| Desulfurization using gas—liquid membrane contactor is one of the most effective methods to remove SO2.The properties of membrane material,such as hydrophobic,chemical stability,thermal stability,and processing properties,produce an obvious effect on the performance of gas-liquid membrane contactor.Polymeric membranes are popular in the membrane market for their low manufacturing cost and good membrane-forming ability.However,polymeric membranes are restricted in the membrane contactor applications because of their low chemical and thermal stability.Inorganic membranes may be the favorite membrane material used in gas-liquid mnembrane contactor because of its better chemical performance,thermal stability,and high mechanical property.However,disadvantages of inorganic membrane material,such as high cost,poor flexibility,molding,and component assembly difficulties,limited its practical application in gas-liquid membrane contactor.Organic-inorganic composite membranes are supposed to not only unite essential advantages of polymeric membranes and inorganic membranes but also supply specific properties of the composite membranes.In this paper,weak hydrophobic poly(ether sulfone)(PES)membrane is used as the membrane of gas-liquid membrane contactor.The effects of small molecule additives on the properties of PES membrane structure and SO2 absorption by gas-liquid membrane contactor were investigated.High hydrophobic fluorinated silica-graft-poly(ether sulfone)(fSiO2-g-PES)organic-inorganic composite membranes were prepared by plasma initiated grafting.The single-side superhydrophobic PES membrane for SO2 absorption was prepared by depositing the fluorinated silica particles on the top surfaec of PES membrane via vacuum-filtrating.A series of characterization and desulfurization evaluation of these membranes were investigated.Binding mechanism and hydrophobic stability of organic/inorganic composite membranes were discussed.The main contents could be summerized as follows:PES membranes were fabricated via a phase-inversion method using glycerol,polyethylene glycol,acetone,phosphoric acid and lithium chloride as the additives.Also,PES membrane without additives was fabricated.The precipitation rate of the polymer dopes with the different additives was studied using cloud point measurement.The effect of the additives on the resulting membrane structure,surface porosity,pore size,permeability performance,liquid entry pressure(LEPw),and SO2 absorption performance in a gas—liquid membrane contactor were investigated and compared.Results of gas permeation tests showed that lithium chloride and acetone as additives provided the membranes with the largest and smallest pore size,respectively.The morphological structure of PES membranes with different additives were analyzed by scanning electron microscope.The results showed that the membrane structure became the main factor affecting LEPw,as the contact angle of membrane surface was not very different.Considering that the membrane contactor is used for a long time,the PES membrane prepared with phosphoric acid as a small molecular additive has a high SO2 absorption flux.High hydrophobic fSiO2-g-PES organic-inorganic composite membranes were prepared by plasma initiated graft polymerization.It was confirmed that peroxide free radicals(-COOH and-OH)were produced on the surface of p-PES membrane after O2 plasma treatment by attenuated total reflectance Fourier transform infrared spectroscopy(ATR-FTIR)and X-ray photoelectron spectroscopy(XPS).More radical was formed on surface of p-PES-150 membrane,which provided strong combination between SiO2 particles and PES membrane with chemical bond.The permeability of the fSiO2-g-PES composite membranes was not significantly lower than that of the PES membranes.The SO2 absorption flux of fSiO2-g-PES-150 membrane(8.36E-4 mol/m2s)was higher than that of PES membrane in the long time(120 h)desulfurization operation.The single-side superhydrophobic PES membrane for SO2 absorption was prepared by depositing fluorinated silica(fSiO2)particles on top surface of PES membrane via vacuum-filtrating.The results showed that the water contact angle of PES/3fSiO2-30 membrane was 155.2±0.5 °,as n(PFDTES):n(TEOS)=3 and filtration of liquid volume being 30 mL.The SO2 absorption flux of PES/3fSiO2-30 composite membrane(7.78E-4 mol/m2/s)was better than that of the PES membrane,which indicated that single-side superhydrophobic PES membrane was suitable for SO2 absorption in gas liquid membrane contactor.The formation mechanism of hydrophobic organic/inorganic composite membranes was studied by different interfacial compound methods.It was clear that the forming process of SiO2 nanoparticles complied with the "perfect law".The coagulation of fSiO2 inorganic layer on the PES membrane related to not only the deposition of the three-dimensional net structure of SiO2 nanoparticles,but also the non-covalent bond between PES membrane and SiO2 nanoparticles such as electrostatic interaction,hydrogen bond force and Van Edward force.The ATR-FTIR analysis showed there were Si-O-C chemical bonds between silica particles and the surface of fSiO2-g-PES-150 membrane.Meanwhile,the results of ATR-FTIR and thermal gravimetric(TG)analysis showed that 1H,1H,2H,2H-perfluorodecyltriethoxysilane(PFDTES)were combined on the surface of SiO2 through physical adsorption and chemical adsorption.The thermal stability,weatherability and absorptive property of PES/fSiO2 membrane,fSiO2-g-PES-150 membrane and PES/3fSiO2-30 membrane are so excellent that those membranes all have good potential for SO2 absorption in gas-liquid membrane contactor. |
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