由盐酸法浸出磷矿的氯化钙溶液制备CaSO4·2H2O晶须

建立了以盐酸法磷酸产生的氯化钙溶液为原料,在常压、较低温条件下（T<90 ℃）制备硫酸钙（CaSO₄·2H₂O）晶须的方法。考察了不同晶形控制剂对所制备CaSO₄·2H₂O晶须的形貌和长径比的影响,并利用扫描电镜和X射线衍射对样品做了分析和表征。筛选并确定了十二烷基三甲基溴化铵（DTAB）为较适宜的晶形控制剂,通过对DTAB用量、反应温度、Ca²⁺浓度等条件的优化,确定最佳的工艺条件：DTAB用量为3%（质量分数）、反应温度为90 ℃、Ca²⁺浓度为0.1 mol/L、反应时间为25 min、钙硫比（钙离子与硫酸的物质的量比）为1:1.1。此条件下,所制备的CaSO₄·2H₂O晶须长径比可达130,晶须沿平行于（040）晶面的法线方向优先生长,样品的（020）、（040）晶面衍射峰的相对强度明显增强,并依据螺旋生长定理对晶形控制剂作用机制做了初步探讨。

Preparation of calcium sulfate dihydrate whiskers from leachate of phosphate ore by hydrochloric acid

A method was established for preparing calcium sulfate dehydrate whiskers under normal pressure and low tem-perature conditions（T<90 ℃） using the intermediate by-product CaCl₂ from the leachate of phosphate ore by hydrochloric acid as raw material.The effects of different crystal shape control agents on the morphology and aspect ratio of the calcium sulfate whiskers were investigated and the samples prepared were characterized by FESEM and XRD.DTAB was selected as the more suitable crystal form control agent.The conditions of DTAB dosage,reaction temperature and concentration of Ca²⁺etc. were optimized.The optimum process conditions were determined as follows:DTAB dosage was 3%,reaction temperature was 90 ℃,the concentration of Ca²⁺ was 0.1 mol/L,reaction time was 25 min,and the amount-of-substance ratio of calcium to sulfur 1:1.1.Under the conditions,the L/D ratio of as-prepared calcium sulfate whiskers achieved 130.The obviously enhanced intensity of the（020） and（040） crystal planes in X-ray diffraction patterns of the whiskers sample showed preferential gro-wth along the normal direction of the（040） crystal plane.The action mechanism of the crystal shape controlling agent was preliminarily discussed based on the spiral growth theorem.