Preparation Of High Purity And Ultrafine Magnesium Hydroxide By Ion Exchange Resin Method

In the thesis, high purity and ultrafine magnesium hydroxide was prepared by ion-exchange resin method and electrochemical methods. According to the reported preparation of nano-magnesium hydroxide methods, urea, sodium hydroxide and ammonia were used to be precipitating agent more often.The advantages of using these precipitating agent are low cost,easy-stoichiometric and the precipitation rate of magnesium is high.However,the use of such precipitating agent made the reaction to synthesize magnesium hydroxide while the remaining anions in solution were hard to wash.On the one hand, it may affect the purity of the product,on the other hand, it produce massive cleaning wastewater,which would pollute the environment, and waste water.In this article anion exchange resin was used tobe precipitating agent, which formed precipitation at the same time,replaceing the interfering ions to the resin.It can solute the difficulty of anion elution in previous precipitation method, so that can reduce the water consumption and cost.In the thesis, high purity and ultrafine magnesium hydroxide was prepared by one-method combining with anion exchange resins and magnesium chloride as raw materials. Ultrafine magnesium hydroxide was prepared in water bath and in the condition of stiming at optimal temperature and time, and it was characterized by chemical titration method, differential thermal balance, SEM and XRD. Finally, an initial exploration was made by electrochenecal method.When other conditions weren't changed, the temperature, the time and concentration of MgCl2 were respectively changed. It was confirmed that 60℃is optimal temperature, 16h is optimal time and 0.1mol/l is optimal concentration to prepare ultrafine magnesium hydroxide. As-prepared ultrafine magnesium hydroxide was characterized that ultrafine magnesium hydroxide has better dispersion, and is regular hexagonal flake structure, and the average particle size of the product is 18nm. In addition, the thermal decomposition temperature of the product above 300℃, which is sutible for fire-retardant materials.Then this thesis has explored the electrochemical method that used to prepare ultrafine magnesium hydroxide. The method uses the electrolysis reactor which has cathode and anode interdigital conjunction, in the role of external electric field, using D113 macroporous weak acidic resin as template, and using MgCl2 as raw material. Then the ultrafine magnesium hydroxide was directly synthesized by electrolyzing magnesium chloride. According to the settling performance of three electric current, it can be seen that the product of 4 ampere and 20 volt has high purity and regular hexagonal flake structure.