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Room-temperature ionic liquids (RTILs) provide an alternative for elimination of solvent emissions to the atmosphere for many reactions, but the subsequent separation of the products by conventional methods can be a challenge. However, the use of supercritical carbon dioxide (scCO2) as an extractant offers potential for a novel class of environmentally benign media for chemical reaction and downstream separation. We have investigated the solvent properties of mixtures of 1-butyl-3-methyl imidazolium hexafluorophosphate ([bmim][PF6]) and CO2 as functions of temperature (35−50 °C) and CO2 pressure (0−230 bar). We report the Kamlet−Taft dipolarity/polarizability parameter, volume expansion, and microviscosity. The results are consistent with a picture of local enhancement of RTIL composition around a chromophore, maintaining solvent strength even at fairly high loadings of CO2, whereas the microviscosity in the vicinity of the solute is dramatically reduced, leading to enhanced mass transport and facilitated separation.

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TiO2/GO nanocomposites were synthesized successfully and exhibited an excellent ability to reduce heavy metal ions in reverse osmosis concentrate.

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Neutron reflection and surface tension measurements have been used to study the composition and structure of a mixed (alkane + surfactant) monolayer at the air-water surface, formed either by adsorption from vapor or by spreading dodecane from small lenses placed on the surface of an aqueous solution of tetradecyltrimethylammonium bromide (C,,TAB). The highest concentration of dodecane in the mixed monolayer occurs when the solution concentration of surfactant is about one-third of the critical micelle concentration (cmc), at which point the area per surfactant molecule is about 60 A*, some 20% higher than its value at the cmc but similar to its value in the absence of dodecane. At lower bulk surfactant concentrations (and hence lower surface concentrations), the amount of dodecane in the mixed layer also decreases. At a surfactant concentration of 2.6 mM (cmc = 3.7 mM) the surfactant chain is found to be slightly more extended (20 A when modeled as a uniform layer) in the presence of dodecane than in its absence, while the dodecane forms a layer significantly thicker (22 A) than its fully extended chain length (17 A). The separation of the centers of the surfactant chain and dodecane distributions at this concentration was found to be 5 f 2 A, which together with the separation of each component from the water subphase, 7.5 and 13 A, respectively, indicates that the oil is completely out of the water and that the surface of the mixture is very similar to that of pure dodecane.

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