This thread took a humorous turn but maybe
@Abdoulapapatte and
@100tific become the refining power couple! I certainly can think of worse places to meet a partner
Both of you definitely have very good chemistry...knowledge!
Back to business though, as Miss 100tific is here to make money.
For cases such as yours, Miss 100tific, I always proceeded as follows:
1. granulate the material after assay confirming silver <5%w/w
2. Dissolve in aqua regia
3. Remove excess nitrates with sulfamic acid solution until ebullition of N2O stops. Sulfuric acid is produced in the reaction which will precipitate lead.
4. Dilute to approximately 2-3 M in HCl then filter any lead sulfate and silver chloride; rinsing filter cake with 0.1 M HCl until colorless. This filter cake goes to silver smelting where traces of gold and other PGMs are recovered.
5. To the mother liquor, I would remove the gold any which way (ferrous sulfate, as noted above is more selective than SO2 and its associated salts) until negative stannous test
6. Cementation of residual PGM with copper sheet as described above until negative stannous test for Pt/Pd, filtered and then then barren solution then goes for copper recovery with iron sheets. The air stirring recommended is not my preference because it can make allergenic mists and generate some chlorine if the HCl concentration is too high-- so I prefer a slow stir.
7. For the reduced PGM blacks recovered in
6., these I like to dissolve in HCl/H2O2. At this point, decisions must be made to get pure platinum and that depends on how much other anionic impurity is present (Pd/Rh/Ir/Ru). In some instances, a simple precipitation as the ammonium salt is enough to obtain 99.9% w/w Pt. In others, it is best to boil the solution to decompose Pd(IV), add a trace of reducing agent (i.e. sodium nitrite) and end up with Ir(III) remaining in solution and
then precipitate the bulk of the Pt with ammonium chloride as the chloroplatinate. Everything at this stage depends on Pt to Pd:Ir:Ru:Rh ratios. For ratios when Pt to other PGMs is say >20:1, hydrolysis is usually indicated but as that gap narrows, some of the older classic methods are more appropriate to flip the ratio.
In general, Pt will easily be contaminated with Pd/Ir (especially if the solution is highly oxidized and/or cold) and less so with Ru/Rh (especially if the solution is filtered from precipitate warm, as these metallates are reasonably well soluble). Again, these coarse separations are made depending entirely on solution characteristics.
Edit: some emoji auto formatting needing fixed.