An improved process for the purification of white mineral carbonates

Abstract

Abstract The degree of whiteness of a mineral carbonate containing humic acids which are organic colour-imparting impurities is improved by treating the carbonate at 20-100 DEG C. with a halogen, an oxygen-containing halogen acid, or a salt thereof, e.g. HOCl, HClO4, CaOCl2, CaCl2, NaOCl, or ozone, or oxidizing agents in alkaline media, e.g. H2O2, Cl2, Br2, or transforming into a soluble form, e.g. by a salt of phosphoric acid or a polyphosphoric acid. The degree of whiteness of all mineral carbonate fillers, e.g. calcite, dolomite and chalk, can be improved. Treatment may be carried out in an aqueous medium, thereafter separating the carbonate, washing and drying it.

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