Adsorbent suitable, characteristics

The most common method of regeneration is by purging the bed with a hot gas. Operating temperatures are characteristic of the adsorbent suitable values at atmospheric pressure are shown in Table 15.1. The exit temperature of the gas usually is about 50°F... 

Desiccants. A soHd desiccant is simply an adsorbent which has a high affinity and capacity for adsorption of moisture so that it can be used for selective adsorption of moisture from a gas (or Hquid) stream. The main requkements for an efficient desiccant are therefore a highly polar surface and a high specific area (small pores). The most widely used desiccants (qv) are siHca gel, activated alumina, and the aluminum rich zeoHtes (4A or 13X). The equiHbrium adsorption isotherms for moisture on these materials have characteristically different shapes (Fig. 3), making them suitable for different appHcations. 

A plot of column effluent composihon as a function of time or volume of solvent and feed reveals the adsorption and desorphon behaviors of the components in the feed mixture and illustrates whether the adsorphon system is suitable for separating the components. Particularly important is the sequence and hme when each of the feed components exit the packed adsorbent column because these characteristics describe the specific adsorbate and adsorbent interactions. From... 

Desorbent features are illustrated in Table 6.8 using Cg-aromatic adsorbates with BaX and KY adsorbents. The results in Table 6.8 further emphasize the desorbent characteristic requirement mentioned above. For instance, phenyldecane is a suitable desorbent for PX separation using BaX adsorbent. However, phenyldecane is too weak to desorb PX from KY adsorbents. In contrast, diphenylmethane offers good separation of PX with KY adsorbent but not with BaX. With BaX adsorbent, PX is separated from other Cg-aromatics using 1,4-diisopropylbenzene but not with other isomers of diisopropylbenzene, such as 1,3-diisopropylbenzene. 

Argon is analyzed by mass spectrometry (characteristic ion m/z 40) or by gas-solid chromatography. Its concentration can be increased by several times by selective adsorption over a suitable adsorbent followed by thermal desorption of the gas onto the GC injection port. 

Selection of solvents for adsorption chromatography. The choice of solvent for transferring the mixture to be chromatographed to the column will naturally depend upon the solubility characteristics of the mixture. If it is already in solution, for example as an extract, this is usually evaporated to dryness under reduced pressure and the residue dissolved in the minimum volume of the most non-polar solvent suitable. As concentrated a solution as possible is desirable to achieve a compact band at the top of the column of adsorbent, so that during subsequent development the separation will hopefully proceed with formation of discrete bands. 

Supercritical fluid extraction (SFE) is a suitable process for many separation problems. The regeneration of the supercritical fluid is as important as the extraction step itself Therefore this paper presents a method to do this in a more isobaric way than the customary pressure reduction regeneration. For the example of soil remediation we have investigated the activated carbon regeneration of supercritical carbon dioxide loaded with the low-volatile polycyclic aromatic hydrocarbon (PAH) pyrene. Characteristics of supercritical fluid extraction for soil remediation are elevated temperatures and pressures up to 370 K and 300 bar. For this reason adsorption isotherms of pyrene on activated carbon up to these conditions are measured first. Subsequently this method is used to regenerate carbon dioxide in a closed solvent cycle plant with a 4 1 extractor. An economic analysis using these results indicate that the soil remediation costs will decrease for about 20 - 30 % by means of an activated carbon adsorber. 

It is generally understood that a suitably flame retarded fabric should retain this property under conditions of wear, wash and weather. Furthermore, the flame retardant component should not effectively alter the fabric characteristics including hand, drape, adsorbency, strength and durability. In addition, this component should not adversely modify other chemicals designed to impart color, size, mildew resistance, water repellency and the like. Finally, the incorporation of a flame retardent treatment in the processing cycle of the fabric should not burden the user with excessive cost. 

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