Study On Stability Of Supported Ionic Liquid Membrane

Hydrophobic ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate?[Bmim]PF₆?was a new green solvent with good stability in water and air,high ionic mobility and low volatility.A new supported ionic liquid membranes?SILMs?was prepared by changing the liquid composition of the membrane.The supported ionic liquid membranes had the advantages of ionic liquid?ILs?and high selectivity,energy saving and high efficiency of SLMs.It was applied to the mass transfer separation of cyanide wastewater and phenol wastewater.The effects of different liquid composition and related conditions on the stability of liquid membrane were discussed.The main mechanism of the stability of supported ionic liquid membranes was clarified.The theoretical basis and technical reference were provided for the preparation and application of high performance supported ionic liquid membranes.?1?Using[Bmim]PF₆ as the membrane carrier,kerosene as the membrane solvent and PVDF as the supporting membrane,the supported ionic liquid membranes were preparedbynormaltemperatureimmersionmethodandN₂pressure method,respectively.By means of scanning electron microscope?SEM?,X-ray photoelectron spectroscopy?XPS?and contact angle?CA?,it was found that the surface of supported ionic liquid membranes prepared by the normal temperature immersion method was flat and uniform.The structure of[Bmim]PF₆ was not destroyed by solvent and PVDF support membrane,and the prepared supported ionic liquid membranes remained hydrophobic.?2?The Electrochemical impedance method showed that the lose of membrane liquid in cyanide containing wastewater was mainly caused by the excessive HLB value?hydrophilic equilibrium value?of supported ionic liquid membranes in cyanide wastewater.From the macroscopic point of view,the lose rate of the membrane liquid was 79.68%.When the volume concentration of Tween80 was 10%,the membrane liquid was almost completely lost.The results are consistent with each other.The higher the HLB value of the membrane liquid?>10?,the more easily the membrane fluid was lost in the adjacent water phase.Membrane liquid emulsification was most closely related to membrane liquid lose of supported ionic liquid membranes.And osmotic pressure mechanism is the most close.The solubility mechanism was not the main mechanism of liquid lose of supported ionic liquid membranes.The interaction between hydrogen bond structure and hydrophobicity of ionic liquids played an important role in the mass transfer of cyanide.The removal rate of cyanide in supported ionic liquid membranes was up to 95.27%.?3?In the process of phenol extraction and separation,when the volume concentration of ionic liquid is 10%?30%and 100%respectively,the higher the concentration of ionic liquid,the more likely the membrane liquid was lost.Which was due to the increase of ionic liquid concentration.The aggregation behavior in organic wastewater liquid was more likely to occur.The emulsification of membrane liquid would be the main mechanism of membrane liquid lose.Controlling the HLB value of membrane liquid could improve the stability of supported ionic liquid membranes in this system.The highest removal rate of phenol in the membrane liquid of supported ionic liquid membranes was only about 63%.And the removal rate of phenol was only determined by the solubility or diffusion of phenol in the membrane liquid phase,which belonged to pure migration.?4?The results of contact angle before and after the use of liquid membrane showed when the volume concentration of ionic liquid was 10%,with the extension of liquid membrane extraction time,the wetting effect of the supported ionic liquid membranes would have an important effect on the liquid phase lose of membrane liquid.When the volume concentration 10%Tween80 was added into the membrane liquid,the contact angle of the liquid was less than 90.And the hydrophobicity of the liquid membrane became hydrophilic.According to the change rate of the resistance and capacitance of the membrane liquid and the force acting on the membrane liquid in the membrane pore,it could be seen that the lose rate of the membrane liquid phase was first faster and later slower.