Synthesis of mesoporous silica-phosphate hybrids and their adsorption competency for rare earth metal cations

Abstract

Mesoporous silica-phosphate hybrids were successfully prepared by three processes: hybridization post synthesis by H3PO4, hybridizations during synthesis by Na2HPO4 and by PO(OC2H5). X-ray diffraction patterns confirm that the hexagonal pore structure was maintained after the hybridization process. The maximum phosphate amount was 2.9 mol % in the sample prepared by hybridization during synthesis from Na2SiO3 and PO(OC2H5)3. The specific surface area showed a large value of approximately 1000 m2/g despite the hybridization. The SiOP bonds were confirmed by nuclear magnetic resonance and X-ray photoelectron spectroscopy. The maximum adsorption amount of rare earth metal cations into the hybrid was approximately 70% of the initial concentration (50 mg/L) for each rare earth metal cation in coexistence with 13 rare earth metal cations.