Process for obtaining high purity magnesium compounds from magnesium containing materials
AssigneeMaterials-Concepts-Research Limited
InventorsDonald W. Kirk, Murray C. Robinson
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Abstract
Processes for the selective leaching of magnesium-containing solids, which contain calcium and/or heavy metals, and the selective precipitation and crystallization of the leached magnesium are provided. The leaching is conducted with aqueous sulphur dioxide at elevated temperatures with feed pulp densities which are sufficiently high to produce a leach liquor which is substantially saturated with magnesium. The selective crystallization and precipitation processes which preferably follow the selective leaching process, utilize controlled cooling, heating and pH conditions to yield a high purity magnesium sulphite product.
Claims17
A process for extracting magnesium from a solid containing magnesium in one or more of the forms of magnesium carbonate, magnesium hydroxide and magnesium oxide, said magnesium-containing solid also containing at least 5 weight percent of calcium impurities and optionally containing heavy metals, which process comprises:
- slurrying the magnesium-containing solid with an aqueous treating agent consisting essentially of solubilized sulphur dioxide at a temperature of at least about 50.degree. C. but below the boiling point, at a pH less than about 3.5, and at a feed pulp density of from about 200 to about 400 g/l to obtain a leach liquor substantially saturated in magnesium ions and to produce a magnesium depleted residue.
A process for extracting magnesium from a solid containing magnesium in one or more of the forms of magnesium carbonate, magnesium hydroxide and magnesium oxide, which solid also contains at least 5 weight percent of calcium impurities and optionally contains heavy metals, which process comprises:
- leaching the magnesium from the magnesium-containing solid with an aqueous treating agent consisting essentially of solubilized sulphur dioxide at a pH less than about 3.5, at a temperature of at least 50.degree. C., and at a feed pulp density of from about 200 to about 400 g/l to produce a leach liquor substantially saturated with magnesium ions and a magnesium depleted residue and subsequently separating the leach liquor from the residue;
- and
- cooling the leach liquor to about ambient temperature while increasing the pH of the leach liquor, to precipitate substantially pure magnesium sulphite, and subsequently separating the magnesium sulphite.
Dependencies are inferred from the claim text.