| In recent years,room temperature ionic liquids(RTILs)are considered as green solvents to replace the traditional organic solvent.RTILs have low melting point,negligible vapor pressures,and non-:flammability,strong ability to dissolve many chemicals and fine-tuning ability for the physical and chemical properties.RTILs have many favorable properties which make them attractive for a number of applications such as chemical reaction and separation processes.In order to explore the applications of RTILs more effectively,the chemical and physical properties of ionic liquids-containing systems have received considerable attention recently.Based on the continuous works by our group on rubium and cesium halides,we carried out the investigation of the solid-liquid equilibrium and thermodynamic properties of the mixture with ionic liquid and RbCL/CsCl.The ionic liquids involved were[C2mim]Cl,[C4mim]Cl,[C6mim]Cl,[Csmim]Cl,[C2mim]Br,[C4mim]Br,[C6mim]Br,[C8mim]Br.The main research and conclusions are as follows:(1)Densities and refractive index for aqueous solutions of ionic liquids([C,mim]X,n=2,4,6,8;X=Cl,Br)have been measured at T = 288.15,298.15 and 308.15 K as a function of ionic liquid concentrations.The results showed that the densities and refractive index for the binary systems RTILs + H2O increased with the increasing ionic liquid content.Moreover,for a constant mass fraction of the ionic liquid,the density and refractive index of the binary systems decreased with increasing the alkyl carbon atoms of ionic liquids and temperature.The values of refractive index were calculated using the theoretical formulan?1??sipDM,.The result shows that max deviation between calculated values and measured values were 0.01.This formula applies to correlate and predict the refractive index of binary systems containing ionic liquids.(2)To obtain deeper insights about the interaction of the ionic liquids and water molecules in aqueous solution,the excess molar volumes of the binary systems RTILs ?H2O have been studied in this work.It is shown that the ionic liquid mixed system composed of water has a negative excess molar volume due to the interaction of ionic liquids and water molecules.As a result,it is indicated that the hydrogen bonding between the RTILs and water are probably formed in the mixtures of RTILs + H2O.The values of excess molar volumes for the binary systems RTILs + H2O have been fitted to Redlich-Kister equation.(3)The solubility of RbCl/CsCl in ionic liquid([Cnmim]X,n=2,4,6,8;X=Cl,Br)aqueous solution were studied by the isothermal method at different temperature.The effects of temperature and ionic liquid on the dissolving behavior of RbCl/CsCl were examined.The results suggest that the solubility of RbCl/CsCl decreased sharply when adding ionic liquid in the aqueous solution.That is,ionic liquids induce the salting-out effect.The solubility of RbCI/CsCl decreased with the increasing of ionic liquid concentration,and increased with the increasing number of carbon atoms in the alkyl chain of cation of ionic liquids.Forth more,little influence of the temperature on the solubility.The solubility data were correlated by the NRTL(nonrandom two-liquid)model.By comparison of the experimental data and calculated data,it shows that NRTL model can qualitatively represent the equilibrium behavior.(4)The densities and refractive index for ternary system RbCI/CsCl +[Cnmim]X +H2O(n=2,4,6,8;X=Cl,Br)are measured by a digital densimeter and refractometers.The effects of temperature,content of each component and the nature of their saturated solution on the density and refractive index of the saturated solution were examined.The reliability of the measured mass fraction,density and refractive index of the saturated solutions were correlated using an empirical equation V = A?BwIh + CwIL3 + DwIL3.The result shows that the deviation between calculated values and measured values were less than 0.01.(5)On the basis of our theoretical analysis and the improvements introduced by the other researchers,a new apparatus was designed and manufactured.The sample cup of this apparatus was made of niobium-titanium alloy for its stable chemical properties and lower price.An automatic lid-lowering mechanism made of magnetic material was installed to cover sample cups within the isopiestic container.We have studied the osmotic coefficient of KCl+ H2O solution at 298.15 K using this apparatus.By comparing the experimental results found good agreement with literature values to verify the reliability of the device.(6)By using our specially designed and manufactured isopiestic apparatus,the thermodynamic behaviors of ternary systems RbCI/CsGl +[Cnmim]Cl + H2O(n=2,4,6)were studied at 298.15 K.It is shown that the RbCI/CsCl +[Cnmim]Cl + H2O(n=2,4,6)systems didn't follow the linear concentration rules little and they deviated from the partial ideal solution model.In the same line of equal water activity,the deviated value of the unsaturated ternary aqueous solution system was largest when the concentration of RTILs and RbCl/CsCl are similar.If RTILs and RbCl/CsCl have large variations,the deviated value was very small.Obviously,the interaction of ionic liquids and RbCl/CsCl in unsaturated solution has the effect on the linear isopiestic behavior.The interaction of the solute in the mixed solution couldn't be neglected. |
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