MgCl_2溶液中杂质离子的存在对氨气法制备Mg(OH)_2粒径的影响

Effect of Impurity Ions in MgCl_2 Solution on the Size of Mg(OH)_2 Particles Prepared by Gaseous Ammonia Method

MgCl_2是Mg(OH)_2 (MH)化学沉淀中常用的前驱体,但来自海水、菱镁矿和白云石等的MgCl_2中可能存在一些杂质,可能会影响所制备MH的质量。介绍了在MgCl_2溶液中分别加入不同种类的杂质离子,通过氨气沉淀法制备Mg(OH)_2(MH)产品,以此研究杂质离子的存在对所制备MH产品粒径的影响规律。实验结果表明,在MgCl_2溶液中阳离子的存在对所制备MH的粒径没有明显的影响,但阴离子的存在对所制备MH的粒径有显著的影响。当多价阴离子或单价AC^-存在时,甚至当杂质离子与MgCl_2的摩尔比低至1:120时,所制备的MH的平均粒径也可显著增加,而且其粒径分布也明显变宽。但是当阴离子杂质为单价的NO_3^-或Br^-时,对所制备的MH的粒径却没有明显的影响。

Some kinds of impurities may exist in the MgCl2 precursors from sea water,magnesite, dolomite, etc, which may affect the quality of prepared Mg(OH)2. In this paper, Mg(OH)2 was precipitated from MgCl2 aqueous solution via gaseous ammonia method. Before the precipitation of Mg(OH)2, different impurity ions were respectively added to the MgCl2 solution in order to study the effect of the presence of impurity ions in MgCl2 solution on the particle size of prepared Mg(OH)2. The results showed that the presence of cation in MgCl2 solution had not obvious effect on the particle size of prepared Mg(OH)2,while anions had obvious effect. The presence of multivalent anion or univalent acetate ion not only markedly increased the average particle size, but also obviously broadened the particle size distribution, even when the molar ratio of impurity ions to MgCl2 was as low as 1:120. However, the presence of NO3 -or Br- had no obvious effect on the particle size of prepared Mg(OH)2.