Adsorption and desorption kinetics with systems having a concentration-dependent coefficient of diffusion

In many adsorbents, surface diffusion is the governing mechanisms of transport, The coefficient of surface diffusion may be concentration dependent. The model equations for adsorption and desorption processes controlling both the diffusive-convective mass transfer in the bulk and surface diffusion in the adsorbent have been solved for some cases for a range of parameter values which may apply for many adsorption systems. The equations to calculate(a) the surface diffusion coefficient, D-i, (b)the activation energy for surface diffusion, (-Delta H), (c) the relaxation times characterizing the adsorption and desorption processes, and (d) the times needed, t(Gamma)(ad), t(Gamma)(des), to reach the quasiequilibrium state for the adsorption and desorption processes are derived. (C) 1998 Academic Press.