Contact adsorption

As the adsorption affinity of redox particles on the electrode interface increases, the hydrated redox particles is adsorbed in the dehydrated state (chemical adsorption, contact adsorption) rather than in the hydrated state (ph3 ical adsorption) as shown in Fig. 7-2 (b). Typical reactions of redox electron transfer of dehydrated and adsorbed redox particles on electrodes are the hydrogen and the oxygen electrode reactions in Eqns. 7-6 and 7-7 ... 

Single-Stage Adsorption Contact filtration can be carried out as a single-stage operation (Figure 10.8) either in a batch or a continuous mode. If we assume that the amount of liquid retained with the solid is negligible, the material balance for a solute gives... 

Polarity of Vinyl Acrylic Latex and Surfactant Adsorption Contact angle measurements, dispersion and polar contribution to latex film surface tension and polarity of polymer calculated according to the method of Kaelble (10) of the three latex films are whown in Table V. It is seen that the polarity of the latex film decreases with increase in butyl acrylate content of the vinyl acrylic co-polymer. The polarity of the 70/30 (VA/BA) latex is very similar to that of the polybutyl acrylate homopolymer estimated to be about 0.21 (1). ... 

The mechanism of adhesion is a multistep process involving four phases adsorption, contact, attachment and spreading (Grinell, 1978). 

The very serious problem of fouling by proteins is corroborated by many publications [41,70,71]. Various parameters influencing the fouling behaviour have been studied. Clark et al. [70] discuss the influence of protein concentration, trans-membrane pressure, cross flow velocity and pH. For pore sizes of 0.1 pm (Membralox membranes), filtering bovine serum albumin, the flux has a minimum at the pH of the protein isoelectric point. Dumon and Barnier [71] show that the amount of protein adsorption depends on previous adsorption. Contacting with citrate or phosphate lowers a subsequent protein adsorption contacting with nitrate increases the protein adsorption. 

In order to find the partition function and statistical properties of the growing macroradical, Berezkin et aJ introduced a variable a (r) that was defined as follows a (r) = 1 if the nth unit located at the point r = x,y,z is adsorbed, and a (r) = 0 if the unit is not adsorbed. If the macroradical of length n has in some conformation k adsorption contacts with the surface, and its active center is located at the point r, the possible number of such conformations is denoted as f (fe,r). The following recurrence equation determines the value of P (fe,r) ... 

In the case of chemical spills due to process upsets, particularly fire and explosion, the chemical spillage on-site may be extensive and the water used on the fire can become contaminated with one or more process chemicals. Containment for fire water mnoff should be planned for all manufacturing plants at the design stage. Containment volume should also be provided on-site to ensure that no contaminated water leaves the site after a small or a major incident. Such water should not be flushed into a ditch, sewer, or drain or off the road since this would spread the chemical farther. The key feature of a well-designed chemical spill or contaminated water containment system is the ability to pump the spilled liquid into recovery containers for treatment. These large containers of contaminated liquid can then be treated by the conventional adsorption contacting systems as described in Section 15.3. 

Figure 1. Histograms of the silver particles size distribution for 1% Ag/Si02 catalysts prepared with (a) impregnation of the support (b) preliminary support wetting (c) (b) combined with a low-temperature adsorption-contact drying.

When a cell comes into contact with a biomaterial, the degree of interaction can generally be taken as adsorption, contact, attachment and/or spreading, as illustrated in Fig 11.1. 

Original methods of synthesis of highly dispersed silver catalysts (based upon the application of strong reducing properties of electrons solvated in soldium-ammonia solutions, the adsorption-contact method of drying and a weak solubility in nitric acid of the Si02-supported small silver clusters) allowed us to synthesize Si02-supported silver particles of sizes less than 6 nm. It makes possible some unusual catalytic and other physico-chemical properties of these particles to be discovered. 

In this case, we used the traditional method of impregnation, carried out in conditions leading to the formation of highly dispersed Ag particles on the support surface (1) samples were prepared with a low content of Ag ( 2 wt.%) (2) Ag was supported by adsorption on SiC>2 surface of the ammonia complex of the diluted silver nitrate solutions. In this case, the formation of the supported particles at the later stages of the sample preparation was mainly performed from the adsorbed silver complex. Contribution of this complex being in volume of support pores was practically excluded. (3) samples with supported silver complex were dried by the method of sublimation or by the adsorption-contact method which preserved the uniformity of adsorbed silver complex distribution on the support surface. This contributed to the obtention of a more homogeneous distribution of metal particles after subsequent reduction. The application of the adsorption-contact drying method for the preparation of the supported metal catalysts has not been found in literature. 

For the drying by sublimation, a wet sample was introduced in an ampoule and immediately frozen in liquid nitrogen. Evacuation under vaccum was carried out by keeping the sample temperature lower than 268 K (sample 7). Sample 8 was dried by the adsorption-contact method developed in the Institute of Catalysis (Novosibirsk, USSR). This method is based on the contact of dehydrated desiccant with the grains of the catalyst impregnated with the solution of the active... 

Drying the samples in a cabinet drier, in contrast with the adsorption-contact method and that of sublimation, is probably favourable to the formation of larger aggregates from the complex salt molecules adsorbed on support surface. It is accompanied by the partial decomposition of the salt into silver oxide or even (according to X-ray data), into metallic Ag. This is indicated by electron spectra of diffused reflection of the samples dried by these methods. 

The use of the adsorption-contact drying and the sublimation method leads to the obtention of Ag particles on a support with a practically equal particle size distribution. However, the adsorption-contact drying has some advantages, as it is less time-consuming (usually a few minutes) than drying by sublimation (pumping out lasts for about 20 h) and does not require special equipment (vacuum system). 

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