氨基功能化氧化石墨烯对PVDF超滤膜表面改性的研究

发布时间：2018-08-04 15:49

【摘要】：本文通过氧化石墨烯（GO）与乙二胺（EDA）发生脱水缩合反应生成氨基功能化改性的氧化石墨烯（GO-NH2），再利用多巴胺的自聚合性和化学特性，将功能化的GO与涂覆在超滤膜表面的聚合多巴胺形成共价键，，从而将功能化的GO接枝到聚偏氟乙烯(PVDF)超滤膜表面，形成亲水性强、导电性强的膜表面。本文的研究重点为氨基功能化氧化石墨烯的合成方法和PVDF超滤膜接枝功能化GO后的膜面表征与抗污染性能，利用GO的片状结构在超滤膜表面形成更致密的石墨烯膜分离层，从而达到更精密的过滤效果。 通过脱水缩合反应形成功能化氧化石墨烯，利用傅里叶红外光谱（FTIR）、热重分析（TGA）和环境扫描电镜（ESEM）对产物进行检测，结果显示，氨基成功接枝到氧化石墨烯片层结构上。利用膜表面的聚合多巴胺将改性氧化石墨烯接枝到PVDF超滤膜表面，采用ESEM和FTIR分别对改性前后膜表面结构形态和化学组成进行观察，利用不同接枝浓度和接枝时间的超滤膜表面的接触角及其变化来表征改性对膜亲水性和润湿性的影响，并将改性膜过滤机油乳化液、牛白蛋白（BSA）和海藻酸钠（SA）溶液三种模拟废水体系，研究改性对膜抗污染性能和截留能力的影响，最后进行改性膜的酸碱稳定性测试。 结果显示，接枝功能化GO使膜孔径缩小和孔隙率降低，但使其亲水性和润湿性增强。膜表面的亲水性和润湿性随接枝浓度的增大和接枝时间的增长而增强，而纯水通量随接枝浓度的增大和接枝时间的增长呈现先上升后下降的趋势。实验采用的PVDF超滤膜的平均接触角为77°，经接枝改性后接触角平均值减小为61°，PVDF超滤膜的纯水通量由206.8L/(m2.h)减小为120.4(m2.h)。最佳的GO-NH2接枝浓度为2mg/mL，接枝时间为60min。 通过利用机油乳化液、BSA和SA三种溶液模拟废水体系对改性膜进行过滤实验研究了改性膜的抗污染性能，结果显示，改性使得膜的抗污染能力有所提高；通过对改性膜进行酸碱浸泡，利用膜的纯水通量和膜表面接触角进行了膜的稳定性测试，结果显示，改性膜具有良好的耐酸性，但耐碱性相对较弱些。最后，通过利用55℃、1%的表面活性剂水溶液对机油乳化液污染膜进行清洗以及55℃、1%NaOH溶液对BSA溶液和SA溶液污染膜进行清洗发现，改性膜的恢复率都在60%以上。
[Abstract]:In this paper, graphene oxide (GO-NH2) was synthesized by dehydration and condensation of graphene oxide (GO) with ethylenediamine (EDA) to form amino-functionalized graphene oxide (GO-NH2), and the self-polymerization and chemical properties of dopamine were used. The functionalized go was covalently bonded with the polymerized dopamine coated on the surface of the ultrafiltration membrane, and the functionalized go was grafted onto the surface of the polyvinylidene fluoride (PVDF) ultrafiltration membrane to form a surface with strong hydrophilicity and conductivity. In this paper, the synthesis method of amino-functionalized graphene oxide and the surface characterization and antifouling performance of PVDF ultrafiltration membrane grafted with go were emphasized. A denser graphene membrane separation layer was formed on the surface of ultrafiltration membrane by using the sheet structure of go. Thus, a more precise filtration effect is achieved. The functionalized graphene oxide was formed by dehydration and condensation reaction. The products were detected by Fourier transform infrared spectroscopy (FTIR),) thermogravimetric analysis (TGA) and environmental scanning electron microscopy (ESEM). The results showed that the amino groups were grafted onto the graphene oxide lamellar structure successfully. The modified graphene oxide was grafted onto the surface of PVDF ultrafiltration membrane using polymeric dopamine on the membrane surface. The surface structure and chemical composition of the modified membrane were observed by ESEM and FTIR, respectively. The influence of the modification on the hydrophilicity and wettability of the membrane was characterized by the contact angle and change of the surface of the ultrafiltration membrane with different grafting concentration and grafting time, and the oil emulsion was filtered by the modified membrane. The effects of modification on membrane antifouling performance and retention ability were studied in three simulated wastewater systems of bovine albumin (BSA) and sodium alginate (SA) solution. Finally, the acid-base stability of modified membrane was tested. The results showed that graft functionalization of go reduced the pore size and porosity of the membrane, but enhanced its hydrophilicity and wettability. The hydrophilicity and wettability of the membrane surface increased with the increase of grafting concentration and grafting time, while the pure water flux increased firstly and then decreased with the increase of grafting concentration and grafting time. The average contact angle of the modified PVDF ultrafiltration membrane was 77 掳, and the average contact angle decreased to 61 掳(m ~ (2) h) from 206.8L/ (m ~ (2 路h) to 120.4 (m ~ (2) h). The optimum grafting concentration of GO-NH2 was 2 mg / mL and the grafting time was 60 min. The anti-fouling performance of modified membrane was studied by using three kinds of simulated wastewater systems of oil emulsion BSA and SA. The results showed that the anti-fouling ability of modified membrane was improved. By soaking the modified membrane with acid and alkali, the stability of the modified membrane was tested by using the pure water flux and the contact angle of the membrane surface. The results showed that the modified membrane had good acid resistance, but the alkalinity resistance was relatively weak. Finally, by using 55 鈩

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