Ionic Strength Intelligent Switch Solvent-organic System Phase Equilibrium Thermodynamics Research

Switchable ionic strength aqueous solvents are a series of amines(N,N-dimethylcyclohexylamine(DMCA)or triethylamine)when dissolved in water and reacted with CO2,generate aqueous solutions of significantly greater ionic strength than pure water through the formation of ammonium hydrogen carbonates.This increased ionic strength is easily reduced by removing CO2 through moderate heating and sparging with N2.A practical application of this technology would be the reversible separation of water-miscible organic liquids from water.Because the property and phase equilibrium thermodynamic data of switchable ionic strength aqueous solvent are scarce,which affects its application in salting out process.So the property of switchable ionic strength aqueous solvent and liquid-liquid equilibrium of switchable ionic strength aqueous solvent,organic solvent and water were studied,which provides the basic data and theoretical basis for industrialization.The lack of physical properties,phase equilibria thermodynamic data of the intelligent switch solvent,which has encountered some difficulties in the practical application of the separation process.The physical and chemical properties and liquid-liquid equilibrium of solvent-organic-water system was studied,which provides the basic data and theoretical basis for its high theoretical value and industrial application value.Specifically completed the following aspects of the work:(1)The rate of DMCAH-bicarbonate was determined by gravimetric method in DMCA-water system,when the CO2 was introduced into DMCA-water system.The density,viscosity of aqueous phase was measured by Ubbelohde viscometer and vibrating tube densitometer,and characterized by NMR(C13)spectroscopy.The effects of temperature and the volume ratio of DMCA and water on the physical properties were discussed.The Vogel-Tamman-Fulcher equation was used to correlate the measured density and viscosity data.The standard deviation was small and the correlation was better.The apparent molar volume of DMCA-bicarbonate solution were calculated by the experimental density data.(2)DMCA and trimethylamine were used as representative switchable ionic strength aqueous solvent and toluene as the target organics,the liquid-liquid equilibrium data of four ternary systems(water + DMCA + toluene;water + trimethylamine + toluene;water +DMCAH-bicarbonate + toluene;water + trimethylamine-bicarbonate + toluene)at 298.15K,303.15K and 308.15K were measured and the corresponding ternary liquid-liquid equilibrium phase diagram was drawn.The reliability of the experimental data is verified by the Othmer-Tobias equation.The accuracy of the liquid-liquid equilibrium data of the four ternary systems at different temperatures is close to 1,which confirms the accuracy of the experimental data.The NRTL liquid-liquid equilibrium model was used to correlate the four ternary systems,and the calculated values were in good agreement with the experimental ones.The results of this study provide a theoretical basis for the recovery of organic matter in aqueous solutions by the switchable ionic strength aqueous solvent.(3)The liquid-liquid equilibrium data of two ternary systems(Triethylamine + water +1,3-dioxane;trimethylamine-bicarbonate + water + 1,3-dioxane)at 298.15K,303.15K and 308.15K were measured with triethylamine as switchable ionic strength aqueous solvent,and the corresponding ternary liquid-liquid equilibrium phase diagram was drawn.The Othmer-Tobias equation was used to verify the reliability of the experimental data.The linear correlation coefficients were more than 0.99,which verified the reliability of the data.The NRTL model employed to study the system provides the theoretical basis for industrialization,RMSD of the experimental value and the simulated value is relatively small,which shows that the correlation effect is good,the precision is relatively high.It also provides a theoretical basis for salting out extraction.