无水硫酸钙晶须的制备及表征

以某稀土厂生产过程中产生的硫酸铵废水为原料,用氯化钙作为钙源,采用水热法制备高长径比的硫酸钙晶须。首先采用正交实验研究反应时间、反应温度和陈化时间对硫酸钙晶须长径比的影响,确定最佳工艺条件。在正交实验最佳工艺条件的基础上,研究了pH对制备硫酸钙晶须形貌的影响。使用扫描电子显微镜（SEM）、X射线衍射仪（XRD）,红外分析仪（FT-IR）和热重-差热分析仪（TG-DSC）对制得的硫酸钙晶须的表面形貌和物相进行了表征和分析。研究结果表明:在制备硫酸钙晶须的最佳工艺条件下（即反应时间为5 h、反应温度为140 ℃、陈化时间为4.5 h）,溶液体系pH为1时,制备得到纯态无水硫酸钙晶须,其形貌最佳、长径比最大,平均长度达到117.44 μm、平均长径比为40.2。

Preparation and characterization of anhydrous calcium sulfate whisker

Calcium sulfate whiskers with high aspect ratio were prepared by hydrothermal method using ammonium sulfate wastewater produced in the production process of a rare earth plant as raw material and calcium chloride as calcium source. Firstly,the effects of reaction time,reaction temperature and aging time on the aspect ratio of calcium sulfate whisker were studied by orthogonal experiment to determine the optimal process conditions.Based on the optimal process conditions of orthogonal experiment,the effect of pH value on the morphology of calcium sulfate whiskers was studied.The surface morphology and phase of calcium sulfate whiskers were characterized and analyzed by scanning electron microscopy（SEM）,X-ray diffraction（XRD）, infrared analyzer（FT-IR） and thermogravimetric-differential thermal analyzer（TG-DSC）.The results showed that the optimum preparation conditions of calcium sulfate whisker were reaction time of 5 h,reaction temperature of 140 °C,aging time of 4.5 h.When the pH value of the solution system was 1,pure anhydrous calcium sulfate whiskers were prepared,which had the best morphology and high aspect ratio.The average length was 117.44 μm and the average aspect ratio was 40.2.