Recovery of salts, especially magnesium hydroxide for production of magnesium metal and also fertilizer materials, comprises dissolution from magnesium sulfate-containing residues, e.g. from potash works waste

摘要

Method for the recovery of salts comprises using magnesium sulfate-containing residues (especially residue dumps from the potash or rock salt industries) or of magnesium sulfate-containing natural or synthetic brines, and recovering e.g. water-soluble magnesium- and sulfate-salts. Method for recovery of salts e.g. magnesium ions comprises selectively precipitating magnesium hydroxide with the aid of ammonia or ammonium hydroxide. The ammonia is recovered and recycled from a subsequent sulfate ion recovery and gypsum production stage by being driven off with a strong base, especially quicklime or calcium hydroxide, which is used in the recovery of the sulfate ions. The residual salt solutions of the process can be partially or completely evaporated to give further useful salts or substances, especially sodium-, potassium-, sulfate-, carbonate-, chloride- or bromide-salts.