| Chlorinated polyvinyl chloride(CPVC)is one of the commonly used membrane materials in membrane bioreactors.However,chlorinated polyvinyl chloride microfiltration membranes have shortcomings such as low flux,poor mechanical properties,and poor anti-pollution performance.Therefore,how to obtain a high-performance CPVC microfiltration membrane is a problem that must be solved in water treatment applications.In this paper,CPVC was used as the membrane-forming polymer.We systematically explored the influence of different influencing factors on the phase separation behavior of the system and the membrane structure and performance during the film formation process.This provides a theoretical basis for the use of chlorinated polyvinyl chloride microfiltration membranes in membrane bioreactors.In this subject,N,N-dimethylacetamide(DMAc)is used as the solvent and polyethylene terephthalate(PET)nonwoven fabric is used as the support layer.The CPVC/PET composite microfiltration membranes are fabricated by the solidified coating process and the non-solvent induced phase separation method.By exploring the mass transfer and phase separation behavior of the film during the formation process,this paper discusse the membrane formation process conditions such as non-woven fabric structure,membrane scraping speed,coagulation bath temperature how to influence the membrane structure morphology and performance.The results show that the PET non-woven fabric with low density and loose structure is used as the support material of CPVC microfiltration membrane,which makes the surface opening of CPVC/PET composite microfiltration membrane increased,the internal sponge-like structure becomes looser,and the pure water flux also increased.Composite microfiltration membrane has good retention performance,tensile strength and elongation at break increased significantly.In addition,different membrane-making process conditions have different degrees of influence on the appearance and performance of the film products.Surfactant Tween 80(Tween 80)and porogen polyethylene glycol(PEG)were used to construct the microstructure of the membrane.The effects surfactant and the molecular weight and content of PEG on the phase separation behavior and membrane structure of the CPVC/DMAc system were mainly studied.The results show that the addition of surfactant can adjust the interaction between the hydrophobic polymer-solvent-water system,which reduces the surface tension of the casting solution and forms more pores on the surface and inner layer of the CPVC/PET composite microfiltration membrane.The addition of porogen does not change the phase separation mechanism of the system,but the differences of PEG molecular weight and content have a great influence on the membrane structure.It leads to the pure water flux of CPVC/PET composite microfiltration membrane is greatly increased.In order to improve the anti-fouling performance of the CPVC composite microfiltration membrane,polyvinyl butyral(PVB)is used as the hydrophilic agent.The mechanism of PVB hydrophilic modification and the effect of blending ratio on the hydrophilic properties of the membrane were mainly discussed.The results show that the use of the PVB can significantly reduce the contact angle of the CPVC/PET composite film.The static contact angle decreases from 132°to about 88°.And as the blending ratio increases,the contact angle decreases faster.Which means that the more water droplets easy to spread on the membrane surface.At the same time,when the blending ratio is 19:1,the stable pure water flux of the modified membrane is as high as 1318.29L/m~2·h.In addition,compared with the original membrane,the modified membrane water flux recovery rate increased from 64%to 88%,and irreversible pollution decreased from 36%to 11%.These results indicate that the use of the PVB can significantly improve the anti-fouling performance of the separation membrane. |
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