Preliminary Results of Tests to Investigate Effects of Hydraulic Gradient and Leaching Time in Column Leaching Tests on Sorption Behavior of Zinc in Illite Clay

摘要

The capacity of soil to attenuate pollution is an important parameter to be considered in designing liners of waste containment systems. The attenuation is done through sorption, where a portion of the concentration of the contaminant in the pore fluid is retained in the soil particles. Sorption is quantified by the partitioning coefficient which relates the concentration of the solute sorbed to the equilibrium concentration in solution. To be able to predict the behavior of contaminant in soil accurately, contaminant transport parameters such as dispersion coefficients as well as the partitioning coefficient have to be well-defined. One method of determining the partitioning coefficient is through the use of column leaching tests where a contaminated solution is made to leach through a normally consolidated layer of clay. The1 amount of contaminant retained through the profile is used to estimate the retardation factor. There are several factors to consider in the design of the experiment, one of which is the leaching time, or the length of time the soil particles were exposed to the contaminant. Another factor to investigate is the effect of the hydraulic gradient Five column leaching tests were conducted with varying leaching times and hydraulic gradients using illite clay. A fixed concentration of zinc solution was used as the leachant for all tests. The amounts of solute retained in the layers were determined after the leaching procedure using acid digestion. The amount of solute retained in the layers decrease with depth, with most of the solute retained at the topmost layer. Results show that the two factors being investigated do not have a significant effect on the determination of the partitioning coefficient.