Abstract: Aminophosphonic acid functionalized silica synthesized by chemical grafting method was utilized as the sorbent for separation of platinum (Pt) and palladium (Pd) from aqueous solution. The effects of pH, contact time, initial metal concentration, ionic strength and solid-liquid ratio on the sorption of Pt and Pd by functionalized silica were investigated. The sorption capacity is strongly dependent on pH but independent on the ionic strength and solid-liquid ratio. The sorption process fits the pseudo-second-order kinetic model and Langmuir isotherm very well. Equilibrium sorption capacities of 18.5 mg/g for Pt at pH=2 and 29.9 mg/g for Pd at pH=6 are achieved respectively. The distinct sorption behavior of functionalized silica for Pt and Pd with pH can be used for separation of these two metal ions in aqueous solution. The sorbed Pt or Pd can be completely eluted using 6% sulfourea in 5 mL 0.1 mol/L HNO₃. The synthesized sorbent material can be recycled and reused.