Sorption of Zinc in Bentonite, Illite and Kaolin Clay Using Column Leaching Tests

Abstract

Sorption is an important contaminant transport process with special significance in retarding the movement of contaminants. Determination of the capability of a clay liner to attenuate contaminants is necessary for the proper design of offshore waste containment sites. The sorption process in clay can be investigated using the column leaching test where a solution with a constant concentration is made to leach through a normally consolidated clay layer. In this study, two column tests were conducted using two different kinds of clay in each test. Bentonite and illite clay were used as the sorbent material and zinc nitrate solution was used as the contaminant made to leach through the clay layer. Results show that the amount of zinc retained in the clay decreases as the distance from the source of contamination increase s. Batch equilibrium tests were also conducted for three kinds of clay — bentonite, illite and kaolin. For the range of concentrations used, linear adsorption isotherms were formed. Comparing the three kinds of clay, bentonite shows t he highest attenuating capacity while kaolin clay has the least capacity to retain zinc. Comparing the results of the batch tests with the column leaching tests, it can be shown that batch equilibrium tests overestimate the attenuation capacity of the soil.