Amount water adsorbed

The water removal mechanism is adsorption, which is the mechanism for ad Class 4 drying agents. The capacity of such materials is often shown in the form of adsorption isotherms as depicted in Figures 9a and 9b. The initial adsorption mechanism at low concentrations of water is beheved to occur by monolayer coverage of water on the adsorption sites. As more water is adsorbed, successive layers are added until condensation or capidary action takes place at water saturation levels greater than about 70% relative humidity. At saturation, ad the pores are fided and the total amount of water adsorbed, expressed as a Hquid, represents the pore volume of the adsorbent. 

A large amount of water is added to the dehydrated material in order to cause it to swell the swollen structure is preserved when the material is frozen and subsequently dried in vacuo (in the frozen state) to a low moisture content. Some leaching occurs during the treatment with water and this, undoubtedly, further contributes to the increase in the porosity of the solid. Drying of the lyophilized substance can.be completed in a relatively short time in a vacuum oven at an elevated temperature, or at room temperature in the presence of an efficient water adsorbent. 

On account of the very great difficulty of measuring the extremely small amounts of adsorbed substance at a liquid/gas or liquid/liquid interface, very few experiments are available for testing Gibbs s equation. Zawidski(13) (1900) pointed out that the concentration of the foam of a solution should be different from that of the latter in bulk, and Miss Benson (14> (1903) by the analysis of a solution of amyl alcohol in water found... 

It is well known that biopolymers adsorbed water during dry storage and its quality depends on water content. For example the length of keratin depends on water content and therefore it is used as a hygrometer. The amount of adsorbed water depends on temperature and pressure of water vapor. 

The long tail on the OH stretching band that extends from 3700 to 3400 cm is due to a small amount of residual water adsorbed on the surface. Hydrogen bonding interactions cause the peak to be broad. 

Thus, in the relatively simple case of oil in water emulsions, where a surface active agent such as a soap is used as the emulsifying agent, it is known that the soap adsorbed on the surface of the oil particles decreases the interfacial tension, thus stabilizing the emulsion. The adsorbed soap ions also give a net electrostatic charge to the dispersed oil droplets, serving to repel other oil droplets, with the net effect that flocculation is hindered (and stability is increased). It is even possible to measure the amount of adsorbed soap ions and to calculate the values of the surface potential. 

Sharma et al. [153] have devised a gentle accelerated corrosion test using a kinetic rate equation to establish appropriate acceleration factors due to relative humidity and thermal effects. Using an estimate for the thermal activation energy of 0.6 eV and determining the amount of adsorbed water by a BET analysis on Au, Cu and Ni, they obtain an acceleration factor of 154 at 65°C/80% RH with respect to 25 °C/35-40% RH. 

Figure 4c shows that the amount of adsorbed proteins is rapidly saturated within several minutes of exposing serum-containing medium to a surface. Albumin, the most abundant serum protein, was expected to preferentially adsorb onto the surfaces during early time points. Then, adsorbed albumin was expected to be displaced by cell adhesion proteins. To investigate the effect of preadsorbed albumin displacement on cell adhesion, SAMs were first exposed to albumin then, HUVECs suspended in a serum-supplemented medium were added [21, 42]. Very few cells adhered to hydrophobic SAMs that had been pretreated with albumin, due to the large interfacial tension between water and the hydrophobic surfactant-like surface. Albumin was infrequently displaced by the cell adhesive proteins Fn and Vn. One the other hand, HUVECs adhered well to hydrophilic SAM surfaces that had been preadsorbed with albumin. In that case, the preadsorbed albumin was readily displaced by cell adhesive proteins. 

Adsorption of water by cellulose displays hysteresis. The adsorption isotherm is not identical to the desorption isotherm and the amount of adsorbed water in equilibrium with the atmosphere at a particular relative humidity is higher during desorption from a higher humidity than during adsorption from a lower humidity. A plot of the adsorption/desorption isotherm is shown in Figure 5.4. 

Where Co and Ce are the initial and equilibrium concentrations (mg mL ) of oil solution, respectively, V is volume of oil-in water dispersions (mL) and m the amount of adsorbent in gram. 

A NMR study of water adsorbed on silica gel has been made by Zimmerman el al. 18). Transverse (Ta) and longitudinal (Ti) relaxation times of various amounts of water adsorbed at 25° have been obtained with the use of the spin-echo technique and a two-phase behavior of both Ta and T relaxation times has been observed as illustrated in Figs. 10a and b. Generally only one T value is obtained, as for a single phase, except for x/m g HaO/g solid) values in the vicinity ol x/m = 0.126. Two values of Ta... 

To test this theory, the authors measured water vapor adsorption isotherms for RAMEB-treated soils. The amount of water adsorbed (kg water/kg soil) was monitored as a function of the partial pressure of water (p/po), the dose of RAMEB in the soil (0, 1, or 9%), and the type of soil. Seven soils were studied and arranged in order of increasing clay content (3, 8, 11, 16, 25, 36, and 49% clay content for SI, S2, S3,... S7, respectively). 

The water adsorption isotherms were determined by the liquid-volumetric method [21] The rust samples were put in an atmosphere with certain amount of water up to obtaining an established equilibrium, the pressure is measured and the water adsorbed may be calculated. 

Although this type of transformation can take place in solution, usually under hydrothermal conditions, it has been most intensively investigated in the dry state. A precise separation of a transformation in the dry state from that in the presence of vater is, ho vever, often difficult because the minimum amount of water with which a via-solution transformation is still possible may be very small (see 14.3.5). This applies especially to poorly ordered and nano-sized oxides, such as ferrihydrite, with high surface areas and, therefore, high amounts of adsorbed water. 

A minimum amount of adsorbed water is required (ca.100-150 g kg" of ferrihydrite) below which no transformation takes place,... 

The gel of gelatine differs from that of silica in that in the former the sol-gel transformation is reversible and not in the latter. The coalescence of the amicrons of gelatine to form streptococcic fibrils occurs at low temperatures, a process readily reversed by elevation of the temperature which decreases the amount of adsorbed water, increases the mobility of the fibrils, and permits of their rupture into smaller units. Gelatine is thus readily rendered more disperse by water. 

The amount of water adsorbed by a solid can be expressed in a number of ways. Many investigators report the amount of water sorbed, but do not taken into account the amount of water initially in the sample. The calculation of percent moisture uptake relative to the dry weight of the sample normalizes samples to the same initial point, and makes data from various samples comparable. The percent sorbed relative to dry weight is calculated from the following ... 

The Accurel EPIOO carrier, macro porous polypropylene granulates, was obtained from Akzo Nobel. Particle size was in the range of 200-1000 m. 1 gram of carrier was washed with 96% ethanol and water prior to the immobilization. Lipase solution (purified and concentrated solution of Humicola lanuginosa lipase (103 KLU/ml), pH 7.5) was added to the wet carrier. The lipase loadings were in the range of 125-500 KLU/g carrier. The amount of adsorbed lipase activity was calculated from the difference in lipase activity in the supernatant before subtracted the lipase activity after adsorption. 

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