Fabrication Of Multilayer Molecularly Imprinted Nanocomposite Membranes And The Selective Separation Performance And Mechanism For Norfloxacin

Norfloxacin,as an outstanding representative of the third generation of synthetic fluoroquinolones antibiotics,has been applied diffusely in livestock and aquaculture industry.But most of norfloxacin can not fully absorbed by human and animals,which flowed into the water environment in the form of original or metabolites,will be harm to human health and survival of the biology.Therefore,it is urgent to separate residual norfloxacin in the environment.There are many ways to separate the antibiotics in the water environment,but most of them have disadvantages such as high cost,high energy consumption and complicated operation.Membrane separation technique?MST?with low energy and high-efficiency,is one type of promising separation technology.However,the traditional MST does not have the specific selective recognition capability which result in common membranes cannot separate specific target.At present,molecular imprinting technique?MIT?has become one of the most promising methods for constructing artificial receptors,which can selectively identify targets under certain conditions.The molecularly imprinted membranes?MIMs?having the characteristics of specific recognition performance and high separation energy,which were prepared by combining MIT with membrane separation technology?MST?.However,common molecularly imprinted membranes have the disadvantages of low mechanical strength,low utilization of imprinted sites,and poor stability.And it has been found that the molecularly imprinted membranes can be greatly improved by modifying the surface of the polymer membrane material with various nanocomposites such as GO,Ag,TiO₂ and BiOCl,which have high hydrophilicity,stability,and anti-fouling performance.The synthesized molecular imprinted nanocomposite membrane?MICMs?is a kind of low cost,environmental protection,and efficient separation material,which is widely used in the treatment of environmental water pollution.In this paper,MIT and MST were combined to design and synthesize three kinds of norfloxacin imprinted composite membranes with norfloxacin as the template molecule.The details are as follows:?1?The dopamine?DA?was used as both cross-linker and functional monomer and norfloxacin was selected as a template molecule to synthesize molecularly imprinted polymers?MIPs?on the surface of TiO₂ microspheres.The MICMs were then synthesized by modification of the imprinted TiO₂ nanospheres in the channel of the porous RCMs via vacuum filtration.Meanwhile,these obtained MICMs exhibited the superior adsorption capacity,separation efficiency and selective recognition ability for norfloxacin molecules.In addition,a variety of characterization methods were used to systematically characterize the nanoparticles and membranes material.And the adsorption and separation mechanism were discussed in detail.The results show the prepared molecularly imprinted composite membranes not only have good mechanical strength,reproducibility and good morphological features,but also have high adsorption capacity?MICMs,25.35 mg/g?and separation ability?separation factor,4.43?for norfloxacin.?2?The norfloxacin imprinted composite membrane?NFIcMs?for the selective separation of norfloxacin were synthesized by combing the advantages of surface imprinting technique,hydrophilic graphene oxide and PVDF membranes.GO/PVDF blended membranes were as the base membranes were synthesized by phase inversion method using graphene oxide?GO?and polyvinylidene fluoride?PVDF?.Afterwards,the TiO₂ nanospheres were modified the surface of the GO/PVDF membranes was to enhance the anti-dirty ability of NFIcMs.Then the as-obtained TiO₂@GO/PVDF membranes were modified by a functionalized process of KH570 for further imprinting process.After the prepolymerization process of AM and EGDMA,a polymeric network around norfloxacin was generated on the surface of TiO₂@GO/PVDF membranes,bringing about the formation of norfloxacin-imprinted composite membranes?NFIcMs?.Finally,the structure and morphology of NFIcMs were investigated by means of SEM,WCA,TEM,AFM,and XPS.In addition,the saturated adsorption quantity of NFIcMs was 44.81 mg/g,which was more than five times that of the non-imprinted composite membrane?NFNIcMs,7.68 mg/g?,and NFIcMs showed excellent selective separation capability?separation factor of 5.73?.?3?Ag nanoparticles were initially deposited at the surface of BiOCl/PVDF blended membranes by reduction reaction for the synthesis of Ag@BiOCl/PVDF composite membranes,and then prepared norfloxacin-imprinted composite membranes?ABP-MIMs?by sol-gel surface imprinting technique with norfloxacin as template molecule.The characterization of the ABP-MIMs was studied by means of characterizations such as SEM,AFM,XPS,WCA and FT-IR.At the same time,the selective adsorption and penetration mechanism of synthetic ABP-MIMs for norfloxacin and its structural analogues were investigated.The results showed that the synthesized ABP-MIMs showed high selective recognition ability??is of 6.06?and accorded with the mechanism of delayed mass transfer,indicating that a large number of imprinting sites existed on the surface of the synthesized molecularly imprinted nanocomposite membranes.In addition,ABP-MIMs exhibited good hydrophilicity through water contact angle test,and showed outstanding stability?96%?after cyclic adsorption experiments.