Heats of adsorption of water vapour on X-zeolites containing Li+, Na+, K+, Rb+, and Cs+ cations

1971 ◽  
Vol 67 ◽  
pp. 458 ◽  
Author(s):  
O. M. Dzhigit ◽  
A. V. Kiselev ◽  
K. N. Mikos ◽  
G. G. Muttik ◽  
T. A. Rahmanova
Keyword(s):  
Water Vapour ◽  
Heats Of Adsorption ◽  
X Zeolites ◽  
Adsorption Of Water

ON THE ADSORPTION OF WATER VAPOUR BY CELLULOSE

1942 ◽  
Vol 20a (9) ◽  
pp. 143-172 ◽  
Author(s):  
J. D. Babbitt
Keyword(s):  
Water Vapour ◽  
Internal Surface ◽  
Mean Value ◽  
Experimental Fact ◽  
Adsorbed State ◽  
Internal Surface Area ◽  
Heats Of Adsorption ◽  
Adsorption Of Water ◽  
Repulsive Forces ◽  
Different Sources

In this paper an attempt is made to gather together the best available data on the adsorption of water vapour by cellulose and to draw from this data a unified picture of the phenomenon. In the first place the various theories explaining the adsorption isotherm are tested. The Langmuir isotherm is shown to fit a small portion of the curve at low relative humidities, and the polymolecular theory of Brunauer, Emmett, and Teller is found to give agreement up to the point where capillary adsorption is assumed to become predominant. It is pointed out, however, that the assumptions involved in the theory of Brunauer, Emmett, and Teller are such that an equally satisfactory agreement might be obtained by assuming that the adsorption was confined to a monomolecular layer in which, owing to repulsive forces between neighbouring atoms, the adsorbing force varied with the number of atoms. Thus it is still doubtful whether the adsorption is monomolecular or polymolecular. The investigation shows that the adsorption on cotton is similar to that on wood, except for the fact that the internal surface area available for adsorption is less by a factor of 1.86.An analysis is made of the data available for calculation of the heats of adsorption, and the values obtained from the different sources are compared. It is found that when the heats of adsorption are plotted against the relative humidity there is no appreciable difference between the values obtained with cotton and with wood. A mean value for the heats of adsorption is obtained. The relation between heats of adsorption and the latent heat of condensation is developed, and it is shown that there is an excess of internal energy in the adsorbed state over that of the liquid state.Finally, an explanation is advanced to account for the experimental fact that there is a reduction in total volume when water vapour is adsorbed on cellulose. An attempt is also made to show (i) how the water molecule may be attached to the cellulose surface by hydrogen bonds in such a way that the energy will be greater than that in liquid water, and, (ii) that, on the basis of such a picture a volume contraction is to be expected.

scholarly journals Adsorption of Water Vapour by Zinc Oxide, II

1949 ◽  
Vol 70 (1-2) ◽  
pp. 3-4
Author(s):  
Yutaka Miyahara ◽  
Isamu Sano
Keyword(s):  
Zinc Oxide ◽  
Water Vapour ◽  
Adsorption Of Water

Adsorption of Water Vapour on a Cleavage Surface of Lithium Fluoride

1962 ◽  
Vol 1 (4) ◽  
pp. 234-234 ◽  
Author(s):  
Koreo Kinosita ◽  
Hiroomi Kojima ◽  
Hideshi Yokota
Keyword(s):  
Water Vapour ◽  
Lithium Fluoride ◽  
Cleavage Surface ◽  
Adsorption Of Water

Study of the reaction CaSO4.½H2O (β-hemihydrate) = CaSO4 (β-soluble anhydrite)+½H2O in the temperature range 20–100° C

1965 ◽  
Vol 34 (268) ◽  
pp. 327-345 ◽  
Author(s):  
J. D. C. McConnell
Keyword(s):  
Water Vapour ◽  
Vapour Pressure ◽  
Physical Adsorption ◽  
Linear Increase ◽  
Water Vapour Pressure ◽  
Hydration Reaction ◽  
Temperature Range ◽  
Dehydration Reactions ◽  
Adsorption Of Water ◽  
Hydration And Dehydration

SummaryA thermogravimetric vacuum microbalance has been used to study the reaction between β-soluble anhydrite and water vapour in the temperature range 20–100° C. Equilibrium water-vapour pressures for the hydration reaction in this temperature range were determined directly and have been compared with available data obtained by Kelly, Southard, and Anderson (1941) in the temperature range 80–120° C. The kinetics of the hydration and dehydration reactions have also been studied in a series of isothermal experiments with varying water-vapour pressure. These experiments indicate that in a vapour-pressure range close to the equilibrium value very low rates for both hydration and dehydration are observed. Outside this range of vapour pressures both hydration and dehydration rates increase suddenly and show an approximately linear increase with imposed water-vapour pressure.At low temperatures (25° C) the dehydration reaction has an associated activation energy of approximately 10 kcal mole−1. In the same temperature range additional, physical adsorption of water vapour by the specimen was noted.

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.

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