Theory Of Physical Adsorption Research Articles

The effect of organic matter fraction extracted on micropores development degree and CH4 adsorption capacity of coal

The percentage of micropores in the pore structure of coal plays a significant role in methane (CH4) adsorption, whereas the fraction of organic matter in coal has a positive effect on CH4 adsorption. Ultrasonic waves were used to excite mixtures of organic solvents and coals with different degrees of deterioration. This process facilitates the induction of surface organic matter in coal and the shedding of non-closed-ring side chains in the main structure of coal and the opening of closed rings. The samples extracted by organic solvents were subjected to electron microscopy detection, elemental analysis, and functional group analysis. The porosity of the samples showed distinct changes, and the sample with the best organic solvent extraction effect showed a sharp decrease in organic main carbon and a change in the distribution of partial functional group peaks. Through the experimental results of CH4, N2, and CO2 adsorption, the physical adsorption theory and density flooding theory with micropore filling theory were combined. It was found that the CH4 adsorption decreased, macro-and mesopore channels developed, and the percentage of micropores decreased. Overall, the filling effect caused by microchemistry had a significant influence on the macroscopic physical adsorption. Our research results provide theoretical guidance and a reference for the efficient exploitation of coalbed methane and mine gas control.

Research Progress of Polymers/Inorganic Nanocomposite Electrical Insulating Materials.

With the rapid development of power, energy, electronic information, rail transit, and aerospace industries, nanocomposite electrical insulating materials have been begun to be widely used as new materials. Polymer/inorganic nanocomposite dielectric materials possess excellent physical and mechanical properties. In addition, numerous unique properties, such as electricity, thermal, sound, light, and magnetic properties are exhibited by these materials. First, the macroscopic quantum tunneling effect, small-size effect, surface effect, and quantum-size effect of nanoparticles are introduced. There are a few anomalous changes in the physical and chemical properties of the matrix, which are caused by these effects. Second, the interaction mechanism between the nanoparticles and polymer matrix is introduced. These include infiltration adsorption theory, chemical bonding, diffusion theory, electrostatic theory, mechanical connection theory, deformation layer theory, and physical adsorption theory. The mechanism of action of the interface on the dielectric properties of the composites is summarized. These are the interface trap effect, interface barrier effect, and homogenization field strength effect. In addition, different interfacial structure models were used to analyze the specific properties of nanocomposite dielectric materials. Finally, the research status of the dielectric properties of nanocomposite dielectric materials in the electrical insulation field is introduced.

Research Progress on Polymeric Inorganic Nanocomposites Insulating Materials

With the rapid development of power energy, electronic information, rail transit, and aerospace industries, nanocomposite dielectric materials have been widely used as new materials. Polymer/inorganic nanocomposite dielectric materials possess excellent physical and mechanical properties. In addition, numerous unique properties such as electricity, thermal, sound, light, and magnetic properties are exhibited by these materials. First, the macroscopic quantum tunneling effect, small‐size effect, surface effect, and quantum‐size effect of nanoparticles are introduced. There are a few anomalous changes in the physical and chemical properties of the matrix, which are caused by these effects. Second, the interaction mechanism between the nanoparticles and polymer matrix is introduced. These include infiltration adsorption theory, chemical bonding, diffusion theory, electrostatic theory, mechanical connection theory, deformation layer theory, and physical adsorption theory. The mechanism of action of the interface on the dielectric properties of the composites is summarized. These are the interface trap effect, interface barrier effect, and homogenization field strength effect. In addition, different interfacial structure models were used to analyze the specific properties of nanocomposite dielectric materials. Finally, the research status of the dielectric properties of nanocomposite dielectric materials is introduced.

Adsorption performances and refrigeration application of adsorption working pair of CaCl2-NH3

The adsorption performance of CaCl2−NH3 is studied under the condition of different expansion spaces for adsorbent, and the relationships between adsorption performance of CaCl2−NH3 and the phenomena of swelling and agglomeration during adsorption are researched. It is found that the performance stability is related to the ratio of expansion space to the volume of adsorbent r as, and the performance attenuation is serious in the case of large r as. Severe adsorption hysteresis exists in the process of adsorption and desorption at the same evaporating and condensing temperatures, which is related to the stability constant of chemical reaction. This phenomenon cannot be explained by the theory of physical adsorption. Moderate agglomeration will be beneficial to the formation of ammoniate complex; the magnitude of expansion space will affect adsorption performance. Analysis shows that the activated energy needed in the process of adsorption for the sample with r as. of 2∶1 is less than that for the sample with r as of 3∶1. The refrigeration performance of CaCl2−NH3 is predicted from experiments. The cooling capacity of one adsorption cycle is about 945.4 kJ/kg for the adsorbent with an r as of 2∶1 at the evaporating temperature of 0°C.

EFFECT OF TEMPERATURE ON WATER SORPTION EQUILIBRIUM OF ONION (ALLIUM CEPA L)

ABSTRACT Results of the experimental measurement of sorption isotherms at different temperatures obtained by the standard gravimetric method showed the typical sigmoid shape of products rich in carbohydrates. The temperature had the expected effect predicted by the theory of physical adsorption i,e the quantity of sorbed water at a given water activity increased as the temperature decreased. The amount of adsorbed or desorbed water per unit weight of solid depends on the equilibrium temperature. The increase of the temperature results in increase of water activity for the same moisture content which in increases the rates of reactions leading to quality deterioration. As the water activity is raised beyond the intermediate region, water is sorbed by low molecular weight constituents resulting in shifting the isotherm upward. The values of the net isosteric heat of desorption were found to be higher than those or adsorption, which indicates that the binding energy for the latter is higher. At low moisture content the heats of desorption is much higher than that of adsorption.

A General Model for Adsorption of Organic Solutes from Dilute Aqueous Solutions on Heterogeneous Solids: Application for Prediction of Multisolute Adsorption

A general model describing the adsorption process from the single-component and multicomponent dilute aqueous solutions of dissociating organic substances on activated carbon is studied. The theoretical considerations are based on the theory of physical adsorption on energetically heterogeneous solids. The effect of solution pH and ionic strength is also taken into account. The theoretical considerations are illustrated by the experimental data for single-, bi-, and trisolute adsorption systems.

Gas/particle partitioning before and after flue gas purification by an activated-carbon-filter

The following paper shows an investigation of the distribution of PCDD/F in the flue gas of waste incineration plants. A model, based on the physical adsorption theory, is derived to describe the gas/particle partitioning of the PCDD/F in the flue gas up- and downstream an Activated-Carbon Filter (ACF). In comparison to the theoretical investigation, measurings in the flue gas of waste incineration plants with ACF technologie were performed.

Anomalous effects of weak chemisorption on desorption kinetics of alkenes: The desorption of propylene and propane from Ag(110)

Temperature programmed desorption (TPD), using x-ray photoelectron spectroscopy for absolute coverage determinations, was used to compare the desorption kinetics of weakly bound propane and propylene from Ag(110). The dependence of the activation energy on coverage was quantified by a linear relationship obtained from a leading edge analysis of the TPD curves. Whereas propane shows very weak attractive lateral interactions, propylene shows clear evidence for repulsive interactions in desorption. Weak attractive interactions are expected for both the propane and propylene based on theories of physical adsorption, since the second virial coefficients for both in the gas phase are negative below 550 K. Adsorption of propylene introduces repulsive intermolecular forces that are not present in the gas phase. We suggest that these repulsive forces originate in local interactions resulting from weak chemical bonding interactions between the surface and adsorbed propylene, which give rise to a preferred orientation of the double bond perpendicular to the surface. Fourier transform infrared spectroscopy results indicate that two adsorption states of propylene exist on the surface simultaneously. In the high coverage region the increase in repulsive interactions gives rise to a change in the dominant binding configuration as crowding increases.

Lateral interactions in the desorption kinetics of weakly adsorbed species: unexpected differences in the desorption of C 4 alkenes and alkanes from Ag(110) due to oriented π-bonding of the alkenes

Temperature programmed desorption (TPD), X-ray photoelectron spectroscopy, and near-edge X-ray absorption fine structure (NEXAFS) techniques were used to compare the desorption kinetics of butanes and butenes. Even though these molecules are weakly adsorbed and of similar molecular weight, alkane desorption shows evidence of weak attractive intermolecular interactions, whereas alkenes show clear evidence for moderately strong repulsive interactions in desorption. This behavior is contrary to the weak attractive intermolecular interactions expected for both the butanes and the butenes based on theories of physical adsorption, since the second virial coefficients for both in the gas phase are negative below 550 K. Adsorption of the alkenes clearly introduces repulsive intermolecular forces that are not present in the gas phase. The origin of these intermolecular forces is revealed by NEXAFS measurements for the alkenes, which show a strong orientation of the double bond axis parallel to the surface, indicative of weak directional bonding between the surface and the alkene. It appears that this preferred orientation caused by the surface alters the intermolecular forces between colliding pairs of alkenes, leading to the repulsive interactions that produce the decrease in the activation energy for desorption with increasing alkene coverage. This effect does not occur for butane, whose weak intermolecular interactions in the adsorbed layer are consistent with the predictions for physical adsorption.

Molecular theory of physical adsorption on heterogeneous surfaces: Temperature dependence of henry constant

Abstract The atomic structure of a heterogeneous surface of highly dispersed oxide was simulated as a dense random packing of hard balls (oxygen ions) by the Bernal model. For this model adsorbent, the Henry constants were calculated for Ar and Xe in a broad range of temperatures on the basis of the atom-ion approximation and the general formula that is valid for heterogeneous as well as for homogeneous surfaces. The Henry constants of the same atoms on a homogeneous surface with a regular dense packing of oxygen ions were calculated for comparison. The logarithm of the Henry constant depends linearly on the reciprocal of temperature for homogeneous surfaces; for heterogeneous surfaces, the dependence is nonlinear, but asymptotically approaches the two intersecting straight lines at high and low temperatures. Diagrams of the Henry constant density distribution over the surface show that at high temperatures adsorption on a heterogeneous surface occurs as on a homogeneous one. At low temperatures the Henry constant is determined by the strongest adsorption sites.

Computer simulation of adsorption

Abstract Despite the large number of theories of physical adsorption which have been proposed over the years. progress in this field has been slow, mainly because such theories must deal, at one and the same time, with matter in a variety of densities, ranging from those usually associated with the dilute gas to dense liquids and even solids. Since understanding of liquids, in particular, has made substantial progress only in the last 20 years, it is not surprising that the more difficult problems arising from adsorption have not succumbed to theoretical attack by ordinary methods.

Argon in a type a zeolite

1. The potential of the interaction of two similar atoms of a noble gas can be represented in the form of a Buckingham potential for which the principle of corresponding states is satisfied, one of the manifestations of this being the constancy of the complex C8/(R2C6) for different gases. 2. In accordance to the principle of corresponding states the coefficient C8 in the Buckingham potential for adsorption interactions is ∼ 6 times greater than the value adopted at the present time in the theory of physical adsorption. 3. In order to accelerate the calculation of the lattice sums in various calculations on the zeolites and other adsorbents it is possible to calculate the lattice sum by the usual method at reference points and write the result in the memory of a computer and in all the subsequent calculations to find the value of the lattice sum at a given point by interpolation. With an accuracy of 0.5% this method leads to an acceleration of the calculation by a factor of 2.103.

Absorption of Carbon Mono-oxide by the Barium Getter Part II. Theory of Physical Adsorption

The simple theory of physical adsorption was found to hold only for the getter having already absorbed a sufficient amount of carbon mono-oxide. The large absorption ability of at fresh getter is due to the existence of large number of lattice imperfections in it. The activation energy of physical adsorption, desorption and activated adsorption for Ba–CO system were found 1.0, 1.4 and 6.5 Kcal/gmol respectively. The new theory assuming the existence of lattice imperfections was developed.

Colloid Symposium Brings Attacks On Theories of Physical Adsorption

Colloid Symposium Brings Attacks On Theories of Physical Adsorption

THE DENSITY OF ADSORBATES

The apparent density of the adsorbate and the adsorption isotherm have been measured in the systems carbon tetrachloride – charcoal and diethyl ether – charcoal. In both, the apparent density of the adsorbate is lower than the normal liquid density. These abnormally low values cannot be explained on the basis of the coexistence of 'vapor' and 'liquid' adsorbed phases. The results are consistent with the concept of the adsorbatc's blocking-off a portion of the internal voids of the charcoal. The Langmuir equation represents the isotherm only when the quantity adsorbed exceeds two-thirds of the saturation value. The Harkins–Jura equation is valid at low relative pressures in the carbon tetrachloride – charcoal system, but not in the diethyl ether – charcoal system. Neon is adsorbed appreciably on charcoal at 25 °C. and therefore cannot be employed to examine the effect that the gas being used for the measurements has on the apparent density of the adsorbate. Until more accurate data are available for the adsorption of helium on charcoal, both in the absence and presence of other adsorbates, the density of charcoal and the density of the adsorbate measured by helium displacement remain suspect. In view of the uncertainties, the utility of apparent density values of adsorbates in checking the concepts of the various theories of physical adsorption is limited.