粘土科学

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Methylene blue (MB) adsorption test, which measures the amount of this dye adsorbed on bentonite, is one of the major methods to evaluate the quality of bentonite. To conduct the MB test, we disperse bentonite in tetrasodium pyrophosphate (TSPP) solution. Conventional methods to disperse bentonite are i) “ultrasonic,” where ultrasonic dispersion of bentonite is performed for 10 min and ii) “boiling,” where the solution of TSPP and bentonite is boiled for 10 min. We proposed three new methods to disperse bentonite: 1) “stirring,” which involves stirring the dispersion overnight; 2) “standing,” where the dispersion is allowed to stand overnight; 3) a “combination,” where bentonite is dispersed by conventional methods, followed by stirring the dispersion overnight or letting the dispersion stand overnight.

The stirring method gave the comparable adsorbed amounts to the conventional methods in the cases of Mikawa (Na-type), Tsukinuno (Na-type) and Dobuyama (Ca-type) bentonites. The standing method gave comparable amounts in the cases of Mikawa and Tsukinuno, but a smaller amount in the case of Dobuyama. Among the combination methods, “ultrasonic+stirring” had greater effect in enhancing the amounts than the conventional methods only in the case of Dobuyama bentonite, whereas “boiling+stirring” had more effect in enhancing the amounts in the cases of both Mikawa and Dobuyama bentonites.

We recommend using “stirring” or “boiling” or “boiling+ stirring” to disperse bentonite in TSPP solution, because these methods can give good dispersion of bentonite, are easy to implement and require only inexpensive devices.

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