Preparation of Magnesium Hydroxide from Magnesium Sulfate by Ammonia Method with a Pilot-scale Apparatus

Preparation of magnesium hydroxide from boric magnesium fertilizer(with MgSO4·7H2O as the main component) by NH3-bubbling method was carried out in a self-designed pilot-scale apparatus.The properties of prepared magnesium hydroxide particles were measured with SEM,XRD and TG-DTA,respectively.The influences of operation forms and reaction conditions on the particle properties were investigated.The results showed that the products obtained in batch and continuous operations were of remarkable difference in their particle morphology,which changed gradually with transition from batch operation to continuous operation and tended to be in the same morphology while the reaction time lasted 13 h.The pH value of reaction solution and conversion rate of Mg2+ were maintained at about 9.5～10.0 and 80%,respectively.Hydrothermal treatment of the products obtained in continuous operation resulted in that the magnesium hydroxide particles were hexagonal platelets in morphology,2 μm in size,more than 2 in the value of I001/I001 and at 393.2℃ of the strongest endothermic peak,which could be used as flame retardant additive in polymer materials.