Surface Properties of Japanese Colloidal Earth

Abstract

Japanese colloidal earth is a weathering product of volcanic ashes whose mineralogical main component is allophane, and chemically it is an amorphdous clay rich in almina content.
Many studies have hitherto been carried out on the adsorption capcity of this earth, and it has already been utilized as an industrial material for adsorbent and by hygroscopic substances.
In this report, to study the surface properties of this clay, the alumina gel, on the surface and in the interior of the clay has been treated with sulphuric acids of various concentrations and the changes of the conditions of the surface have been examined by the following methods.
(1) Measurement of specific surface area (by BET method).
(2) Measurement of pore distribution (by Kelvin method).
(3) Measurement of the heat of wetting.
As a result, the values of specific surface area were found to be 274m²/g, 172m²/g, 308m²/g, and 334m²/g for purified Japanese colloidal earth, 3%acid treated earth, 20% acid treated earth, and 35% acid treated earth, respectively. It was inferred that there exists on the surface of Japanese colloidal earth an alumina gel which increases the adsorptive surface area. The measured values of the heat of wetting showed a similar tendency and it was concluded from these results that Japanese colloidal earth consists of an alumina gel and a silica gel, which are on the surface and have high adsorption capacity, and a nucleus of silica-alumina gel.