Hydrochloric acid (pool acid, muratic acid, brick cleaner) will dissolve the copper and leave the gold intact. Bubbling air thru the acid will make it work faster. Even so, plan a week or two for all the copper to dissolve.
The resulting green liquid is toxic to some water creatures. Instead of dumping it, remove the gold(a coffee filter works well for this) then put a piece of rust free iron in the solution. The copper will precipitate out as a sediment and the fluid will change from green/black to rusty. This you can dump down the drain without guilt. However I suggest adding baking soda first so the acid doesn't eat your pipes.
Also eye protection throughout of course since eyes don't grow back
Disclaimer: don't use acid without proper training and don't be an idiot