Study On Surface And Interfacial Tension Of Ionic Liquid

Ionic liquids or room temperature ionic liquids (RTILs)are a class of organic salts that remain liquid at room temperature or near room temperature, usually composed of organic cations and organic or inorganic anions. Compared with traditional organic solvents, RTILs have tremendous advantages, such as negligible vapor pressure, good solvation ability for organic or inorganic materials, and have the function of both solvent and catalyst. Furthermore, through different combinations of cations and anions, there is a tremendous variety of "designer" solvents. Their status as "green" or "designer" solvents explains the large amount of studies concerning their possible industrial use as reaction or extraction media. These special properties of ILs are in close connection with their microscopic structures, but how the microscopic structures affect their properties has not yet been understood completely.Surface tension is one of the basic physical and chemical properties of a liquid (including solid). It is very important to study the property of ionic liquid surface and interface (including the interfacial tension), because it is useful to further study and reveal the interaction of ionic liquids in various fields, and it is helpful to study the interaction between interface structure and interface elements. And it is necessary to study the process development, design, simulation, as well as industrial production about the ionic liquid.In this paper, the surface tensions of N-alkyl-N-alkyl -imidazolium ionic liquid and mixture of ionic liquid, the interface tension between ionic liquids and Alkanes were experimentally studued. The hard-sphere model theory is proposed to calculate the surface tension of ionic liquid. The following results were obtained.The first, with the temperature increasing, the surface tension of pure ionic liquid decreased. Reiss molecular hard-sphere model was applied to calculate the surface tension of 28 pure ionic liquids, the corresponding correlation parameters were obtained, and the average deviation of surface tension between calculation value and experimental one is 0.51%.The second, surface tensions of two mixture of ionic liquids were also studied, and the results showed that with the temperature increasing, the surface tension of ionic liquids mixture decreased. At the same temperature, fixed in one of two substances, another to contain the same anion series of ionic liquids with cations of nitrogen on the imidazole ring a substituent carbon chain increases, the surface tension of the mixture decreased. It is same with the trend of pure ionic liquids . After introducing the mixing rule into the model of pure ionic liquid, the calculation surface tension of ionic liquid mixture was established. Then 16 pairs of ionic liquid systems were predicted, and the calculation results are very successful.The third, interface tensions between ionic liquids and n-alkanes were studied. The results showed that, with the temperature increasing, the interface tension between ionic liquids and n-alkanes decreased, and with the growth of a nitrogen substituent carbon chain,its surface energy and surface entropy increased. If we consider the interface tension of pure ionic liquids and organic solvents as a function of the surface tension of pure ionic liquids and organic solvents, a correction parameter is given,and the results inosculate with the rule that correction parameter of non-polar / polar systems is lower than one.