A hydrometallurgical process for the recovery of metals selected from the group consisting of platinum, palladium, rhodium, ruthenium, iridium, and gold (PM) from solids includes dissolving the PM and base metals in an acidic halide aqueous solution and precipitating the PM using substituted quaternary ammonium salts (SQAS). PM having multiple oxidation states may be oxidized or reduced to separate through differential solubility. Au-SQAS is separated by washing the precipitate with a suitable organic solvent. Rh-SQAS and other PM with multiple oxidation states are dissolved in a strong halide acid solution and oxidized to separate soluble Rh. Pb and Pd are separated by boiling the initial acidic halide aqueous solution of metals in an excess of SQAS. The Pb and Pd filtrate is oxidized and then Pd-SQAS is dissolved in aqueous ammonia and separated from insoluble Pb. A slurry of Ir-SQAS and Pt-SQAS are separated through dissolution of Ir-SQAS with NaNO2.