A novel functionalized polysiloxane material with covalently bonded 4-acylpyrazolone Schiff base ligand was prepared by polycondensation of 4-[1-(3-triethoxysilyl-propylamino)-ethylidene]-5-methyl-2-phenyl-2, 4-dihydro-pyrazol-3-one with four equivalents of tetraethoxysilane under basic conditions. This polysiloxane material was characterized using elemental analysis, solid-state CP MAS 13C, 29Si NMR, TG-DTA and FT-IR spectroscopy. Lanthanide ion adsorption properties of this polysiloxane material were studied for seven trivalent lanthanide ions and are shown to be selective in the adsorption of Yb3+ ions from dilute aqueous solutions, in which 99% adsorption was observed from a 1.00 × 10 -5 M aq. solution of pH 6.7, after 24 h at room temperature. Six other lanthanides studied, Gd3+, Tb3+, Eu3+, La3+, Nd3+ and Sm3+ showed moderate to weaker adsorptions of 36, 36, 28, 17, 14, and 11% respectively under identical conditions. © 2009 Springer Science+Business Media, LLC.