Extraction of hexachloroplatinate from hydrochloric acid solutions with phosphorylated hexane-1,6-diyl polymers

A series of diols (diethylene glycol, triethylene glycol, butane-1,4-diol and hexane-1,6-diol) were immobilized onto Merrifield resin and subsequently phosphorylated with dialkyl chlorophosphate (alkyl = Me, Et, Bu). The resins bearing hexane-1,6-diyl groups exhibited very good extraction abilities in regard to precious metal chloro complexes like platinum(IV), palladium(II) and rhodium(III). In batch experiments, more than 98% of Pt(IV) is extracted even when the metal and the hydrochloric acid concentration is enhanced significantly. Elution can be achieved with a solution of 0.5 mol L−1 thiourea in 0.1 mol L−1 hydrochloric acid. In the presence of other noble metals, platinum(IV) is preferentially bound. The extraction yield decreases in slightly acidic solution in the following order: Pt(IV) ≈ Pd(II) > Rh(III) and changes with increasing hydrochloric acid concentration to Pt(IV) > Pd(II) ≫ Rh(III). At different ratios of metal and acid, the temperature has nearly no influence on the platinum extraction. On slightly acidic media, the extraction of rhodium decreases by 30% when the temperature is increased from 10 °C to 40 °C. When the acid and metal concentration is enhanced, the palladium extraction decreases by 7-9%, depending on the resin.