Physical sorption

The sorption of ions of heavy metals (Cu(II), Zn(II), Cr(VI), Cd(II), Pb(II)) on ChCS in static and dynamic conditions were studied. For an estimation of selective sorbate ability ChCS the distribution factor was determined. Sorption, physical and chemical properties of complexes received by different methods were analyzed by a compai ative method. 

Sorbent filters remove gas-phase air contaminants using either physical adsorption or chemical sorption. Physical adsorption results from the electrostatic interaction between a molecule of gas or vapor and a surface (NIOSH, 2003), and chemical sorption results from the reaction between a molecule of gas or vapor and a solid sorbent or reactive agents impregnated in the sorbent material. A variety of sorbents are available for different applications, and they vary in their abilities to remove different chemicals. 

P. P. Con Stan tin ides. Lipid microemulsion.s for improving drug dissolution and ora] ab.sorption physical and biopharmaceutica aspects. Pharm Res 12 1561-1.572. 1995. 

A real porous solid is substituted by an approximately equivalent model. Equivalence may vary in different properties geometrical, sorption, physical, etc. To have a model fitted to an ob-... 

An extensive pesticide properties database was compiled, which includes six physical properties, ie, solubiUty, half-life, soil sorption, vapor pressure, acid pR and base pR for about 240 compounds (4). Because not all of the properties have been measured for all pesticides, some values had to be estimated. By early 1995, the Agricultural Research Service (ARS) had developed a computerized pesticide property database containing 17 physical properties for 330 pesticide compounds. The primary user of these data has been the USDA s Natural Resources Conservation Service (formerly the Soil Conservation Service) for leaching models to advise farmers on any combination of soil and pesticide properties that could potentially lead to substantial groundwater contamination. 

Physical and ionic adsorption may be either monolayer or multilayer (12). Capillary stmctures in which the diameters of the capillaries are small, ie, one to two molecular diameters, exhibit a marked hysteresis effect on desorption. Sorbed surfactant solutes do not necessarily cover ah. of a sohd iaterface and their presence does not preclude adsorption of solvent molecules. The strength of surfactant sorption generally foUows the order cationic > anionic > nonionic. Surfaces to which this rule apphes include metals, glass, plastics, textiles (13), paper, and many minerals. The pH is an important modifying factor in the adsorption of all ionic surfactants but especially for amphoteric surfactants which are least soluble at their isoelectric point. The speed and degree of adsorption are increased by the presence of dissolved inorganic salts in surfactant solutions (14). 

Fig. 3. Effects of composition on physical properties. A, acetyl B, butyryl C, cellulose. 1, increased tensile strength, stiffness 2, decreased moisture sorption 3, increased melting point 4, increased plasticizer compatibiUty 5, increased solubiUties in polar solvents 6, increased solubiUties in nonpolar...

The conducted researches of complexing processes of noble metals on a sulfur-containing CMSG surface formed the basis for development of sorption-photometric, sorption-luminescent, soi ption-atomic-absoi ption, sorption-atomic-emission and sorption-nuclear-physic techniques of the analysis of noble metals in rocks, technological objects and environmental objects. Techniques of separation and detenuination of noble metals in various oxidation levels have been proposed in some cases. 

The (I)-(III)-samples sorption ability investigation for cationic dyes microamounts has shown that for DG the maximum rate of extraction is within 70-90 % at pH 3. The isotherm of S-type proves the physical character of solution process and a seeming ionic exchange. Maximal rate of F extraction for all samples was 40-60 % at pH 8 due to electrostatic forces. The anionic dyes have more significant affinity to surface researching Al Oj-samples comparatively with cationic. The forms of obtained soi ption isotherms atpH have mixed character of H,F-type chemosorption mechanism of fonuation of a primary monolayer with the further bilayers formation due to H-bonds and hydrophobic interactions. The different values of pH p for sorbents and dyes confirm their multifunctional character and distinctions in the acid-base properties of adsoi ption centers. 

An absorbent material is one which changes either chemically, physically, or both during the sorption process. Certain chemicals, in absorbing moisture during this process, will dissolve into the water from the initial crystalline structure. Further added water results in a phase change from solid to liquid. An adsorbent is another material in which there are no chemical, phase, or physical changes during the sorption process. 

In order to evaluate the effect of hygrothermal fatigue on the physical and mechanical properties of composites in actual service, it is crucial to resolve the basic phenomena driving the complex water sorption behaviour and degradation mechanisms in various combinations of moist environment and temperature. 

In general, three basic kinds of sorption mechanisms for trace elements in geologic aqueous systems can be distinguished (56). Due to non-specific forces of attraction between sorbent and the solute, a physical adsorption may occur. This sorption mechanism results in the binding of species from the solution in several consecutive layers on exposed solid surfaces. This would be a rapid non-selec-tive and reversible process, fairly independent of nuclide concentration and only little dependent on ion exchange capacity of the solid. 

For plutonium in the tri- and tetravalent state, when hydrolysis would dominate the solution chemistry, most sorption phenomena in geologic systems can be looked upon largely as physical adsorption processes. Ion exchange processes, as defined above, would be... 

The key features of soot are its chemical inertness, its physical and chemical adsorption properties, and its light absorption. The large surface area coupled with the presence of various organic functional groups allow the adsorption of many different materials onto the surfaces of the particles. This type of sorption occurs both in the aerosol phase and in the aqueous phase once particles are captured by cloud droplets. As a result, complex chemical processes occur on the surface of soot particles, and otherwise volatile species may be scavenged by the soot particles. 

Physical properties of the prepared catalysts were measured by an adsorption analyzer [Quantachrome Co., Autosorb-lC]. The structure of prepared catalysts were investigated by XRD [Simmazdu Co., XRD-6000] with a Cu-Ka radiation source (X = 1.54056 A), voltage of 40.0 kV, ciurent of 30.0 mA and scan speed of 5.0 deg/min. Also, temperature-programmed reduction (TPR) profiles of the samples were investigated by a sorption analyzer [Micromeritics Co., Autochem II] and obtained by heating the samples from room temperature to 1100°C at a rate of lOTl/min in a 5 % H2/Ar gas flow (50 ml/min). 

Influence of U colloidal transport in organic-poor surface waters has been far less studied. Riotte et al. (2003) reported U losses from 0 to 70% during ultrafiltration experiments for surface waters of Mount Cameroon without nearly any DOC. Even in the low concentration waters, U can be significantly fractionated from other soluble elements by the occurrence of a colloidal phase, probably inorganic in origin. However, such fractionations are not systematic because of the occurrence of various colloidal phases, characterised by different physical and chemical properties, and hence different sorption and/or complexation capacities (Section 2.1). 

Chromatography is essentially a physical method of separation in trtiich the components to be separated are distributed between two phases one of which is stationary (stationeury phase) while the other (the mobile phase) percolates through it in a definite direction. The chroaatographic process occurs as a result of repeated sorption/desorption acts during the movement of the sample components along the stationary bed, and the separation is due to differences in the distribution constants of the Individual sample components. 

The adsorption action of activated carbon may be explained in terms of the surface tension (or energy per unit surface area) exhibited by the activated particles whose specific surface area is very large. The molecules on the surface of the particles are subjected to unbalanced forces due to unsatisfied bonds and this is responsible for the attachment of other molecules to the surface. The attractive forces are, however, relatively weak and short range, and are called Van der Waals forces, and the adsorption process under these conditions is termed as a physical adsorption (physisorption) process. In this case, the adsorbed molecules are readily desorbed from the surface. Adsorption resulting from chemical interaction with surface molecules is termed as chemisorption. In contrast to the physical process described for the adsorption on carbon, the chemisorption process is characterized by stronger forces and irreversibility. It may, however, be mentioned that many adsorption phenomena involve both physical and chemical processes. They are, therefore, not easily classified, and the general term, sorption, is used to designate the mechanism of the process. 

A closed sorption system is shown in Figure 8. It is based on the same physical effect as the open storage. However the engineering is quiet different from open sorption systems. Closed system could be more precisely described as evacuated or air-free systems. The operation pressure of the fluid to be sorbed can be adjusted in theses systems. In closed systems components, which are not existing in the atmosphere, can be used, because there is no connection to the ambience. 

HB Hopfenberg, V Stannett. Diffusion and sorption of gases and vapors in glassy polymers. In RN Haward, ed. The Physics of Glassy Polymers. New York Wiley, 1973, pp 504-547. 

Modeling relaxation-influenced processes has been the subject of much theoretical work, which provides valuable insight into the physical process of solvent sorption [119], But these models are too complex to be useful in correlating data. However, in cases where the transport exponent is 0.5, it is simple to apply a diffusion analysis to the data. Such an analysis can usually fit such data well with a single parameter and provides dimensional scaling directly, plus the rate constant—the diffusion coefficient—has more intuitive significance than an empirical parameter like k. 

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