Anti-pollution Oil-water Separation Polyvinylidene Fluoride Composite Membrane

Poly(vinylidene fluoride)(PVDF)is a kind of membrane material with excellent characteristics.In this thesis,fouling-resistant membranes for separating oil-in-water emulsions were prepared by three hydrophilic modification methods. The effects of preparating conditions on the structures and properties of PVDF membranes were studied.Besides,the structure and performance of self-made fouling-resistant membranes were characterized.Fouling-resistant PA/PVDF composite membranes for separating oil-in-water emulsions was prepared by the interfacial polymerization of terephthaloyldichloride (TPC)with m-phenylene diamine on the surface of pure PVDF microporous membrane.The effect of monomer concentration,heat-treating time and temperature on the separating performance was studied.The experimental results show that the optimal reaction conditions are:C(TPC)=5g/L,C(m-phenylene diamine)=10g/L, C(ethyle-nediamine)=2g/L,heat treating time=10min,heat treating temperature= 35℃;The removing ratio of composite membrane for 100mg/L oil-in-water emulsions is 91.76%and the flux is 50.77 L·m^-2·h^-1.the analysis of contact angles,FITR-ATR and SEM show that the aromatic polyamide function thin layer was produced on the surface of composite membrane;the contact angle of composite membrane reduced 47.60%,the hydrophilic performance of composite membrane increased;the amount of pores of composite membrane decreased;The pure water flux,COD removing rate and BSA adsorption amount of pure PVDF membrane and polyamide composite membrane were compared.Its cleaning method and flux recovery ratios were discussed in this article.The experimental results show that the aromatic polyamide function thin layer was generated on the surface of composite membrane,this layer helps increasing hydrophilic on the surface of membrane, decreasing the amount of pores and increaseing removingratios for emulsion oil; After continuous filtration for 60min,the pure water flux of composite membrane stable approached 55 L·m^-2·h^-1,COD removing ratios reached 95%;The composite membrane's fouling-resistant performance was more effectively than pure PVDF membrane;The flux renew ratios of composite membrane was greater than pure PVDF membrane,the performance of three cleaning methods is:akali＞pure water＞ acid.TiO₂/PVDF composite membranes were prepared with coating method.The influence of TiO₂ concentration on the separating performance and structure of the composite membranes were studied.The results indicate that the nano-TiO₂ can improve the separating characteristic,hydrophilicity,thermal and mechanical strength; The structure of composite membranes were characterized by XRD,XPS,BET and SEM.The results show that the 8.8nm anatase were embedded into the surface of PVDF membrane,which improved the hydrophilicity of membrane;The lower average pore size and higher specific surface area can improve separating performance of the composite membrane.The pure water flux of composite membrane reached 45 L·m^-2·h^-1and the COD removing ratios for 100mg/L Oil-in-water Emulsions reached 90%and above;The composite membrane's fouling-resistant performance was more effectively than that of pure PVDF membrane.TiO₂/PVDF doped membranes were prepared by incorporation of different TiO₂ content sol.The crystalline structure,thermal stability and surface structure of doped membranes were characterized by FT-IR,TG and SEM.The results show that the microstrucure of doped membrane was improved;The hydrophilic property, separation property,fulling-resistant performance and mechanical strength of doped membrane were studied by experiment of contact angle,separation of emulsified oil solution,BSA adsorption amount and tensile intensity.The experimental results show that the hydrophilic performance of composite membrane obviously increased compared to PVDF micropore membrane,the contact angle from 79.2°down to 38.3°;The pure water flux of composite membrane reached 211.11 L·m^-2·h^-1and the removing ratios for 100mg/L Oil-in-water Emulsions reached 93%and above;The BSA adsorption amount of doped membrane less than that of PVDF micropore membrane,fulling-resistant performance enhanced;The mechanical strength of composite membrane increased obviously.Research found that higher TiO₂ content resulted in the performance decline of TiO₂/PVDF doped membrane.