THE HEAT OF WETTING OF SILK FIBROIN BY WATER

1955 ◽  
Vol 33 (5) ◽  
pp. 904-912 ◽  
Author(s):  
H. Brian Dunford ◽  
John L. Morrison
Keyword(s):  
Water Vapor ◽  
Adsorption Isotherm ◽  
Thermodynamic Properties ◽  
Silk Fibroin ◽  
Adsorption Process ◽  
Film Formation ◽  
Adsorbed Water ◽  
Water Vapor Adsorption ◽  
Free Energies ◽  
Heat Of Wetting

The heats of wetting by water of silk fibroin initially containing various amounts of adsorbed and desorbed water have been measured. These measurements along with the water vapor adsorption isotherm of Hutton and Gartside have been used to calculate the integral and differential heats, free energies, and entropies of adsorption. In contrast with cellulose, silk containing desorbed water evolves less heat than that containing adsorbed water. This fact suggests that any contribution by a heat of swelling term is very small for silk fibroin, so that the calculated thermodynamic properties probably can be assigned almost entirely to the adsorption process. The changes in the heats and entropies of adsorption appear to parallel the sequence of changes in film formation as revealed by surface area calculations.

Adsorption Isotherm and Kinetics of Water Vapor Adsorption Using Novel Super-Porous Hydrogel Composites

2020 ◽  
Author(s):  
Hemant Mittal ◽  
Ali Al-Alili ◽  
Saeed M. Alhassan
Keyword(s):  
Water Vapor ◽  
Adsorption Isotherm ◽  
Adsorption Capacity ◽  
Polymer Matrix ◽  
Adsorbed Water ◽  
Water Vapor Adsorption ◽  
Water Molecules ◽  
Vapor Adsorption ◽  
Highly Effective ◽  
Desiccant Material

Abstract Deliquescent salts have high water vapor adsorption capacity, but they dissolve in water by forming crystalline hydrates. That restricts their use in different water vapor adsorption applications. However, this limitation can be overcome by incorporating deliquescent salts within a polymer matrix which will keep the salt solution in place. Furthermore, if the polymer matrix used is also capable of adsorbing water vapor, it will further improve the overall performance of desiccant system. Therefore, in this work, we are proposing the synthesis and use of a highly effective new solid polymer desiccant material, i.e. superporous hydrogel (SPHs) of poly(sodium acrylate-co-acrylic acid (P(SA-co-AA)), and subsequently its composite with deliquescent salt, i.e. calcium chloride (CaCl2), to adsorb water vapors from humid air without the dissolution of the salt in the adsorbed water. Parental PAA-SPHs matrix alone exhibited an adsorption capacity of 1.02 gw/gads which increased to 3.35 gw/gads after incorporating CaCl2 salt in the polymer matrix. Both materials exhibited type-III adsorption isotherm and the experimental isotherm data fitted to the Guggenheim, Anderson and Boer (GAB) isotherm model. However, the adsorption kinetics followed linear driving force model which suggested that this extremely high adsorption capacity was due to the diffusion of water molecules into the interconnected pores of SPHs via capillary channels followed by the attachment of adsorbed water molecules to the CaCl2 salt present in the polymer matrix. Furthermore, the adsorbents were used successively for six cycles of adsorption with a very little loss in adsorption capacity. Therefore, the proposed polymer desiccant material overcomes the problem of dissolution of deliquescent salts and opens the doors for a new class of highly effective solid desiccant material.

THE EXCHANGE OF OXYGEN-18 BETWEEN CELLULOSE, ADSORBED WATER, AND WATER VAPOR

1959 ◽  
Vol 37 (11) ◽  
pp. 1829-1833 ◽  
Author(s):  
A. R. G. Lang ◽  
S. G. Mason
Keyword(s):  
Water Vapor ◽  
Adsorption Isotherm ◽  
Adsorbed Water ◽  
Regenerated Cellulose ◽  
Vapor Pressures ◽  
Dilution Technique

The adsorption on regenerated cellulose of water at vapor pressures of 0 to 40 μ Hg has been measured by an oxygen-18 dilution technique. The results showed that cellulose may be dried to less than 0.04% moisture by evacuation at 70 °C. The adsorption isotherm was compared with that of Taylor for viscose rayon.It was also shown that oxygen-18 does not exchange between cellulose and water.

scholarly journals Prediction of storage conditions of dehydrated foods from a water vapor adsorption isotherm

2017 ◽  
Vol 16 (1) ◽  
pp. 207-220 ◽  
Author(s):  
L.A. Pascual-Pineda ◽  
◽  
L. Alamilla-Beltrán ◽  
G.F. Gutiérrez-López ◽  
E. Azuara ◽  
...  
Keyword(s):  
Water Vapor ◽  
Adsorption Isotherm ◽  
Storage Conditions ◽  
Water Vapor Adsorption ◽  
Vapor Adsorption

Equilibrium Adsorption Isotherm Mechanism of Water Vapor on Zeolites 3A, 4A, X, and Y

2017 ◽  
Author(s):  
Amged Al Ezzi ◽  
Hongbin Ma
Keyword(s):  
Water Vapor ◽  
Adsorption Isotherm ◽  
Water Vapor Adsorption ◽  
Equilibrium Adsorption ◽  
Characteristic Energy ◽  
Adsorption Sites ◽  
X Zeolites ◽  
Energy Signature ◽  
Adsorptive Properties ◽  
Equilibrium Adsorption Isotherm

Many researchers have analyzed the equilibrium adsorption isotherm mechanism of water vapor molecules on 4A, 3A, Y and X zeolites for decades. The demand for moisture removal continues to increase along with the increasing stringency of requirements for product quality control and production energy efficiency. Due to the negative charge of the zeolite framework, exchangeable compensation cations such as Na+, Li+, K+, Ba2+, Mg2+, and Ca2+ might be added. These cations are located at different sites within the framework and with different concentrations. Each cation shows a strong affinity to bond with water molecules. Adsorption sites must show a characteristic energy signature corresponding to the adsorbed amount. The values of enthalpies and entropies at each site are different since the bonding strength between the moisture molecules and cations of the site is also different. These exchangeable cations have a very important contribution in determining the zeolites adsorptive properties and selectivity. This investigation of the water vapor adsorption mechanism reveals that size, location, and type of exchangeable compensation cations have a concrete relationship to the adsorption process and zeolite cage capacity.

Chemisorption of Moisture-Induced Hydrogen and the Embrittlement Effects in Transition Metal Aluminides

1994 ◽  
Vol 364 ◽  
Author(s):  
Jian-Sheng Wang
Keyword(s):  
Water Vapor ◽  
Transition Metal ◽  
Thermodynamic Properties ◽  
Solid Solutions ◽  
Free Energies ◽  
Thermodynamic Models ◽  
Metal Aluminides

AbstractBased on simple thermodynamic models free energies of chemisorption of water vapor in transition metal aluminides and enthalpies and entropies of formation of solid solutions of hydrogen in the aluminides are derived. Susceptibilities of the aluminides to moisture-induced embrittlement are evaluated with these thermodynamic properties and compared with the susceptibilities to hydrogen-induced embrittlement.

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