Method for reprocessing waste acid to form gypsum and iron oxide

US6416723B1 · kind B1 · utility

Assignee

• BAYER HEALTHCARE LLC · DE

Inventors

• Gerhard Auer · Krefeld, DE
• Gunter Lailach · Krefeld, DE
• Ulrich Meisen · Kall, DE
• Werner Schuy · Tönisvorst, DE

Key dates

• Filing date: Sep 15, 2000
• Grant date: Jul 9, 2002
• Expiry date: Sep 15, 2020

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C01P2006/64
• WIPO field: Materials, metallurgy
• WIPO sector: Chemistry

Abstract

Process for the production of gypsum and also of an iron-oxide pigment from the waste acid that accumulates in the course of the production of titanium dioxide in accordance with the sulfate process, characterized in that in a first stage a partial neutralization of the waste acid is effected with a calcium compound subject to precipitation and optionally direct separation of gypsum, subsequently the remaining solution is neutralized further in a second stage subject to precipitation of a deposit containing Ti, Al, Cr, V and optionally Fe(III) and from the solution containing iron sulfate that is obtained after separation of the solids an iron-oxide pigment is produced in a third stage by addition of alkaline compounds and also optionally addition of ammonia and also of an oxidizing agent, ammonia being liberated by addition of CaO and/or Ca(OH)2 from the solution containing (NH4)2SO4 that is obtained after separation of the iron-oxide pigment.