Comparison between diffusional and first-order kinetic model, and modeling the adsorption kinetics of pyridine onto granular activated carbon

Abstract: In this work, a surface diffusion model (SDM) obtained in a previous work was verified in a wide range of experimental conditions to predict the adsorption kinetics of pyridine on activated carbon. Moreover, the predictions of SDM model were compared with that obtained by using the first-order kinetic model. The results showed that the first-order model adjusted satisfactorily the experimental data. The effect of the stirring speed, mass of pyridine adsorbed, (qe), and temperature on the rate constant of the first-order model, (k1), was analyzed and equations were proposed to correlate k1 as functions of qe and temperature. Nevertheless, the dependence of k1 regarding the temperature, stirring speed, and qe cannot be accurately correlated, indicating that the overall adsorption rate of pyridine on activated carbon is controlled by the intraparticle diffusion. Moreover, it was shown that the rate of adsorption on active site is not controlling the overall adsorption rate. On the other hand, the SDM model provided a much better prediction than the first-order kinetic model. The surface diffusion coefficient can be readily estimated from a correlation recommended in this work, whereas the value of k1 could not be predicted for some of the experimental conditions studied in this work. © 2015 Balaban Desalination Publications. All rights reserved.

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