So these are antineoplastic (anti-cancer) drugs, obviously. It would require a chemical process, since the platinum is covalently bound within the molecule.
Might also require different processes for the different drugs.
Cisplatin is Pt bound to 2 chlorines and 2 ammonia ligands.
Carboplatin also has two ammonia ligands, but the other 2 binds are metalloester bonds to an organic molecule (cyclobutan-1,1-dicarboxylic acid). It's derived from cisplatin. Interestingly, in the reaction which creates it, silver nitrate is used.
Oxaliplatin again derives from the base drug cisplatin, contains a dicarboxylic acid group, but instead of ammonia groups, it features 2 bonds to trans-1,2-diaminocyclohexane.
The key is going to be finding a reaction which will liberate the Pt from those various side groups. I suspect cisplatin might be converted to tetrachloroplatinate ion in a reaction with HCl, given cisplatin's synthesis appears to be done under basic conditions with silver nitrate and potassium chloride. HCl should cleave off the ammonia groups, creating acidic ammonium salts. It might require the presence of a chloride salt to facilite the additional ions. The tetrachloroplatinate should then be able to be directly reduced.
But the other 2 drugs could be more complicated with their organic side groups.