Preparation,Characterization And Properties Of Polyionic Liquid Grafted Ceramic Composite Membranes

Compared with traditional separation technology,membrane separation technology has the advantages of energy saving,high efficiency,simple separation process,etc..In particular,ceramic membrane has many advantages such as good thermal stability,good chemical stability,resistance to organic solvents,strong antimicrobial degradation ability,excellent pore structure,and controllable microstructure.Therefore,it has been widely used in chemical industry,food industry,biomedicine,water treatment and other industries.However,ceramic membrane also shows the disadvantages of poor anti-pollution performance.Ionic liquids have received extensive research due to their high boiling point,low vapor pressure,low solubility(in the oil phase)and high sulfur partition coefficient.However,the high viscosity of pure ionic liquid will cause solvent loss and difficult operation,which is not conducive to industrial promotion and application;on the other hand,the large amount of ionic liquid used during desulfurization also increases the cost of desulfurization.In this thesis,ionic liquid was grafted onto the surface of ceramic membrane via in-situ polymerization to construct a poly-ionic liquid ceramic composite membrane,which could not only exert the advantages of ionic liquid,but also have the advantages of ceramic membrane,such as high efficiency,energy saving and simple separation.The main works include the following:(1)1-vinyl-3-ethylimidazoliumbromide(VEIMBr)was used as a monomer,and3-Methacryloxypropyltrimethoxysilane was used as a modifier,Poly-1-vinyl-3-ethylimidazoliumbromide(PVEIMBr)was covalently grafted onto the surface of ceramic membrane(CM)via in-situ polymerization to obtain a polyionic liquid grafted ceramic membrane(PVEIMBr / CM)composite membrane.SEM,EDS,FTIR,TG and other characterization methods were used to characterize the raw and composite membranes.And the simulative fuel oil desulfurization and printing and dyeing wastewater were used to evaluate the separation performance of PVEIMBr / CM.The results showed that PVEIMBr was successfully covalently grafted onto the surface of CM;and the grafting ratio of PVEIMBr on CM was 28.68%.As for the simulative fuel oil desulfurization,the rejection rate of PVEIMBr / CM was 75.92%,which was36.02% higher than CM;the flux recovery of PVEIMBr / CM after five consecutive filtrations was 98.70%,which was 32.05% higher than CM;the rejection rate of the PVEIMBr / CM was 62.70% after repeated use five times,and CM was only 36.27%;indicating PVEIMBr / CM had better desulfurization performance than the raw CM.As for the simulative printing and dyeing wastewater,anionic dye(Congo red),cationic dye(methylene blue)and nonionic dye(Solvent Red 23)were used.The results showed that the PVEIMBr / CM had the highest separation efficiency for anionic dyes(100%),followed by cationic dye(5%),and the worst was for nonionic dye separation(2.6%).As for anionic dyes,the rejection rate of composite membrane was 51.9% higher than CM;the rejection rate and the flux recovery rate of the composite membrane 98% and 94.12%,which was higher than that of CM.These results showed that the PVEIMBr / CM had better separation performance than CM in the separation of printing and dyeing wastewater.(2)1-vinyl-3-ethylimidazoliumbromide was used as a monomer,divinylbenzene as a cross-linking agent,and 3-Methacryloxypropyltrimethoxysilane as a modifier,the cross-linked poly 1-vinyl-3-ethylimidazoliumbromide was covalently grafted to the surface of the ceramic membrane(CM)via in-situ polymerization to prepare the crosslinked poly ionic liquid grafted ceramic composite membrane(DVB-PVEIMBr / CM);SEM,contact angle and other characterization methods were used to characterize the composite membrane,and fuel oil desulfurization and oil-water separation was used to evaluated the separation performance of the composite membrane.The results showed that DVB-PVEIMBr was successfully covalently grafted onto the CM surface according to the increased contact angle.In the separation experiment of fuel desulfurization,the optimal molar ratio of VEIMBr to DVB was optimized by using the rejection rate and membrane flux as evaluation indexes.The results showed that the molar ratio of VEIMBr to DVB was not related to the desulfurization rate.When the molar ratio of VEIMBr to DVB was 1: 2,the DVB-PVEIMBr / CM had the largest flux of 339.20 LMH,showing an increase of 26.4% than CM;the rejection rate of the DVB-PVEIMBr / CM was 69.71%,showing an increase of 29.81% than CM.In the oil-water separation experiment,two-phase oil-water system(carbon tetrachloride and water)and emulsified oil(toluene,water and a certain amount of surfactant span 80)were used as the separation system.When the molar ratio of VEIMBr to DVB was 1: 1,the flux was the largest for two-phase oil-water(carbon tetrachloride and water);when the molar ratio of VEIMBr to DVB was 2: 1,The flux to emulsified oil was the largest.The rejection rate of the composite membrane was 98%(carbon tetrachloride and water),which was increased by 48%;and the flux recovery rate of the composite membrane was 93.04%(carbon tetrachloride and water)and 97.63%(emulsified oil),showing an increase of 19.76%(carbon tetrachloride and water)and19.28%(emulsified oil).After three repeated use,the rejection rate of the composite membrane was 97%(carbon tetrachloride and water),while the blank CM was only60%;indicating DVB-PVEIMBr / CM composite membrane had better separation performance than the blank CM in oil-water separation.