Method for lowering the iron content in calcium carbonate

摘要

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 slurry 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.