عنوان مقاله [English]
In the current research, mass transfer resistances of various steps of uranium biosorption using Pseudomonas putida @ Chitosan biosorbent in a fixed bed column was calculated. Description of process dynamic parameters using dimensionless numbers showed that the Biot number was greater than 30 in all experiments which confirmed the high mass transfer rate of the liquid film in comparison with intraparticle diffusion. Increase in the mass transfer driving force across the liquid film via enhancement in the inlet concentration along with a decrease in the liquid film thickness through a reduction in the sorbent particle size caused a decline in the mass transfer resistance of the liquid film. Furthermore, the Peclet number was found to increase with increasing the bed height and decreasing the sorbent particle size which indicates a shortening in the mass transfer region thickness and decreasing in the axial dispersion resistance. The biosorbent structure caused the pore diffusion flux to be negligible in comparison to surface diffusion flux and surface diffusion was the dominant intraparticle diffusion mechanism. The obtained results showed that intraparticle diffusion resistances were several times greater than liquid film resistances and axial dispersion resistances in all experiments and were the rate-controlling step. Since the change in operational conditions has little effect on the intraparticle diffusion, the column efficiency was only proportional to the process residence time and varied from 0.00% to 53.00%.