| Nowadays, a large amount of oily wastewater is produced in daily life and in many industrial processes. The direct discharge without any effective treatment of oily wastewater could cause serious environmental pollution and waste of resources. Therefore, it is necessary to purify the oily wastewater, in order to achieve the emission standards.Compared with traditional methods, the membrane separation technology, is an more efficient and greener separation technology, which has been generally accepted as the most effective method of the oily wastewater treatment Polyethersulfone (PES) is one of the most extensively used materials in preparation of microfiltration, ultrafiltration as well as nanofiltration membranes. Its wide application is a result of excellent chemical and thermal stability, easy processing and environmental endurance. However, PES is hydrophobic, which often leads to severe membrane fouling. Recently, research hotspot has been paid to the preparation of antifouling organic-inorganic composite membranes, which are often fabricated through blending PES with inorganic NPs. But inorganic NPs with high surface free energy are easy to agglomerate, resulting in non-uniform distribution in the membranes. Furthermore, the inorganic NPs are easy to leach out during the long filtration process, which results from the weakness of the interaction between inorganic NPs and hydrophobic polymers.The present work is aimed to solving the serious fouling of the PES ultrafiltration membrane during the filtration of oil-in-water emulsions. The hydrophilic antifouling organic-inorganic composite membranes and antifouling self-cleaning organic-inorganic composite membranes were fabricated via the blending PES with the modified SiO2 NPs. Our specific studies are concentrated on the following aspects:In order to overcome SiO2 NPs agglomerations, improve the dispersity and stability of SiO2NPs in the matrix of PES and the interaction between two phases, SiO2-g-(PDMAEMA-co-PDMAPS) NPs were synthesized via surface-initiated activators regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP). The PES/SiO2-g-(PDMAEMA-co-PDMAPS) organic-inorganic composite membrane were prepared by the NIPS process. In the membrane formation process, the SiO2-g-(PDMAEMA-co-PDMAPS) NPs migrated spontaneously to the membrane surface in order to reduce interfacial energy between the casting solution and water, which can be confirmed by ATR-FTIR analysis. The surface hydrophilicity, the pure water permeability and anti-fouling property of the composite membranes were all enhanced significantly. The SiO2-g-(PDMAEMA-co-PDMAPS) NPs had better dispersibility in organic solvent. At the same time, the interaction of PDMAEMA-co-PDMAPS and PES improved the bonding ability between the SiO2-g-(PDMAEMA-co-PDMAPS) NPs and the PES membrane matrix, which made the NPs stably entrapped in the PES membrane for a long time.In order to achieve further functionalization of the organic-inorganic composite membranes, the SiO2-g-PAA NPs were prepared by grafting reactive poly(acrylic acid)(PAA) brushes from SiO2 NPs surface via surface-initiated ARGET ATRP. Then the PES/SiO2-g-PAA organic-inorganic composite membranes were prepared from the blending solutions of PES and the synthesized NPs. The ATR-FTIR and surface SEM results showed that well dispersed SiO2-g-PAA NPs tended to migrate toward the membrane top surfaces. Therefore, the porosity, water permeability, hydrophilicity and antifouling of the composite membrane were significantly improved. In addition, the SiO2-g-PAA NPs showed good stability in/on PES membrane due to the intertwisting of polymer chains between PAA and PES. More importantly, the reactive PAA chains enriched on membrane surface, which provided a strategy to further surface modification. Subsequently, the PES/SiO2-g-PAA composite membranes were transformed into highly hydrophilic PES/SiO2-g-PAA/PEI composite membranes by amidation between polyethyleneimine (PEI) and PAA. It was confirmed that the PES/SiO2-g-PAA/PEI composite membranes had excellent antifouling abilities.During the filtration of oil-in-water emulsions, the PES/SiO2-g-PAA/PEI and PES/SiO2-g-(PDMAEMA-co-PDMAPS) membranes exhibited satisfactory flux recovery properties, but the flux decline of them was still a serious phenomenon, which needed to be improved. In this chapter, the SiO2-g-(PAA-co-PHFBM) NPs were synthesized by grafting hydrophilic polyacrylicacid (PAA) brushes and low surface energy polyhexafluorobutylmethacrylate (PHFBM) from SiO2 NPs surface via surface-initiated ARGET ATRP. Then the PES/SiO2-g-(PAA-co-PHFBM) organic-inorganic composite membranes were prepared by the blending of PES and the SiO2-g-(PAA-co-PHFBM) NPs. The well dispersed SiO2-g-(PAA-co-PHFBM) NPs tended to migrate toward the membrane top surfaces, which can be confirmed by ATR-FTIR and surface SEM analysis. Consequently, amphiphilic membrane surfaces, which were composed of the hydrophilic fouling resistant domains and hydrophobic fouling release domains, were constructed. The PES/SiO2-g-(PAA-co-PHFBM) membranes exhibited superior antifouling and self-cleaning abilities, simultaneously achieving 95.41% permeation flux recovery and 29.12% total permeation flux-decline during the filtration of oil-in-water emulsions.The fluorocarbon surfactants (FSN-100), which contained the hydrophilic segment and low surface energy segment, were excellent materials for constructing the versatile antifouling and self-cleaning membranes surfaces. In this chapter, the FPEGMA was synthesized by direct reaction of the FSN-100 with acryloyl chloride in the presence of triethylamine. The SiO2-g-PFPEGMA NPs were prepared via the surface-initiated RAFT polymerization. After blending the PES with the SiO2-g-PFPEGMA NPs, the PES/SiO2-g-PFPEGMA organic-inorganic composite membranes were prepared by NIPS. The well dispersed SiO2-g-PFPEGMA NPs tended to migrate toward the membrane top surfaces, which can be confirmed by ATR-FTER. and surface SEM analysis. Consequently, the antifouling and self-cleaning membranes surfaces were constructed, endowing the membranes with superior antifouling and self-cleaning abilities. The PES/SiO2-g-PFPEGMA membranes exhibited superior antifouling and self-cleaning abilities, simultaneously achieving 90% permeation flux recovery and 25.38% total permeation flux-decline during the filtration of oil-in-water emulsions. |
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