In what form is the copper? Its not sitting there as copper metal, that's a solid. Copper persulfate, while it may exist, doesn't sound to me like the most common form -- I'm suspecting its another salt. Do the two salts have different solubilities? That's something you can exploit. Where did you get this particular mix, and what is this typically used for. Copper isn't cheap, but its not exactly hard to find in a reasonably pure form, if you need it for a home experiment.