Salvaging -purifying mixed alloys ?

[J.B.]

Hello from Down Under. This may be a lost cause but I'll give it a shot regardless. ( pardon the pun). I've been casting off and on for a few years now and my first attempts were with mixed lots of lead & commercially cast bullets of dubious origin. A few years back, I gave up on commercial bullets for the Shiloh and commenced with pure lead and pure tin and mixed accordingly. Far better and more consistent results.
My question ? With a bucket full of commercial bullets & ingots poured from contaminated pots that contain antimony , arsenic and do doubt some zinc, I wondered if it is actually possible to heat these to a point where they actually separate and I can at least salvage the lead from them or is it a lost cause. Just throwing one or two pistol bullets into a pot containing a known 20/1 ratio of lead/tin seems to corrupt the whole lot and crystal like formations occur through the mix so I dont mix anymore when I dont know what I'm working with. Can it be saved or should I just leave it in the 'dont touch' bucket and let it be ?