Pollution Prevention
Ask the Expert Question-and-Answer Archive

by George Cushnie
December, 2009

Decontamination of Potassium Cyanide Plating Equipment

Q. Can you please give me some guidance on decontamination of materials exposed to potassium cyanide at an industrial site? We have a site where potassium cyanide is added to an electroplating bath to facilitate the electroplating process. This processing line will be decommissioned and we are looking at alternatives to manage the equipment, specifically how to decontaminate and dispose of it (or recycle it). The equipment consists of metal, rubber, plastic, and cloth. I have read where bleach can be used to decontaminate contaminated material. Do you think this would be an effective and complete approach? Or do you have any other thoughts.

Greatly appreciate it – Thanks!

A. I dont have any experience with equipment decontamination, so please check with other sources before starting the job.

I can tell you that alkaline chlorination is a proven method for treating cyanide. Is is performed at a pH of 11.0 to 11.5. Presumably, a dilute solution of household bleach (sodium hypochlorite) should do the trick. However, I recommend that you do some experimentation to determine the best bleach concentration, contact time and procedures for complete cyanide destruction. Be certain not to use acids for cleaning. Acids coming into contact with cyanide can form a deadly cyanide gas.

A different approach that you may want to look into is ozone oxidation of cyanide. Portable ozone units (they look like a pressure sprayer), like those used by the food processing industry (e.g., wineries) for sterilization should be effective.

In any case, the resultant wastewater (equipment rinsing/washdown, etc.) will likely be a hazardous waste due to the presence of toxic metals. If so, you will need to follow RCRA hazardous waste rules for identification, management and disposal of it.

Regards,
George Cushnie