The question here has been a replacement for the persulfate.
From Wikipedia, the free encyclopedia
"The term
persulfate (sometimes known as peroxysulfate) refers to ions or compounds containing the anions
SO2−
5 or
S
2O2−
8. . . . These salts are strong oxidizers."
I'm not sure what the copper reaction with the persulfate would be, but it obviously doesn't involve HCl, and since the persulfate is an oxidizer, won't require H
2O
2. If you use the CuCl or FeCl etchants, you can't avoid HCl in the process - it's part of the reaction.
It's been too long (65+years) since my high school/college chemistry!
Norm