Re-using used etch solutions for plating

We use ammonium persulphate and sulfuric acid bath to etch/mill copper. After the bath is saturated(used) can we use this for a plating bath? We currently dispose of it, but would like to get another use of it, or sell it.

Why don't you recycle the bath and just remove the copper from it? Unless you kill the persulphate completely - and adjust the copper concentration - and add chloride and remove some of the free acidity - and remove the trace contaminants from the bath, such as chromium and other ions, I do not think that you would be pleased with your plating results, nor would it be a "saleable process solution".

You can easily remove most of the copper from the bath - and if you generate enough of it, there is technology that can restore the persulphate back to the process conditions continuously and remove the copper as a resaleble by-product.