Hydrophilic Study Of Pvdf UF Membrane Modification Technology

Polyvinylidene fluoride (PVDF) that has semi-crystalline structure of polymers is a high molecular organic materials,the nature of the acid-proof, alkali resistance and stable performance.It has been widely used in the preparation of the ultrafiltration membrane. However, because its surface energy was low, its hydrophobicity was strong.The polymer matrix by adding a small amount of inorganic nanoparticles has become an important method to improve the performance of the material.Because inorganic nanoparticle has strong hydrophilicity and high mechanical strength,the preparation of the membrane have advantages of inorganic and organic.Based on the comprehensive investigation and analysis of existing research doocuments in and beyond the county,defect-free skined asymmetric Polyvinylidene fluoride (PVDF) ultrafiltration(UF) membranes was investigated by dry/wet phase inversion technique in this paper.The main research and conclusions are as follows.1.The effects of different factor,such as PVDF concentration,the type and concentration of additives and nanoparticles,mixed-solvent content were systematically investigated respectively to obtain the optimal technique parameters. A series of PVDF asymmetric UF membrane with different morphology and performance have been successfully prepared by optimizing operating paremeters.2.A new type of polyvinylidene fluoride(PVDF)ultrafiltration membrane was prepared with N,N-dimethylacetamide(DMAC) and N-methyl pyrrolidone(NMP) as mixed solvent. The effect of mixed solvent in different proportions on the performance and structure of hybrid membranes was investigated. The results showed membrane performance and structure was influenced.The Sublayer structure and the average pore diameter is effected,but porosity and membrane surface contact angle was unchanged.When the ratio of the mixed solvent DMAC/NMP was1:2,the performance of UF membrane was optimal, flux was9.3L/(m2·h), retention rate was88%.3. The structure and performance of the composite membranes by adding the mixed additives in different proportions was PEG600/LiCl, acetone/LiCl, glycerol/ LiCl and PVP/LiCl were investigated.The results showed that all of PEG600/LiCl, acetone/LiCl, glycerol/LiCl and PVP/LiCl can improve membrane performance, which added PVP/LiCl to in the casting solution, the hydrophilicity of PVDF surface membrane significantly improved, and membrane surface contact angle reduced to554. The prepared of nano TiO2sol use sol-gel method.The effects of TiO2sol and its content on the membrane performance and structure were discussed.The TiO2/PVDF composite membrane was modified by nano-TiO2sol,the performance and structure of the membrane were optimal.And mixed TiO2sol and γ-Al2O3nanoparticles in different proportions add to the casting solution can increase hydrophilic and mechanical strength of PVDF membrane by the phase-inversion. The effects of TiO2sol and γ-Al2O3nanoparticles on pure water flux, retention rate and mechanical properties of UF were discussed.And flux was13.7L/(m2-h), retention rate was60%, tensile strength maximum loading was35N and tensile strain was22%.The innovation of this paper is that prepared of nano TiO2use sol-gel,and particles weren’t reunite with each other in the casting solution.The ultrafiltration membrane prepared with particles has a good separeting performance.And the problem of declining Nanoparticles lead to membrane performance was overcomed.And both of TiO2sol and γ-AlO3nanoparticles were able to play to their own advantages of characteristics, increase hydrophilic and mechanical strength of PVDF membrane at the same time.