PRECIPITATED CALCIUM CARBONATE FROM PULP MILL WASTE HAVING AN IMPROVED BRIGHTNESS, METHOD FOR THE PRODUCTION AND USE THEREOF

摘要

The present invention relates to a process for the production of a precipitated divalent metal ion carbonate product from a divalent metal ion carbonate which was recovered from waste, the precipitated divalent metal ion carbonate product having an improved brightness, the process comprising the steps of: providing a low-purity divalent metal ion carbonate material, the divalent metal ion carbonate material being recovered from waste; calcining the divalent metal ion carbonate material in order to obtain a divalent metal ion oxide; slaking the divalent metal ion oxide in order to obtain an aqueous suspension of a divalent metal ion hydroxide; carbonating the aqueous suspension of the divalent metal ion hydroxide with a carbon dioxide containing compound in order to obtain fine precipitated divalent metal ion carbonate particles; post-treating the fine precipitated divalent metal ion carbonate particles to obtain fine discrete precipitated divalent metal ion carbonate particles; adding the fine discrete precipitated divalent metal ion carbonate particles to an aqueous suspension of divalent metal ion hydroxide that was obtained by slaking high-purity divalent metal ion hydroxide in order to obtain a resulting reaction mixture; and carbonating the resulting reaction mixture in order to obtain the precipitated divalent metal ion carbonate product having an improved brightness.

主权项

1. An aqueous suspension comprising a precipitated divalent metal ion carbonate obtained by the process comprising the steps of:
(a) providing a low-purity divalent metal ion carbonate material; (b) calcining the divalent metal ion carbonate material of step (a) to obtain a divalent metal ion oxide; (c) slaking the divalent metal ion oxide obtained in step (b) to obtain aqueous suspension of a divalent metal ion hydroxide; (d) carbonating the aqueous suspension of the divalent metal ion hydroxide obtained in step (c) with a carbon dioxide containing compound to obtain fine precipitated divalent metal ion carbonate particles; (e) subjecting the fine precipitated divalent metal ion carbonate particles obtained in step (d) to deagglomeration to obtain fine discrete precipitated divalent metal ion carbonate particles; (f) mixing the fine discrete precipitated divalent metal ion carbonate particles obtained in step (e) with an aqueous suspension of high-purity divalent metal ion hydroxide to obtain a resulting reaction mixture; and (g) carbonating the resulting reaction mixture of step (f) to obtain a precipitated divalent metal ion carbonate product having an improved brightness as compared to the precipitated divalent metal ion carbonate particles obtained in step (d).