The Change in the Surface Characteristics of Amorphous Clay Mineral Separated from Kanuma Pumice Layer by Treatment with Aqueous NaOH Solution

Abstract

An amorphous clay sample having mean particle diameter of about +15 pva was separated from Kanuma pumice layer, a kind of volcanic ash-weathering product,; by NQbJe eiutriation apparatus. The changes in the surface properties for this amorphous clay have been studied by adsorption measurements. The amorphous clay sample was composed of allophane ((1~2) SiO2.Al2O3-mH2O) as the main component and had an aggregate structure. It was treated by the Hashimoto-Jackson method using an aqueous 0. 5 M.-NaOH solution. The changes in the surface characteristics of chemically treated and recovered cakes were investigated by the adsorption of Methylene Blue, P043- ion and NH4+ ion from the respective aqueous solutions. The following results were obtained: (1) The separated clay sample was in a laminar structure composed mainly of a surface particulate layer and an inner particulate layer. The latter contained a small amount of crystalline rockforming minerals. (2) The surface particulate layer had a positive charge and the inner particulate layer had a negative charge in solution. (3) The surface particulate layer was composed of free aluminum hydroxide-base substance, and the inner one was composed of particles having relatively large pore sizes. (4) As the f' value increased, Na+ ions were introdued into the surface of chemically treated sample, and the charge changed from positive to negative. The changes in surface charge result in the increases in the amount of adsorption of Methylene Blue and NH4+ ion and the decrease of PO43- ion. (5) The liquid phase adsorption method using different charge and ion diameter was effective for the characterization for the amorphous clay samples. © 1989, The Chemical Society of Japan. All rights reserved.