A novel intraparticle mass transfer model for the biosorption rate of methylene blue on white pine (Pinus durangensis) sawdust. Diffusion-permeation

Abstract

The removal of contaminants from water solution by biosorption on biowaste materials, such as natural wood sawdust (NWS), has been extensively studied recently. The interpretation of the experimental biosorption rate data is an important issue and has to be performed using mathematical models based upon phenomenological principles. An experimental stirred tank batch adsorber was employed to obtain the biosorption rate data of methylene blue (MB) on NWS, which were interpreted using kinetic and diffusional models. The pseudo-second order (PSO) kinetic model adequately represented the experimental data, but its kinetic constant changed significantly with the operating conditions, hampering its practical application. A new diffusion-permeation model (DPM) is proposed by assuming that the intraparticular transport of pollutants is due to the simultaneous diffusion in the voids and permeation through the biosorbent walls. The DPM model fitted the experimental data satisfactorily, and the diffusion-permeation coefficient, DPM, varied slightly with the experimental conditions. The DPM model matched the experimental data adequately using an arithmetic mean of the DPM coefficient, DPM¯. Finally, the predictions of the DPM model using DPM¯ were compared to those estimated with the PSO model. In most of the experimental cases, the experimental data was better predicted by the DPM model.