Changes in Physicochemical Surface Properties of Magnesium Silicate due to Hydrothermal Treatment
1971 Volume 20 Issue 213 Pages 786-789
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1971 Volume 20 Issue 213 Pages 786-789
Hereunder is given a report of experimental studies that have been performed of the adsorption of argon and pyridine, using magnesium silicate specimens prepared respectively by coprecipitation and by hydrothermal treatment. The heat of adsorption of argon have been obtained from adsorption isotherms at -196° and -191°C. The initial heats of adsorption of argon on two kinds of magnesium silicate specimens were about 6kcal/mole and 4kcal/mole, respectively. The gradual fall, on the isosteric heat curve against coverage was observed at an early stage of adsorption on the sample through the hydrothermal treatment, but the secondary peak after the gradual fall appeared in the heat curve on the sample through the coprecipitation method. The specific surface area vs. SiO2/MgO did not agree with the amount of the acid point vs. SiO2/MgO which was obtained by the adsorption of pyridine.
These facts reveal the fact that both kinds of magnesium silicate specimens have heterogeneous surfaces.
The amount of the acid point on the sample prepared by the hydrothermal treatment was less than that on the coprecipitated sample.
It is concluded that the surface of the magnesium silicate specimens subjected to hydrothermal treatment has smaller amount of acid points, but these acid points are stronger than those on the surface of coprecipitated specimens.
