| Removal of aromatic contaminants with high toxicity and refractory from wastewater has been facing enormous challenges.Though the traditional adsorption and catalytic technologies can degrade the aromatic organic matter,the separation and recycling of adsorbent and catalyst not only increase the cost of water process,but also cause secondary pollution.Membrane separation has been widely used as an efficient way to treat municipal and industrial waste water due to the high selectivity,mild operation and low running investment etc.This study was based on the preparation of catalytic nanoparticles?AuNPs?and hydrophilic PVDF micro membrane was chosen to construct multifunctional polymer membrane with catalytic and separation properties for removal of aromatic contaminants.Firstly,AuNPs?40-50 nm?were synthesized by traditional method of sodium citrate reduction of HAuCl4.Non-solvent induced phase separation?NIPS?,templating method and interfacial crosslinking strategies were used to get superhydrophilic PVDF membrane with micro/nano surfaces.Then PVDF membrane with micro/nano structured surface was decorated with AuNPs via poly?dopamine??PDA?for construction of catalytic reactor.Besides,hydrophilic PVDF membrane with massive finger-like pores could be obtained by adjusting NIPS process.Thus,large amounts of AuNPs were anchored inside the membrane via PDA by dynamic filtration,showing better catalytic performance with high loading density of AuNPs.The catalytic membrane reactor realized instantaneous and continuous reduction of 4-NP and MB.Besides its catalytic performance for 4-NP in chloroform-in-water emulsion was also evaluated.Finally,we also preliminarily studied the loading of W18O499 nanaowires on PVDF membrane and the prepared membrane was applied in adsorption of MB.Following details are the specific research contents and results:?1?Loading of AuNPs on the surface of micro PVDF membrane and its catalytic reduction performanceReduction method of HAuCl4 by sodium citrate in aqueous solution system is employed to prepare the AuNPs?40-50 nm?.Pure PVDF membrane with multi-scaled surface structure was fabricated via NIPS and templating method.Then interfacial crosslinking strategy was used to get superhydrophilic PVDF membrane.This could promote the dopamine and AuNPs adsorption,forming the microporous membrane with AuNPs loading on the surface for the catalytic reduction of 4-NP.We found that the hydrophily and micro-nano structure on the surface can influence the final loading amounts of AuNPs:unlike the hydrophilic membrane?without micro-nano structure?and super-hydrophobic membrane?with micro-nano structure?,the superhydrophilic PVDF membrane with micro/nano surface?2 h PDA process,24 h Au solution process?realized the largest extent loading of AuNPs.The membrane reduced 90%4-NP in 5 minutes in static catalytic experiment and its dynamics reaction constant is47.84×10-22 min-1.In addition,the catalytic membrane also showed great catalytic stability and reutilization capacity.?2?Construction of finger-like catalytic reactor based on PVDF membrane and its catalytic performance in instantaneous and continuous reactionIn order to further improve the loading of AuNPs and catalytic performance of PVDF membrane,the micro-reactor with finger-like pore was constructed.Dopamine and AuNPs were loaded in finger-like pore of PVDF membrane through the method of dynamic filtering method and the amount of AuNPs reached 1.19×10-66 mol/cm2.The finger-like micro-reactor showed great catalytic performance in the instantaneous and continual reduction of 4-NP and MB.When the residence time of fluid was 1.12 s and the linear velocity was 0.021 cm/s in dynamic catalytic experiment,the catalytic rates of 4-NP and MB was 471.96 s-11 and 947.71 s-11 respectively.Besides,the catalytic conversion rates of 4-NP and MB could remain stable above 75%in 30 min.Meanwhile,the prepared membrane could also realize the oil-in-water separation and the catalytic reduction of 4-NP simultaneously in the flowing circulation. |
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