Patent ID: 6530987
Filing Date: 2003-03-11
Classification: C01G,C01P

Abstract:
A process for the preparation of an iron oxide pigment from the waste acid resulting from the preparation of titanium dioxide by the sulfate process comprisinga) obtaining a precipitate containing at least one of Ti, Al, Cr and V compounds by partially neutralizing in a first stage the sulfuric acid contained in the waste acid with metallic iron and/or an iron compound, wherein the metallic iron and the basic iron compounds have a manganese content of <0.8% by weight of Mn, based on Fe. b) optionally obtaining a precipitate containing at least one of Ti, Al, Cr and V compounds by further neutralizing the sulfuric acid with a further alkaline compound, c) separating the precipitate containing Ti, Al, Cr and/or V compounds from the resulting reaction product to form an iron sulfate containing solution, and d) precipitating an iron oxide pigment from the Iron sulfate containing solution by adding an alkaline compound and an oxidizing agent.