Method for preparing rod-like magnesium hydroxide from salt lake brine

Abstract

The invention discloses a method for preparing rod-like magnesium hydroxide from salt lake brine. The method comprises the following steps of: concentrating and crystallizing salt lake brine, from which elements such as potassium and lithium are extracted, serving as a raw material to obtain bischofite; dissolving the bischofite separated by crystallization into water to prepare magnesium chloride solution; introducing ammonia gas to perform magnesium precipitation reaction; when the pH value reaches 7-8, stopping introducing the ammonia gas, reacting at the temperature of 30-50 DEG C for 0.5-2 hours, aging and filtering to obtain alkaline magnesium chloride and magnesium precipitation mother liquor; dispersing the alkaline magnesium chloride in mixed solution of ethanol and water to obtain alkaline magnesium chloride suspension; adding sodium hydroxide to further precipitate to obtain rod-like magnesium hydroxide; filtering and separating to obtain magnesium precipitation mother liquor; replenishing the bischofite and circulating for precipitating the alkaline magnesium chloride; feeding to an ammonia still process along with concentration enrichment of magnesium precipitation mother liquor in ammonia chloride; performing ammonia still with lime; and circulating the produced ammonia gas to precipitate the alkaline magnesium chloride of a next batch and producing byproduct calcium chloride, wherein the magnesium content in the brine is not less than 93.4 g/L. The method has the advantages of high product purity, good economic benefit, no environmental pollution, high operability and easiness for industrial production.

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