Abstract: Hydromagnesite is an important chemical raw material and product.A reactive crystallization method was provided to prepare hydromagnesite microspheres directly in experiments.The effects of stirring time, reactive temperature and reactant concentrations on the morphology and particle size were studied.The formation mechanism of hydromagnesite microspheres was analyzed.The results show that hydromagnesite microspheres with controllable size and good shape can be obtained by controlling the stirring time.The size of particles is 10—43 μm with the coefficient of variation of 28%—43%.It is found that the amorphous substance is first generated by the reaction of magnesium chloride and sodium carbonate in the crystallization process.The amorphous substance gradually transfers to crystal phase.The study shows that the stirring has a significant impact on the phase transfer of amorphous substance.Crystal nuclei form during the stirring process.Under the static condition, the growth process of amorphous substance onto the pre-existed crystals is dominant.As a result, the crystal size and morphology can be regulated by the stirring time.

Key words: reactive crystallization, hydromagnesite, amorphous substance, morphology

摘要： 碱式碳酸镁是一种重要的化工产品和原料。实验提供一种反应结晶直接制备碱式碳酸镁微球的方法,考察了搅拌时间、反应温度和反应物浓度对产物形貌和粒度的影响,分析了其形成机制。结果表明,采用控制搅拌时间的方法,制备出粒度在10～43 μm、变异系数为28%～43%的尺寸可控、形态良好的碱式碳酸镁微球。通过对结晶过程晶型晶貌研究发现,氯化镁和碳酸钠反应首先生成无定形物,逐步相转移为结晶相。研究表明,搅拌作用对无定形物相转移具有显著影响。在搅拌过程中,以产生晶核过程为主,在静置状态下,以无定形物生长在已有晶体过程为主,搅拌时间对晶体粒度和形貌起到调控作用。

关键词: 反应结晶, 碱式碳酸镁, 无定形物, 形貌