The authoritative public forum
  for Metal Finishing since 1989
-----

Difficulties in total cyanide testing

Q. My name is Reid Clausen, I am the Environmental Compliance Manager for a wholesale jewelry manufacturer. I have permit limits set on all my categorical waters (any water which comes into contact with precious metals is considered categorical). One of my parameters which I test is Total cyanide. This has been my problem child because I have not been able to find a solution that really works and is cost effective. Our waste stream is co-mingled and my wastewater treatment area treats around 2000 gallons/day. I am in the process of trying hydrogen peroxide. Can someone tell me how much 25% hydrogen peroxide I should use in treating 400 gallons of wastewater and also if there is a better and more cost effective way to treat Cyanide what is it?

Reid Clausen
Env. Compliance Manager - Lafayette, Louisiana
July 27, 2009

---

"Cyanide processes" on AbeBooks or Amazon (affil links) A. Peroxide is mainly for batch treating, in my experience. For continuous flow operations, hypochlorite is better. You're not at all specific about what the problem is. A common one is lack of control of cyanide destruct pH. Optimum is 10.5 - 11. Another problem is iron cyanides. These cannot be destroyed with chlorine - they must be precipitated. What are your numbers like? Dave Wichern Consultant - The Bronx, New York July 30, 2009 A. Keep your CN waste stream separate as it forms cyanide complexes with stuff like iron that are really hard to break, but the acid reflux will break it and give you a high test value. What pH and material are you currently using to oxidize the CN to cyanate and finally to N2 and CO2 gas. James Watts - Navarre, Florida July 30, 2009 A. Please see letter 4251, the responses should answer your questions. Mark Baker process engineer - Malone, New York July 30, 2009