磷石膏制备α型半水石膏晶型调控及生长机制研究

Research on crystal regulation and growth mechanism of α-hemihydrate gypsum prepared by phosphogypsum

以柠檬酸钠为转晶剂,研究磷石膏制备α型半水石膏的晶型调控方法和晶体生长机制。结果表明,柠檬酸钠对α型半水石膏向短六棱柱状生长调控效果显著。在温度140℃,时间60 min,固液比1∶2,柠檬酸钠掺量0.40%条件下,可制备出晶粒大小均一、表面光滑完整、晶体长径比小于1的高强α型半水石膏;通过研究不同反应时间晶体生长过程,认为α型半水石膏的生成遵循脱水-溶解-重结晶机制,且二水石膏溶解和半水石膏结晶是同步进行的,晶体生长完整可以在5 min内完成。

The sodium citrate was used as a crystal modifier to study the crystal form control method and crystal growth mechanism ofα-hemihydrate gypsum prepared from phosphogypsum.The results indicate that sodium citrate has a significant effect on the short columnar growth ofα-hemihydrate gypsum.Under the conditions of temperature 140℃,time 60 min,solid-liquid ratio 1∶2 and sodium citrate content 0.40%,high-strengthα-hemihydrate gypsum can be prepared which have uniform crystal size,smooth and complete surface and crystal aspect ratio less than 1.Research on crystal growth processes at different reaction temperatures and time suggests that the formation ofα-hemihydrate gypsum follows the dehydration-dissolution-recrystallization mechanism,and the dissolution of dihydrate gypsum and crystallization of hemihydrate gypsum occur synchronously.The complete crystal growth can be completed within 5 min.