are that the pH of solution is between 1.5 and 2.0,the volume ratio of solution to ethanol is 1∶1.5,the crystallization temperature is room temperature and the initial concentration of magnesium sulfate is greater than 1.5 mol/L.Under this condition,the crystallization rate of magnesium sulfate can reach 97.73％.The product is determined as magnesium sulfate heptahydrate by XRD and TG,and the purity of it is 99.10％,which fits the first grade of class Ⅰ industrial products under the chemical industrial standard of China (HG/T 2680-2009) for magnesium sulfate heptahydrate.