Applications of Surface Active Ionic Liquids

Abstract

The overall objective of this thesis is to take advantage of the existence of polar/non-polar domains in ionic liquids, specifically surfactants, to develop new applications of these salts. Silver chloride nanoparticles were synthesised using solely the surfactant ionic liquid trihexyl(tetradecyl)-phosphonium chloride and AgCl bulk powder. The nanoparticles were characterised and tested as nanocatalysts in the photodegradation of Orange II. An almost complete degradation can be achieved, in optimal conditions, and the nanoparticles can be recycled. The same method of synthesis was used to prepare ionanofluids consisting of AgI nanoparticles in the ionic liquid trihexyl(tetradecyl)phosphonium chloride. High concentrate and stable nanofluids were obtained and characterised. The use of this method, with a careful consideration in the selection of the ionic liquid and nanoparticles, allows obtaining nanofluids of enhanced properties. The capability of 1-alkyl-3-methylimidazolium surfactant ionic liquids to improve surfactant enhanced oil recovery methods was analysed. Liquid–liquid equilibria of water + [Cnmim][NTf2] (n = 10 or 12) + n-dodecane ternary systems were measured at 298.15 and 348.15 K. These systems can be classified as Winsor III. Some drawbacks were detected to use these ionic liquids in oil recovery. However the PC-SAFT equation of state was able to predict the equilibria. Thus, this model can be a fast and cheap initial method for the screening of possible surfactants for this application. The bistrifluoromethylsulfonylimide anion of the previously tested ionic liquids was changed for acetate. The dynamic interfacial tensions between several formulations, containing the ionic liquid, and crude oil (Saharan blend) were evaluated by the spinning drop method. The results obtained significantly improve upon previous results obtained up to with other ionic liquids. Surfactant ionic liquids can be used for the synthesis of nanoparticles and ionanofluids, and are promising alternatives to evaluate for oil recovery.