Study On Adsorption And Mechanism Of Organic Micro-pollutants By NVP Graft Modified Polypropylene Fiber Membrane

Organic micro-pollutants(OMPs)have been frequently detected in water sources worldwide due to the fast growth of industry,agriculture and consumer goods markets.Endocrine disruptors(EDCs)account for a large part of OMPs,among which organic raw material bisphenol A(BPA)and plasticizer phthalate esters(PAEs)pollutants have a serious impact due to the abuse of plastic products.Although the environmentally relevant concentrations of EDCs are at trace level,they could be enriched in the bodies of creatures,which causes a variety of serious diseases.In recent years,adsorption method is considered to be the most potential method to remove EDCs from water.Adsorptive membranes,a class of free-standing adsorbents,can combine the advantages of adsorption material and separation membrane.The adsorptive membranes also have many advantages(large water flux,low mass-transfer resistance,easy recycling,and low cost).Therefore,water treatment using adsorptive membranes has great potential for large-scale applications.However,there are still many problems,such as low adsorption capacity,poor removal of trace EDCs and poor fouling resistance.More importantly,there are no adsorptive membranes with antifouling performance have been reported,which restricts their application in complex water environments.In this work,hydrophobic polypropylene fiber membrane(PPM)is employed as the substrate,and the N-vinylpyrrolidone(NVP)is selected as the functional monomer.A novel poly(N-vinylpyrrolidone)(PNVP)modified adsorptive membrane(PVPM)was prepared by UV surface grafting.Main contents are as follows:1.NVP was grafted on the surface of PPM to prepare PNVP modified polypropylene fiber membrane(PVPM)via one-step UV-initiated surface polymerization.In addition,the PVPM has excellent water permeability and ultrahigh water flux.The water flux of the single-layer membrane reaches 50,000 L/(m~2h)under gravity pressure drop(～1.4 k Pa),which is 10 times that of PPM.2.BPA as a representative pollutant,confirmed that different flow rates,ionic strengths,and initial concentrations of pollutants had no significant effect on the adsorption performance of PVPM.The broad-spectrum adsorption performance of PVPM was explored through continuous flow-through experiments,revealing that PVPM can effectively adsorb various OMPs in the water environment.The adsorption performance of PVPM at high and trace concentrations of BPA was investigated.The removal efficiency of PVPM for high and trace concentrations of BPA is 3-50 times that of unmodified PPM and commercial available hydrophobic membranes made of polytetrafluoroethylene(PTFE),poly(ether sulfone)(PES),or polyamide(PA).In addition,the adsorption performance of PVPM for typical trace concentrations(10μg/L)of PAEs was investigated,and the removal efficiency of trace EDCs is over 95%even at a water flux of 1270 L/(m~2h).The antifouling and adsorption performance of the hydrophilic modified membrane,hydrophobic modified membrane and the hydrophilic modified membrane were explored.Revealing the antifouling mechanism of PVPM and overcoming the tough trade-off problem between hydrophobic interaction and antifouling performance.3.The adsorption behavior of PVPM was fitted by adsorption kinetic and isotherm model.The pseudo-second-order model and Freundlich isotherm model are more suitable for describing the adsorption process of PVPM,which suggests that the adsorption of BPA on the PVPM is not monolayer adsorption.The influence of temperature,p H of solution,and hydrophobicity of OMPs on the adsorption performance of PVPM was explored,revealing that there are hydrophobic interactions and hydrogen bonds in the adsorption of PVPM.Modified membranes were prepared using different hydrophobicities substrates for BPA adsorption,confirming that the large-scale hydrophobic interactions provided by the matrix PPM is a fundamental adsorption driving force that should not be ignored during the adsorption process.Based on the results of adsorption and antifouling,a new strategy was proposed to prepare adsorption membranes with excellent adsorption and antifouling performance by constructing dual-scale hydrophobic interactions.4.The application of PVPM in different water environments was investigated.The removal efficiency of PVPM for BPA and mixed pollutants solution prepared by pure,tap and river water was maintained above 90%.In addition,the removal efficiency of PVPM for PAEs at 10μg/L prepared by river water also remained above 95%.Although the PVPM in river water and pure water after 10 and 20 adsorption/elution cycles,respectively,its adsorption performance did not decrease significantly.FTIR and XPS indicated the excellent cyclic and chemical stability of PVPM.Thus,the PVPM exhibits the super durability.