Two-phase theory is applied to solid–liquid fluidization in the Stokes flow regime. Because inertial terms can be neglected in the Stokes flow regime, the momentum balances are simplified to an algebraic relation between drag, buoyant, and diffusive forces. The resulting convection-dispersion model is then applied to an experimental expanded-bed adsorption system. Two flows are investigated, namely, step changes in the fluidization velocity and step changes in the fluid properties. Experimental data and model simulations are in excellent agreement for both flow configurations. Furthermore, the two-phase model provides an accurate prediction of the observed time delay in bed expansion for step changes in fluid properties, as well as a mechanistic explanation for its observation.