Effect of ${\text{Cu}}^{2+}$ Ions and Buffering Capacity on Smectite Microstructure and Performance

Smectite is usually used as buffer clay for contaminant of high level nuclear waste canisters. Corrosion of the canisters will expose the buffer clay to ${\text{Cu}}^{2+}$ ions as one of the corrosion products. This study investigates the effect of ${\text{Cu}}^{2+}$ cations in a smectite, with and without addition of sodium carbonate in the clay, on its consolidation behavior and transmission characteristics. Characterization experiments conducted in the study included determination of changes in the buffering capacity and permeability properties of the clay in relation to the presence of varying concentrations of ${\text{Cu}}^{2+}$ , and consolidation experiments. Double-layer swelling forces and buffering capacity are seen to be dominant factors in the performance of the clays—apparently through their influence on formation and restructuring of microstructures in the overall smectite clay mixtures.