Cyanides are important industrial chemicals used in electroplating, mining, manufacturing of various fibers and resins etc. The wastes from these processes are highly toxic contaminants in wastewater. The general waste treatment process is to oxidize the cyanide radical (CN-) to carbon dioxide and nitrogen. Depending on concentration, metals and other components in the waste stream, the cyanide may be easy or very difficult to oxidize. Generalized treatments are for dilute solutions, refractory solutions and concentrated solutions.

General Oxidation of Dilute Solutions

The addition of one or more or the following chemicals will typically accomplish the oxidation of cyanides to carbon dioxide and nitrogen: chlorine, sodium hypochlorite, hydrogen peroxide, ozone etc. Oxidation, in special cases, may be completed or enhanced by ultraviolet radiation, adaption of bacteria in a biological treatment system and electrolytically. In most of the above cases, pH and oxidation reduction potential (ORP) controls are implemented.

Oxidation of Refractory Cyanides

Their resistance to breakdown to innocuous products usually identifies refractory cyanides by the general oxidation systems. The most common refractory cyanide is iron cyanide. Iron cyanide is a stable typically non-reactive cyanide that passes through generalized treatments unaffected. It is now realized that iron cyanide will break down when exposed to the UV radiation from the sun releasing free cyanide in receiving lakes and rivers. Treatment systems employ elevated temperature oxidation principals potentially combined with a catalyst to reach low parts per billion (ppb) treatment levels.

Oxidation of Concentrated Cyanides

Concentrated cyanides are treatable by any of the above methods but the cost of treatment is prohibitive. Their use normally involves diluting the solution and high chemical usage. Electrolytic destruction of concentrated solutions is the lowest cost method of treatment. A typical electrolytic system will reduce concentrations to ~1 gram per liter where conventional treatments will polish the process to ppb levels.

Manchester Cyanide Oxidation Systems

Manchester will provide systems for all types of cyanide oxidation depending on other chemistries present with the goal of providing the most reliable and efficient system for the desired output.