Sorptivity

Plutonium oxidation state Wavelength maximum, nm Molar ah sorptivities, L/(molcm) ... 

Material and uses Shape"of particles Size range, U.S. standard mesh f Internal porosity, % Bulk dry density, kg/L Average pore diameter, nm Surface area, kmVkg Sorptive capacity, kg/kg (dry)... 

Rate equations are used to describe interphase mass transfer in batch systems, packed beds, and other contacting devices for sorptive processes and are formulated in terms of fundamental transport properties of adsorbent and adsorbate. 

Chromatography Chromatography is a sorptive separation technique that allows multicomponent separations in both gas and Hquid phase. As a preparative tool, it is often used as a displacement-purge process, although many applications employ an inert-displacement mode, especially for use in analysis. General characteristics and operating modes are discussed in a separate part of this section. 

Maenair, R. N. and Arons, G. N., Sorptive textile systems containing activated carbon fibers. In Carbon Adsorption Handbook, ed. P. N. Cheremisinoff and F. Ellerbusch, Ann Arbor Science, Ann Arbor, 1978, pp. 819 859. 

The amorphous orientation is considered a very important parameter of the microstructure of the fiber. It has a quantitative and qualitative effect on the fiber de-formability when mechanical forces are involved. It significantly influences the fatigue strength and sorptive properties (water, dyes), as well as transport phenomena inside the fiber (migration of electric charge carriers, diffusion of liquid). The importance of the amorphous phase makes its quantification essential. Indirect and direct methods currently are used for the quantitative assessment of the amorphous phase. 

Fig. 4. Moisture uptakes as a function of water partial pressure for DGEBA-TETA net resin. Influence of previous exposure to 60 °C and 95% relative humidity on the apparent sorptivity. Open circles conditioned samples full circles reference samples. (22)...

The problem of accessibility in microporous solids is extreme in zero-dimensional zeolite structures such as clathrasils, that is, zeolite-related materials consisting of window-connected cages. The pore openings in these caged structures are restricted to six-membered rings of [Si04] units at most, which corresponds to pore diameters of approximately 0.2 nm [58]. These pores are too small for the removal of templates and, afterward, are impenetrable to typical sorptive molecules for characterization such as N2 and Ar or reactants such as hydrocarbons. Therefore, the intrinsic... 

In Section 24.3, use of electrosorption for effluent purification was mentioned. The same principle of an electrochemically controlled hemosorption (sorptive blood purification) is used in modem toxicology to extract toxins from blood. By appropriate potential control of the carbon sorbent, particular toxins can be removed selectively without traumatizing the blood, that is, without removing essential blood components such as the thrombocytes. 

FIGURE 5.28 Influencing factors of chamber climate in a trough chamber 1 — evaporation of low volatile components of the mobile phase from the trough bottom until saturation, 2 — sorptive saturation, 3 — evaporation from the layer, 4 — adsorption of the vapor phase. 

To overcome the problems of relatively low sample capacity associated with SPME, a technique known as stir-bar sorptive extraction has been reported by Baltussen etal. A glass-coated magnetic stir bar was coated with 50-100 iL of PDMS. Sample extraction was performed by placing the stir bar in the sample with subsequent stirring for 30-120 min. After extraction, the stir bar was removed and analytes were thermally desorbed at 150-300 °C for 5 min for GC, or liquid desorbed for LC. Qualitative analysis of organochlorine residues in wine has been reported using a commercially available product known as Twister. ... 

Experimental variables such as temperature, flow rate, sample concentration and mobile phase composition can cause changes in the elution volume of a polymer [439,457,460-464]. Chromatographic measurements made with modem equipment are limited more by the errors in the absolute methods used to characterize the molecular weight of the calibration standards than any errors Inherent in the measurements themselves, since the determination of molecular weights by SEC is not an absolute method and is dependent on calibration [462]. The Influence of temperature on retention in SEC is not very great, since no strong sorptive interactions are involved in the retention mechanism. Temperature differences between the column and solvent delivery... 

The penetration front was measured from the images in Figure 3.4.9 and plotted against the square root of time in Figure 3.4.10. The plot indicates that this relationship is linear and its slope is a measure of the sorptivity [28]. This type of experiment, coupled with gravimetric measurements, allow for the modeling of... 

Fig. 3.4.10 Sorptivity determined from Figure 3.4.9 [27]. There is a linear relationship between penetration depth and the square root of time.

The practices of isocratic and gradient sorptive chromatography are very different. Isocratic chromatography tends to be very sensitive to the details of mobile phase preparation, temperature, pump speed, and sample composition. Gradient chromatography is usually more tolerant of small variations in these factors but may be extremely sensitive to column history, equilibration time, and gradient preparation. 

Another recently developed technique is headspace sorptive extraction (HSSE) with PDMS stir bars [552]. HSSE-GC was compared with SHS and HS-SPME. SBSE and HSSE extract organic analytes from aqueous or vapour samples. In SBSE, the stir bar is inserted into the aqueous sample and extraction takes place during stirring whereas in HSSE the glass rod is suspended within the headspace volume and sampling takes place during headspace equilibration. New trends are the development of selective sorbents. 

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