Abstract:

In this paper,first,the adsorption equilibrium data of phenol on activated carbon were fitted by using the Freundlich and the Langmuir models.Next,the adsorption kinetics of phenol in a finite batching stirred vessel was investigated at variable activated carbon dosage and initial phenol mass concentration.Then,a homogeneous surface diffusion model (HSDM),which considers both the film mass transfer and the surface diffusion resistances under nonlinear equilibrium isotherm,was set up and was solved by the finite element method.Moreover,the film mass transfer coefficient k_f  and the surface diffusion coefficient D_s were calculated by means of the least squares method including alternate optimization search of the simplex and the Levenberg- Marquardt algorithm.Finally,the confidence intervals of k_f and D_s were analyzed during the calculation with the Levenberg- Marquardt algorithm.The results show that the Langmuir model well describes the adsorption isotherm of phenol on activated carbon,that the proposed HSDM effectively evaluates the dynamic adsorption of phenol,that both the activated carbon dosage and the initial phenol mass concentration have little effects on the values of k _f and D_s at constant stirring speed,that the k_f value is much larger than the D_s value,meaning that the kinetic adsorption behavior of phenol on activated carbonis controlled by surface diffusion,and that the evaluated k_f value is more precise than D_s value.

Key words: phenol, activated carbon, adsorption kinetics, homogeneous surface diffusion model, film mass trans-fer coefficient, surface diffusion coefficient