Abstract: 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 mm 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.

Key words: magnesium sulfate, magnesium hydroxide, flame retardant, ammonia method

摘要： 以硼酸生产中副产的硼镁肥(主要成分MgSO4×7H2O)为原料，进行了氨气法制备Mg(OH)2的中试研究，对制备的产品颗粒晶体结构与热分解性能进行了表征，考察了制备过程的操作方式与反应条件对产品颗粒性质的影响. 结果表明，间歇与连续操作方式下产品颗粒形貌相差很大，在操作由间歇向连续的转换过程中，产品颗粒形貌逐渐变化并在反应13 h后达到一致，反应液pH值为9.5~10.0，镁离子单程转化率达80%. 水热处理后，Mg(OH)2呈六方晶片形貌，平均粒径约2 mm，(001)与(101)面峰强度比值大于2，热分解的最强吸热峰温度为393.2℃，满足Mg(OH)2阻燃剂的使用要求.

关键词: 硫酸镁, 氢氧化镁, 阻燃剂, 氨气法