Linear driving force approximation for diffusion in spherical adsorbents with binary non-linear adsorption

This paper presents a new linear driving force approximation applicable to the cyclic steady-state in the case of pore diffusion in the presence of binary Langmuirian adsorption for a spherical particle under a periodic boundary condition in composition, total pressure or both. This approximation uses two parameters Ω, one for each solute, calculated for a square wave with the same period and a second pair of parameters that correct the approximation for the phase lags.

An assessment of the quality of the approximation was made by measuring the differences between the cumulative fluxes calculated by the diffusion and the linear driving force models through an average relative quadratic error. It is shown that this error is less than 5% for equilibrium, diffusion and frequency conditions in the range of practical adsorption systems. The same approximation can be used in the case of homogeneous diffusion.