First of all, I'm truly sorry if I have any mistake, because I'm not English and I'm not used to chemistry specific terms.
So last week, we were working on copper recycling in the school lab, and in the end of the first experience, which involved adding NHO3, Na2O, HSO4, solid Zn and HCl (in this order) to 0.3g of Cu. However, we ended up having a yield of 105%. Suspecting it was because of some Zn that hadn't reacted we added more HCl to the copper.
Then we left it there for 5 days, reacting and allowing the particles to reach the bottom of the beaker. But when we came back to the lab we noticed that the solution was an intense green, instead of the usual blue we were supposed to have. So we added some Zn for it to react with whatever was the intense green component, which led us to a solution that no color at all with plenty of what looked like a dark salt in the bottom.
We actually thought it was some kind of copper oxide, so we added some HSO4 which led to a "boiling" reaction that didn't have any noticeable changes to the naked eye.
So we know that the dark substance isn't copper oxide, and we suppose that it's some kind of copper salt, but we have no idea of what it specifically is, and how are going to have solid and pure copper again.
Hope you can help me...