Sorbents properties

Eor a long time there have been discussions about which type of sorbent is the best for SEC separations in various mobile phases. In principle, organic (copolymer) and inorganic packings can be used. Each type of packing has its benefits and drawbacks. Table 9.3 summarizes major sorbent properties and reveals some interesting aspects of SEC separations and its requirements on packings. 

All packing materials produced at PSS are tested for all relevant properties. This includes physical tests (e.g., pressure stability, temperature stability, permeability, particle size distribution, porosity) as well as chromatographic tests using packed columns (plate count, resolution, peak symmetry, calibration curves). PSS uses inverse SEC methodology (26,27) to determine chromatographic-active sorbent properties such as surface area, pore volume, average pore size, and pore size distribution. Table 9.10 shows details on inverse SEC tests on PSS SDV sorbent as an example. Pig. 9.10 shows the dependence... 

Table II. Assumed Sorbent Properties Used to Estimate the Time to Equilibrium...

The selective sorbent properties of zeolites have many uses, of which we will describe just a few. Table 7.2 gives a brief summary of the industrial uses that are made. The zeolites are regenerated after use by heating, evacuation, or flushing with pure gases. 

Table 113 Sorbent Properties of Pure Solids Commonly Present in Aquatic Environments... 

Fly ash increases the density, decreases the permeability, and increases the leaching resistance of Ordinary Portland Cement (OPC). It is a truism that The leach resistance of solidified cement-waste systems can be improved by any process which accelerates curing, limits porosity, or chemically bonds fission product or actinide elements. (Jantzen et al., 1984). Supercritical C02 treatment of a modified Portland cement is expected to further increase the density over the untreated material, so that a reduced porosity and improved leachability should result. In addition, the high silica content of fly ash, with its well-known sorbent properties toward actinides and certain other radionuclides, enhances the immobilization characteristics. 

The correlations of KF-values with sorbent properties by Hand and Williams (1987) as well as Matthijs and De Henau (1987) give no clear indication which sorbent properties govern surfactant sorption. LAS sorption appears brought about by specific as well as unspecific hydrophobic interactions, and the prevalent mechanism depends on the nature of the sorbent. 

Based on their data for sorption onto a lake sediment, Kiewiet et al. (1996) derived an equation predicting sorption coefficients of CnEOms as a functions of alkyl chain length and the number of oxyethylene units. Di Toro et al. (1990) proposed a model for description of sorption of anionic surfactants which includes sorbent properties (organic carbon content, cation exchange capacity, and particle concentration) and the CMC as a function of the solution properties (ionic strength, temperature). The CMC is used as a relative hydrophobicity parameter. Since the model takes the contribution of electrostatic as well as hydrophobic forces explicitly into account, it is an example of an attempt to model surfactant behavior on the basis of the underlying mechanisms. 

The necessary feature for all sorbents is their selectivity, their distinct level of interaction with any given fluid component relative to the others. This property enables the sorbent to accomplish the required separation or purification. Another necessary sorbent property is the ratio of its active surface area relative to its mass. This allows reasonable unit operations equipment size for high-volume processing. The sorbents should also be possible to be regenerated for extended use (Reynolds, 1982 Perry and Green, 1997). 

This chapter is organised as follows firstly, enhanced processes concepts are presented (Section 6.2), then the sorbent properties and performances (Section 6.3), thirdly enhanced reactor configurations (Section 6.4) are discussed and finally, examples of performances and economic benefits of sorption-enhanced processes for CO2 capture are shown (Section 6.5). 

Efficiency of the desulfurization is mainly determined by the sorbent properties its adsorption capacity, selectivity for the sulfur compounds, durability and regenerability [11]. There has been an ongoing effort to develop new sorbents to remove the sulfur compounds from liquid fuels as summarized in Table 2. 

The main fluid bed reactor quantities that influence the degree of desulfurization in a fluid bed combustor are respectively (21-25) the soibent residence time, the superficial gas velocity, the stoichiometric air ratio, the bed temperature and the mean bed particle size the main sorbent properties of influence are respectively the mean soibent particle size, the maximum sorbent CaO conversion and the sulfation kinetic rate constant The most important system parameter is, of course, the (Ca/S) molar ratio in the reactor feed. 

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