Absorption/desorption method

The H2S formed in the hydro-desulphurisation process can be removed from the product stream in a variety of ways. Commonly used methods are chemical reaction with, for example, zinc oxide or iron oxide, caustic scrubbing and absorption processes. For the H2S decomposition processes treated in this chapter, only the absorption/desorption methods are of importance. Most used are absorber/stripper combination units with an alkanolamine as absorbing compound [2],... 

The absorption/desorption method is more involved experimentally compared to the membrane permeation technique, since the protein must be incorporated into the hydrogel, but not adsorbed, and subsequently dried. The dissolution study is typically carried out in USP no. 2 apparatus, with media continuously being monitored by UV analysis. Penetration of the dissolution media into the dehydrated polymer complicates the diffusion process, commonly producing a lag time prior to protein release. 

Porosity and surface area are routinely measured by nitrogen absorption-desorption, mercury intrusion, and low-angle X ray. The electron microscope (EM) provides direct visual evidence of pore size and pore-size distribution. Thus, a combination of EM and conventional methods of pore-size measurement should provide reliable information on the pore structure of polymers. 

All AB, alloys are very brittle and are pulverized to fine particles in the hydrid-ing-dehydriding process (see Sec. 7.2.1). Thus electrodes must be designed to accommodate fine powders as the active material. There are several methods of electrode fabrication Sakai et al [35] pulverize the alloy by subjecting it to several hydrogen absorption-desorption cycles, before coating the resulting particles with Ni by chemical plating. The powder is mixed with a Teflon dispersion to obtain a paste which is finally roller-pressed to a sheet and then hot-pressed to an expanded nickel mesh. The fabrication of a simple paste electrode suitable for laboratory studies is reported by Petrov et al. [37],... 

While for macroporous structures the inner surface can be calculated from the geometry, meso and micro PS layers require other methods of measurement First evidence that some PS structures do approach the microporous size regime was provided by gas absorption techniques (Brunauer-Emmet-Teller gas desorption method, BET). Nitrogen desorption isotherms showed the smallest pore diameters and the largest internal surface to be present in PS grown on low doped p-type substrates. Depending on formation conditions, pore diameters close to, or in, the microporous regime are reported, while the internal surface was found to... 

To determine PCT cnrve by volnmetric method at first we have to know mass of analyzed powder (hydride or pnre metal). The typical mass of powder used in volumetric method is in a range 50-500 mg and depends on (reactor volume with volume of connecting pipes, valves, and transdncer). After the mass measurement, the powder is loaded into specimen holder and then it is placed in the Sieverts apparatus reactor. To prevent any oxidation and for safety reason the system must be purged a few times by argon and then evacnated. However, one must be careful how much powder is appropriate for the absorption/desorption volume of a Sieverts-type apparatus. 

In PEMFC systems, water is transported in both transversal and lateral direction in the cells. A polymer electrolyte membrane (PEM) separates the anode and the cathode compartments, however water is inherently transported between these two electrodes by absorption, desorption and diffusion of water in the membrane.5,6 In operational fuel cells, water is also transported by an electro-osmotic effect and thus transversal water content distribution in the membrane is determined as a result of coupled water transport processes including diffusion, electro-osmosis, pressure-driven convection and interfacial mass transfer. To establish water management method in PEMFCs, it is strongly needed to obtain fundamental understandings on water transport in the cells. 

Absorption-Desorption Using a Batch Equilibrium Method (updated guideline, adopted January 21, 2000)... 

The preparation of sample for both methods is done in the same way as was shown for column chromatography. However, both methods differ in the solvents used for desorption. In the case of the desorption method, the solvents used should have a stronger absorption ability than the compounds in the sample mixtures. Solvents used for analyzing crude oil and its products include alcohols, ketones, ethers, chlorine-containing solvents, benzene, toluene and so on. It is possible to... 

Analysis can be performed by GC-FID and GC/MS. Its presence in air can be detected in the same manner as for acetonitrile (NIOSH 1984, Method 1606) following successive steps of charcoal absorption, desorption with benzene, and GC analysis. 

Pore size is more difficult to determine than specific surface area, particularly where microporous materials with a broad distribution of pore sizes are concerned. A number of data treatments are used to obtain information concerning the pore sizes and their distributions from N2 absorption-desorption data. The most appropriate method for determining pore volumes is a matter of some debate, and will not be covered further here (58, 60-62). The reader is referred to the paper of Lukens, Jr. et al. (61) for a discussion of the relative merits and shortcomings of the various methods. Newer approaches for measuring porosity, such as the use of variable-temperature NMR, which avoids the need for dedicated instrumentation, are also emerging (63). 

Matrix assisted laser desorption/ionisation (MALDI) For laser desorption methods a pulsed laser is used to desorb species from a target surface. Therefore, a mass analyser compatible with pulsed ionisation methods has to be used. Typically, time-offlight (TOF) analysers are employed, but several hybrid systems (Q-TOF) and, recently, high resolution Fourier transform ion cyclotron resonance (FT-ICR) analysers have been successfully adapted (see Section 10.2.4). Direct laser desorption rehes on the very rapid heating of the sample or sample substrate to vapourise molecules without decomposition. The more recent development of MALDI relies on the absorption of laser energy by a solid, microcrystalline matrix compound such as a-cyano-4-hydroxy ciimamic acid or sinapinic acid [8, 34]. MALDI has become an extremely popular method for the rapid and sensitive analysis of high-molecular-weight compounds [4]. 

The conventional method of producing sulfur dioxide is by combustion of sulfur followed by absorption-desorption, drying, and cryogenic condensation. This process is capital intensive, hazardous, saddled with corrosion, and involves high utility consumption ... 

Absorption/desorption (dissolution) Easy method Options for data analysis UV-detectable groups are abundant in proteins Protein adsorption onto hydrogel is possible Pol5Tner swelling complicates diffusion process... 

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