Study On Preparation And Application Of Surface Ion Imprinting Materials Based On Carboxylated Carbon Nanotubes

With the rapid development of modern industry,various metal ions are continuously discharged into natural environment.The iron ion content in the human body is closely related to the health status.The human health will be affected by intaking too many or too few iron ions.Rubidium as a kind of rare metals is widely used in high-tech fields.However,the efficient extraction of rubidium from water is still a technical difficulty.Ion-imprinted polymer is a kind of polymers with specific identification and selective adsorption which is widely used in separation and extraction of metal ions.In this work,Fe2+surface imprinted polymers(Fe2-IIPs)based on single-wall carbon nanotubes(SWNTs)and Rb+ surface imprinted polymers(Rb+-IIPs)based on SWNTs were prepared by surface ion-imprinting techniques and mainly used for adsorption of ferrous and rubidium ions from water.The Fe2+-IIPs based on carbon nanotubes were prepared by layer-by-layer self-assembly method with carbon nanotubes as carrier,chitosan as polyanion electrolytes,polyacrylic acid as polyamion electrolytes,Fe2+ as template ion and glitaraldehyde as cross-linking agent.Then the prepared Fea+-IIPs on the surface of carbon nanotubes were characterized by Fourier transform infrared spectrometer(FT-IR),scanning electronic microscopy(SEM),transmission electron microscope(TEM)and thermogravimetric analysis spectrometer(TGA).The results showed that the diameter of the carrier carbon nanotubes increased and the weight loss of Fe2+-IIPs reached up to 30.8%after the preparation of the imprinted material,indicating that Fe2+-IIPs were successfully prepared.The number of assembled polyelectrolyte layers,dosage of cross-linking agent,and cross-linking time were optimized during the preparation process of Fe2+-IIPs.The maximum adsorption capacity of Fe2+-IIPs for Fe2+ reached up to 39.4 mg·g-1 at pH 5.Through the study of kinetics,it was found that the adsorption behavior of Fe2+ by Fe2+-IIPs agreed well with the pseudo-second-order kinetic model,indicating that the adsorption process was mainly determined by chemical adsorption.The selectivity coefficients of Fe2+-IIPs for Fe(Ⅱ)/Zn(Ⅱ),Fe(Ⅱ)/Ni(Ⅱ),Fe(Ⅱ)/Co(Ⅱ)and Fe(Ⅱ)/Cu(Ⅱ)were 16.880,22.911,4.683 and 1.135,respectively.After 10 cycles of recycling,Fe2+-IIPs could still maintain good adsorption performance,which indicates that the prepared material has good reusable performance.The were prepared by with carbon nanotubes as carrier,carbon nanotubes-polyacrylic/calix[6]arene(SWNTs-PAA/CA)prepared by grafting method as functional monomer and Rb+ as template ion.The preparation conditions like grafting temperature of calix[6]arene,crosslinker content and cross-linking time were optimized.The Rb+-IIPs were characterized by FT-IR,SEM and TGA,the results of which demonstrated that Rb+-IIPs on the surface of carbon nanotubes had been successfully prepared.The adsorption capacity of Rb+-IIPs for Rb+ was 6.68 mg·g-1 at pH 7 with 10 mg·L-1 initial Rb+concentration.In addition,the adsorption equilibrium was reached within 10 min,indicating that the adsorption kinetics of Rb+-IIPs was fast.The adsorption behavior of Rb+-IIPs for Rb+ agreed well with the pseudo-second-order kinetics model,which demonstrated that the adsorption process was mainly determined by chemical adsorption.The results of adsorption isotherm showed that the adsorption behavior of Rb+-IIPs for Rb+agreed well with the Langrmuir equation,indicating that the adsorption process belonged to monolayer adsorption.The selectivity coefficients of Rb+-IIPs for Rb(Ⅰ)/Na(Ⅰ),Rb(Ⅰ)/Li(Ⅰ)and Rb(Ⅰ)/Mg(Ⅱ)were 2.661,1.533 and 2.908,respectively.After 10 times of adsorption-desorption processes,the prepared Rb+-IIPs could still maintain good adsorption performance.