Cyclochrome—The Recycle of Sodium Dichromate in Sodium Chlorate Manufacture

Abstract

Sodium dichromate is used in the electrochemical manufacture of sodium chlorate to both buffer the electrolyte and to minimize undesirable cathodic reactions.

Increasing quantities of chlorine dioxide are being produced from chlorate solutions as the use of environmentally undesirable chlorine is reduced in pulp mill bleaching operations. Such processes result in the contamination of mill effluents with chromium species which cause environmental concerns.

Several processes are known for dichromate removal, but they are expensive to operate. This paper will discuss a process utilizing ammonia and sodium hypochlorite, both generally available at sodium chlorate producing plants, to recover dichromate at a reagent cost less than the value of the recovered dichromate.