Patent ID: 6299846
Filing Date: 2001-10-09
Classification: C01F

Abstract:
A process for producing aluminum hydroxide, which comprises the steps of:(a) mixing a first portion of an alumina-containing ore with a first alkaline solution to obtain a first alumina-containing slurry,(b) mixing said first alumina-containing slurry obtained in step (a) with a preheated alkaline aqueous solution, to obtain a first alkaline aqueous mixture,(c) extracting alumina as sodium aluminate from said first alkaline aqueous mixture obtained in step (b), to provide a mixture of an extract solution of sodium aluminate and a dissolution residue of a reactive silica,(d) separating said dissolution residue from said mixture provided in step (c), to obtain the extract solution of sodium aluminate,(e) mixing the extract solution of sodium aluminate obtained in step (d) with a second alumina-containing slurry obtained by mixing a second portion of an alumina-containing ore with a second alkaline solution, and mixing the extract solution with a third alkaline solution to obtain a second alkaline aqueous mixture,(f) extracting alumina as sodium aluminate from said second alkaline aqueous mixture obtained in step (e), to obtain a mixture comprising an extract solution of sodium aluminate,(g) desilicating said mixture comprising the extract solution of sodium aluminate obtained in step (f), to provide a mixture containing a desilication product and a desilicated-extract solution,(h) separating the desilication product from said mixture provided in step (g), to obtain the desilicated-extract solution, and(j) adding seeds of aluminum hydroxide to said desilicated-extract solution obtained in step (h), to precipitate aluminum hydroxide.