粘土科学

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Smectite clays such as acid clay or bentonite have various characteristic values such as the adsorption amount of methylene blue (MB adsorption amount), the amount of exchangeable cations (Na^＋, K^＋, Mg^2＋, Ca^2＋) or the cation-exchange-capacity (CEC). Generally, the MB-adsorption amount has been quantified by the standard test method (JBAS-107-91) established by the Japan Bentonite Industry Association or the Japanese Industrial Standards (JIS Z 2451) established by the Japan Industrial Standards Committee, and the amount of exchangeable cations (Na^＋, K^＋, Mg^2＋, Ca^2＋) and the CEC have been quantified by the method established by the Soil Standard Analysis and Measurement Method Committee.

We emphasized the simplicity and speed of measurement, and conducted repeated studies to further simplify these measurement methods. As a result, following simple measurement methods were proposed. In the measurement of MB adsorption amount, at first, the sample is dispersed at room temperature in an aqueous solution of sodium oxalate having a predetermined concentration. Next, a predetermined concentration of MB aqueous solution is added to shake for a predetermined time. Finally, the MB concentration of the separated supernatant is measured using a spectrophotometer and the MB adsorption amount (mmol/100 g) is calculated from the concentration value of MB. The two simple measurement methods were obtained on the amounts of exchangeable cations and the CEC. One is a method of measuring the amounts of exchangeable cations (Na^＋, K^＋, Ca^2＋) eluted by replacing with NH₄^＋ ions by using a convenient measuring device such as a simplified type of ion meter. Another is a method of measuring the amounts of exchangeable cations (Na^＋, K^＋, Mg^2＋, Ca^2＋) and the CEC at once by using an ion chromatography.

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