PVDF/DA改性膜抗污染性能研究

PVDF/DA modified membrane antifouling performance study

为降低疏水性聚偏氟乙烯(Polyvinylidene Fluoride,PVDF)微滤膜在膜生物反应器(Membrane Bioreactor,MBR)中的膜污染情况,采用多巴胺(Dopamine,DA)对PVDF膜进行表面改性,制得PVDF/DA改性膜。通过多种分析手段对改性膜进行化学结构、形态结构、亲水性表征,并评估抗污染性能;同时考察PVDF膜和PVDF/DA改性膜的胞外聚合物组分。结果显示:添加多巴胺可以增加PVDF膜的粗糙度和亲水性,PVDF/DA改性膜的接触角降至33.9°。PVDF/DA改性膜还具有良好的抗污染性能,海藻酸钠(Sodium Alginate,SA)截留率为86.71%,牛血清白蛋白(Bovine Serum Albumin,BSA)吸附量为223μg/cm^(2),通量恢复率高达98.92%,远高于PVDF膜90.24%的通量恢复率。在挂膜对比试验中,相较于PVDF/DA改性膜,PVDF膜的胞外聚合物(Extracellular Polymers,EPS)总量增加了1.46倍,膜表面滤饼层中蛋白质、多糖和DNA含量均高于改性膜。

To reduce membrane contamination of hydrophobic polyvinylidene fluoride(PVDF)microfiltration membranes in MBR,dopamine(DA)was used to modify the surface of PVDF membranes to produce PVDF/DA—modified membranes.The modified membranes were characterized by various analytical methods,including chemical structure,morphological structure,hydrophilicity,and anti-pollution properties.The extracellular polymers(EPS)fraction and effluent quality of PVDF membranes and PVDF/DA—modified membranes were also investigated.The results show that the addition of dopamine increased the roughness and hydrophilicity of the PVDF membranes and reduced the contact angle from 69°to 33.9°.A homemade membrane assembly device was used to test.The results show that the retention rate of sodium alginate(SA)in the PVDF/DA modified membrane was 86.71%,which was much higher than that of the PVDF membrane at 63.25%;the adsorption amount of the PVDF/DA modified membrane in the bovine serum albumin(BSA)solution was 223μg/cm^(2),which was much lower than that of the PVDF membrane at 414μg/cm^(2);after physical cleaning,the flux recovery rate of the PVDF/DA modified membrane was 98.92%,which was significantly better than the flux recovery rate of the PVDF membrane of 90.24%.This reflects that the PVDF/DA—modified membranes can not only effectively reduce the formation of the membrane cake layer,but also make it easier to remove membrane contamination.In a parallel test using MBR,the total amount of extracellular polymer in the PVDF membrane was increased by 1.46 times compared to the PVDF/DA modified membrane,and the content of protein,polysaccharide,and DNA in the cake layer on the membrane surface was higher than that of the modified membrane.During the experiment,the average COD removal rate of the PVDF/DA modified membrane was 93.59%,which was slightly better than the 91.16%removal rate of the original membrane;the ammonia nitrogen removal rates of the PVDF/DA modified membrane and the original membrane effluent was comparable,the effluent is maintained between 2.06.0 mg/L,indicating that the dopamine modification did not adversely affect the separation performance of the PVDF microfiltration membrane.