Concentration dependence of effective surface diffusion coefficient in aqueous phase adsorption on activated carbon

Sudo, Yoshitaka; Misic, Dragoslav M.; Suzuki, Motoyuki

doi:10.1016/0009-2509(78)85097-0

Cited by 76 publications

(26 citation statements)

References 7 publications

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“…The calculated U s and k b values in Table 2 are reasonably constant. The measured values of U s are comparable to previously reported values obtained using a single intraparticle parameter model (Crittenden and Weber, 1978a;Fritz et al, 1979;Sudo et al, 1978). This correspondence is to be expected as the micropore uptake is only significant in the latter stages of adsorption, a region not normally investigated in a batch kinetic study.…”

Section: Resultssupporting

confidence: 87%

A branched pore kinetic model for activated carbon adsorption

1981

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A branched pore kinetic model for aqueous phase activated carbon adsorption is presented in which the carbon particle is separated into rapidly and slowly diffusing regions. The model was developed to overcome problems arising from a single rate parameter analysis and is shown to describe experimental data well. In addition to very different rates of transport in the two regions, parameters estimated by regression analysis indicated differences in the adsorptive characteristics. RUSSELL G. PEEL SCOPEActivated carbon is gaining ever-increasing usage as a general purpose adsorbent for organics from the aqueous phase. However, the actual mechanisms of transport and adsorption within the activated carbon particle are not yet well understood. Because of the complexity of the internal pore structure, activated carbon kinetics have generally been modelled with a single effective diffusion parameter active throughout the particle (Fleck, 1973;Crittenden and Weber, 1978a;Fritz et al, 1979), even though it is accepted that activated carbons have heterogeneous surface properties and a wide range of pore sizes.This single intraparticle parameter approach has led to inconsistencies between observed equilibrium and kinetic behavior. Consequently, it is the objective of this study to develop a model, based on present knowledge of the internal structure of activated carbon, which would enable a consistent treatment of both equilibrium and kinetic data. Such a model should give an accurate description of the adsorption process from initial contact through to equilibrium.In the phenolic adsorption studies of Snoeyink (1969) and Zogorski (1976), among others, a rapid initial uptake phase followed by a slow approach to equilibrium was noted. Such behavior is not consistent with the single effective diffusion parameter model. In addition, several authors (Beck and Schultz, 1970;Satterfield et al., 1973) have demonstrated that the effective diffusion parameter in small pores is a strong function of the pore diameter to solute diameter ratio, and that diffusion rates decrease with decreasing pore size. Since activated carbons have a wide range of pore sizes, a corresponding range of diffusion rates should be expected. Rapid saturation of the fast diffusing pores would result in a net decrease in effective diffusion rate as adsorption proceeds.As an approximation to the microscopic description of the diffusional process, a model has been developed in this work which divides the carbon particle into two regions of different diffusion rates. The regions are loosely termed macropores and micropores. (These terms should not be confused with their conventional uses to define certain pore size ranges.) Relatively rapid diffusion and adsorption occur in the macropores, and the remaining slow approach to equilibrium occurs in the micropores.The micropores are assumed to be homogeneously distributed throughout the particle and to branch off the larger macropore network which is responsible for radial transport. A schematic diagram of the propos...

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Section: Resultssupporting

confidence: 87%

A branched pore kinetic model for activated carbon adsorption

1981

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“…Figure 3 shows a dependence between diffusivity and equilibrium metal adsorbed, as the diffusion coefficient increased with loading. Such a relationship was also observed in adsorption of organics onto plain GAC (Sudo et al 1978) and indicates an "effective" diffusion coefficient, related to metal ion concentration and hence subsequent uptake level. Qe (mg metal/g GAC) Figure 3."…”

Section: Biofdm/gac Metal Biosorption Diffusion Coefficientmentioning

confidence: 81%

Adsorption isotherms and diffusion coefficients for metals biosorbed by biofilm coated granular activated carbon

Scott¹,

Karanjkar²

1995

Biotechnol Lett

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“…It was also suggested that the contribution of the bond breaking was approximated as a certain fraction of the heat of adsorption. Sudo et al (1978) interpreted concentration dependence of 0, by applying a function of a final amount adsorbed. Suzuki and Fujii (1982) studied aqueous adsorption of propionic acid onto an activated carbon.…”

Section: Aiche Journalmentioning

confidence: 99%

Model for surface diffusion in liquid‐phase adsorption

Miyabe

Takeuchi

1997

AIChE Journal

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Based on the absolute-rate theoly, a consistent interpretation was provided for the dependence of surface-difiion coeffiient, D,, on temperature and the amount adsorbed in various liquid-phase adsorption systems, such as the Langmuir-, Freundlichand Jossens-type adsorption. It was demonstrated that a restricted molecular diffusion model for surface diffusion was useful for the analysis of the characteristic features of 0,. A formulation of D, was derived based on the model and was applied to the analysis of surface-diffusion phenomena in various adsorption systems. The temperature dependence could be interpreted by assuming surface d i f i i o n as an activated process. By taking into account the change in both the logarithmic slope of an adsorption isotherm and an adsorption potential, the concentration dependence of 0, could be interpreted irrespective of the type of the adsorption isotherms.

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Concentration dependence of effective surface diffusion coefficient in aqueous phase adsorption on activated carbon

Cited by 76 publications

References 7 publications

A branched pore kinetic model for activated carbon adsorption

A branched pore kinetic model for activated carbon adsorption

Adsorption isotherms and diffusion coefficients for metals biosorbed by biofilm coated granular activated carbon

Model for surface diffusion in liquid‐phase adsorption

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