Cosolvents extracting solution

This transition from reverse micelles to a tridimensional H-bond network has a direct consequence on third-phase formation. Moreover, the structure of the solution does not depend on the nitric acid concentration. Third-phase formation is thus prevented. Significant variations in extraction properties can be expected concurrently with this micelle-to-cosolvent microstructural transition. Without octanol, polar microdomains are clearly separated from the apolar solvent by an interface, whereas in the second system, the transition between polar and apolar areas is spatially more extended and probably creates an open structure as in a network. Nevertheless, a systematic study with structural determination in relation with the extraction ability is not yet available in the literature. Regarding the efficiency of the extractant solution containing modifiers, the key issue is also the competition for complexation between the complexing agent and the cosurfactant head-group. 

Adsorption and Desorption Adsorbents may be used to recover solutes from supercritical fluid extracts for example, activated carbon and polymeric sorbents may be used to recover caffeine from CO9. This approach may be used to improve the selectivity of a supercritical fluid extraction process. SCF extraction may be used to regenerate adsorbents such as activated carbon and to remove contaminants from soil. In many cases the chemisorption is sufficiently strong that regeneration with CO9 is limited, even if the pure solute is quite soluble in CO9. In some cases a cosolvent can be added to the SCF to displace the sorbate from the sorbent. Another approach is to use water at elevated or even supercritical temperatures to facilitate desorption. Many of the principles for desorption are also relevant to extraction of substances from other substrates such as natural products and polymers. 

The first application of ionic hquids for salen complexes dealt with the epoxidation of alkenes [14]. Jacobsen s Mn complex was immobilized in [bmimjlPFe] and different alkenes were epoxidized with aqueous NaOCl solution at 0 °C. As the ionic solvent sohdified at this temperature, dichloromethane was used as a cosolvent. The recychng procedure consisted of washing with water, evaporation of dichloromethane, and product extraction with hexane. The results (Table 3) were excellent and only a slow decay in activity and enantioselectivity was detected after several cycles. 

Cosolvent flooding is accomplished by the introduction of a cosolvent solution, with subsequent extraction of contaminated groundwater and NAPL. In one reported field test study that focused on enhanced dissolution, the use of about nine pore volumes of a 70% ethanol, 12% pentanol solution injected into a test cell resulted in about 81% bulk NAPL removal, with a higher removal efficiency for several other individual compounds. In another field test study, where mobilization removal was emphasized, injection of about four pore volumes of a mixture of tert-butanol and w-hcxanol into a test cell resulted in the removal of about 80% of the bulk NAPL, and higher removal efficiency of the more-soluble NAPL compounds. 

One of the primary components in the cost of cosolvent flushing technology is the cost of the cosolvent solution. Reuse of the flushing solution has shown the potential to greatly reduce the cost of treatment by reducing both chemical costs and the treatment and disposal costs of the extracted contaminants (D21314Z, p. 5). 

Cosolvent effects on SCF solution behavior allow the tailoring of solvents for extractions and separations. The strong interactions in these systems currently defy prediction by popular computational methods. Only by understanding these interactions at a molecular level will we be able to guide the development of phase equilibria models successfully. One way of exploring the molecular level interactions is with spectroscopy of various kinds and we have demonstrated here an attempt to look at the cosolvent/solute interaction. 

Radio frequency heating, 500 Steam stripping, 500 Vacuum extraction, 500 Aeration, 501 Bioremediation, 501 Soil flushing/washing, 502 Surfactant enhancements, 502 Cosolvents, 502 Electrokinetics, 503 Hydraulic and pneumatic fracturing, 503 Treatment walls, 505 Supercritical Water Oxidation, 507 Solid Solution Theory, 202 Solubility products, 48-53 Metal carbonates, 433-434 Metal hydroxides, 429-433 Metal sulfides, 437 Sorption, 167 See Adsorption Specific adsorption, 167 See Chemisorption Stem Layer, 152-154 Sulfate, 261... 

Supercritical fluids such as carbon dioxide can be used as solvents to extract organic compounds from aqueous solutions. In order to achieve recoveries of these products often in low concentration, cosolvents as methanol or other alcohols have been added to improve the solubility and the selectivity of the primary fluid. To optimize the extract recovery, the knowledge of phase equilibria of the ternary system carbon dioxide-methanol-water is required at different temperatures and pressures. 

Product recovery from reversed micellar solutions can often be attained by simple back extraction, by contacting with an aqueous solution having salt concentration and pH that disfavors protein solubilization, but this is not always a reliable method. Addition of cosolvents such as ethyl acetate or alcohols can lead to a disruption of the micelles and expulsion of the protein species, but this may also lead to protein denaturation. These additives must be removed by distillation, for example, to enable reconstitution of the micellar phase. Temperature increases can similarly lead to product release as a concentrated aqueous solution. Removal of the water from the reversed micelles by molecular sieves or silica gel has also been found to cause a precipitation of the protein from the organic phase. 

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