反应结晶过程中二水硫酸钙晶粒性能

设计了CaHPO₄·2H₂O-H₂SO₄-H₃PO₄-H₂O体系结晶温度、液相SO₄^2-含量、液相P₂O₅含量、搅拌速率和结晶时间的五因素四水平正交实验,通过测量晶体平均粒径优化出平均粒径最大的工艺参数:结晶温度80℃、液相SO₄^2-含量50g·L^-1、液相P₂O₅含量260g·L^-1、搅拌速率50r·min^-1和结晶时间2h。在该工艺参数下进行结晶过程研究,通过分析液相SO₄^2-浓度和P₂O₅浓度,XRD、SEM、EDS和激光粒度分析仪表征晶体,研究发现:0~40min为反应阶段,平均粒径减小;40min之后结晶过程遵从Ostwald递变法则,从CaSO₄·0.5H₂O过渡到CaSO₄·2H₂O,平均粒径几乎不变。

Characteristic and structure of calcium sulfate dihydrate crystallites in crystallization process during reaction

In CaHPO₄·2H₂O-H₂SO₄-H₃PO₄-H₂O system, an orthogonal experiment with five factors and four levels, including crystallization temperature, SO₄^2- concentration and P₂O₅ concentration in liquid phase (solution), stirring rate and crystallization time was designed. Based on the measurement of average particle size, the optimized process parameters for the maximum mean particle size are, 80℃ of crystallization temperature, 50 g·L^-1 of SO₄^2- concentration, 260 g·L^-1 of P₂O₅ concentration, 50 r·min^-1 of stirring speed, and 2 h of crystallization time. Under the optimum conditions of the crystallization process, by means of analyses on the concentrations of SO₄^2- and P₂O₅ in solution, and the techniques of XRD, SEM, EDS and laser particle size measurement, it showed that the reaction stage was the first 40 min with a decrease in mean particle size, and after 40 min, the procedure of crystallization follows the Ostwald grading rules, along with the evolution from CaSO₄·0.5H₂O to CaSO₄·2H₂O, but with almost identical particle size.