Membrane behavior of bentonite-amended Fukakusa clay in K, Na and Ca solutions

Abstract

Bentonite has been proven to be effective in enhancing the membrane property of clay, by which landfill liners can have better barrier performance with regard to the migration of contaminants. In this work, 5% sodium bentonite amended with locally available Fukakusa clay was utilized to evaluate the membrane behavior toward different kinds of ions: K, Na and Ca. The chemico-osmotic efficiency coefficient, ω, was obtained in electrolyte solution with different concentrations of 0.5, 1, 5, 10, and 50 mmol/L. According to the results, solute type and ion valence have a significant effect on membrane behaviors. Additionally, ω continually decreased as the Na and Ca concentrations increased, which is consistent with the Gouy-Chapman theory. The membrane behavior toward Na was similar to that toward K, according to the chemico-osmotic efficiency coefficient ω. In the case of the divalent ion Ca, the membrane behavior was lower compared to monovalent ions Na and K at the same concentration. The mechanisms of the membrane performance change were discussed with the assistance of XRD patterns, free-swelling results and SEM images.