PORE DIFFUSION - DEPENDENCE OF THE EFFECTIVE DIFFUSIVITY ON THE INITIAL SORBATE CONCENTRATION IN SINGLE AND MULTISOLUTE BATCH ADSORPTION SYSTEMS

The present work studies the intraparticle diffusivity in batch adsorption systems as a function of the initial sorbate concentration. The systems under investigation are basic dyes, namely Basic Blue 69, Basic Red 22 and Basic Yellow 21 and their binary and ternary combinations, all adsorbing onto activated carbon Filtrasorb 400. They study is based on the film-pore diffusion model and the output is a combination of the external mass transfer coefficient, k(f) and the effective diffusivity, D(eff) that yields congruent experimental and theoretical kinetic data. It has been found the D(eff) varies with C(o) in an exponential decay function. Furthermore, D(eff) values undergo a general reduction in the multisolute systems compared to the single component systems. Also, the relative diffusion rates in the multisolute systems are found to change such that D(eff) of the slower diffuser is enhanced and that D(eff) of the faster diffuser is inhibited.