Reactive crystallization process of hydromagnesite microspheres

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.