Study On The Preparation Of MOFs/PVDF Hybrid Membranes And Their Surface Adsorption Properties Toward Dyes

With the development of industry,the problem of wastewater containing organic pollutants has become more seriously,and the treatment of organic wastewater is one of the important research topics.Metal-organic frameworks(MOFs)have broad application prospects in the surface adsorption due to its high porosity,controllable pore structure and abundant open active sites.Polyvinylidene fluoride(PVDF)featured excellent thermal property,outstanding chemical resistance and mechanical strength,and long service life,have been widely applied for liquid separation.Fabication of hybrid membranes of MOFs and PVDF combines the advantages of two components,meanwhile perfectly solve the problem of recycling inconvenience in the application of MOFs powder materials,and also may obtain the enhanced adsorption activity because of the interface synergism.Firstly,we study the adsorption properties of NH2-MIL-101(Cr)nanoparticles in the removal of several organic dyes.Their results showed that NH2-MIL-101(Cr)has the selective adsorption activity toward congo red(CR),and the maximum adsorption capacity at 25? of CR was 1205 mg/g,which value is higher than most reported adsorption results of CR on other adsorbents.The adsorption mechanism was discussed.Secondly,NH2-MIL-101(Cr)with different mass percents of 1%,2%and 4%were added into the PVDF casting solutions for the fabrication of NH2-MIL-101(Cr)/PVDF hybrid membranes;at same time,the direct dipping of NH2-MIL-101(Cr)on PVDF membranes pre-treated with hydroxyl groups and sodium dodecyl sulfate(SDS)was also applied in the fabrication of hybrid membranes.Some means,such as X-ray diffraction(XRD),Field-emission scanning electron microscope(SEM),Fourier transform infrared spectroscopy(FT-IR)and Thermo-gravimetric(TG)were used to character the hybrid membranes.Results showed that for the hybrid membranes synthesized by doping method,the NH2-MIL-101(Cr)was uniformly deposited in the PVDF;for the hybrid membranes by the dipping method,larger amount of NH2-MIL-101(Cr)nanoparticles was diposited on the surface of PVDF film.Compared with pristine PVDF film,all the hybrid membranes presented significantly improved adsorption ability toward different dyes,and also displayed good recyclability.At last,the MIL-68(Al)synthesized by solvothermal method were also added into PVDF casting solution with different concentrations(1%,2%,4%and 6%)to prepare MIL-68(Al)/PVDF hybrid membranes.The MIL-68(Al)/PVDF hybrid membranes showed excellent adsorption performance for p-nitrophenol(PNP)and methyl blue(MB).Compared with pristine PVDF,MIL-68(Al)/PVDF hybrid membranes also showed enhanced adsorption activities.The selective adsorption mechanism was proposed.