| With the rapid developments of industrialization and urbanization,the consume and discharge of various kinds of heavy metal increase day by day,which causes increasingly serious metal pollution.Heavy metal ions have the characteristics of hard degradation,strong penetrability and enrichment,which bring a serious threat to the human healthy and ecosystems’ safety.Adsorption is considered as a simple and effective separation method,which has been widely applied in separation and enrichment of heavy metal ions.Since the environment system has complicated composition and various systems,the adsorbent with good adsorption selectivity for target ion is required,which is beneficial to rapid detection and resource recovery.Ion imprinted polymer(ⅡP)has good affinity and selectivity for target ion,which is suitable for separation and enrichment of heavy metal ions.In order to improve the adsorption capacity,adsorption kinetics and adsorption selectivity of IIP,the metal ion imprinting process was deeply investigated in this work,including metal cation and oxygenate anion imprinting processes,and then the recognition mechanism was revealed.In order to solve the problems of traditional bulk polymerization,such as incomplete template removal,large mass transfer resistance,and poor homogeneity of imprinting sites,the graphene oxide surface Cu(Ⅱ)ion-imprinted and nanostructured magnetic surface Pb(Ⅱ)ion-imprinted adsorption materials were prepared using surface imprinting technique for selective removal of metal ions in aqueous solution.First,a sandwich-like surface copper ion-imprinted polymer was prepared using functional graphene oxide as the imprinted support and acrylamide as the functional monomer.The results showed that the maximum adsorption capacity ofⅡP prepared by the surface imprinting method was significantly higher than that prepared by bulk polymerization.Adsorption by the IIP was fast and followed a pseudo-second-order kinetic and Freundlich isotherm model.Moreover,the IIP prepared by surface imprinting method also showed good adsorption selectivity for copper ion.Then,in order to better investigate the metal cation surface imprinted process,new functional monomer and magnetic separation technique were introduced into the preparation process of polymer to realize the rapid separation of solid adsorbent from aqueous solution.In this study,a novel nanostructure magnetic Pb(Ⅱ)ion-imprinted surface polymer was prepared using the functional nano-Fe3O4@SiO2 as the imprinted polymer support,bidentate ligand itaconic acid as functional monomer,ethyleneglycol dimethacrylate and 2,2-azobisisobutyronitrile as cross-linker and initiator.The prepared IIPs were characterized by FT-IR,BET analyzer,XPS,TGA and TEM.The results confirmed the presence of nano-imprinted shell layer on the surface of Fe3O4@SiO2.The maximum adsorption capacity of ⅡP(51.2 mg·g-1)was about three times of that of NIP(17.9 mg·g-1).The adsorption process was very fast,and followed well with the pseudo-second-order kinetic and Langmuir adsorption model,indicating that the process was chemical and single molecular layer adsorption.The selective factors for Pb(Ⅱ)/Co(Ⅱ),Pb(Ⅱ)/Cu(Ⅱ),and Cu(Ⅱ)/Zn(Ⅱ)binary mixtures were 45.6,6.45,and 8.3,respectively.In order to improve the adsorption performance and biocompatibility,and simplify polymerization process,a novel copper ion imprinted magnetic biomaterial which composes of chitosan(CS)enwrapping nanosized Fe304 and graphene oxide(GO)was prepared using the technique combining ion imprinting and inverse suspension crosslinking for selective removal of Cu(Ⅱ)from aqueous solution.Complicated free radical polymerization and extra grafting reaction could be avoided during the preparation process of imprinted material using crosslinking modification and ion imprinting technique,which is beneficial to the preparation of Cu(Ⅱ)ion imprinted chain macromolecular microsphere.Results indicated that the adsorption capacity of microsphere could be effectively increased by low level of crosslinking and the addition of GO and triglycine in preparation process.The maximum adsorption capacity was about 132 mg·g-1.Freundlich isotherm and pseudo-second-order kinetic models could be used to describe the adsorption process.The selective factors for Cu(Ⅱ)/Zn(Ⅱ),Cu(II)/Ni(Ⅱ),Cu(Ⅱ)/Co(Ⅱ),and Cu(Ⅱ)/Cd(Ⅱ)binary mixtures were 45.44,85.04,86.90 and 29.83,respectively.In order to expand the imprinted object,and explore the mechanism of anion imprinted process,two Cr(Ⅵ)anion imprinted materials were prepared using Cr(Ⅵ)ion as the target ion by the bulk polymerization and surface imprinting technique,respectively.In the bulk polymerization process,4-vinyl pyridine and N,N-Diethylaminoethyl methacrylate were selected as functional monomers based on the acid-basic property of Cr(Ⅵ).Meanwhile,NaOH solution was used as the elution solution,which simplified the elution process.Effects of pH,initial concentration of Cr(Ⅵ)in aqueous solution,temperature and adsorption time on adsorption performance were investigated.The adsorption equilibrium was achieved at 9 min,and the maximum adsorption capacity was 286.56 mg·g-1.The adsorption process followed the pseudo second-order equation and the Langmuir isotherm model.Additionally,the adsorption process was an endothermic and spontaneous chemical adsorption process.The selectivity factors for Cr(VI)/Cu(Ⅱ),Cr(VI)/Cd(Ⅱ),Cr(Ⅵ)/Cr(Ⅲ)binary mixtures were 135.78,145.44 and 69.91,respectively.To further increase the adsorption selectivity,and realize the solid-phase extraction and rapid determination of Cr(Ⅵ)ion,a surface Cr(Ⅵ)ion imprinted polymers(Cr(Ⅵ)-ⅡP)with fluorescence quenching response to the target ion was prepared.The Cr(Ⅵ)-ⅡP was synthesized using the functional nano-Fe304@SiO2 as imprinted polymer support,4-vinyl pyridine and N-vinyl carbazole as functional monomer and fluorescence monomer,respectively.The successful preparation of polymer and existence form of Cr(Ⅵ)were confirmed by FT-IR,BET,TEM,XPS and TGA characterizations.The static and dynamic adsorption experiments were performed to evaluate the adsorption performance.Effects of flow rate,solution concentration,and bed depth on adsorption performance of solid-phase extraction column were studied.In addition,the fluorescence performance of Cr(Ⅵ)-ⅡP was investigated and the fluorescence quenching mechanism was revealed.Then the corresponding Stern-Volmer equation was obtained.The selective factors for Cr(Ⅵ)/Cu(Ⅱ),Cr(Ⅵ)/Cr(Ⅲ),Cr(VI)/S042-and Cu(Ⅱ)/PO43-binary mixtures were 257.15,73.4,6.252 and 1.716,respectively. |
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