Solvents performance-enhancing role

FIGURE 26.4 Stagewise depiction of the detergents action on the surfaces and the role of solvents in enhancing the performance. 

Supercritical Fluids (SFs) allow analytes to be extracted from solid samples, i.e., marine sediments, faster and more efficiently since they have lower viscosity and higher diffusivity than liquid solvents (56). CO2 is the most widely used supercritical fluid with or without a modifier, e.g. methanol and toluene. A very exhaustive discussion on the role of a modifier in the enhancement of the extraction efficiency was recently published (39). Few procedures have been described in the literature based on SFE of organic pollutants from environmental samples, including PCBs and PAHs (39, 41, 56-59). Generally, the extraction is performed... 

The mechanism of extraction and the complexes that are formed depend on the ionic liquid concerned and are quite different than the mechanisms involved with conventional solvents. Knowledge of the mechanisms involved and the species formed would be necessary for comprehensive characterisation and modelling of two-phase extractors. Task specific ionic liquids (TSILs) could also play an important role in extractions, wherein the functional groups in both cations and anions would enhance the extraction efficiency and selectivity. Since most studies deal with single component extraction it would be extremely useful to investigate the performance of ionic liquids in the selective separation of a certain component from mixtures that simulate the actual nuclear waste. Finally, the possibility to recycle the actinides that are immobilized in the ionic hquids should be the next research area of the near future. 

It is well documented that the surface chemistry and morphology of the membranes play an important role in the transmembrane transport of permeates (Khayet and Matsuura 2003a,b). To enhance the overall performance of a membrane, it is often necessary to modify the membrane material or its structure. Generally, the objective of modification is not only to increase the flux and/or selectivity, but also to control the pore size, eliminate defects, and improve the chemical resistance, for example, the solvent resistance, swelling, or fouling resistance. 

Thus, the incorporation of solvents in detergent formulations would help in the homogenization of the complex formulations on the one hand and would aid in the performance of the formulation once used for a given purpose of cleaning surfaces on the other. In other words, if surface-active substances can modify interfaces, then solvents play a key role in enhancing the effect of surfactants in more than one way. 

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