Physico-chemical studies of cation exchanging properties of Japanese acid clay in aqueous media (author's transl)

Abstract

When Japanese acid clay is dispersed in an aqueous medium, pH of the solution deviates to acidic because of dissociation of H+ from clay minerals. Addition of neutral salt to this solution decreases pH values further. The order of electrolytes having common anion, Cl-, to decrease pH of the solution was found to be Na+, K+, and Ba2+, the latter being the most effective. The pH value of final equilibrium, (pH)f, was found to be constant in the range of initial pH of medium, (pH)i, between 3 and 11, which is prepared by adding hydrochloric acid or alkali hydroxide tb the salt solution. It was, therefore, concluded that Japanese acid clay has both buffer function and ion-exchanging property. On the other hand, the amount of alkali adsorbed to this clay increases with the concentration of hydroxide in the medium, and KOH is absorbed more than NaOH. It was, therefore, concluded that ion-exchanging capacity for K+ is larger than that for Na+. The rate of reaction of alkali adsorption was measured at constant pH by using pH-statt. It was concluded from analysis of the amount of adsorbed alkali as a function of time, that there are two ion-exchanging mechanisms which are competitive; the one is on the outer surface and the other in the inner layer of the clay mineral. It was concluded that the capacity of ion-exchange, α1, and the rate constant, k1, of the former is larger than those of the latter.