Method for preparing high-purity magnesium oxide with high boron salt lake brine

Abstract

Provided is a method for preparing high-purity magnesium oxide with high boron salt lake brine. Salt lake brine is evaporated through a salt pan, concentrated to crystallize potassium sulfate, sodium chloride and potassium chloride and is drawn with lithium in adsorption mode so as to obtain master sauce brine containing magnesium and boron. Concentrated sulfuric acid is added into master sauce brine for reacting, and coarse boracic acid and acidized brine are obtained after cooling and filtering. Potential of hydrogen (pH) value of acidized brine is adjusted to be 5.5-6.5, and acidized brine passes through ion exchange resin adsorbing boron. When boron concentration in effluent liquid is higher than 5 mg / L, brine is not injected, boron-removed brine is obtained, then boron-removed brine and ammonium chloride solution are filled with ammonia for stirring and to produce magnesium sedimentation reaction, reaction temperature ranges from 60 DEG C to 80 DEG C, pH ranges from 7.5 to 8.0, the reaction is stopped when concentration of free ammonia reaches 1.8-2.2 mol / L, and magnesium hydroxide and magnesium sedimentation mother solution are obtained. Magnesium oxide is obtained by calcining magnesium hydroxide, content of magnesium oxide is larger than 99.8%, and magnesium extraction ratio is larger than 90%. Sedimentation mother solution adopts lime to steam ammonia, and generated ammonia circulates to magnesium sedimentation reaction. Mother solution after ammonia steaming is evaporated, concentrated and crystallized to obtain calcium chloride. Ion exchange resin adsorbing boron is washed, analyzed and regeneratively cycled for use. Boron-containing analysis solution is concentrated and cooled to pick up coarse boracic acid, and coarse boracic acid is recrystallized to obtain refined boracic acid with purity larger than 99%. High-purity magnesium oxide prepared by the method is high in purity, good in economic benefit, free of environment pollution, strong in operability and favorable for industrial production.

Description

technical field [0001] The invention relates to the field of comprehensive utilization of salt lake resources, in particular to a method for extracting boric acid and preparing high-purity magnesium oxide by using high-boron salt lake brine as a raw material. technical background [0002] High-purity magnesium oxide is a magnesium salt fine chemical product, widely used in high-grade plastics, steel, ceramics, paint, medicine and other industries. At present, there are two ways to produce magnesium oxide in the world. One is to use magnesite or dolomite as raw material, and it is produced by electrothermal method. This method is mostly used in China. The product purity can only reach 98.5% at most, and the product qualification rate Low, high production cost. The other is to use seawater or salt lake brine as raw material to produce magnesia. This method is mostly used in western developed countries, and the product purity is 96%-99%. [0003] With the development of scien...

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Problems solved by technology

[0004] In summary, there are problems of low purity and poor product performance in the direct preparation of magnesium oxide from brine after boric acid extraction by acid method

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