TITLE:
Stabilization of Silica Gel against Hydrolysis by Doping with Fˉ or Zr(IV)
AUTHORS:
Khaled S. Abou-El-Sherbini, Peter G. Weidler, Detlef Schiel, Mohey H. A. Amr, Henning Niemann, Shady El-Dafrawy, Wolfgang H. Höll
KEYWORDS:
Silica Gel; Doping; Hydrolysis; Fluorine; Zirconium
JOURNAL NAME:
Green and Sustainable Chemistry,
Vol.4 No.1,
February
25,
2014
ABSTRACT:
Silica gel (SG)
was synthesized via acidification of sodium silicate solution then doped with Fˉ or Zr(IV) in molar ratios of F/Si 3/100, and Zr/Si 0.75/100 and 3.75/100 and
sintered at 500°C, 800°C and 1000°C. The samples were investigated by X-ray
diffractometry, infrared absorption and Raman spectra, surface area
measurement, and inductively coupled plasma-optical emission spectrometry-monitored silica hydrolysis. All samples are mesoporous with BET surface areas 181.5 - 523.9 m2·gˉ1. The
surface area of the silica samples decreases as the sintering temperature increases. The hydrolysis process
of silica decreases as the sintering temperature increases and as the surface
area decreases. The pH and the type of buffer solution affect the hydrolysis of
silica samples due to a SN2 reaction mechanism favored in basic
media using ammonia buffer. Zr(IV) increases the stability of silica samples
against the hydrolysis as confirmed by the structural investigation, surface
area and silica hydrolysis.
Fˉ observably decreases the silica hydrolysis process when presenting on the surface of SG.