Study On New Preparation Processes Of Magnesium Hydroxide From Dolomite

In recent years, with the development and innovation of industrial technology as well as the enhancement of people’s consciousness on the environmental protection, the exploitation and utilization of the mineral resources were paid more and more attention in our country. Dolomite is an important kind of mineral containing magnesium; it can be used to produce the magnesium hydroxide with weak alkaline through a certain technological process by us. Its performance of buffer, activity of reaction, capacity of adsorption, thermal decomposition is very outstanding. Both it can be used as chemical materials or intermediates and can also be used for the polymer material industry as the environmental flame retardant agent or additives friendly. For example, rubber, plastic, fiber, resin and so on. At present, in the field of environmental protection, magnesium hydroxide can be application to the flame retardant, acidic wastewater, heavy metal removal, flue gas desulfurization, etc. Now how can prepare the excellent magnesia materials is one of the important research topics in China. Nanometer magnesium hydroxide of high purity, good crystallinity and dispersion are prepared by using dolomite as raw material, and it is one of the hot research projects in related fields.The optimal processing conditions of prepared magnesium hydroxide using dolomite as raw material were systematically explored by acid leaching method and carbonization in this article. It studied on the influence between the factors of reactions and the extraction rate of magnesium hydroxide; the factors include the temperature of calcinations and carbonization, the proportion, time, temperature of digestion and the selection of precipitation agent. The structure and composition of product were analyzed and characterized by means of Fourier transform infrared spectrometer (FT-IR), X-ray diffraction (XRD) and electron microscopy (SEM).The results show that:dolomite was calcined at950℃for2.5hours;60℃processed in water for50min with digest ratio1:40; the hydrochloric acid consumption and calcium ions molar ratio was2:1in first acid immersing process; the sulfuric acid consumption and magnesium ions molar ratio was1:1in second acid immersing process; the pH of solution was11in the process of precipitation. The max extraction rate of magnesium hydroxide was85.2%. The purity and dispersion of magnesium hydroxide was general and it is sheet. The temperature of carbonization was30℃; the selection of precipitation agent was ammonia. In these conditions, the magnesium extraction rate of calcium and magnesium separation could be up to90.02%with the high purity and dispersion, and the yield of magnesium hydroxide is88.21%. The product is sheet, too. The experiments had been by-product of ammonium sulfate using sulfuric acid as a solvent, and its applications were more extensive. This process improved the malpractice of the traditional carbonization technology that waste by-product greatly. This method has kinds of advantages, such as simple operation, low costs of production and investment, high quality of product, eliminating the environmental pollution, comprehensive utilization of by-products and so on.