Study On Preparation And Characterization Of PVDF/PVDF-g-PMABSA Blend Membrane

Membrane separation technology has emerged as an effective approach for applications in the water purification and wastewater treatment fields in view of its outstanding performance in the removal of various water contaminants.PVDF membranes have been extensively applied in distillation,ultrafiltration,and microfiltration owing to its excellent chemical resistance,good thermal stability and high mechanical strength.Nevertheless,the intrinsic hydrophobic property of PVDF membranes results in low water permeability and severe membrane fouling when treating an aqueous solution containing organic,colloidal matters,and biological substances,which are susceptible to adsorption and deposition onto the membrane surface,blocking the surface pores.This inevitably depresses the lifetime of the membrane and subsequently leads to more operation cost of replacement.It is generally accepted that an increase in Hydrophilicity offers better membrane fouling resistance,which can prevent the adsorption and deposition of hydrophobic pollutants onto the membrane surface.Compared with chemical grafting or surface coating modification,physical blending modification does not require pretreatment and complicated process optimization,whichis suitable for industrial application.Blending modifiers include inorganic nanomaterials,hydrophilic polymers,and amphiphilic polymers:the compatibility between inorganic nanomaterials and PVDF matrix is poor and it is difficult to disperse uniformly in the casting solution;hydrophilic polymers are easily soluble in water and easily lost during the preparation of separation membranes;the compatibility between amphiphilic polymer and PVDF matrix is better,and it also improves the hydrophilicity of PVDF.Therefore,we have innovatively designed and synthesized a novel amphiphilic copolymer,PVDF-g-PMABSA,as a modifier that improves the performance of PVDF membranes by blending.In this work,a functional monomer of p-methacrylamidobenzenesulfonic acid?MABSA?,was designed and synthesized through the amidation reaction between 2-methylacryloyl chloride and sulfanilic acid.Utilizing PVDF and the obtained MABSA as reaction monomers,a novel amphiphilic copolymer was prepared by radical polymerization method.The composition and structure of the amphiphilic copolymer PVDF-g-PMABSA were characterized by¹H NMR and FTIR.The resulting PVDF-g-PMABSA was used as a hydrophilic additive in the fabrication of PVDF porous membranes via Non-solvent induced phase inversion?NIPS?.The surface chemical compositions,structure morphologies and chargeability of as-prepared blend membranes?PVDF/PVDF-g-PMABSA?were characterized by ATR-FTIR,X-ray photoelectron spectroscopy?XPS?,scanning electron microscopy?SEM?,and Zeta potential instrument,respectively.Contact angle measurement and cross-flow permeation test were employed to evaluate the hydrophilicity,permeability and antifouling properties of the membranes.The optimized blend membrane was applied to the treatment of wastewater treatment containing oil.,and the effect of oil/water separation was studied under different conditions.The main experimental results are as follows:?1?Chemical structure analysis of PVDF-g-PMABSA:The peaks at 1664 cm^-1and 1524cm^-1of FTIR spectra was attributed to the characteristic absorption C=O and O=C-NH.¹H NMR analysis showed that at 1.23 and 7.5 ppm,hydrogen proton peaks of methyl and benzene rings appeared,respectively.All indicates that the monomer MABSA had been successfully grafted to the PVDF backbone.?2?Analysis of surface chemical compositions,structure morphologies,hydrophobicity and chargeability of PVDF/PVDF-g-PMABSA Blend membranes:The peak at 1654 cm^-1of ATR-FTIR spectra was assigned to the characteristic absorption C=O.In the wide-scan XPS spectra of the blend membranes,as compared with the PVDF membrane two additional peaks with binding energies of 285.8 ev and 287.4 ev are attributable to C-N and H-N-C=O signal can be observed,respectively.It shows that PVDF-g-PMABSA is obviously enriched on the membrane surface;SEM observation showed that a large number of micropores appeared on the top morphology,and the cross-section consisted of finger-like macropores and a few spongy-like structures.;The zeta potential value declined with the increasing of copolymer PVDF-g-PMABSA content at each testing pH.?3?It was found that the blend membrane?M3?exhibited a noticeable pure water flux?110.51±4.37 L/m²?and a remarkable flux recovery ratio(F_RR)of 89.41%in comparison with the pristine PVDF membrane?63.37±3.21 L/m²h and 36.85%,respectively?.BSA static adsorption experiments showed that the surface adsorption decreased from 75.50±7.32?g/cm^-2for M0 to12.67±5.15?g/cm^-2for M3.All mean that the amphiphilic copolymer PVDF-g-PMABSA effectively improves the permeation flux and antifouling properties of PVDF membranes.?4?The oil-water separation experiments of PVDF/PVDF-g-PMABSA blend membrane showed that the permeation fluxes of soybean oil-water emulsion for M0 and M3 filtration were32.42 L/m²h and 95.9 L/m²h respectively,and the soybean oil removal rates were 95.2%and97.2%,respectively.M3 has higher separation efficiency.Membrane resistance calculation results show that M0 flux attenuation is mainly caused by membrane fouling,while M3 flux attenuation is mainly due to concentration polarization.The highly effective separation properties impart the PVDF/PVDF-g-PMABSA blend membranes with potential application in oil/water separation and wastewater treatment containing oil.