Freundhch adsorption isotherm

As aheady mentioned, the Freundhch adsorption isotherm, unlike the others in Table 5.2, does not become linear at low concentrations, but remains convex to the concentration axis. Moreover, it does not show a saturation or limiting value. Hence, for the Freundhch adsorption isotherm in Table 5.2 F, is a parameter scaling the adsorption (rather than saturation adsorption). This isotherm can be derived assuming that the surface (as a rule solid) is heterogeneous. Consequently, if the data fit the Freundhch equation, this is an indication, but not a proof, that the surface is heterogeneous. ... 

Isoproturon, atrazine, diuron, chlorotoluron, and simazine absorb well into MN-200. To the largest extent, this sorbent extracts isoproturon while the smallest loading was observed for simazine [68]. Nevertheless, the capacity of MN-200 even for this pesticide is pretty high. From the Freundhch adsorption isotherm obtained under static conditions, it follows... 

According to Eq. (E7.10d), the constant C is the intercept in Fig. E7.2. Thus, the ratio of the adsorbed ions could be estimated if the FreundHch adsorption isotherm constants are known. 

It is often found that the simple Langmuir isotherm does not adequately describe adsorption systems of theoretical and practical interest. Another classic isotherm that has found apphcation in describing adsorption, especially at moderate pressures, is the so-called Freundhch adsorption isotherm... 

Table 12.5 Summary of the R -values for both Langmuir and Freundhch adsorption isotherm models for the different dye adsorption rates for the different sample treatments.

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. 

In addition to these characterizations of adsorption curves, mathematical descriptions of adsorption isotherms, based on physical models, often are used to study solid interactions with contaminants. The main adsorption isotherms include those of Langmuir, Freundhch, and Brunauer-Emmet-TeUer (BET) they are depicted in Fig. 5.2. 

The amount of adsorbed chemical is controlled by both properties of the chemical and of the clay material. The clay saturating cation is a major factor affecting the adsorption of the organophosphorus pesticide. The adsorption isotherm of parathion from an aqueous solution onto montmorillonite saturated with various cations (Fig. 8.32), shows that the sorption sequence (Al > Na > Ca ) is not in agreement with any of the ionic series based on ionic properties. This shows that, in parathion-montmoriUonite interactions in aqueous suspension, such factors as clay dispersion, steric effects, and hydration shells are dominant in the sorption process. In general, organophosphorus adsorption on clays is described by the Freundhch equation, and the values for parathion sorption are 3 for Ca +-kaoUnite, 125 for Ca -montmorillonite, and 145 for Ca -attapulgite. 

Surfactant keeps emulsion droplets and latex particles colloidally stable against coalescence/aggregation. The surfactant plays another important role in emulsion polymerisation besides stabilisation. Surfactant is critically involved in the nucleation mechanism (i.e., how the particles are formed) of the polymer latex particles (418,419). The amount of surfactant used is critical in controlling the latex particle size distribution. As surfactant is added to an emulsion, some remains dissolved in the aqueous phase, and some adsorbs onto the surface of the emulsion droplets according to an adsorption isotherm (e.g., Langmuir, Freundhch, or Frumkin adsorption isotherms) (173). 

It should be mentioned, that the adsorption isotherm of this acid on hematite is of the Langmuir type and on chromium hydroxide it is of the Freundhch type. On crystalline a-Fe203 the saturation is achieved in less than four hours, and at the maximum uptake essentially a monolayer of this acid is formed on the adsorbent. 

Design data are available for the specific organics on the EPA s priority pollutant Hst. For mixed wastewaters, a laboratory study is necessary to determine adsorption characteristics. Wastewater is contacted with a range of concentrations of powdered carbon and adsorption occurs, as graphed ia the form of a Freundhch Isotherm, shown ia Figure 19. 

The Freundhch isotherm model takes the multilayer and heterogeneous adsorption into account. Its hnearized form can be given as follows... 

The exponent n usually is less than unity. Both gas and liquid adsorption data are fitted by the Freundhch isotherm. Many liquid data are fitted thus in a compilation of Landolt-Bornstein (II/3,... 

The Freundlich isotherm relates surface heterogeneity. The n values obtained from Freundhch isotherm were above unity for the entire heavy metal ions as well as for total organic acid anions uptake which also indicates favorable adsorption. It predicted the constant (kp) for total organic anions removal to be 0.0118 at 23°C. 

This adsorption follows the Freundhch isotherm. AFM images of the films obtained in 10 mM ethanolic solution of the studied acid exhibited dramatically different morphologies, which were ascribed to the formation of multilayered aggregates. 

Solid-gas phase interfaces are therefore described by other means, such as by the FreundHch, Langmuir and BET isotherm. Heat of adsorption during the physical adsorption is of the same order as heat of condensation. Adsorption heat during chemisorption is of the same order as the reaction heat. ... 

Determine the Freundhch and Langmuir isotherm coefficients for the following adsorption test data on granular activated carbon (GAC). The liquid volume used in the batch adsorption tests was 1 L. The initial concentration of the adsorbate in solution was 3.37 mg/L. Equilibrium was obtained after 7 days. 

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