Most of the time we can normally eliminate much of the lead from our scrap with mechanical separation or pretreatment.
Another method we can use as a pretreatment is to remove lead by attacking the lead solder (lead/tin solder) with HCl without an oxidizer so that the tin goes into solution, breaking down the finely divided lead enough, to oxidize it into an insoluble lead chloride powder. Leaving the more unreactive metals intact, (metals like copper and gold that are below hydrogen in the reactivity series), that will not dissolve without the oxidizer added to the HCl acid),
Copper II chloride used as a leach will also dissolve tin and copper into solution, and break down lead to an insoluble lead chloride powder, but will not dissolve much of the gold, if you do not add too much oxidizer, what fine gold that does get attacked will end up as fine black powder mixed in with the insoluble materials like the lead chloride.
Lead chloride is pretty insoluble in cold water (or solutions), but can become pretty soluble in hot water, here is another tool we use to remove lead chloride from our material.
When we are working with an acidic chloride solution, like HCl (with an oxidizer) or aqua regia, most of the lead will become an insoluble lead chloride which if it is left to settle can be removed by careful decanting of the solution and filtering, what lead does carry through the process with this solution can then be removed with a few drops of sulfuric acid, and precipitated out of solution as a lead sulfate.
Normally by this stage you do not have much lead left in solution to remove (if you done your work well in previous steps), so it does not take much sulfuric acid to remove the lead from solution.
