Inorganic physical adsorption

In this article, we will discuss the use of physical adsorption to determine the total surface areas of finely divided powders or solids, e.g., clay, carbon black, silica, inorganic pigments, polymers, alumina, and so forth. The use of chemisorption is confined to the measurements of metal surface areas of finely divided metals, such as powders, evaporated metal films, and those found in supported metal catalysts. 

A.K. Stubos, Th. A. Steriotis, A.Ch. Mitropoulos, G.E. Romanos and N.K. Kanellopoulos, Inorganic membranes pore structure characterisation. In Physical Adsorption Experiments, Theory and Applications, J. Fraisard (eds.), Kluwer Academic Publishers, The Netherlands, 1997... 

Adsorption of complexes of radionuclides with inorganic or organic ligands (in particular complexes with humic substances) and of colloidal species of radionuclides may also markedly influence the migration behaviour. The predominant kind of interaction is physical adsorption. 

Voltammetry is widely used by analytical, inorganic, physical, and biological chemists for fundamental studies of( 1) o.xidation and reduction processes in various media, (2) adsorption processes on surfaces, and (3) electron transfer mechanisms at chemically modified electrode surfaces. For analytical purposes, several fonns of... 

The surface chemical and morphological characteristics of inorganic sorbents such as silicas, aluminas, talc, micas define both their chemical and physical adsorption potentials (surface energy). But the existence of mineral and organic surface pollutants will indeed strongly influence those properties. 

Generally, preparation of metal-loaded zeolite catalysts involves initial introduction of the metal component by impregnation, cation exchange, or—occasionally—physical adsorption of a volatile inorganic (such as Ni(CO)4), followed by an in situ thermal decomposition or reduction step. Thus, a Pt-containing zeolite catalyst was prepared by Rabo et al. 

Immobilization of enzymes can be accomplished in several ways, including physical cnirapmeni in a polymer gel, physical adsorption on a porous inorganic support such as alumina, covalent bonding of the enzyme to a solid surface such as glass beads or a polv-rner. or copolynierizattt)nof the enzyme with a suitable monomer. 

Originally, application of activated carbon in drinking water treatment was focused on the removal of the taste and odor of the water. Although these effects are the most obvious, the role of activated carbon is far wider and goes beyond simple physical adsorption [41-42], Purification on activated carbon is now considered to be an attractive and inexpensive option for the removal of organic and inorganic contaminants from both surface and ground waters [43-44],... 

The properties of supported enzyme preparations are governed by the properties of both the enzyme and the carrier material. The interaction between the two provides an immobilized enzyme with specific chemical, biochemical, mechanical and kinetic properties. The support (carrier) can be a synthetic organic polymer, a biopolymer or an inorganic solid. Enzyme-immobilized polymer membranes are prepared by methods similar to those for the immobilized enzyme, which are summarized in Fig. 22.7 (a) molecular recognition and physical adsorption of biocatalyst on a support membrane, (b) cross-linking between enzymes on (a), (c) covalent binding between the biocatalyst and the membrane, (d) ion complex formation between the biocatalyst and the membrane, (e) entrapment of the biocatalyst in a polymer gel membrane, (f) entrapment and adsorption of biocatalyst in the membrane, (g) entrapment and covalent binding between the biocatalyst and the membrane, (h) entrapment and ion complex formation between the biocatalyst and the membrane, (i) entrapment of the biocatalyst in a pore of an UF membrane, (j) entrapment of the biocatalyst in a hollow-fiber membrane, (k) entrapment of biocatalyst in microcapsule, and (1) entrapment of the biocatalyst in a liposome. 

Figure 2.2 shows the correlation between the characteristics of adsorbed water on the filler surface and the DMFC power density at high temperatures. Multiple layers of adsorbed water may form subsequently by physical interaction involving Van der Waals bonds. In this case, no displacement of water should occur. Such bonds become weaker as the distance of the physically adsorbed water from the surface increases. Whereas, chemically adsorbed water can involve up to a monolayer, physical adsorption and water condensation in the pores may build up a shell of water molecules surrounding the primary particles and agglomerates of the inorganic filler [14]. 

Some commercially available protein-inert polymers commonly used in microfluidic applications, all of which require permanent surface modification, are polyacrylamide, poly(N-hydroxyethylacrylamide), poly(NJl -di-methylacrylamide) (PDMA), polyvinylpyrrolidone (PVP), poly(vinyl alcohol) (PVA), hydroxyethylceUulose (HEC), and hydroxypropylmethylcellulose (HPMC). To permanently attach protein-resistant materials to the channel surface, high-energy sources, special chemistries, or even strong physical adsorption have been employed to introduce reactive functionalities. After activation, protein-resistant polymers can be anchored via UV-initiated free-radical polymerization. Polymeric materials usually do not have good solvent and heat resistance compared with inorganic materials, and hence it is necessary to take precautions during surface treatment to avoid serious damage to the microstructure or alteration of the physical properties of the bulk material. 

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