用 MgSO4制备不同水合碳酸镁晶体及晶体转变过程

以MgSO4为原料,通过向MgSO4溶液中滴加(NH4)2CO3得到碳酸镁水合物。借助X射线衍射、扫描电子显微镜、差热分析及Raman光谱分析了转变过程中晶体组成和形态变化。研究发现,在25～45℃制备的产物均为单斜晶系、空间群为P21/n(14)的MgCO3 3H2O晶体;在50～60℃结晶产物存在由针状的MgCO3 3H2O晶体向单斜晶系、空间群为P21/c(14)的片状4MgCO3 Mg(OH)2 4H2O晶体的转变。从pH值变化和生长基元的形成对碳酸镁水合物晶体转变过程进行了分析。

Effects of Temperature on the Preparation of Magnesium Carbonate Hydrates by Reaction of MgCI2 with Na2CO3

Homogeneous(unseeded)precipitation of magnesium carbonate hydrates by the reaction of MgCl2 with Na2CO3 in supersaturated solutions between 273 and 363K was investigated.The compositions,morphologies and filtration characteristics of the precipitates were studied in detail.The magnesium carbonate hydrates obtained at 313K and in the range of 343-363K showed good morphologies and filtration characteristics.Magnesium oxides(MgO)with high purity(97.6%-99.4%)were obtained by calcining magnesium carbonate hydrates at 1073K.