Investigation of Consolidation-Induced Solute Transport. I: Effect of Consolidation on Transport Parameters

This paper presents an experimental investigation of the effect of clay consolidation on parameters that govern the advective-dispersive transport of an inorganic solute. Batch, diffusion, dispersion, and solute transport tests were conducted using kaolinite clay and dilute solutions of potassium bromide (KBr). Batch tests produced the highest levels of ${\text{K}}^{+}$ sorption and indicated that equilibrium sorption was achieved in approximately 10–30 min. The increase in sorption observed in the batch tests, as compared to the dispersion or solute transport tests, reflects the significantly lower solids-to-solution ratio and more efficient mixing process. By comparison, kaolinite consolidation had little effect on sorption due to the relatively small change in porosity. Values of hydrodynamic dispersion coefficient $\left(D_h\right)$ , effective diffusion coefficient $\left(D^{\ast }\right)$ , and apparent tortuosity factor decreased with decreasing porosity. Values of $D^{\ast }$ obtained for ${\text{Br}}^{-}$ were generally larger than for ${\text{K}}^{+}$ , whereas $D_h$ values for ${\text{Br}}^{-}$ were significantly smaller than for ${\text{K}}^{+}$ . Values of longitudinal dispersivity $\left(\alpha \right)$ were larger for ${\text{K}}^{+}$ than ${\text{Br}}^{-}$ and showed no clear trend with decreasing void ratio. In general, the experimental results suggest that changes in $D^{\ast }$ and $D_h$ should be taken into account during clay consolidation whereas the sorption isotherm and $\alpha$ may be considered as unchanged during the consolidation process.