Freundlich maximum adsorption capacity

The main limitation of the Freundhch equation is that it does not predict a maximum adsorption capacity, because linear adsorption generally occurs at very low solute concentration and low loading of the sorbent. However, in spite of this limitation, the Freundlich equation is used widely for describing contaminant adsorption on geosorbents. 

The frequent good fit of adsorption data to the Freundlich equation is influenced by the insensitivity of log-log plots and by the flexibility afforded curve fitting by the two empirical constants K and n. This flexibility does not guarantee accuracy, however, if the data are extrapolated beyond the experimental range. The Freundlich equation has the further limitation that it does not predict a maximum adsorption capacity, however mythical the adsorption maximum may be. Despite its shortcomings, the Freundlich equation is a common adsorption equation and is included in several models for predicting pesticide behavior in soil. 

Beside kinetic and thermodynamic studies, equilibrium studies were done in order to determine the influence of the initial concentration of the metals ions upon the efficiency of the adsorption process and in order to determine the maximum adsorption capacities of the phosphorylated chitin and chitosan materials in the removal process of various metal ions from aqueous solutions. The experimental equilibrium data were fitted to the Langmuir and Freundlich isotherms. In all the cases the experimental results showed a better fit to the Langmuir than to the Freundlich equation. The maximum adsorption capacities obtained from the Langmuir isotherm plot in the... 

We wUl now touch upon some of these factors. First, let s look at what we mean by system isotherm. Freundlich liquid phase isotherm studies can be used to establish the adsorptive capacity of activated carbon over a range of different concentrations. Under standard conditions, the adsorptive capacity of activated carbon increases as the concentration increases, until we reach a point of maximum saturation capacity. An example of an isotherm for phenol is shown in Figure 8. 

The Freundlich liquid phase isotherm can be used to determine the effect of solubility on the adsorptive capacity of activated carbon over a range of different concentrations. Phenol is highly soluble due to its polar nature whilst, in comparison, tetrachloroethylene (PCE) has a low solubility due to being non-polar. In the isotherms illustrated, the concentration of phenol is low relative to its solubility limit and consequently, the adsorptive capacity peaks at 18% maximum (see Figure 9). In comparison the concentration of tetrachloroethylene is relatively close to its solubility limit and, accordingly, the adsorptive capacity is exceptionally good. 

Henry and Freundlich isotherms did not provide for C. value growth limit. Irving Langmuir (1881-1957) in 1916 introduced such limit C and proposed a more complex but more accurate equation. He viewed the adsorption balance as a result of the competition between the rates of adsorption and desorption. If maximum adsorbent capacity relative component i is j> it may be assumed that the adsorption rate is proportion-... 

Doping dodecyl benzene sulfonic acid (DBSA) into PANI/carbon nanotube composite can fabricate PANI/carbon nanotube-DBSA nanocomposite [56]. The preparation, as well as the adsorption to Cr(VI), is depicted in Figure 11.11 with the pseudo-second-order kinetics and Freundlich isotherm model with maximum monolayer adsorption capacity of 55.55 mg/g. Electrostatic interactions between PANI and Cr(VI) anions are the predominant driving forces for this adsorption process. 

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