Method for purification of calcium carbonate
AssigneeMinerals Technologies Inc.
InventorDonald Kendall Drummond
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Abstract
A method for lowering the iron content of calcium carbonate is disclosed. The method involves addition of an iron chelating agent to an aqueous calcium carbonate slurry, reducing the pH of the aqueous calcium carbonate by employing carbon dioxide containing gas, while maintaining the aqueous calcium carbonate slurry at an elevated temperature. The slurry is stirred, filtered, washed and dried. The calcium carbonate product resulting from the process of the present invention has a reduced iron content. Calcium carbonate produced according to the method of this invention is particularly suitable for use as food or pharmaceutical additives and may also be useful as a filler in papermaking processes or as additives in plastic products.
Claims10
A process for lowering the iron content of calcium carbonate which contains iron comprising treating an aqueous slurry of said calcium carbonate with a chelating agent, heating said aqueous calcium carbonate slurry containing said chelating agent and treating said aqueous calcium carbonate slurry containing said chelating agent with carbon dioxide gas, wherein said treating with said chelating agent is performed while heating and agitating said slurry and introducing said carbon dioxide gas to maintain a pH of said slurry in the range of about 5.5 to no higher than 7.0.
Dependencies are inferred from the claim text.