Distribution of Water in Na-and Na/Al-montmorillonite Pastes between Interlayer Space and Inter-packet Voids

Abstract

In Na-and Na/Al-montmorillonite pastes, two types of spaces accommodating water exist; interlayer space and inter-packet voids. The amount of water in the former was determined from the basal spacings (001) obtained by X-ray diffractometry. The amount of water in the latter was determined by subtracting the amount of interlayer water from the total amount of water in the pastes. In the montmorillonite pastes prepared, the proportion of interlayer water was about 90% at the water content from 0.61 to 1.2ml/g, and it decreased with increasing water content and reached 60% at the water content of 5.5 ml/g. The addition of Al³⁺resulted in the decrease in the proportion of interlayer water, which was influenced significantly by the amount of the Al³⁺ added. In a paste having water content of 5.5ml/g, for example, the proportions were 40, 30, and 7%, when the Al³⁺ added was 10, 20, and 30% of CEC, respectively. Furthermore, when the amount of water was fixed (2.2ml/g), the amount of interlayer water abruptly decreased at the Al³⁺ concentration of about 20% of CEC. From the comparison of the basal spacing influenced by the Al3+ concentration with that by the excess Na⁺, the effect of Al³⁺ itself was considered to appear at its concentration of about 20% of CEC, thereby the decrease in the amount of interlayer water decreased abruptly and greatly.