The main reaction formula of the process for preparing high-purity magnesium hydroxide by calcium hydroxide method is:
The process operation is also relatively simple and has similarities with the sodium hydroxide method. Since the market price of calcium oxide is low and easy to purchase, the cost of this process has obvious advantages over the sodium hydroxide method and other methods. However, since the purity of calcium oxide is not high, it easily contains many heavy metal impurities, which can easily cause the produced magnesium hydroxide to precipitate and adsorb or contain impurities, which affects the purity of the produced magnesium hydroxide. In addition, the calcium hydroxide emulsion is in a suspended state, and the reaction speed of calcium hydroxide and magnesium hydroxide is relatively slow. Therefore, the addition speed of calcium hydroxide emulsion must be controlled to fully react with calcium hydroxide and magnesium hydroxide. Otherwise, the reaction will be insufficient, and the easily produced magnesium hydroxide precipitate will contain unreacted calcium hydroxide impurities, which will not only cause a waste of raw materials, but also reduce the quality of the product magnesium hydroxide.
Hebei Messi Biology Co., Ltd. said that it uses natural salt lake brine blocks as raw materials, uses lime milk as precipitant, controls the temperature at 40℃~90℃, and uses special calcium removal technology to make the mass fraction of magnesium hydroxide in the product greater than 98%. , the particle size is about 80nm, the particles have a flaky crystal structure, and the specific surface area of the magnesium hydroxide product is 39.22m2/g.
Using the hydrocite-milk of lime precipitation method, when the reaction temperature is 85°C, the concentration of hydrocite is 1.0mol/L, and the concentration of lime milk is 0.90mol/L, seed crystals are added. When the lime milk dripping rate is 10mL/min, the purity of the prepared magnesium hydroxide can reach 96.79%.