Pollution Research Paper

IMPORTANCE OF TRANSPORT PARAMETERS OF IONS IN THEDESIGN OF SOIL LINERS

SHANKARA, S. N. MAYA NAIK AND P. V. SIVAPULLAIAH

Abstract

Design of the thickness of soil liners for any waste disposal facilities depends on the rates ofmigration of ions in the leachates generated within the waste disposal facility. But the migrationrates of ions within the leachate vary considerable depending on several factors such as diffusioncoefficients of ions and retardation factors and in-situ properties of liner material. Generally thediffusion coefficients of any given ions may not significantly vary and are range bound. But theretardation factor of ions can vary considerably depending on clay liner and contaminant ionspresent in the leachate. The variation in the retardation factor of potassium ion, in the commonlyused montmorillonitic clay as liner material, has been studied in this paper. The transport rates of sodium, which is considered as conservative ions also have been studied. The transport rates ofions are determined through soil column tests. The diffusion coefficient and the retardation factorsare determined by comparing the experiments column break through curves with a theoreticalcurve. The transport parameters are varied so that the theoretical curve matches with experimentalcurve. The set of values with which the theoretical curves closely match with the experimentalcurves are taken as the transport parameters of the concerned ion. It was shown in this paper thatspecific interaction that takes place between potassium ion and montmorillionite clay, whichincreases the retardation factor considerably for potassium unlike sodium in the same clay.Consequently the breakthrough times for any given thickness of the liner increases if potassiumis the critical contaminating ion.