scholarly journals The adsorption of vapours on mercury III. Polar substances

1947 ◽  
Vol 190 (1020) ◽  
pp. 117-137 ◽  
Keyword(s):  
Double Layer ◽  
Adsorbed Water ◽  
Liquid Films ◽  
Heat Of Adsorption ◽  
Water Molecules ◽  
Two Dimensional ◽  
Triple Layer ◽  
Adsorption Of Water ◽  
Multilayer Formation ◽  
Low Pressures

Water, acetone and the normal alcohols from methyl to hexyl have been adsorbed on mercury. All substances gave reversible adsorption and, with the exception of water, gaseous films were formed at low pressures. Methyl and ethyl alcohols showed the adsorption of a second layer at higher pressures, the double layer having half the co-area of the original monolayer. Actone gave rise to a double layer and finally a triple layer (with one-third of the original co-area). The property of multilayer formation was thought to be one of small partially polar molecules. For the gaseous films of n -butyl, n -amyl and n -hexyl alcohols the co-areas and the thermodynamic data indicated that the molecules were lying flat on the surface. These three substances showed two-dimensional condensation to liquid films at higher pressures. This phase change was accompanied by an increase of entropy which led to a decrease of the surface-vapour pressure with rise of temperature. The large entropy and heat of adsorption of water were taken as evidence for the association of the adsorbed water molecules and this probably occurred, to some extent, with methyl alcohol as well. The heat of adsorption of acetone was smaller than expected for a substance with a large dipole moment.

Restricted Rotational Motion of InterlayerWaterMolecules in Vanadium Pentoxide Hydrate, V2O5·n D2O, as Studied by Deuterium NMR

2002 ◽  
Vol 57 (6-7) ◽  
pp. 419-424 ◽  
Author(s):  
Sadamu Takeda ◽  
Yuko Gotoh ◽  
Goro Maruta ◽  
Shuichi Takahara ◽  
Shigeharu Kittaka
Keyword(s):  
Double Layer ◽  
Vanadium Pentoxide ◽  
Rotational Motion ◽  
Interlayer Space ◽  
Layer Structure ◽  
Bond Distance ◽  
Adsorbed Water ◽  
Deuterium Nmr ◽  
Water Molecules ◽  
Layer Structures

The rotational behavior of the interlayer water molecules of deuterated vanadium pentoxide hydrate, V2O5.nD2O, was studied by solid-state deuterium NMR for the mono- and double-layer structures of the adsorbed water molecules. The rotational motion was anisotropic even at 355 K for both the mono- and double-layer structures. The 180° flipping motion about the C2-symmetry axis of the water molecule and the rotation around the figure axis, which makes an angle Ɵ with the C2-axis, occurred with the activation energy of (34±4) and (49±6) kJmol-1, respectively. The activation energies were almost independent of the mono- and double-layer structures of the water molecules, but the angle Ɵ made by the two axes varied from 33° for the monolayer to 25° for the double-layer at 230 K. The angle started to decrease above 250 K (e. g. the angle was 17 at 355 K for the double-layer structure). The results indicate that the average orientation of the water molecules in the two dimensional interlayer space depends on the layer structure and on the temperature. From the deuterium NMR spectrum at 130 K, the quadrupole coupling constant e2Qq/h = 240 kHz and the asymmetry parameter η= 0.12 were deduced. These values indicate the average hydrogen bond distance R(O H) = 2.0 Å for the D2O molecules in the 2D-interlayer space

Analysis of Water Adsorption on Chitosan and Its Blends with Hydroxypropylcellulose

e-Polymers ◽  
2007 ◽  
Vol 7 (1) ◽  
Author(s):  
Maria Mucha ◽  
Kazimierz Wańkowicz ◽  
Jacek Balcerzak
Keyword(s):  
Hydrogen Bonds ◽  
Thermodynamic Parameter ◽  
Solid Surface ◽  
Mass Fraction ◽  
Water Adsorption ◽  
Vapour Phase ◽  
Heat Of Adsorption ◽  
Water Molecules ◽  
Monomolecular Layer ◽  
Adsorption Of Water

AbstractChitosan (CH) and hydroxypropylcellulose (HPC) adsorb water easily by hydrogen bonds formed with hydroxyl and amide groups present in their structures. Heat of adsorption is a thermodynamic parameter which is used to estimate the type of adsorbate molecule bond on a solid surface, among the others. Adsorption of water from vapour phase on chitosan, hydroxypropylcellulose and blends of both biopolymers in the form of films were carried out. Isotherms of water adsorption in the samples were described by the GAB equation. Correlations between mass fraction of chitosan in the sample (wf) and the values of GAB coefficients were obtained. From parameter c in the GAB equation mean heat of adsorption of the first monomolecular layer of water molecules E1, and pure molar heat of adsorption q were determined.

Hydration effects and negative dielectric constant of nano-confined water between cation intercalated MXenes

Nanoscale ◽  
2021 ◽  
Author(s):  
Hossein Jalali ◽  
Farhad Khoeini ◽  
Francois M. Peeters ◽  
Mehdi Neek-Amal
Keyword(s):  
Dielectric Constant ◽  
Double Layer ◽  
Electric Double Layer ◽  
Water Molecules ◽  
Electric Double Layer Capacitor ◽  
Two Dimensional ◽  
Confined Water ◽  
Double Layer Capacitor

A model for the electric double layer capacitor is constructed where water molecules are strongly confined in two-dimensional slits of MXene.

Specific adsorption of sulfamate ions at the mercury/solution interface

1982 ◽  
Vol 60 (13) ◽  
pp. 1643-1647 ◽  
Author(s):  
Ernesto R. Gonzalez
Keyword(s):  
Ionic Strength ◽  
Activity Coefficient ◽  
Double Layer ◽  
Adsorbed Water ◽  
Water Molecules ◽  
Electrostatic Model ◽  
Solution Composition ◽  
Solution Interface ◽  
Double Layer Capacity ◽  
Mercury Electrodes

The adsorption of sulfamate ions on mercury electrodes has been studied by measuring the double layer capacity in constant ionic strength solutions of composition xM NH4SO3NH2 + (1−x)M NH4F. It was found that sulfamate ions are weakly adsorbed on mercury, the amount adsorbed being significant only for x > 0.1 at positive charges on the electrode. Because of this, the properties of the inner layer were found to be strongly dependent on the adsorbed water molecules and the structure of the diffuse layer. It was determined that the adsorption of sulfamate ions can be described by an isotherm based on the electrostatic model of the double layer. The possible effects of the activity coefficient variation with solution composition are discussed.

scholarly journals Water Structure in Proteins in Solid State Studied by Near Infrared Spectroscopy

2017 ◽  
Vol 735 ◽  
pp. 168-172
Author(s):  
Siraporn Soonthonhut ◽  
Alfred A. Christy
Keyword(s):  
Infrared Spectroscopy ◽  
Near Infrared Spectroscopy ◽  
Water Adsorption ◽  
Near Infrared ◽  
Free Water ◽  
Adsorbed Water ◽  
Water Molecules ◽  
Combination Frequency ◽  
Adsorption Of Water ◽  
Combination Frequencies

Water adsorption in proteins is the crucial process of protein folding and structure stabilizing. Adsorption of water on proteins can be evaluated by near-infrared spectroscopy, a useful technique for observing combination frequency of a water molecule. In this work, albumin, lysozyme, and silk, were used as models for α-helix and β-pleated sheet proteins. Their NIR spectra during water adsorption process were measured by using an NIR spectrometer equipped with a transflectance accessory. Moreover, the quantitative adsorption of water was determined by gravimetric technique. The results indicate that, there are five different NIR absorptions arise from the OH combination frequencies of water adsorbed by albumin in the 5300-5100 cm-1 region. But there are only four absorptions for lysozyme and silk. The OH combination frequencies arising from water molecules in albumin indicate that it acquires free water molecules (5280 cm-1) and adsorbed water molecules through carbonyl-water interactions (5248 and 5160 cm-1) and amino-water interactions (5200 and 5120 cm-1). Interestingly, there is no indication for the presence of free water molecules in lysozyme and silk. Furthermore, the gravimetric results indicate that the rate of water adsorbed follows the order RW.Alb<RW.Lys<RW.Sil and total mass of water adsorbed per gram solid follows the order WAlb<WLys=WSil.

scholarly journals Comparison of Water Adsorption Characteristics of Oligo and Polysaccharides of α-Glucose Studied by Near Infrared Spectroscopy

2014 ◽  
Vol 1035 ◽  
pp. 476-482 ◽  
Author(s):  
Alfred A. Christy
Keyword(s):  
Near Infrared ◽  
Adsorbed Water ◽  
Water Molecules ◽  
Hydrogen Bond Formation ◽  
Oh Groups ◽  
Adsorption Characteristics ◽  
Near Infrared Spectra ◽  
Adsorption Of Water ◽  
Ethereal Oxygen ◽  
Combination Frequencies

The adsorption properties of water molecules on oligo and polysaccharides are attributed to the OH groups of the glucose rings in the molecules. The water molecules are adsorbed onto OH groups by hydrogen bond formation. Near infrared spectroscopic and gravimetric techniques were used in analysing the adsorption characteristics of malto-oligosaccharides and some polysaccharides. Near infrared spectra of the dry oligo and polysaccharides were acquired during the adsorption of water molecules at a relative humidity of 50-55%. The amounts of water adsorbed by the samples were also recorded by an analytical balance. Second derivative techniques were used in decomposing the OH combination frequencies of the adsorbed water molecules in the region 5300-5000 cm -1.The results indicate that the water molecules are adsorbed on to C2 and C3-OH groups at a higher rate compared to the adsorption onto C1-OH groups in the molecules. Adsorption also takes place onto the ethereal oxygen atoms in the glucose rings in malto-oligosaccarides. The gravimetric results show that the adsorption of water molecules increases with the number of glucose units in the malto-oligosaccharides except maltotriose which has the highest adsorption over a period of 75 minutes. Furthermore, the adsorption characteristics of amylose and amylopectin are similar.

Dielectric relaxation of water adsorbed on chemically treated woods

Holzforschung ◽  
2006 ◽  
Vol 60 (5) ◽  
pp. 549-557 ◽  
Author(s):  
Masaki Sugiyama ◽  
Misato Norimoto
Keyword(s):  
Dielectric Relaxation ◽  
Relaxation Times ◽  
Untreated Wood ◽  
Adsorbed Water ◽  
Picea Sitchensis ◽  
Water Molecules ◽  
Frequency Range ◽  
Chemically Treated ◽  
Adsorption Of Water ◽  
Rate Processes

Abstract Changes in the dielectric relaxation due to water adsorbed on eight types of chemically treated woods, as well as untreated wood (Picea sitchensis Carr.), with moisture content (MC) were investigated in the temperature range between −150°C and 20°C and in the frequency range between 100 Hz and 1 MHz. Cole-Cole's circular arc law was applied to the results of dielectric measurements conducted at seven levels of relative humidity (RH), and the relaxation spectra at −75°C were calculated. The theory of rate processes was applied to the dielectric relaxation resulting from the motions of water molecules adsorbed on the untreated and chemically treated woods, and the binding state of adsorbed water was examined. The relaxation magnitude increased with increasing MC, irrespective of the chemical treatment. The distribution of relaxation times decreased in the MC range below 1%, but increased with increasing MC at higher levels. The generalized relaxation time increased up to 5% MC, then decreased. The enthalpy-entropy compensation phenomenon was observed in the dielectric relaxation, which was derived from the adsorption of water molecules on the chemically treated woods. The binding states of adsorbed water and ice were similar. The water molecules adsorbed on wood may have produced a very wide variety of cohesive structures in the chemically treated woods.

A First-Principles Computational Comparison of the Aqueous Anatase TiO2 (001) Interface and the Disordered, Fluorinated TiO2 Interface

2018 ◽  
Author(s):  
Kyle Reeves ◽  
Damien Dambournet ◽  
Christel Laberty-Robert ◽  
Rodolphe Vuilleumier ◽  
Mathieu Salanne
Keyword(s):  
Density Of States ◽  
Density Functional ◽  
Water Dissociation ◽  
Water Molecules ◽  
Chemical Doping ◽  
Charge Balance ◽  
Functional Theory ◽  
Adsorption Of Water ◽  
Properties Of Materials ◽  
Computational Comparison

Chemical doping and other surface modifications have been used to engineer the bulk properties of materials, but their influence on the surface structure and consequently the surface chemistry are often unknown. Previous work has been successful in fluorinating anatase TiO<sub>2</sub> with charge balance achieved via the introduction of Ti vacancies rather than the reduction of Ti. Our work here investigates the interface between this fluorinated titanate with cationic vacancies and a<br>monolayer of water via density functional theory based molecular dynamics. We compute the projected density of states for only those atoms at the interface and for those states that fall within 1eV of the Fermi energy for various steps throughout the simulation, and we determine that the<br>variation in this representation of the density of states serves as a reasonable tool to anticipate where surfaces are most likely to be reactive. In particular, we conclude that water dissociation at the surface is the main mechanism that influences the anatase (001) surface whereas the change in<br>the density of states at the surface of the fluorinated structure is influenced primarily through the adsorption of water molecules at the surface.

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