Study On The Preparation And Properties Of Perfluorooctane Sulfonate Molecularly Imprinted Nanomaterials

Perfluorooctane sulfonate?PFOS?is widely used in industry and consumption field due to its hydrophobicity and oleophobicity.PFOS is widely distributed,having refractory degradation,persistence,bio-accumulation and potential toxicity.As a new persistent organic pollutant,it can be highly enriched with food chain in organisms,which is potentially harmful to human beings.In addition,PFOS has higher solubility than other perfluorinated chemicals?PFCs?,and it can reach a high concentration in water medium.Therefore,it is of great significance to develop a simple,efficient and rapid separation and enrichment method to remove PFOS in water medium.In this paper,molecularly imprinted polymers?MIPs?were synthesized based on surface molecularly imprinted technology.We discussed the adsorption properties of the MIPs,and the MIPs were applied to the adsorption of PFOS in environmental water samples,as the following:?1?Magnetic molecularly imprinted polymers?MMIPs?were synthetized for selective removal of PFOS in water.Concretely,the template molecule?PFOS?and functional monomer?acrylamide?were dissolved in acetonitrile to form a preassembled solution.After joining the crosslinking agent and initiator,a complex network structure was formed on the surface of the core shell structure of Fe₃O₄.Then the template molecule was removed with eluant,and the binding sites were left at the corresponding position of the template molecule,thus the MMIPs material was obtained.Based on MMIPs material,magnetic nonmolecularly imprinted polymers?MNIPs?were synthesized to comparatively study the adsorption properties of MMIPs.Transmission electron microscope?TEM?,Fourier transform infrared spectrometer?FTIR?,X-ray diffraction?XRD?and Vibrating sample magnetometry?VSM?were investigated to characterize the MMIPs.The effects of temperature and pH on the adsorption process were investigated.MMIPs were applied to water samples to discuss the adsorption process.Resonance light scattering?RLS?method was used to detect PFOS in the supernatant.The study shows that in the Britton-Robinson?BR?buffer solution of pH 1.81,the electrostatic interaction between acrylamide and PFOS is the strongest,showing that MMIPs have the largest adsorption capacity for PFOS.In addition,as the temperature increases,the adsorption capacity increases gradually,indicating that the adsorption of MMIPs towards PFOS is an endothermic process.The static adsorption experiments showed that the maximum adsorption capacity of MMIPs towards PFOS was 2.401 mg/g,which was higher than that of MNIPs towards PFOS by1.164 mg/g.The adsorption isotherms were fitted,and the results showed that the adsorption process of MMIPs towards PFOS was in accordance with the Langmuir isothermal adsorption model and showed monolayer adsorption.Kinetic studies showed that the adsorption of MMIPs on PFOS was a pseudo-second-order kinetic model,indicating that the chemical process may be the rate-limiting step in the adsorption process,and the adsorption equilibrium was reached within 60 min.MMIPs have good selectivity and reproducibility for PFOS,showing that the adsorption efficiency is only reduced by 3%after repeating use of 5 times.The application of MMIPs to the actual water samples showed that the standard recovery rate of MMIPs towards PFOS was53.06%⁵5.66%.So,MMIPs are expected to be used for the separation and enrichment of PFOS in real water samples with RSD?2.12%.?2?Mesoporous silica nanoparticles molecularly imprinted polymers?MSNs@MIPs?were prepared for the separation and enrichment of PFOS in water samples.The polymers were obtained by utilizing the electrostatic interaction between3-aminopropyltriethoxysilane?APTES?and PFOS,and combining with the hydrolysis of tetraethylorthosilicate?TEOS?under alkaline conditions,to form a complex network structure on the surface of the silica nanoparticles,finally eluting template molecules.In addition,mesoporous silica nanoparticles non-molecularly imprinted polymers?MSNs@NIPs?was synthetized to contrastive study the adsorption properties of MSNs@MIPs.The polymers were characterized by TEM,FTIR,XRD and N₂adsorption/desorption experiments.The static adsorption experiments showed that the saturated adsorption of PFOS by MSNs@MIPs was 21.10 mg/g,while that of MSNs@NIPs was 9.78 mg/g.At the same time,the influence of mesoporous on the adsorption capacity was investigated.The results showed that the mesoporous structure helps to increase the adsorption capacity of adsorbent to adsorbate.The adsorption isotherms were fitted.The results showed that the adsorption process of MSNs@MIPs towards PFOS accorded with Freundlich isothermal model,indicating that the adsorbent surface was inhomogeneous,and MSNs@MIPs was a multimolecular adsorption of PFOS.The kinetic studies showed that the adsorption process was accordance with the pseudo-second-order kinetic model,which indicated that the chemical adsorption was the rate-limiting step of the adsorption process,and the adsorption reached equilibrium at 25 min.When the structural analogs of PFOS existed,MSNs@MIPs exhibited good selectivity.In repetitive experiments,the removal rate of MSNs@MIPs towards PFOS was only reduced by 5%after 5 adsorption desorption cycle.MSNs@MIPs were used in the actual water samples and the removal rate of PFOS was 61.86%⁷6.12%,indicating that MSNs@MIPs are expected to be used for the removal of PFOS in environmental water samples with RSD?4.64%.