The authoritative public forum
  for Metal Finishing since 1989
  

  -----

Cyanide is not sufficiently captured or destroyed in copper recovery DI process

I have an ion exchange unit for copper recovery. I'm getting cyanide out of the system. Probably have always had the problem, but my allowable cyanide discharge levels are dropping so I must reduce (or preferably eliminate) it.

There is copper (with ammonia ⇦ this on eBay or Amazon [affil links] and DI water among some proprietary solutions) going in at various times. Copper is later stripped from resins with sulfuric acid to regenerate the resins. Some of this sulfuric solution is saved (sometimes for 2-3 days) and re-used in next regen. Could the residual copper and sulfuric be causing this problem? No virgin materials being used are known to contain cyanide. We are having our city water tested - it is used to make the DI water for the process.

Mike Roberts
Operation Supervisor - Mississippi
October 4, 2011

---

First of two simultaneous responses -- October 6, 2011

Is there cyanide in any of your process solutions? If so, which?

Cyanide (as ferricyanide) is used as a catalyst in certain solutions for chromating aluminium.

Dave Wichern
Consultant - The Bronx, New York

---

I doubt that either the copper or the sulfuric acid is causing the problem. Since there are no cyanides in your process, I'd be suspicious that something else is a positive interference to the cyanide analysis.

Lyle Kirman
consultant - Cleveland Heights, Ohio
Second of two simultaneous responses -- October 7, 2011