Effects of fundamental differences between batch and miscible displacementtechniques on sorption distribution coefficient

A circulation-through-column (CTC) technique was developed and employed to evaluate the influence of fundamental differences between batch and miscibl e displacement (MD) techniques on the value of the sorption distribution co efficient (K). Batch, MD, and CTC experiments were conducted to determine s orption equilibrium parameters for dimethylphthalate (DMP), diethylphthalat e (DEP), and dipropylphthalate (DPP) using two natural soil samples with 0. 36 and 1.48% organic carbon. Batch sorption isotherms of DMP and DEP were l inear while that of DPP was nonlinear. Batch-determined K values for the co mpounds were 30 to 170% higher than the corresponding values obtained from breakthrough curves (BTCs) generated through MD experiments. Similarities b etween values of K derived from batch and CTC techniques suggest that under estimation of K determined from BTCs is not due to fundamental differences between batch and MD techniques. The extent of deviation between the K valu es determined by batch and MD experiments was inversely related to the valu e of K. This was well explained by a fixed percent reduction in the retarda tion coefficient determined from solute BTCs, suggesting a possible leftwar d shift of these curves.