杂质对于磷酸二氢铵结晶的影响

Influence of Impurities on Ammonium Dihydrogen Phosphate Crystallization Process

采用间歇结晶法研究了杂质Fe3+、Al3+、F-、SO42-对MAP结晶的影响。实验结果表明:Fe3+、Al3+对于MAP成核和晶体生长均有明显的阻碍,随着其浓度的增加,介稳区变宽,诱导时间延长,结晶生长速度变慢,晶体由棱柱状变为针状,粒径减小,直至成细粉状;随着Mg2+含量增加,介稳区略有增大,晶体的平均粒径减小,单晶长径比略有变小;F-浓度的增大,介稳区宽度略有增大,晶体粒径略有减少,单晶长径比逐渐减小,晶体由长柱状变为方柱状;SO42-对于KDP结晶过程影响很小。研究结果对于工业级磷酸二氢铵的生产有重要的指导意义。

The influences of Fe^3＋, Al^3＋, F^-, SO4^2- ions on the crystallization process of ammonium dihydrogen phosphate（MAP） were studied by means of batch crystallization process. The results showed that the dopant of Fe^3＋ ,Al^3＋ had siginificate effect on MAP crystallization process, which made the crystal shape changeing from prism to spiculate; with the increase of dopant, the metastable zone width （MZW） increased, the crystallization induction period increased obviously, the crystal growth rate decreased and the average crystal size decreased; With the increase of Mg^2＋ , the metastable zone width widened, the average crystal size and l： d decreased; The existence of F- widened the metastable zone, minished the ratio of length to diameter of crystal, shape changed the crystal from long prism to short prism ;The effect of SO4^2- on crystallization process was neglectable. The experiment results are quite valuable to MAP production.