entropy of adsorption

2020 ◽  
Author(s):  
R. Imbihl
Keyword(s):  
Entropy Of Adsorption

scholarly journals The adsorption of vapours on mercury. I. Non-polar substances

1946 ◽  
Vol 187 (1008) ◽  
pp. 53-73 ◽  
Keyword(s):  
Free Energy ◽  
Total Energy ◽  
Langmuir Equation ◽  
Phase Changes ◽  
Two Dimensional ◽  
Surface Phase ◽  
Standard State ◽  
Spreading Pressure ◽  
Benzene Toluene ◽  
Entropy Of Adsorption

Reversible results for the adsorption of benzene, toluene and n -heptane vapours on mercury have been obtained. The films were found to be gaseous and obeyed the Volmer eqution F ( A - b ) = kT , where F = spreading pressure, A =area per molecule and b = co-area. The possibility that the films might be immobile was considered and the Langmuir equation was applied but found unsatisfactory. A standard state for the surface phase was defined and the free energy, total energy and entropy of adsorption evaluated. The heat of adsorption was shown to increase with the amount on the surface. A number of phase changes were found to occur after the completion of monolayer adsorp­tion, the most striking being interpreted as the change over from ‘flat’ to ‘vertical’ adsorp­tion of the toluene molecules. Others were thought to be either two-dimensional condensation or adsorption of a second layer.

scholarly journals The adsorption of vapours on mercury. II. The entropy and heat of adsorption of non-polar substances

1946 ◽  
Vol 187 (1008) ◽  
pp. 73-87 ◽  
Keyword(s):  
Heat Of Adsorption ◽  
Attractive Potential ◽  
Intermolecular Distance ◽  
The Third ◽  
Striking Result ◽  
Surface Mobility ◽  
Repulsive Potentials ◽  
Benzene Toluene ◽  
Entropy Of Adsorption ◽  
Rotational Freedom

An attempt has been made to interpret the entropy of adsorption of benzene, toluene and n -heptane on mercury. These investigations have indicated with fair accuracy the amount of translational and rotational freedom possessed by the substances on the surface of mercury. The most striking result was obtained with benzene, where by denying all rotation except in the plane of the ring and denying the third degree of translational freedom, the calculated entropy of adsorption agreed closely with the experimental value. The surface mobility of toluene was found to be considerably hindered, and the entropy of adsorption of n -heptane confirmed the view that the molecules were partially rolled up. An attempt has been made to derive the theoretical heat of adsorption of benzene from various relations for the attractive and repulsive potentials for the van der Waals forces near a metal surface. The values obtained were of the same magnitude as the experimental value. The calculations gave some evidence of the ranges of intermolecular distance over which the different equations for the attractive potential were accurate.

scholarly journals Adsorption Equilibrium of 1, 1-Dichloro-1-fluoroethane (HCFC-141b) on a Hydrophobic Zeolite

1998 ◽  
Vol 16 (2) ◽  
pp. 67-75 ◽  
Author(s):  
Wen-Tien Tsai ◽  
Ching-Yuan Chang ◽  
Chih-Yin Ho
Keyword(s):  
Experimental Data ◽  
Free Energy ◽  
Thermodynamic Properties ◽  
Adsorption Isotherms ◽  
Ozone Depletion ◽  
Adsorption Equilibrium ◽  
Stratospheric Ozone ◽  
Stratospheric Ozone Depletion ◽  
Equilibrium Isotherms ◽  
Entropy Of Adsorption

Of the major replacements for chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs) are now accepted as being prime contributors to stratospheric ozone depletion. As a consequence, the development of adsorbents capable of adsorbing and recovering specific HCFCs has received great attention. This paper describes an investigation of the adsorption equilibrium of 1, 1-dichloro-1-fluoroethane (HCFC-141b) vapour on a commercial hydrophobic zeolite. The corresponding Henry, Freundlich and Dubinin–Radushkevich (D–R) equilibrium isotherms have been determined and found to correlate well with the experimental data. Based on the Henry adsorption isotherms obtained at 283, 303 and 313 K. thermodynamic properties such as the enthalpy, free energy and entropy of adsorption have been computed for the adsorption of HCFC-141b vapour on the adsorbent. The results obtained could be useful in the application of HCFC adsorption on the hydrophobic zeolite studied.

scholarly journals Changes in the Adsorption Properties of Activated Carbon due to Partial Oxidation of the Surface

1995 ◽  
Vol 12 (3) ◽  
pp. 211-219 ◽  
Author(s):  
A.M. Youssef ◽  
A.A. El-Khouly ◽  
A.I. Ahmed ◽  
E.I. El-Shafey
Keyword(s):  
Water Vapour ◽  
Surface Coverage ◽  
Activated Carbons ◽  
Textural Properties ◽  
Isosteric Heat ◽  
Adsorption Properties ◽  
Adsorption Of Water ◽  
Oxygen Groups ◽  
Initial Adsorption ◽  
Entropy Of Adsorption

The textural properties (surface area and porosity) of activated carbons change upon treatment with oxidizing solutions. The extent of this change is related to the strength of the oxidizing agent. Oxidation also changes the chemistry of the surface by forming carbon–oxygen groups which are the sites upon which the initial adsorption of water vapour takes place. The adsorption of water vapour at 300–320 K is mainly physical and the isosteric heat of adsorption decreases continuously as the surface coverage increases. The entropy of adsorption of water vapour on untreated and oxidized carbons, at different adsorption temperatures, has been calculated.

Calculation of Entropy of Adsorption for Small Molecules on Mineral Surfaces

2018 ◽  
Vol 122 (15) ◽  
pp. 8236-8243 ◽  
Author(s):  
A. Budi ◽  
S. L. S. Stipp ◽  
M. P. Andersson
Keyword(s):  
Small Molecules ◽  
Mineral Surfaces ◽  
Entropy Of Adsorption

Heat capacity and entropy of adsorption of benzene on FAS carbon

2007 ◽  
Vol 81 (7) ◽  
pp. 1113-1116 ◽  
Author(s):  
A. A. Lopatkin ◽  
A. A. Moreva ◽  
B. V. Kuznetsov
Keyword(s):  
Heat Capacity ◽  
Entropy Of Adsorption

scholarly journals Local Polarization, Charge Compensation, and Chemical Interactions on Ferroelectric Surfaces: a Route Toward New Nanostructures

2001 ◽  
Vol 688 ◽  
Author(s):  
Dawn A. Bonnell ◽  
Sergei V. Kalinin
Keyword(s):  
Chemical Reactivity ◽  
Charge Compensation ◽  
Switching Behavior ◽  
New Approach ◽  
Domain Specific ◽  
Ferroelectric Surfaces ◽  
Local Polarization ◽  
Enthalpy And Entropy ◽  
Specific Reactivity ◽  
Entropy Of Adsorption

AbstractThe local potential at domains on ferroelectric surfaces results from the interplay between atomic polarization and screening charge. The presence of mobile charge affects surface domain configuration, switching behavior, and surface chemical reactions. By measuring the temperature and time dependence of surface potential and piezo response with scanning probe microscopies, thermodynamic parameters associated with charge screening are determined. This is illustrated for the case of BaTiO3 (100) in air, for which the charge compensation mechanism is surface adsorption and enthalpy and entropy of adsorption are determined. The local electrostatic fields in the vicinity of the domains have a dominant effect on chemical reactivity. Photoreduction of a large variety of metals can be localized to domains with the appropriate surface charge. It has been demonstrated that proximal probe tips can be used to switch polarization direction locally. Combining the ability to ‘write’ domains of local polarization with domain specific reactivity of metals, vapors of small molecules, and organic compounds leads to a new approach to fabricating complex nanostructures.

Thermodynamics of Adsorption of Methyl Formate on Metal Dopant/Active Carbon Systems

1993 ◽  
Vol 58 (3) ◽  
pp. 474-482 ◽  
Author(s):  
Muhammad Afzal ◽  
Fazal Mahmood
Keyword(s):  
Free Energy ◽  
Active Carbon ◽  
Methyl Formate ◽  
Nitrogen Adsorption ◽  
Detailed Examination ◽  
Adsorption Affinity ◽  
Adsorption Data ◽  
Enthalpy And Entropy ◽  
Metal Doped ◽  
Entropy Of Adsorption

It has been found that doping of active carbon with metals (Ni, Cu, Zn, Cd) decreases its surface area due to dispersion of metal resides on the surface. A detailed examination of nitrogen adsorption indicates differences in the mode of dispersion of metals on the surface of active carbon. The adsorbing behavior of metal doped carbon for methyl formate was also studied as a function of temperature. From adsorption data, thermodynamic parameters such as free energy, enthalpy and entropy of adsorption were calculated using virial isotherm expression and interpreted. Results show that metal dopant/active carbon systems are synergic, exhibiting greater adsorption affinity for methyl formate than the sum of its constituents.

THERMODYNAMIC PROPERTIES OF HYDROCARBONS ADSORBED ON RUTILE II

1955 ◽  
Vol 33 (2) ◽  
pp. 259-267 ◽  
Author(s):  
H. P. Schreiber ◽  
R. McIntosh
Keyword(s):  
Thermodynamic Properties ◽  
Heat Of Adsorption ◽  
The State ◽  
Molar Entropy ◽  
Adsorption Sites ◽  
Adsorbed Methane ◽  
Entropy Of Adsorption ◽  
Adsorption Curve ◽  
Adsorption Of Methane

Integral molar heats and entropies of adsorbed methane and propane on rutile have been computed from data of isotherms at 103.2 ° and 110.2°K. for methane and 166.3° and 224.6°K. for propane. Some resemblance has been found between these functions and those for argon, nitrogen, and oxygen adsorbed on rutile, reported by Drain and Morrison. The integral molar entropy of adsorption made possible a test of the model of a localized film without interactions on a heterogeneous substrate. The model was found to be a reasonable representation of the state of adsorbed methane up to about 0.5 of the monolayer and of propane up to about 0.3 of the monolayer. A unique heat of adsorption curve for the adsorption of methane, ethane, propane, and n-butane has been derived and its significance is briefly discussed. The curve has been employed to derive functions for the distribution of energies among the adsorption sites of the substrate.

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