| Membrane materials play a key role in the development of pervaporation technology. After several years of development, pervaporation membrane materials have made encouraging progress, but are still facing several problems, e.g., low flux, poor solvent resistance and short lifetime. Organisms and biological tissues can efficiently synthesize a wide range of polymeric, inorganic and polymer-inorganic hybrid materials with delicate structures under green and mild conditions. Through precise control of the material structure, size, morphology and assembly, organisms and biological tissues are able to achieve specific functions.In order to improve membrane separation performance and stability, a variety of novel pervaporation membranes with delicate and controllable structures were prepared in the present study. The as-prepared membranes were utilized as pervaporative desulfurization membranes and exhibited excellent separation performance.First, inspired by the phenomenon of facilitated transport in cell membranes, PDMS-Ni2+Y zeolite hybrid membranes were fabricated by incorporating transition metal ions that have specific interactions with organic sulfur compound into PDMS matrix. The permselectivity towards organic sulfur in gasoline was thus significantly increased. With the increase of Ni2+Y zeolite content, the permeation flux increased continuously, while the enrichment factor first increased and then decreased possibly due to the occurrence of defective voids within organic-inorganic interface region. The PDMS membrane containing 5.0 wt% Ni2+Y zeolite exhibited the highest enrichment factor (4.84) with a permeation flux of 3.26 kg/(m2 h) for 500ppm sulfur in feed at 30?C. The effects of operating conditions on the pervaporation performance were investigated in detail. It has been found that the interfacial morphology strongly influenced the separation performance of the hybrid membrane, and it was of great significance to rationally modify the interfacial region in order to improve the organic-inorganic compatibility.Then, physical blend of inorganic fillers with polymeric membranes was proun to generate aggregates of inorganic fillers, which brought about interfacial defects and local stress. Consequently, polymer-inorganic hybrid membrane materials (PDMS-SiO2) were in situ synthesized using w/o reverse microemulsion mimicking the diatom cell walls. Free volume properties could be readily tuned by controlling hydrolysis-condensation of the silane precursor and the oligomer crosslinking reaction. The permeation flux and mechanical strength of membranes were notably enhanced. As testified by TGA, hybrid membranes containing silica nanoparticles were clearly observed up to silica/polymer mass fraction of 6.98%, 10.68% and 14.88%. It was observed that silica incorporation considerably narrowed the free volume pore radius distribution and increased the FFV of the hybrid membranes, which was most possibly ascribed to the disrupting effect of silica nanoparticles toward the PDMS chain packing. The permeation flux of PDMS control membrane was 6.6 kg/(m2 h), while the permeation flux of PDMS-SiO2 hybrid membrane containing 14.88wt% was increased to 10.8 kg/(m2 h). The membrane selectivity towards thiophene was only slightly decreased from 5.8 to 4.8. The DMA analysis of the PDMS control and hybrid membranes containing 14.88wt% silica depicted the curves of the samples over a wide range of temperature. The storage modulus of the specimens increased with higher content of SiO2, revealing that the interactions between PDMS segmental chains and SiO2 allowed a fine load transfer and endowed improved mechanical strengths. The glass transition temperature of the hybrid membranes appeared to slightly increase from -104.74oC to -99.89oC.After that, in order to overcome the inherent shortcomings of silicone rubber polymer membranes, inspired by bio-adhesion and cell membrane structure, ultrathin and anti-swelling pervaporation membranes were fabricated. Inspired by the phenomenon of bio-adhesion, composite membranes were fabricated, which was composed of ultrathin polydopamine separation layer (<100nm) and porous support layer. Nanoindentation measurement revealed the tight adhesion of dopamine onto microporous substrate, which was ascribed to numerousπ-πand hydrogen-bonding interactions. XPS analysis demonstrated the self-polymerization of dopamine. The water contact angle of the dopamine coated membranes was reduced remarkably compared with that of the uncoated counterpart. Stylus profiler measurements display that the poly (dopamine) thickness increased as the coating time increased. Positron annihilation spectroscopy measurement revealed that after dopamine double-coating the active layer became thicker and more compact. Moreover, pH and concentration of the dopamine solution exert notable influence on the fractional free volume of the composite membranes. The permeation flux increased from 6.9 to 8.0 kg/(m2 h) with the pH switched from 7.5 to 9.5. Meanwhile, the enrichment factor decreased from 2.86 to 2.32. The permeation flux decreased from 7.86 to 5.95 kg/(m2 h) with the concentration switched from 1.0mg/ml to 4.0mg/ml. Meanwhile, the enrichment factor increased from 2.05 to 3.21. The effects of operating conditions on the pervaporation performance were investigated in detail.Finally, inspired by the cell wall structure, amphiphilic copolymer Pluronic F127 was employed as a surface modifier to fabricate polyethersulfone (PES) asymmetric pervaporation membranes via surface segregation. The SEM images showed an asymmetric structure of PES/Pluronic F127 membranes. The FT-IR spectroscopy, XPS and static water contact angle measurements confirmed the hydrophilic modification of the membrane surface. Based on the distinct difference of solubility inwater between thiophene and noctane, the prepared membranes were utilized to remove thiophene from n-octane by pervaporation. The effect of Pluronic F127 content on the pervaporation performance was evaluated experimentally. It has been found that both the permeation flux and enrichment factor exhibited a peak value of approximately 60 wt% of the Pluronic F127 content. The highest enrichment factor was around 3.50 with a permeation flux of 3.10 kg/(m2 h) for 500 ppm sulfur in the feed at 30?C. The influence of various operating parameters on the pervaporation performance was extensively investigated. |
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