Getting the waste is up to your social engineering skills.http://www.sciencemadness.org/talk/viewthread.php?tid=5328&page=2http://www.sciencemadness.org/talk/viewthread.php?tid=5700&page=2https://sciencemadness.org/talk/viewthread.php?tid=5700
"I have successfully recovered 34g of pure gold from dental alloys and also the platinum and palladium.
After dissolution in aqua regia, the solution is diluted to make all the AgCl precipitate. The AgCl is boiled with dilute HCl to extract some palladium which has coprecipitated.
The combined solutions are boiled down in a still and evaporated two times with concentrated HCl to ensure that no nitrate ions are left (important).
The gold is then quantitatively precipitated by heating the solution to 80°C and bubbling in sulfur dioxide until no more gold (yellow to brown, crystalline, very dense precipitate) settles out. Don't mess with other reducing agents like dithionite, disulfite, FeSO4 or similar, they intruduce sodium or Fe(III) ions into the solution which will be a nuisance later.
The gold is washed and redissolved in aqua regia, boiled down, evaporated two times with HCl and precipitated by adding oxalic acid in excess, boiling and then slowly neutralizing the solution with ammonia until the solution is colorless.
This purification produces almost 999 fine gold. If gold of certainly 999 fineness is desired, it is redissolved, evaporated with HCl as before and precipitated this time with FeSO4.
The solution from the precipitation of the gold is bubbled with chlorine at room temperature to reoxidise the platinum to IV.
The solution is then boiled for an hour to reduce the oxidised palladium.
Ammonium chloride solution is added, yellow ammonium hexachloroplatinate precipitates which is filtered.
To the solution from before is addedmore ammonium chloride, it is cooled to 10°C and chlorine is bubbled in. Brick-red ammonium hexachloropalladate precipitates. It is rapidly filtered and washed with chlorine- containing NH4Cl solution (not with water!).
If the filtrate is still brown, the treatment with NH4Cl and chlorine and filtering of red precipitate is repeated. "