A diffusion batch method for determination of the adsorption coefficient of benzene on clay soils

The adsorption and desorption of contaminants on soil and sediment are key mechanisms governing the fate and transport of aqueous-phase hydrocarbons i n groundwater. A diffusion batch method for measuring the adsorption coeffi cient was developed in this study. This method provides a simple and reliab le procedure for assessing the adsorption of organic compounds by soil. The method relies on diffusion, rather than shaking and agitation, to bring th e solid and solution into chemical equilibrium. Samples of Regina clay, pre pared by a variety of methods, were tested for benzene adsorption using thi s test. Initial testing indicated that equilibrium was attained within 10 d ays from the start of the adsorption test. The measured adsorption coeffici ent (K-d) for samples of benzene on Regina clay prepared at various initial water contents (air-dried, liquid limit, slurried, or statically compacted ) were in the range of 3.2-7.2 mL/g. A comparison of the diffusion batch me thod and the conventional ASTM batch method showed that the diffusion batch method has lower variability, particularly over low concentration ranges.