Stabilization of quercetin-functionalized silica gel against hydrolysis by blocking silanol groups with TiO2 or ZrO2 and its application for the removal of Hg(II)

• Published in: Journal of sol-gel science and technology 2011, Vol.57 (1), p.57-67
• Main Authors: Abou-El-Sherbini, Khaled S., Schiel, Detlef, Stosch, Rainer, Weidler, Peter, Höll, Wolfgang H.
• Format: Article
• Language: English
• Subjects: Blocking; Ceramics; Chemistry; Chemistry and Materials Science; Colloidal gels. Colloidal sols; Colloidal state and disperse state; Composites; Exact sciences and technology; General and physical chemistry; Glass; Hydrolysis; Inductively coupled plasma; Infrared analysis; Infrared spectra; Inorganic Chemistry; Materials Science; Mercury compounds; Nanotechnology; Natural Materials; NMR; Nuclear magnetic resonance; Optical and Electronic Materials; Optical emission spectroscopy; Original Paper; Pollution monitoring; Porosity; Porous materials; Raman spectra; Recovery; Silica gel; Silicon dioxide; Specific surface; Spinning (materials); Titanium dioxide; Zirconium dioxide
• ISSN: 0928-0707; 1573-4846
• DOI: 10.1007/s10971-010-2324-4

Free silanol groups of silica-gel functionalized with quercetin (QSG) were blocked with TiO 2 or ZrO 2 to produce TiO 2 -QSG and ZrO 2 -QSG, respectively. The silica materials were characterized by infrared, Raman spectra, thermogravimetric, elemental analyses, magic angle spinning 13 C-nuclear magnetic resonance, BET specific surface area measurements and inductively coupled plasma—optical emission spectrometry-monitored silica hydrolysis. Siloxane groups are reinforced in the blocked QSG samples without affecting the hydrophilic nature or the porosity of silica. Quercetin is unaffected by the titania layer in contrary to zirconia. Also, the stability of silica against hydrolysis in TiO 2 -QSG and ZrO 2 -QSG was remarkably improved in the range of pH 3.5–9.1, attributed to the interruption of the intramolecular interaction of silanol groups with the amino groups. The hydrolyzed silica of TiO 2 -QSG and ZrO 2 -QSG decreased to 46.6 and 18.5%, of that of QSG and to 7.6 and 3.1%, of that of 3-aminopropylsilica gel at pH 9.1, respectively. TiO 2 -QSG was applied for the extraction of Hg(II) with separation efficiency of 99.0 ± 0.6% at pH 8.5. The capacity loss of TiO 2 -QSG per recovery cycle of Hg(II) was lowered in comparison with the uncovered material. It was successfully applied for the recovery of Hg(II) from spiked water and referenced samples.