Activated carbon Langmuir model

Adsorption beds of activated carbon for the purification of citric acid, and adsorption of organic chemicals by charcoal or porous polymers, are good examples of ion-exchange adsorption systems. Synthetic resins such as styrene, divinylbenzene, acrylamide polymers activated carbon are porous media with total surface area of 450-1800 m2-g h There are a few well-known adsorption systems such as isothermal adsorption systems. The best known adsorption model is Langmuir isotherm adsorption. 

Abstract Removal of catechol and resorcinol from aqueous solutions by adsorption onto high area activated carbon cloth (ACC) was investigated. Kinetics of adsorption was followed by in-situ uv-spectroscopy and the data were treated according to pseudo-first-order, pseudo-second-order and intraparticle drfiusion models. It was fotmd that the adsorption process of these compotmds onto ACC follows pseudo-second-order model. Furthermore, intraparticle drfiusion is efiective in rate of adsorption processes of these compoimds. Adsorption isotherms were derived at 25°C on the basis of batch analysis. Isotherm data were treated according to Langmuir and Freundhch models. The fits of experimental data to these equations were examined. 

For the preparation of Langmuir-Blodgett multilayers, a Joyce-Loebl Model 4 trough was used. The polymer was spread from a chloroform solution at a concentration of approximately 1 mg/ml. The de-ionized water subphase was passed through an activated carbon adsorber and then distilled in a glass still. Before deposition the... 

Monneyron P., Faur-Brasquet C., Sakoda A., Suzuki M., and Le Cloirec P., Competitive adsorption of organic micropollutants in the aqueous phase onto activated carbon cloth comparison of the IAS model and the neural networks in modeling data, Langmuir 18 (2002) pp. 5163-5169. 

In this section we have assumed that the adsorption isotherm of an adsorbate is unaffected by the presence of constituents other than the adsorbate in the fluid mixture. If such ideaiir> is assumed for the Langmuir isotherm developed in the previous example, you could use the derived expression for any gaseous system containing carbon tetrachloride and the same activated carbon. In reality, however, the presence of other solutes that have an affinity for the carbon surface alters the CCI4 equilibrium behavior. An accurate system representation would require data or models for the complete multicomponent mixture. 

Pan et al. [34] used the nonlocal density functional theory (DFT) [35] and the three-process Langmuir model (TPLM) [36] to predict the adsorption heats of propane and butane on carbon and compared these results with experimental data determined from isotherms measured on BAX-activated carbon (Westvaco) in the 297—333 K temperature interval. Both models agreed in showing that the adsorption heat for butane was c. 10 kj/mol higher than that of propane at the same loading. The satisfactory agreement found prompted the authors to propose the use of the DFT method as it requires only one experimental isotherm in contrast with the numerous isotherms required by the classic technique. 

According to the Langmuir model (Eq.2) the adsorption capacity qm for Cd is 2.5 times grater than for Zn and adsorption capacity qm for Pb is 2 times grater than Zn when granular activated carbon is used. When natural zeolite is used as adsorbent, the adsorption capacity qm for Zn is 5 times lower than Cd and Pb. So, qm varied in the order Cd (II)> Pb(II) >Zn(II) for GAC, and Pb(II) = Cd(II)>Zn(II) for the natural zeolite as adsorbent. Ricordel et al (2001) and Tsoi and Zhao (2004) reported a similar relationship when different adsorbents were used. This can be explained on the basis of their ionic radii, hydration energy, ionic mobility and diffusion coefficient. The explanations of different authors were given on the basis of the surface covered by the adsorbed metal ions or on the basis of metal surface complexation constants and thermodynamic parameters values. 

An example of a phenol adsorption isothenn onto an activated carbon cloth is given in Fig. 3. Experimental data are modeled with the Langmuir and Freundlich equations. A graphical construction is presented the slope of the adsorption path is equal to - Vim according to the mass balance equation between fluid and solid phases. From a given Co, this graphical construction enables the final concentration Cf to be determined. 

Kano, F., Abe, I., Kamaya, H. and Ueda, I. (2000). Fractal model for adsorption on activated carbon surfaces Langmuir and Freundlich adsorption. Surf. Sci., 467,131-138. 

The MPSD model with the local Langmuir equation and 10-4-3 potential is optimized with respect to the isotherm data of eight species measured on Ajax activated carbon (Table 1) at at least three different temperatures for each species. The reference temperature for the adsorption capacity, Tq, is chosen as 273 K. The mode fitting and experimental data (symbols) for ethane and propane are... 

The natural gas consists mainly of methane, and the adsorption of methane on coals and activated carbons has been studied by a number of workers. The adsorption on coal has generally been found to be physical as indicated by small heats of adsorption and the reversibility of the adsorption isotherms. The adsorption at the ambient temperature takes place in the micropores. Ruppel et al. studied the adsorption of methane on coals at temperatures of 0 to 50°C and at pressures from 1 to 15 mPa, and applied Langmuir and Polanyi adsorption models. Ruppel found that the adsorption could be well explained by the Langmuir equation. 

Reed, B.E., and Matsumoto, M.R.. Modeling cadmium adsorption by activated carbon using the Langmuir and Freundlich isotherm expressions, Sep. Sci. Technol., 28(13). 2179-2196 (1993). 

Table 1.7. Adsorption equilibria of nitrogen N2 (5.0) on activated carbon (AC) Norit R1 Extra at T = 298 K. Parameters of data correlation for different models of V = V + V using a generalized Langmuir adsorption isotherm Eqs. (1.41, 1.42).

Although the previous models well describe the binding of surfactant with the polymer network, they do not explain the issue of the electric field and deformation in the first and third steps. We propose and introduce the adsorption equation based on the Langmuir s theory for the second step. The model of simplicity explains the connection between the first and third steps. The following assumptions have been made to apply the theory to the gel a) the gel is the porous plate made of polymers like activated carbon b) the effective surface of the polymer network is the total area of the fine pores c) the bound molecules do not affect the free molecules once the pore is occupied by a certain numbers of molecules. Accordingly, the polymer network is approximated by a three-dimensional monolayer. 

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