Freundlich adsorption isotherm coefficient

The adsorption coefficients (K) were determined using the equation for the Freundlich adsorption isotherm ... 

Due to the effects of molecular size and shape and pore structure on the kinetics, the model cannot be used for general predictive purposes. In practice, in order to predict PAC adsorption, a series of experiments must first be carried out using the compound of interest, the activated carbon to be applied, and the water in which it is to be used. Equilibrium parameters, determined from the Freundlich adsorption isotherm equation, are used as input into a computer-based HSDM, which uses the method of least squares to minimize the difference between the experimental kinetic data points and the HSDM fit of the data [10]. When the best fit is achieved, the resultant kinetic parameters (liquid film mass transfer coefficient, k(, and the surface diffusion coefficient, DJ can then be used for the prediction of adsorption behavior under different conditions. 

Results of adsorption experiments for butylate, alachlor, and metolachlor in Keeton soil at 10, 19, and 30°C were plotted using the Freundlich equation. A summary of the coefficients obtained from the Freundlich equation for these experiments is presented in TABLE IV. Excellent correlation using the Freundlich equation over the concentration ranges studied (four orders of magnitude) is indicated by the r values of 0.99. The n exponent from the Freundlich equation indicates the extent of linearity of the adsorption isotherm in the concentration range studied. If n = 1 then adsorption is constant at all concentrations studied (the adsorption isotherm is linear) and K is equivalent to the distribution coefficient between the soil and water (Kd), which is the ratio of the soil concentration (mole/kg) to the solution concentration (mole/L). A value of n > 1 indicates that as the solution concentration increases the sorption sites become saturated, resulting in a disproportionate amount of chemical being dissolved. Since n is nearly equal to 1 in these studies, the adsorption isotherms are nearly linear and the values for Kd (shown in TABLE IV) correspond closely to K. These Kd values were used to calculate heats of adsorption (AH). 

Monkiedje et al. [10] investigated the fate of niclosamide in aquatic system both under laboratory and field conditions. The octanol/watcr partition coefficient (Kaw) of niclosamide was 5.880 x 10 4. Adsorption isotherm studies indicated that the Freundlich parameters (K, n) for niclosamide were 0.02 and 4.93, respectively, for powder activated carbon (PAC), and 9.85 x 10 5 and 2.81, respectively, for silt loam soil. The adsorption coefficient (Aoc) for the drug was 0.02 for PAC, and 4.34 x 10-3 for the same soil. Hydrolysis of niclosamide occurred in distilled water buffer at pH above 7. No photolysis of the drug was observed in water after exposure to long-wave UV light for 4 h. Similarly, neither chemically volatilized from water following 5 h of sample aeration. Under field conditions, niclosamide persisted in ponds for over 14 days. The half-life of niclosamide was 3.40 days. 

Thus, the passage from an adsorption isotherm of a pure substance to the corresponding adsorption isotherm of a mixture is very easy, supposing that the model of a nonuniform surface is applicable and adsorption coefficients are proportional. If, for instance, adsorption of pure gas A is described by the Freundlich isotherm (135), then for adsorption of A from mixture... 

The Freundlich equation is similar to a linear equation, expect for the presence of the exponent n. For linear distributions, n = 1. With Freundlich isotherms usually have n < 1, which causes the adsorption isotherm to curve downward at higher concentrations as the readily available adsorption sites are filled and lower proportions of the arsenic from the aqueous solutions are adsorbed (Figure 2.8). The distribution coefficient for a Freundlich isotherm is often written as Kt to stress that the isotherm is not linear (Drever, 1997), 89. 

TABLE 4.6. Freundlich Adsorption Constants (1In and K) and Distribution Coefficients (Kd) for Adsorption of Alachlor (Generally Linear Isotherms), Imazethapyr (Nonlinear Freundlich Isotherms), and Rimsulfuron (Langmuir Isotherms) on Humic Acids (HAs) Isolated from Two Sewage Sludges (SSI and SS2), a Soil Amended with 10tha 1yr 1 of SSI for 2 Years (SOI + SSI), and a Soil Amended with 40(ha 1yr 1 of SS2 for 2 Years (S02 + SS2), with the Corresponding Unamended Soils (SOI and S02, Respectively) (from Senesi et al., 2001)... 

Experimental studies of the partitioning of sodium into aragonite, calcite, and dolomite have been carried out by White (1977, 1978), who concluded that the mode of substitution was as Na2CC>3 rather than as Na bicarbonate or hydroxide. The behavior of Na+ does not follow that normally described by a simple partition coefficient, but rather coprecipitation is better described by a Freundlich-type adsorption isotherm equation, implying that adsorption is important. 

Determine the Freundlich 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. 

Adsorption. The solution used to evaluate the pesticide transport equation, Equation 4a, assumes a linear adsorption isotherm that is constant with depth. However, linearity may not be the case for some pesticides and the adsorption coefficient will almost never be constant with depth. The rationale for using a linear model is initially based on the Freundlich isotherm... 

A threedimensional diagram, expressing the amount adsorbed as a function of sorbate equilibrium concentration and total pressure, is drawn using both direct experimental data and computed data for C /N- mixtures on K-clinoptilolite at room temperature. The real adsorption isotherms follow the Freundlich law for Nj and Henry s law for C>2 Freundlich and henry constants are computed and correlated to sorbate equilibrium concentration. Selectivity coefficients,, equilibrium constants, K, and the changes in the standard Gibbs free energy, aG°, are determined. Selectivity towards N. is satisfactory and K-clinoptilolite could be used for industrial air enrichment. 

Tables VI to VIII show the summary of the linear regression equations and values of correlation coefficient R, determined firom the adsorption isotherms of Langmuir, Freimdlich and BET m the treatment of resorcmol 100 mg/1,300 mg/l and 500 mg/l respectively. The average values of the correlation coefficient at the three resorcinol concentrations were 0.987,0.966 and 0.939 respectively for the Langmuir, Freundlich and the BET equations.

Equations (3.75) and (3.76) are valid only if the partition coefficient Kr, does not depend on the contents of the sorbate proper and water composition, i.e., corresponds with Henry s adsorption isotherm. This is possible at very low concentrations of an adsorbed component. At high concentrations, when adsorption corresponds with Freundlich, Langmuir isotherms or depends on ion exchange with another component, the retardation factor is expressed much more complexly. For Freundlich isotherm (equation (2.177)), the retardation factor may be estimated from equation... 

Both Langmuir and Freundlich adsorption equihbrium isotherm models were used to determine the adsorption equilibrium of the samples treated using different types of plasma [56-57]. The correlation coefficient, R -value was determined from the model curve and the results are shown in Table 12.5. 

DDF against time for different adsorption coefficients and a Freundlich type adsorption isotherm. 

For dyeing systems based on the Freundlich and Langmuir adsorption isotherm types, similar resnlts are obtained for both CDEP and DDF, further demonstrating that a higher dispersion coefficient leads to a higher dye uptake and a better levelness of dye distribution across the package, though the effect seems to be minor. 

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