Investigation In Viscosity And Electric Impedance Of Room Temperature Ionic Liquids And Analytical Applications

Room temperature ionic liquids (RTIL),as the name implies,are comprised entirely of ions and are molten at temperatures, lower than 373 K. The RTILs possess many attractive properties such as insignificant vapour pressure, non flammability, heat-resistant, solubility of a wide range of organic and inorganic compounds and polymeric compounds, wide electrochemical window and tunability of properties through the change in the combination of cation and anion. Consequently, there has been a significant increase in the studies on the use of RTILs for various extraction separation processes, as the electrolytic medium to carry out electrodeposition of many metals at near ambient temperatures. The applications of ionic liquids to catalytic reaction or liquid–liquid extraction processes have been gaining attention for the last years.In this thesis, our research were focus on the applications of room temperature ionic liquids'physics qualities in the chemical fields, it includs four parts.1: The electric impedance characteristics of a room temperature ionic liquid (RTIL) was measured in an impedance analysis method. The influence of an organic solvent on the conductivity and dielectric constant of an RTIL was investigated. The model solvents included ethanol, acetone, ethyl acetate and tetrachloromethane. And 1-hexyl- 3-methylimidazolium bromide and 1-hexyl-3-methylimidazolium fluoroborate were used as the model RTIL. It was shown that the addition of ethanol or acetone into the two RTIL caused significant increases in the conductivity and dielectric constant of the mixtures of RTIL and organic solvent. But the influence of on the electronic impedance of the two RTILs was much less than that of acetone or ethanol. The investigation of the electronic impedance of RTILs is helpful to the application of RTILs in electrochemistry.2: A langasite crystal microbalance, as a new type of piezoelectric sensor, is high sensitive to the change in surface mass loading. It is applicable in high viscous liquids. As the viscosity of the liquid increases, the motional resistance of the sensor increases while its resonant frequency decreases, which was used to monitor the changes in viscosity. RTILs are usually highly viscous liquids. The viscosity is an important factor that influences the mass transfer characteristics in room temperature ionic liquids. The changes in viscosity with temperature of a room temperature ionic liquids, 1-hexyl -3-methylimidazolium bromide, was monitored in real time by the sensor. It was shown that the viscosity and viscosity-temperature coefficient of this ionic liquid decrease exponentially as the temperature rises. The piezoelectric method offers a simple and rapid way to measure the viscosity of ionic liquids.3: As room temperature ionic liquids can solubility a wide range of organic and inorganic compounds, a single RTILs was used on the simulation solid phase microex traction xylene and carbon tetrachloride process, we monitor the voltage of RTILs was changed during the microextraction process. The experiment results shown that the equilibrium voltage of RTILs were proportional to the concentration of organic compounds in water.4:As RTIL [C8MIM]PF6 was undissolved in water, an interface between RTIL and aqueous phase was constructed. Te transfer of ion across the interface of RTIL/water was studied by cyclicvoltammetry and differential pulsed voltammogram methods. The experiment results reveal that effective ion transfer across RTIL/water solution interface was observed. In this communication ion transfer was driven by electrogeneration of redox tBuFc .This reaction is monitored by voltammetry and differential pulse voltammetry. The influence of the kinds of electrolytes and the concentration of the affection of electrolyte to the ion transfer process were investigated. It was shown that the ion transfer across the interface of RTIL/water was different from interface of organic compound /water.5:A langasite crystal microbalance, as a new type of piezoelectric sensor, is applicable in high viscous liquids. As the viscosity of the liquid increases, the motional resistance of the sensor increases while its resonant frequency decreases, which was used to monitor the changes in viscosity. The changes in viscosity with temperature of a room temperature ionic liquids, 1-hexyl -3-methylimidazolium bromide, was monitored in real time by the sensor. It was shown that the viscosity and viscosity-temperature coefficient of this ionic liquid decrease exponentially as the temperature rises. The piezoelectric method offers a simple and rapid way to measure the viscosity of ionic liquids.