Adsorption adsorbate

Vibrational energy states are too well separated to contribute much to the entropy or the energy of small molecules at ordinary temperatures, but for higher temperatures this may not be so, and both internal entropy and energy changes may occur due to changes in vibrational levels on adsoiption. From a somewhat different point of view, it is clear that even in physical adsorption, adsorbate molecules should be polarized on the surface (see Section VI-8), and in chemisorption more drastic perturbations should occur. Thus internal bond energies of adsorbed molecules may be affected. 

New Adsorbent Materials. SihcaUte and other hydrophobic molecular sieves, the new family of AlPO molecular sieves, and steadily increasing families of other new molecular sieves (including stmctures with much larger pores than those now commercially available), as well as new carbon molecular sieves and pillared interlayer clays (PILCS), will become more available for commercial appHcations, including adsorption. Adsorbents with enhanced performance, both highly selective physical adsorbents and easily regenerated, weak chemisorbents will be developed, as will new rate-selective adsorbents. 

See also Gas separation adsorption adsorbents for, 1 612 coal gasification, 6 824 commercial separations, l 618t hollow-fiber membrane modules for, 15 823... 

Adsorbate Temp (X ) change Adsorbate diffraction features or surface structure change Substrate struct ure after adsorption Adsorbate diffraction features or surface structures... 

Other terms are sorption, sorptive, sorbate [a distinction being made between a species in its sorbed state (sorbate) and a substance in the fluid phase which is capable of being sorbed (sorptive)], absorption, absorptive, absorbate, absorbent, and adsorption, adsorptive, adsorbate, adsorbentThe term adsorption complex is used to denote the entity constituted by the adsorbate and the part of the adsorbent to which it is bound. 

Similarly, when two or more adsorptives adsorb competitively on a surface, the adsorption isotherm for adsorptive i at a given temperature is a function of the equilibrium partial pressures of all of the adsorptives. In the case of adsorption from a liquid solution, an adsorption isotherm for any preferentially adsorbed solute may be similarly defined in terms of the equilibrium concentration of the respective solution component, but the isotherm usually... 

Polymer adsorption adsorbed polymer retards the flow of solvent and free polymer... 

Abstract Investigations of alternate adsorption regularities of cationic polyelectrolytes a) copolymer of styrene and dimethylaminopropyl-maleimide (CSDAPM) and b) poly(diallyldimethylammonium chloride) (PDADMAC) and anionic surfactant - sodium dodecyl sulfate (SDS) on fused quartz surface were carried out by capillary electrokinetic method. The adsorption/desorption kinetics, structure and properties of adsorbed layers for both polyelectrolytes and also for the second adsorbed layer were studied in dependence on different conditions molecular weight of polyelectrolyte, surfactant and polyelectrolyte concentration, the solution flow rate through the capillary during the adsorption, adsorbed layer formation... 

Substrate Overlayer Adsorption Adsorbate Bond Method... 

Substrate Face Overlayer Unit CelJ Adsorption Adsorbate Bond Site Spacing Length Method... 

Adsorbate Chemical that has been retained by the process of adsorption Adsorbent A solid material on the surface of which adsorption takes place Adsorption A physical process in which molecules of gas of dissolved chemicals or liquids adhere in an extremely thin layer to the surfaces of solid bodies with which they are in contact... 

For the moment no transitional states between these extremes will be considered. For these two limiting modes of adsorption the establishment of equilibrium proceeds via different paths in localized adsorption, adsorbed molecules can move to other sites only by desorption and re-attachment, whereas for mobile adsorption the path of tangential transport is also open. Typical representatives of localized isotherms are those of Langmuir. Frumkln-Fowler-Guggen-helm (monolayer) and BET (multilayer). For mobile adsorbates examples are the Volmer and the Hill-De Boer (or two-dimensional Van der Waals) equations. 

As a direct consequence of 1), the adsorption enthalpy and other thermodynamic properties are composite quantities, containing at least four terms. Some of these terms may dominate, and this is not necessarily the enthalpy of the adsorptive-adsorbent interaction. As a typical illustration, binding of hydrophobic (parts of) molecules on hydrophobic adsorbents from aqueous solution is mainly driven by their dislike for water and not by their attraction to the surface. 

If mass transport occurs by surface diffusion (3b) a solute molecule is adsorbed and transported deeper into the pore system by movement along the pore surface. During the whole transport process, molecules are within the attraction forces of the adsorbent surface. Notably, the attractive forces between the surface and absorbed molecules are so strong (Zhang et al, 2003) that, for many common adsorpt— adsorbent systems encountered in preparative chromatography, surface diffusion is physically implausible (especially in charged adsorpt - charged surface interactions). 

The analysis of multilayer adsorption follows that of Langmuir for monomoleeular adsorption. Adsorbate-adsorbent bonding is involved in the first layer while adsorbate-adsorbate bonding is involved in forming all subsequent layers. The heat of adsorption for the first layer, Eads, is very different from that for subsequent layers where the heat of adsorption is assumed to be the same as the heat of liquefaction, Enq (only approximately true). The mathematieal derivation of the... 

After adsorption, adsorbed proteins can interact with each other since they have already denatured at an interface (Dickinson and Matsumura, 1991). This is evidenced by an increase in the interfacial viscosity with time after adsorption (Dickinson et al., 1990). Over time, the types and nature of proteins at the interface conld farther alter. This is crucial for storage stability. The ability of P-lg and a-la to displace one another previously adsorbed at the interface is slow and irreversible. In contrast, caseins show rapid and reversible displacement with a-la and P-lg (Dickinson et al., 1989). P-lg is more difficult to be displaced by P-casein than is a-la. Nevertheless, P-lg could not displace P-casein at the interface (Dalgleish et al., 1991). However, some P-lg could be found to adsorb at the interface of the emulsion droplets, which were previously stabilized by P-casein. 

Sometimes the adsorption isotherm has been experimentally determined only for a certain temperature, for instance for the room temperature. The equation of Dubinin-Astakov can be used as a basis to extrapolate loadings to other temperatures when the relative pore filling v/v x is plotted against the adsorption potential e = RT %) since the characteristic energy e is constant for a certain adsorptive-adsorbent combination, see Fig. 2.4-5. The Henry coefficient of a certain component / depends on the temperature according to the equation of van t Hoff ... 

A wide variety of experimental and theoretical results have shown that the lAST is a very powerful tool for multicomponent adsorption equihbria of polar or nonpolar adsorptives adsorbed on activated carbon however, comprehensive plysical models (for instance the MSPDM) are necessary in the case of polar (dipole and quadrupole moment, polarizability) adsorptives adsorbed on zeolites with free ions (Mailonaim 1999). 

Keywords Water pollution, water purification, methylene blue, methyl orange, rhodamine B, heavy metal ions, Cr(VI), Hg(II), Pb(II), Cd(ll), Zn(II), Cu(II), adsorption, adsorbent, adsorbate, conducting polymers, polyaniline, polypyrrole, polythiophene, graphene, graphene oxide, carbon nanotubes (CNTs),... 

This book summarizes NMR research results collected over the past three decades that are related to very different materials, from nanomaterials and nanocomposites to biomaterials, cells, tissues, seeds, etc. It will primarily be of interest for PhD students and young scientists, although it may also prove useful to specialists and experts working on adsorption, adsorbent synthesis, surface chemistry, surface physics, biophysics, cryopreservation, and other related fields. 

This has led to the development of the theory of volume filling of micropores (TVFM theory). The theory provides a satisfactory description of the shapes of adsorption isotherms where the adsorption takes place largely in micropores. It is based on the assumption that the characteristic adsorption equation expressing the degree of filling of micropores (i.e., the volume filling of micropores) is a function of the differential molar work of adsorption. The adsorption process in this case involves dispersion forces as the main component in the adsorption-adsorbent interactions. 

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