PRECIPITATED CALCIUM CARBONATE FROM PULP MILL WASTE HAVING IMPROVED BRIGHTNESS, METHOD FOR PRODUCTION AND USE THEREOF Russian patent published in 2016 - IPC C01F11/18 C01B31/24 C09C1/02 C09C3/06 

FIELD: chemistry.

SUBSTANCE: invention relates to a process for production of a precipitated divalent metal ion carbonate product from a divalent metal ion carbonate which was recovered from waste, precipitated divalent metal ion carbonate product having an improved brightness, and process comprises following steps: (a) calcining divalent metal ion carbonate-containing material of low purity, having a degree of whiteness R457 according to ISO of less than 90 % when measured according to ISO 2469, extracted from wastes to obtain containing divalent metal oxide ions; (b) slaking divalent metal ion oxide obtained at step (a) in order to obtain an aqueous suspension of a divalent metal ion hydroxide; (c) carbonating aqueous suspension of divalent metal ion hydroxide obtained at step (b) with a carbon dioxide containing compound in order to obtain fine precipitated divalent metal ion carbonate particles; (d) post-treating fine precipitated divalent metal ion carbonate particles obtained at step (c) to obtain fine discrete precipitated divalent metal ion carbonate particles by de-agglomeration; (e) adding fine discrete precipitated divalent metal ion carbonate particles obtained at step (d) 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 (f) carbonating resulting reaction mixture obtained at step (e) in order to obtain precipitated divalent metal ion carbonate product having an improved brightness in comparison with precipitated carbonate particles containing divalent metal ions obtained at step (c). Invention also relates to an aqueous suspension for producing a pigment for coating compositions or filler in production of paper, plastic, rubber, construction materials and dyes, including precipitated divalent metal ion containing carbonate, and to a product as a pigment in coating compositions or as filler in production of paper, plastic, rubber, construction materials and dyes, containing dried precipitated divalent metal ion containing carbonate.

EFFECT: production of metal.

16 cl, 6 dwg, 2 tbl, 5 ex