SEPARATION OF NOBLE-METAL IONS ON SILICA WITH CHEMICALLY BONDED LIGANDS

The separation of noble metal ions was investigated by chemically bond ed ligands based on the concept of ''hard'' and ''soft'' acids and bas es according to Pearson; influences of ion pairing and chelating effec ts are discussed. Complexing groups containing oxygen, nitrogen and su lphur were immobilized on silica gel. Ag, Au, Ir, Os, Pd, Pt and Rh we re adsorbed in the acidic range (pH 0 to pH 5) and eluted from the gel in the range from pH 0 to pH 7.5 avoiding formation of hydroxides and coprecipitation of the noble metals. The separation is dependent on t he immobilized ligand, the pH-value of sorption and desorption and the eluent.