Fabrication And Separation Properties Of Pt(?) Ion-Imprinted Blending Membrane

Platinum is a precious metal that is lesser availability in nature and is increasing demand in various fields.Hence,it is important to develop high-efficiency technologies for separating and recovering platinum ions in aqueous solution.Ion-imprinted membranes??Ms?have received much attention due to their high selectivity for target ions.In this paper,platinum???ion-imprinted membranes?Pt???-?Ms?were prepared based on amphiphilic block copolymers and graphene derivatives,respectively,and their separation properties were studied.The main contents are as follow:First,An amphiphilic block copolymer poly?methyl methacrylate?-b-poly?4-vinylpyridine??PMMA-b-P4VP?was synthesized via the reversible addition fragmentation chain transfer polymerization,and characterized by hydrogen nuclear magnetic resonance?¹H NMR?,Fourier transform infrared?FTIR?and gel permeation chromatography?GPC?.Subsequently,poly?vinylidene fluoride??PVDF?blend membranes were prepared using PMMA-b-P4VP as a blending additive.Effects of the following factors on performance of blend membranes were systematically examined:P4VP content of PMMA-b-P4VP,solvent type,and PMMA-b-P4VP/PVDF ratio.Further,platinum???ion-imprinted membrane?Pt???-?M?was fabricated by blending polymer-Pt???complexes with PVDF.Scanning electron microscope?SEM?,attenuated total reflection Fourier transform infrared?ATR-FTIR?,contact angle,water flux and adsorption capacity were employed to characterize all membranes.Results indicated that the membrane,which was prepared using the copolymer with high P4VP content?PP3?as a functional polymer,N,N-dimethylacetamide as a solvent and PMMA-b-P4VP/PVDF ratio of30 wt%,exhibited an intriguing morphology and much higher performance.Pt???-?M showed higher adsorption and selectivity for Pt????selectivity coefficients of 27.66 and 77.16 for Pt???/Cu???and Pt???/Ni???,respectively?compared with a non-imprinted membrane?NIM?.During membrane filtration,Pt???-?M was effective and selective for separation of Pt???in the presence of Cu???and Ni???ions.Also,Pt???-?M was chemical stable,and had a good regeneration performance.Second,graphene oxide?GO?was synthesized via a pressurized oxidation.The GO was then functionalized with 3-amino propyl triethoxy silane?APTS?to obtain functionalized graphene oxide?GO-NH₂?,and characterized by X-ray diffraction?XRD?,FTIR and energy dispersive spectroscopy?EDS?.Further,Pt???-?M was fabricated by blending polymer-Pt???complexes with PVDF.SEM,pure water contact angle and water flux were employed to characterize pure PVDF membrane,GO/PVDF blended membrane,GO-NH₂/PVDF blended membrane and Pt???-?M,and the adsorption properties of Pt???-?M and NIM were investigated.Results indicated that GO-NH₂ had good dispersibility in the membrane matrix compared with GO.GO and GO-NH₂ can significantly improve the hydrophilicity and water flux of the blend membrane.The adsorption behavior of Pt???-?M for Pt???was significantly affected by pH value.The experimental results of static adsorption indicated that the adsorption capacities of Pt???-?M for Pt???were 19.49 mg/g at pH 0.5.Pt???-?M had higher ability to adsorb Pt???than NIM,and the adsorption process was fitted well with the Langmuir isotherm and the pseudo-second-order kinetic model.Pt???-?M had higher adsorption capacity and selectivity for Pt???relative to Cu???and Ni???.During membrane filtration,the breakthrough occurs for Pt???at the permeate volume of about 20 mL.Pt???-?M had a 18.7%loss of initial adsorption capacity after five adsorption-desorption cycles.Third,the GO was grafted with 3-methacryloxy propyl trimethoxyl silane?MPS?to obtain modified graphene oxide?GO-MPS?.The functionalized graphene oxide?GO-P4VP?was synthesized via radical polymerization of GO-MPS and 4-vinylpyridine?4VP?,and characterized by XRD,FTIR and EDS.Subsequently,Pt???-?M was fabricated by blending polymer-Pt???complexes with PVDF.SEM,pure water contact angle and water flux were employed to characterize pure PVDF membrane,GO/PVDF blended membrane,GO-P4VP/PVDF blended membrane and Pt???-?M,and the adsorption properties of Pt???-?M and NIM were investigated.Results indicated that GO-P4VP had good dispersibility in the membrane matrix compared with GO.Nanosheets can significantly improve the hydrophilicity and water flux of the blend membrane.The adsorption behavior of Pt???-?M for Pt???was significantly affected by pH value.The experimental results of static adsorption indicated that the adsorption capacities of Pt???-?M for Pt???were 58.62 mg/g at pH 0.5.Pt???-?M had higher ability to adsorb Pt???than NIM,and the adsorption process was fitted well with the Langmuir isotherm and the pseudo-second-order kinetic model.Pt???-?M had higher adsorption capacity and selectivity for Pt???relative to Cu???and Ni???.During membrane filtration,the breakthrough occurs for Pt???at the permeate volume of about 50 mL.Pt???-?M had a high reusability and only 6.6%loss of initial adsorption capacity after five adsorption/desorption cycles.