Effects of Bentonite and Polymer Soil Amendment on Contaminant Transport Parameters

Abstract

The contaminant transport parameters such as hydraulic conductivity and diffusion coefficient are determined and compared for barrier composed of (1) soil, (2) soil-bentonite (SB), and (3) soil-polymer (SP) mixes. Chloride (Cl-) is taken as the contaminant of interest because it is nonreactive. Sodium bentonite (NaB) and super-absorbent polymer (SAP) which is an anionic polyelectrolyte, is used for the study. Addition of NaB reduced the hydraulic conductivity of the soil and the diffusive transport through the soil barrier. Soil mixed with SAP was found to be more efficient in containing contaminants. The values of hydraulic conductivity and diffusion coefficient for SP mixes were lower than those observed for SB mixes. Low values of hydraulic conductivity and diffusion coefficient are attributed to the decrease of free channels for the contaminant transport and increase in the immobile water in the mix along with the increase in effective length. Microanalyses show that the addition of polymer causes the dispersion of soil particles which is similar to the observations from previous studies.