| 摘要 |
A method for recovering a magnesium carbonate of high purity from an aqueous magnesium hydroxide slurry is disclosed. The slurry contains at least 1 percent of magnesium hydroxide and consists of water, magnesium hydroxide and impurities normally associated with magnesium hydroxide slurries. The method involves carbonating the slurry with sufficient carbon dioxide to dissolve a substantial proportion of the magnesium hydroxide therein as magnesium bicarbonate, continuing carbonation until a solution saturated with magnesium bicarbonate is formed, a portion of the magnesium bicarbonate is converted to a crystalline magnesium carbonate and substantially all dissolved calcium is precipitated, so that the slurry contains dissolved magnesium bicarbonate, a crystalline magnesium carbonate precipitate and a calcium carbonate precipitate. Solids are then separated from the magnesium bicarbonate solution, the solution is decarbonated, for example by heat or vacuum, and hydrous magnesium carbonate is separated from the aqueous phase.
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