Sorption Kinetics of Organic Chemicals: Evaluation of Gas-Purge and Miscible-Displacement Techniques

Among the methods for investigating the sorption kinetics of organic chemicals, two of the most widely used are gas-purge (GP) and miscible-displacement (MD) techniques. There has been to date no critical evaluation of the general applicability or the equivalency of these two techniques, which was the purpose of this work. The viability of the GP technique is a function of the Henry's constant of the chemical and the sorptivity of the solute/sorbent combination; that of the MD technique is also a function of the latter and of the texture/structure of the sorbent. The GP technique appears ideal for investigating the sorption dynamics of organic contaminants in sediment/water systems, whereas the MD technique seems ideal for investigating the transport of solutes in soils and aquifer materials. The two techniques provided comparable values of sorption rate constants for similar systems. Values for rate parameters of the bicontinuum model as determined from GP experiments were used to predict successfully the breakthrough curves obtained from MD experiments.