Dialysis Method to Measure Diffusion in Sodium and Enhanced Bentonites

Sodium bentonite (NaB) and enhanced bentonites are used extensively in engineered containment barriers. These high-swelling clays are relied upon to provide long-term, low hydraulic conductivity, k (e.g., 10-10 m/s), to restrict advective transport of contaminants. Although diffusion becomes a significant contaminant transport mechanism relative to advection in barriers with k<10-9 m/s, diffusion data for NaB and enhanced bentonites is limited due to the complexity and long test durations of traditional diffusion test methods. Thus, a dialysis-leaching test (DLT) method was developed and refined for measuring diffusion properties of bentonite specimens with porosities (n) similar to geosynthetic clay liners. The DLT method requires short test durations (<7 d), uses inexpensive and commercially-available equipment (