Study On Surface Modification And Performance Of Polymer Membrane Based On Dopamine

Membrane separation technology has been widely concerned in the field of wastewater treatment because of its advantages of high efficiency,energy saving,easy process control and convenient operation.Polyvinylidene fluoride(PVDF)has become a commonly used ultrafiltration and microfiltration membrane material due to its strong chemical stability and high mechanical strength.However,in practical application,it is still limited by the reduction of separation performance caused by membrane contamination.There are many ways to solve the problem,but the most essential core is to improve the performance of the membrane itself.In this paper,polyvinylidene fluoride(PVDF)was used as the membrane material and polyvinylidinone(PVP)as the additive to form the membrane by phase transformation method.The paper explores the influence of the factors on the water flux,retention rate,mechanical strength and membrane hole structure of the finished membrane in the casting membrane liquid system,and analyzes the mechanism of the influencing factors in the membrane forming process.The optimal ratio of each component of the PVDF membrane is found,so as to optimize the preparation process of PVDF membrane.After comprehensive consideration of various properties of the membrane,the optimal ratio was obtained:polyvinylidene fluoride(PVDF)18wt,polyvinylpyrrolidone(PVP)2wt,and The solvent is N-methylpyrrolidone(NMP).On this basis,the 3-glycidyl ether oxypropyl triethoxylsilane with hydrophilic group(epoxyl)was selected from the silane coupling agent based on the characteristics of dopamine self-polymerization under weak base condition.Polyvinylidene fluoride(PVDF)ultrafiltration membrane was used as the base membrane,and a hybrid coating was formed on the surface of the membrane by means of simultaneous hydrolysis of dopamine and the precursor of hydrophilic substance.The two substances adhere to the membrane surface by chemical bond and physical winding.The PVDF ultrafiltration modified membrane was prepared by adjusting the ratio of 3-(2,3-epoxypropoxy)Propyl triethoxy silane(KH-561)and dopamine.The effects of the formed hybrid coating on the surface morphology,hydrophilicity,pure water flux,intercept rate,mechanical properties and other related properties of the modified membrane were tested in the paper.The results showed that the modified membrane not only improved the hydrophilic ability of the membrane surface,but also improved the hydrophilicity of the inner hole of the membrane to a certain extent.The PVDF modified membrane had good hydrophilicity,and the water contact angle was as low as 37.8°.The membrane water flux reached 174L-m-2-h-1,and the protein retention rate was more than 90%.The hybrid coating formed a layer of water film on the membrane surface,so that the membrane has a good anti-pollution properties,and the attenuation coefficient of the modified membrane can be as low as 0.19.