高纯硼酸制备过程中的结晶动力学

Crystallization Kinetics of High Purity Boric Acid in Preparation Process

采用HCl气体液相酸化硼砂的中和反应,并结合重结晶法与离子树脂交换法,制备了高纯H3BO3产品.实验考察了H3BO3-NaCl-H2O体系中溶液过饱和度、结晶温度、结晶时间、搅拌速度及溶液中所含杂质等因素对H3BO3结晶过程的影响.结果表明,溶液浓度为18.26%、结晶温度为10℃、结晶时间为480min、搅拌速度为300r/min,并选取适当的降温方式有利于H3BO3析晶,结晶率大于83%,晶体呈细小颗粒状.体系中所含的NaCl杂质促进了H3BO3析晶.由实验数据得到该体系中H3BO3的结晶动力学曲线,并建立了结晶动力学方程,结晶反应级数为2.

High purity boric acid was prepared by HCl acidification of borax combined with recrystallization and ion resin exchange. Some influential factors on the crystallization process of H3BO3-NaCl-H2O system such as supersaturation, crystallization temperature and time, stirring speed, and impurity in the solution were studied. The results show that with the solution concentration at 18.26%, and fmal crystallization temperature 10 ℃ held for 480 min, stirring speed 300 r/min, and proper cooling, the formation of boric acid crystals has been optimally achieved. The rate of crystallization can be over 83%, and the crystals are fine granules. NaCl can accelerate boric acid crystallization in the system. Based on the experimental data, the curve of crystallization kinetics is gained and kinetics equation formed with the reaction order of 2.