I'm not sure it is economical, but I had some Sodium Persulfate etchant that was full of copper and accidentally dropped a piece of steel in it. The copper pla

I'm not sure it is economical, but I had some Sodium Persulfate etchant that was full of copper and accidentally dropped a piece of steel in it. The copper plated onto the steel almost instantly. You could probably use iron filings (or some metal that won't dissolve in your acid) to pull most of the copper out of the acid, and then neutralize. I'm not sure what you would do with the solid copper after that. It might take some effort to get a system that was reliable and economical, but the basic idea of precipitating out the copper before neutralization should work.