Organic sorbents

Both inorganic and organic sorbent materials are suitable for apphcation in partition PLC. The relevant material in this connection is cellulose. Celluloses are natural products with the universal chemical formula (CgHioOj),. These native celluloses have a fibrous structure and they need to be groimd and purified before use in PLC. Besides native cellulose, microcrystalline cellulose can also be used in partition PLC. In this case the cellulose has been recrystaUized and is rod-shaped. The specific surface area of celluloses is in the range of about 2 m /g. 

Celluloses (native or microcrystalline) are organic sorbents. They have a low specific surface area and are applied mainly in partition chromatography, especially for the separation of relatively polar compounds. Works on the topic include those by Whitton and coworkers [8], who examined biosynthetic pathways for the formation of taurine in vertebrates. Taurine and its precursor amino acids were extracted from tissues, and the purified supernatant was spotted onto cellulose plates. The... 

Fig. 8. Relationship between polarity index ((O + N)/C) and aromaticity of organic sorbents from the literature. The aromatic carbon was calculated as the product of aromatic carbon content (108-165 ppm) from NMR distribution and percentage of carbon contents from elemental analysis.

A negative correlation was observed between PI and percentage of paraffinic carbon in organic sorbents (Fig. 9). This relationship is similar to the relationship between PI and aromaticity. Thus, polarity and paraffinic carbons, like polarity and aromaticity, could also be interactive... 

Xing B, McGill W, Dudas M (1994b) Sorption of benzene, toluene, and O-xylene by collagen compared with nonprotein organic sorbents. Can J Soil Sci 74 465-469... 

Guta L, Temchenko O, Sopel V, Matsela N (1997) Use of silicon-organic sorbents for endogenous intoxication syndrome correction. In Biosorption methods and preparations in prophylactic and therapeutic practice, Eirst Conference, Kiyv (In Russian), p 35... 

Xing, B., W. B. McGill, and J. J. Dudas, Sorption of a-naphthol onto organic sorbents varying in polarity and aromaticity , Chemosphere, 28,145-153 (1994). 

Polymeric organic sorbents can reportedly be used at virtually any pH, 2 to 12 [75] or 0 to 14 [73,88], increasing the potential to analyze simultaneously multiresidue samples containing acidic, basic, and neutral compounds. Polymeric sorbents contain no silanol groups and thereby avoid the problems caused by residual silanol groups when bonded silica sorbents are used [73,75],... 

Hydrophobic expulsion of hydrophobic substances (this includes nonpolar organic solutes), which are usually only sparingly soluble in water and tend to reduce the contact in water and seek relatively nonpolar environments, thus accumulating at solid surfaces and becoming absorbed on organic sorbents. 

According to Toth and Ott (1970), about 80% of the CEC of modem river and estuarine sediments is due to fresh organic matter. These authors found that sediments from the Eielaware River, Chesapeake Bay, and Bamegat Bay were 2 to 24% organic matter and had a mean CEC of 57 meq/100 g. Of this mean CEC, organic sorbents contributed 41 meq/lOO g, and inorganic sorbents 16 meq/100 g. 

Hydrophobic agent — This is a chemical or material that has the ability to resist wetting by water. Hydrophobic agents are occasionally used to treat synthetic sorbents to decrease the amount of water absorbed and hence increase the volume of oil they can absorb before becoming saturated. (See also Synthetic organic sorbents.)... 

Mineral-based sorbent — Any of a number of inorganic, mineral-based substances used to recover oil because of their adsorptive or absorptive capacities. Mineral-based sorbents include materials such as vermiculite, perlite, or volcanic ash and recover from 4 to 8 times their weight in oil. (See also Natural organic sorbents, Synthetic organic sorbents.)... 

Natural organic sorbents — Natural materials such as peat moss, straw, and sawdust that can be used to recover spilled oil. Natural sorbents generally absorb three to six times their weight in oil by virtue of the criss-cross arrangement of fibres within the material. All natural sorbents absorb water as well as oil, however, and may sink when saturated with water. Indiscriminate used of natural sorbents can add to the problems of oil spill cleanup. Synthetic sorbents are usually favoured due to their greater capacity for oil and relative ease of recovery. (See also Mineral-based sorbents, Synthetic organic sorbents.)... 

Polyethylene — A polymer (substance composed of very large molecules that are multiples of simpler chemical units) of the alkene, ethylene. Polyethylene is highly resistant to chemicals, and has low water absorption and good insulating properties and can be manufactured in a number of forms. Polyethylene also has high oleophilic properties and has been used successfully as a sorbent for cleaning up oil spills. (See also Alkenes, Oleophilic surface skimmers, Synthetic organic sorbents.)... 

Sorbent — A substance that either adsorbs or absorbs another substance. Specifically, it is a natural organic, mineral-based, or synthetic organic material used to recover small amounts of oil that have been spilled on land or water surfaces or stranded on shorelines. (See also Mineral-based sorbents, Natural organic sorbents, Synthetic organic sorbents.)... 

It may be noted that the sorption capacity of organic sorbents can be improved significantly (even by 40%) in relatively small (5%-10% w/w) admixtures with salt or lactose [18]. 

It may be noted that the sorption capacity of organic sorbents can be improved significantly (up to 40%) when in relatively small (5% to 10% w/w) mixture with salt or lactose (Tutova and Kuts, 1987). Another method of improving sorption capacity is drying with internal steam generation. Figure 12.17 depicts a sterilizer for granular peat in which the sterilization process takes place by water vapor evaporated from the peat and superheated due to heat supplied by indirect steam. In addition to the steam-heated jacket of a... 

Presently the only popular organic sorbents are Porapaks and Chromosorb lOO s (Johns Manville). Most of these commercial products are copolymers of styrene, ethylvinylbenzene and divinylbenzene. Some of them contain vinylpyrrolidone or other vinylic monomers. The specific surface areas of these organic adsorbents range from 15 m /g (Chromosorb 103) to 600 m /g (Porapak Q). 

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