Technique for Preparation of Magnesium Hydroxide from Boron Mud

Magnesium hydroxide was prepared by high temperture calcination reaction of sulfuric acid and boron mud to solve the enviroment pollution caused by boron mud and fully utilize magnesium in boron mud.The effects of calcination temperature, calcination time and liquid-solid ratio on the leaching rate of magnesium were studied.It is found that under the optimum conditions of calcintion temperature 300 ℃,calcination time 2 h and liquid-solid ratio about 2∶1 the leaching rate of magnesium is 88%.The magnesium concentrated solution was prepared after impurity-removal of the leaching liquid,in which the recovery of magnesium reaches 91.17% and magnesium hydroxide was prepared,using sodium hydroxide as precipitator.The overall recovery of magnesium in boron mud can reach 80%.The precipitate is magnesium hydroxide verified by XRD measurements and its quality meets the standards of HG/T3607-2000 by analysis.The results measured by SEM show that the diameter of the undried magnesium hydroxide particles is less than 1 μm while the diameter of the dried ones is approximately 70～90 μm with irregular round form.