Showing papers on "Freundlich equation published in 1969"

Evaluation of microporosity, with special reference to a carbon black

Abstract: If an adsorbent yields a type II isotherm (BDDT classification), then the value of the monolayer capacity, and therefore of the specific surface, calculated from the isotherm will be incorrect unless the micropore contribution is allowed for. A method for the evaluation of the micropore contribution of a carbon black to the adsorption isotherm of nitrogen at –195°C is described. The micropores are filled with nonane at –195°C by adsorption from the vapour phase, and the excess pumped off at room temperature. The adsorption isotherm of nitrogen at –195°C is determined on the sample, both before and after thus filling the micropores. The volume of the micropores is then given by the distance between the (parallel) portions of the two isotherms corresponding to the multilayer region.

Influence of properties of adsorbent, and of the surface and bulk solutions on adsorption from solution

Abstract: To elucidate the effect of the molecular field of surface solution on adsorption equilibrium the experimental adsorption isotherms of toluene from solutions in n-heptane on the hydroxylated surface of silica gel and on weakly oxidized and non-oxidized channel carbon blacks were analyzed using expressions following from the model of monolayer adsorption and the thermodynamics of adsorption from solutions. Assuming an ideal surface solution, the thermodynamic equation approximately describes the experimental isotherm only for strong specific adsorption of toluene on the hydroxylated silica gel. It completely fails to describe the isotherm (having an azeotropic point) for weak non-specific adsorption on the non-oxidized carbon black. The calculated activity coefficients in the surface solutions and equilibrium constants reflect the decrease in the specific interaction of toluene with the adsorbents in passing from the hydroxylated silica gel surface through weakly oxidized carbon black to non-oxidized carbon black.

The Adsorption of Hydroxybenzoic Acids by Poly-N-Vinyl Pyrrolidinone

Abstract: The Freundlich system is shown to fit adsorption of the hydroxybenzoic acids by Polyclar-AT. The system also describes removal of phenols from wine when the phenols are calculated as tannic acid. Equilibrium constants for adsorption of the hydroxybenzoic acids are obtained in order to determine the selectivity of the adsorptive process. The effect of solute acidity is also investigated.

Heterogeneous catalysis in solution. Part V. Catalysis by charcoal and silver iodide of the ethyl iodide–silver nitrate reaction

Abstract: The kinetics of the ethyl iodide–silver nitrate reaction in 0·02M-aqueous potassium nitrate solution at 5° were studied in the presence of charcoal and of silver iodide. The rates depended on the concentration of each substrate either raised to a fractional power, as in a Freundlich adsorption isotherm, or arranged in a form analogous to a Langmuir isotherm, and thus indicated a Langmuir–Hinshelwood mechanism. When the difference in surface areas was taken into account, silver iodide was found to be a more effective catalyst than charcoal by a factor of at least 40. The activation energies were 20 kcal. for the homogeneous reaction, 10.4 kcal. for the charcoal-catalysed process, and 8.5 kcal. for the reaction on the silver iodide surface.

Surface properties of metallic solutions

Abstract: 1. An equation was obtained for the isotherm of the surface tension of a two-component ideal solution for systems in which the isotherm of the state of the surface-active substance in the adsorption layer is expressed by the Volmer equation. The equation derived very well describes the isotherm of the surface tension of liquid metallic solutions in the Sn-Bi system within the entire region of composition of the solution and for all the temperatures studied from 250 to 500°. 2. Attention was paid to the theoretical impossibility of conducting a systematic analysis of the surface layers of the solution within the entire interval of compositions on the basis of the values of the Gibbs adsorption Γ2(1)(N2) and to the need for calculating the isotherms of the total content of the components of the solution in the surface layer a2(N2 and a1(N2). 3. An equation was derived for the isotherm of the total content of the surface-active component of the solution in the adsorption layer, permitting conversion from the Gibbs adsorption isotherms to the isotherms a2(N2) and a1(N2). 4. The isotherms Γ2(1), Γ2(v), a2, and a1 were calculated for the Sn-Bi system at the temperatures 300, 400, and 500° within the range of compositions of the solution N2 from zero to one.

Adsorption of hydrochloric acid on polyamide

Abstract: The present investigation concerns with an apllication of the automatic recording liquid chromatography with thermal detection to the adsorption measurement. The adsorption of hydrochloric acid on polyamide powder was measured isothermally at 30°C, 40°C and 50°C. Polyamide powder was packed in two columns with thermo couple and put into double thermostat. Firstly, distilled water was flowed in at the constant flow rate in order to stabilize the thermo couple, then hydrochloric acid was flowed. The heat of adsorption around the thermo couple was recorded as change in temperature and the total variation (peak areas=Hw) was observed. The pH-Hw isotherm was almost agreed to the adsorption isotherm of hydrochloric acid on polyamide and these isotherms were in good agreement with the Langmuir's adsorption isotherm between pH4.30 to pH2.50. From these pH-Hw isotherms, the standard abilities and standard heat of adsorption were obtained. These values [ex. -Δμ°=10.2kcal/mol (40°C), -ΔH=12.0kcal/mol] were essentially identical to values from adsorption isotherm and other reports. From a consideration of these results, it seems most reasonable to conclude that the automatic recording of liquid chromatography with thermal detection is useful to measurement of adsorption.

The adsorption isotherm and thermodynamics of adsorption equilibrium

Abstract: 1. Four previously proposed methods of calculating the differential entropies and heats of adsorption on the basis of one adsorption isotherm were compared, and their possibilities and limits of applicability were discussed. 2. A new thermodynamic method of approximate calculation of the differential heats and entropies of adsorption according to one isotherm, based on the selection of the gas phase at a pressure equal to the product of the degree of filling of the adsorption volume by the saturated vapor pressure as the standard state, and on neglecting one of the factors in the expression for the entropy, the value of which is usually small, was proposed. It was shown for a number of examples that this method is applicable both to microporous and to nonporous adsorbents in the entire region of filling of the adsorption space. Especially good results of calculation of the heats of adsorption are obtained for systems in which the heat decreases with the filling.