Heavy Metal Sorption of the Bentonite-Basalt Mixture as Clay Liner Material

Abstract

The role of clay liner placed in a waste landfill is the retardation and retention of the pollutants leached from waste. In the present paper we assessed the retention capability for bentonite-basalt soil composite potentially used as a clay liner material, using batch equilibrium and column tests, and predicted the heavy metal concentration in pore water leaching from the clay liner by numerical analysis. The relationship between the heavy metals retained and those of equilibrium concentration in soil solution was formulated by Freundlich equation, where the selectivity order of the metals was Pb>Cu>Zn>Cr. In the equilibrium sorption characteristic curve determined by the leaching column test, the heavy metals retained increased with increasing equilibrium concentration for Pb and Cr while exhibited almost constant at a whole equilibrium concentration range for Cu and Zn. The selectivity order of the heavy metal was the same as for the batch equilibrium test. The comparison of heavy metal retention determined by the batch equilibrium tests and by the leaching column tests indicated that the mass of metals retained was almost identical for Pb at a whole equilibrium concentration range while was different for Cu, Zn and Cr depending on the equilibrium concentration. The prediction of Pb concentration in pore water leaching from the clay liner indicated that the bentonite-basalt soil composite exhibits extremely high Pb attenuation capability.