Process for automatically controllable reduction of the nitrite content of nitrite-containing aqueous solutions to values below 1 mg/1

US5306431A · kind A · utility

Assignee

• Degussa AG · DE

Inventors

• Joachim Fischer · Rodgau, DE
• Hubert Wolf · Hammersbach, DE
• Klaus Stuetzel · Frankfurt am Main, DE
• Friedhelm Brandner · Gelnhausen, DE
• Manfred Diehl · Frankfurt am Main, DE

Key dates

• Filing date: Aug 7, 1992
• Grant date: Apr 26, 1994
• Expiry date: Aug 7, 2012

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C23G1/02
• WIPO field: Surface technology, coating
• WIPO sector: Chemistry

Abstract

Reduction of the nitrite content of aqueous solutions by treatment with hydrogen peroxide in the acidic pH range can be controlled by measurement of the redox potential. Contrary to the teaching of the prior art, addition of the hydrogen peroxide in the process according to the invention is terminated not at the highest redox potential, but only after lowering of the potential to a value of 650.+-.10 mV. In this way, nitrite contents below 1 mg/l can be obtained even when the solutions additionally contain fluctuating amounts of various compounds oxidizable by H.sub.2 O.sub.2.