Concentration of hydroxyl groups on the surface and in the volume of silicas

Autor: Agzamkhodzhaev, A. A., Zhuravlev, L. T., Kiselev, A. V., Shengeliya, K. Ya.
Zdroj: Russian Chemical Bulletin; October 1969, Vol. 18 Issue: 10 p1968-1973, 6p
Abstrakt: 1.The concentration of hydroxyl groups on the surfaceaOH for a maximally hydroxylated state of the surface of various samples of silica gels was determined by the method of isotopic exchange with D2O; the values ofaOH amorphous silicas (silica gels, aerosils, aerosilogels) with different pore dimensions and values of the specific surface were compared.2.For the maximally hydroxylated state of the surface of silica, the experimental valuesaOH= 7–9.5µmoles OH/m2 (4.2–5.7 OH groups/100 Å2), obtained by the method of deutero-exchange, practically do not depend on the specific surface of the samples and are close to the least valuesaOH=7.6–9.9µmoles OH/m2, calculated by various authors according to crystallographic data. Each Si atom of the surface in this case corresponds to approximately one OH-group.3.The values of the ratio of the total content of structural water (hydroxyl groups)aOH to the specific surface (µmoles of OH/m2) of samples of maximally hydroxylated silicas with various s were determined according to the experimental data of various authors. The curves bounding the experimental values of aOH /s are similar to those calculated on the assumption that the total content of structural water of the silica globule is equal to the sum of two factors, one of which is directly proportional to the volume, while the other is proportional to the surface of the globules.
Databáze: Supplemental Index
Externí odkaz: