Study On The Separation Of Azeotropic Organics/Water Mixtures By Using Inorganic Salts

Phase separation procedure based on the salting-out principle for organics/watermixtures separation has been proven to be effective and has the important industryapplication background. When inorganic salts are added into the organics/watermixtures, due to the salting-out effect of the inorganic salts, the organicssolubility in water decreases and two phases are formed: the organics-rich phasecontained negligible salt and the water-rich phase contained negligible organics whenthe concentration of inorganic salts in water phase is higher,consequently water isseparated efficiently from the organics/water mixtures,and high separation factorcould be obtained. At present it is quite short of the liquid-liquid equilibrium data forseparation of azeotropic organics/water mixtures by using inorganic salts as salting-out agents,this brings many difficulties to research and development of processesfor separation of azeotropic organics/water mixtures using inorganic salts. Someasurement and calculation of liquid-liquid equilibrium data for organic-water-inorganic salts have high academic and practical value. The phase separation ofethanol-water , 1-propanol-water , 2-propanol-water , 1-butanol-water , 2-butanol-water , tert-butanol-water , acrylonitrile-water , butanone-water ,tetrahydrofuran-water and pyridine-water using KF and K₂CO₃ has been studied,the following research works have been performed in this paper.1. Selection of salting-out agents:By comparing the composition data of the twophases of the ethanol-water-inorganic salts from the literatures with those obtainedfrom our experiments, the salting-out agents are selected for separating theethanol-water system. The polarity of the ethanol is the most intensive comparingwith most other organics forming the azeotropes with water, so the salting-outagents that have good separation effect for the ethanol-water system should be alsogood for the other organics-water systems.2. The determination of liquid-liquid equilibrium for organics-water-inorganic saltsystems :The liquid-liquid equilibrium data for systems of ethanol-water-KF,ethanol-water-K₂CO₃ , 1-propanol-water-KF , 1-propanol-water-K₂CO₃ , 2-propanol-water-KF,2-propanol-water-K₂CO₃,1-butanol-water-KF,1-butanol-water-K₂CO₃,2-butanol-water-KF,2-butanol-water-K₂CO₃,tert-butanol-water-KF , tert-butanol-water-K2CO3 , acrylonitrile-water-KF , acrylonitrile-water-K2CO3 , butanone-water-KF , butanone-water-K2CO3 , tetrahydrofuran-water-KF , tetrahydrofuran-water-K2CO3 , pyridine-water-KF and pyridine-water-K2CO3 were experimentally determined,providing basic data for processes designof separating azeotropic organics/water mixtures by using phase separationprocedure.3. The liquid-liquid equilibrium model research for organics-water-inorganic salts:For modeling liquid-liquid equilibrium for systems of ethanol-water-KF,ethanol-water-K2CO3 , 1-propanol-water-KF , 1-propanol-water-K2CO3 , 2-propanol-water-KF , 2-propanol-water-K2CO3 , 1-butanol-water-KF , 1-butanol-water-K2CO3 , 2-butanol-water-KF , 2-butanol-water-K2CO3 , tert-butanol-water-KF , tert-butanol-water-K2CO3 , acrylonitrile-water-KF , acrylonitrile-water-K2CO3 , butanone-water-KF , butanone-water-K2CO3 , tetrahydrofuran-water-KF , tetrahydrofuran-water-K2CO3 , pyridine-water-KF and pyridine-water-K2CO3,the Pitzer's electrolyte solution theory was adopted and applied tocalculate water activity in the water phase, and the Wilson, NRTL or theUNIQUAC equation were selected to calculate water activity in the organics phaserespectively. The thermodynamics model for organic-water-inorganic salt systemswere then obtained,providing theoretical and computational basis for separatingazeotropic organics/water mixtures by using phase separation procedure.4. Industrial application research: The feasibility of separating of azeotropicorganics/water mixtures was demonstrated by two processes: treatment ofazeotropic pyridine waste water and separation of ethanol-acetone-1-butanol-water.In these two processes,brine was used as salting-out agents, which could beeasily recovered and recycled. The operating conditions were determined by usingthe brine,and the pyridine waste water was treated and ethanol-acetone-1-butanol-water was separated by using this research results.