1982 Volume 8 Issue 6 Pages 685-692
Using active carbon particles of 3 to 10 mm diameter, experiments in adsorption of phenol and benzoic acid from aqueous solution were carried out, and the adsorption rate and intraparticle distribution of local adsorption equilibrium were measured for two cases : a circulation batch method (Case 1) in which the extraparticle concentration is kept constant, and an ordinary batch adsorption method (Case 2). The data obtained were compared with the respective numerical solutions of three sorts of diffusion equations in which different rate-controlling steps were assumed, and the intraparticle diffusion kinetics accompanied by adsorption were studied.
1) The calculated shape of intraparticle distribution of local adsorption equilibrium differs among the rate-controlling steps assumed, but these differences become clearer for the Case 1 than for the Case 2 experiment. Thus the diffusion kinetics can be identified more easily from the Case 1 experiment.
2) The experimental data for the phenol adsorption shows best agreement with results calculated from the equation assuming simultaneous pore and surface diffusion. The benzoic acid adsorption is related most closely to the surface diffusion control.