| Room temperature ionic liquids (RTILs) considered as novel benign solvent and "soft" functional material in green chemical industry, are expected to replace the traditional solvent that causes a heavy pollution to the environment, and to innovate the traditional chemical techniques. Recently, many researches demonstrated that IL as "drowning-out agent" would have a potential application in the fileds of electrolyte crystallization process and solution separation. It is pity that its rearch and application is still at a beginning step. The traditional organic solvent as a medium of separation in the current chemical engineering industry exists some critical defects, in particular the organic solvent at the industry of the extraction and capture of the sulfur from exhausted gases. Thus, a new thought about the use of IL to mediate the property of solution and then to develop a new separation medium and separation process, comes up and deserves us to focus on it. In this thesis, we have done some basic experimental work and theoretical studies on the solid-liquid equilibrium, thermodynamic properties and thermodynamic models of the mixture system with ionic liquid. The highlights of this thesis are following:1. Solubility of potassium chloride (KCl) and sodium chloride (NaCI) in ionic liquid1-butyl-3-methylimidazolium chloride ([Bmim]Cl) aqueous solution and solubility of bromide MBr (M=Na,K) in1-Butyl-3-methylimidazolium bromine [Bmim]Br aqueous solutions were determined by cloud-point method through using the laser beam scattering instrument at different temperatures and standard atmospheric pressures. The effect of temperature and ionic liquid concentration on the solubility of salt was studied. We observed that ionic liquid has "salting-out effect" on salt. The solubility data in our experiments was correlated and calculated with the modified Pitzer electrolyte model. Several interaction parameters of the mixed-electrolyte solution such as θM,[Bmim],ΨM,[Bm,m],Cl, and ΨM,[Bmim].Br, and the average activity coefficient γ±of salts, and osmotic coefficient Φ of solvents, can be obtained on a basis of the experiments. Further, we used these physical parameters to evaluate the solid-liquid phase behavior in a quaternary system KCl-NaCl-[Bmim]Cl-H2O. Finally, we plotted the phase diagram of the quaternary mixture system.2. The solubilities of KCl (and K2SO4) in ionic liquid1-Butyl-3-methyl imidazolium tetrafluoroborate ([Bmim][BF4]) aqueous solution were measured at standard atmospheric pressure, but different temperatures by utilizing laser-cloud point method. An empirical expression of the solubility m as a function of the temperature T was produced. Based on the measured solubility data in the quaternary system composed of KCl (or K2SO4) and [Bmim][BF4], we calculated the standard thermodynamic quantities of transfer of KCl (and K2SO4) when moving from water to the mixed solvent.3. Thermodynamic properties such as density, viscosity, and refractive index in the MX-[Bmim]X-H2O (M=K, Na; X=Cl, Br) aqueous solution were measured in a temperature range of (T=298.15-328.15K) at standard atmospheric pressure. Our experiments indicate that density, viscosity, and the refractive index arise along with the increase of ionic liquids and salt concentration; wheras they decline along with the increase of temperature. In addition, we also calculated the apparent molar volumes VΦ, the limiting partial molar volumes VΦ0, and transfer partial molar volumes△trVΦ0of MX in mixed solutions. All the thermodynamic quantities can give a good interpretation how the solute molecules and the solvent molecules are interacting with each other in the ternary mixture systerm.4. The solubility of the element sulfur in several pure aromatic hydrocarbons, pure aliphatic hydrocarbons as well as their mixtures with ionic liquids were measured by using cloud-point method in a temperature range of (7=293.15to353.15K) at standard atmospheric pressure. Although the measured solubilities of the element sulfur increase as the temperature increases in all cases, the solvent toluene exhibits a best capability to dissolve the element sulfur. Four different imidazolium ionic liquids:1-butyl-3-methylimidazolium hexafluorophosphate ([C4mim][PF6]),1-hexyl-3-methy limidazolium hexafluorophosphate ([C6mim][PF6]),1-butyl-3-methylimidazolium tetrafluoroborate ([C4mim][BF4]), and1-hexyl-3-methylimidazolium tetrafluoroborate ([C6mim][BF4]) were added separately into pure toluene solvent in order to investigate the impact of the addition of IL on the solubility of the element sulfur. The experimental results show that the chemical structure of the IL’s cation and the concentration of ionic liquid are critical to the solubility of the element sulfur in the organic solvents. We employed several different empirical equations to correlate the solubility data measured in the toluene+[C6mim][PF6] mixture system, and calculated the free energy of transfer△trG, the entropy of transfer△trS, and the enthalpy of transfer△trH of the element sulfur moving from the pure toluene to the mixture solution. |
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