The Preparation Of Magnetic Nanotube Molecularly Imprinted Polymers And Its Adsorption Behaviour For Estradiol

Environmental estrogen?EEs?,which exists only at trace level in water environment,can disturb the endocrine system function of human and animal body,affect the normal metabolism of the body,and cause harm to the nervous system and reproductive system.In the water treatment process,the enrichment,separation and detection of EEs in water samples are of great importance.The magnetic molecularly imprinted polymers?MMIPs?was prepared based on the research on the specific adsorption and rapid separation technology of target substances,which can not only improve the efficiency of pretreatment,but also be used for the rapid absorption and removal of the EEs in the polluted water body for improving the water environmental quality.The optimum process for preparation of MMIPs is as follows:?1?activation,dilute nitric acid solution is used to treat natural halloysite nanotubes for purification and expansion;?2?magnetized loading,Fe₃O₄ nanoparticles were loaded in the purified nanotubes for obtaining magnetized nanotubes?MHNTs?by ethylene glycol reducting ferric nitrate in high temperature;?3?Functionalized surface modified,polymerizable vinyl layer was formed by 3-?isobutenyl?propyltrimethoxysilane?MPS?on the surface of MHNTs;?4?magnetic molecularly imprinted polymer with template molecule E2?E2MMIPs?was preparated by modified MHNTs as the carrier,estradiol?E2?as template molecule and 4-vinylpyridine?4-VP?as functional monomer;?5?the target product MMIPs was obtained by eluting the template molecule E2 with methanol/acetic acid?v:v,9:1?.Characterization of FT-IR?TEM?XRD?VSM?TGA reveal that the specific surface area and pore volume of HNTs increased from36.31m²/g?0.20cm³/g to 70.96m²/g?0.29cm³/g,respectively.The magnetic Fe₃O₄particles were successfully loaded in the HNTs tube and the surface molecularly imprinted layer?MMIPs?was formed outside the nanotubes.MMIPs had good magnetic properties and thermal stability which could be separated completely from the complex matrix rapidly under the action of external magnetic field.During the measurement of the adsorption properties of E2 by MMIPs,the adsorption enrichment and separation of E2 in aqueous solution were carried out by using MMIPs prepared by ourselves and imprinted polymer without template E2prepared by the same method as the adsorption material.The content of E2 in solution was determined by high performance liquid chromatography.The results of batch adsorption of E2 showed that the adsorption equilibrium was reached at pH 7 at80min.It is found that the maximum adsorption of E2 by MMIPs and MNIPs is244.21mg/g and 116.31mg/g at 283K?293K?303K,and the adsorption process can be described by Langmuir model.The adsorption of E2 by MMIPs is endothermic and spontaneous.The kinetic adsorption experiments show that the adsorption process of MMIPs is controlled by chemical adsorption which can be described by quasi-second-order kinetic equation;there may be physical adsorption and chemisorption forces between MNIPs and E2.The experimental results of fixed bed adsorption show that the adsorption penetration curve of MMIPs to solution E2 under different conditions can be described by Thomas adsorption model.Increasing the initial concentration of E2 and decreasing the flow rate of sample are all favorable to adsorption process,the saturated adsorption capacity of MMIPs is 192.81mg/g.MMIPs showed good adsorption properties for estrogens similar to E2,such as bisphenol A?BPA?and ethylestradiol?EE?.Therefore,MMIPs can be used to enrich and separate the EEs from the real water samples,which can overcome the interference of the matrix in the water samples and reduce the detection cost.After five times of adsorption,desorption and adsorption cycle regeneration of MMIPs,the adsorption capacity of E2 was changed from 122.41?g/g to 117.77?g/g,and the adsorption capacity was kept at 96%,showing high stability and excellent regeneration.