Adsorption on solid

If a finely divided solid is stirred into a dilute solution of a dye, we observe that the depth of color in the solution is much decreased. If a finely divided solid is exposed to a gas at low pressure, the pressure decreases noticeably. In these situations the dye or the gas is adsorbed on the surface. The magnitude of the effect depends on the temperature, the nature of the adsorbed substance (the adsorbate), the nature and state of subdivision of the adsorbent (the finely divided solid), and the concentration of the dye or pressure of the gas. 

The Freundlich isotherm is one of the first equations proposed to relate the amount of material adsorbed to the concentration of the material in the solution  

We can represent the process of adsorption by a chemical equation. If the adsorbate is a gas, then we write the equilibrium 

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Bound moisture in a solia is that hquid which exerts a vapor pressure less than that of the pure hquid at the given temperature. Liquid may become bound by retention in small capillaries, by solution in cell or fiber walls, by homogeneous solution throughout the sohd, and by chemical or physical adsorption on solid surfaces. 

Adsorption on solids is a process in which molecules in a fluid phase are concentrated by molecular attraction at the interface with a solid. The attraction arises from van der Waals forces, which are physical interactions between the electronic fields of molecules, and which also lead to such behavior as condensation. Attraction to the surface is etihanced because the foreign molecules tend to satisfy an imbalance of forces on the atoms in the surface of a solid compared to atoms within the solid where they are surrounded by atoms of the... 

Avd Avdeyev, D.K., Aleksandrov, G.V., Durdin, Y.V. Proc. 2nd Symposium on Double Layer and Adsorption on Solid Electrodes, Tartu, 1970, p. 58. 

Novl Novoselskiy, I.M., Konevskih, N.L, Egorov, L.Ya. Double Layer and Adsorption on Solid Electrodes, Vol. Ill, Tartu University, 1972, p. 195. 

Bag Bagotskaya, LA., Grigor ev, N.B., Doubova, L., Kalyuzknaya, A., Fateev, S. Double Layer and Adsorption on Solid Eleetrodes, Vol. IV, Tartu University, 1975, p. 14. 

Adsorption on solid matrices, which improves (at optimal protein/support ratios) enzyme dispersion, reduces diffusion limitations and favors substrate access to individual enzyme molecules. Immobilized lipases with excellent activity and stability were obtained by entrapping the enzymes in hydrophobic sol-gel materials [20]. Finally, in order to minimize substrate diffusion limitations and maximize enzyme dispersion, various approaches have been attempted to solubilize the biocatalysts in organic solvents. The most widespread method is the one based on the covalent linking of the amphiphilic polymer polyethylene glycol (PEG) to enzyme molecules [21]. 

Thermal Energy Storage can be realized by utilizing reversible chemical reactions. The number of possible reactions for this application from first principle is huge, however only very few are suitable concerning a usable reaction temperature. The process of adsorption on solid materials or absorption on liquids is the most investigated one. Figure 227 shows the process schematically. 

Adsorption is the preferential concentration of a species at the interface between two phases. Adsorption on solid surfaces is a very complex process and one that is not well understood. The surfaces of most heterogeneous catalysts are not uniform. Variations in energy, crystal structure, and chemical composition will occur as one moves about on the catalyst surface. In spite of this it is generally possible to divide all adsorption phenomena involving solid surfaces into two main classes physical adsorption and chemical adsorption (or chemisorption). Physical adsorption arises from intermolecular forces... 

If the data fit this model, a plot of 1/F0 versus 1/(S0) should be linear with a slope K/Vmax and intercept l/Vmax. It is analogous to that used in determining the constants in the Langmuir equation for adsorption on solid surfaces. Other forms that may be used to prepare linear plots are... 

IMECs of the IR bands of propene adsorbed by the different cationic forms of zeolites were calculated by modifying the Lambert-Beer law in the following way to describe the adsorption on solid wafers ... 

In general, there is an array of equilibrium-based mathematical models which have been used to describe adsorption on solid surfaces. These include the widely used Freundlich equation, a purely empirical model, and the Langmuir equation as discussed in the following sections. More detailed modeling approaches of sorption mechanisms are discussed in more detail in Chap. 3 of this volume. 

Surfactant adsorption on solids from aqueous solutions plays a major role in a number of interfacial processes such as enhanced oil recovery, flotation and detergency. The adsorption mechanism in these cases is dependent upon the properties of the solid, solvent as well as the surfactant. While considerable information is available on the effect of solid properties such as surface charge and solubility, solvent properties such as pH and ionic strength (1,2,3), the role of possible structural variations of the surfactant in determining adsorption is not yet fully understood. 

Ponec V, Knor Z, Cemy S (1974) Adsorption on solids. Butterworth, London Prost R, Gerstl Z, Yaron B, Chaussidon J (1977) Infrared studies of parathion attapulgite interaction. In Behavior of pesticides in soils. Israel-France Symposium INRA, Versailles, pp I08-II5... 

While the bulk behavior of polyampholytes has been investigated for some time now, studies of interfacial performance of polyampholytes are still in their infancy. There are several reasons for the limited amount of experimental work the major one being the rather complex behavior of polyampholytes at interfaces. This complexity stems from a large array of system parameters governing the interaction between the polymer and the substrate. Nearly all interfacial studies on polyampholytes reported to-date involved their adsorption on solid interfaces. For example, Jerome and Stamm and coworkers studied the adsorption of poly(methacryhc acid)-block-poly(dimethyl aminoethyl methacrylate) (PMAA-fc-PDMAEMA) from aqueous solution on sihcon substrates [102,103]. The researchers found that the amount of PMAA-fo-PDMAEMA adsorbed at the solution/substrate interface depended on the solution pH. Specifically, the adsorption increased... 

FIGURE 5.9 Brunuer-Emmett-Teller (BET) model for multilayer adsorption on solids. 

Adsorption on solid surfaces requires the same information about the structure of the adsorbates and the adsorption site and configurations. 

Avena, M.J. Koopal, L.K. (1999) Kinetics of humic acid adsorption on solid-water interfaces. Environ. Sci. Techn. 33 2739-2744 Avnir, D. Jaroniec, M. (1989) An isotherm equation for adsorption on fractal surfaces of... 

On a global scale the air layers within a few kilometers of the earth s surface are rapidly mixed by wind action. This region is called the troposphere. Natural and manmade sources of chemicals such as CH4 and other hydrocarbons, CO, SO, NO, ozone, and chlorine are emitted into the troposphere. Most of these are removed or reacted away to form harmless products by dissolving in rain, adsorption on solids, and chemical reactions. 

King, D. A., and Woodruff, D. P. Adsorption on Solid Surfaces. Amsterdam Elsevier, 1983. 

This overview will outline surfactant mixture properties and behavior in selected phenomena. Because of space limitations, not all of the many physical processes involving surfactant mixtures can be considered here, but some which are important and illustrative will be discussed these are micelle formation, monolayer formation, solubilization, surfactant precipitation, surfactant adsorption on solids, and cloud point Mechanisms of surfactant interaction will be as well as mathematical models which have been be useful in describing these systems,... 

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