【作者】 李瑞云；

【导师】 杨凤林；

【作者基本信息】 大连理工大学 ， 环境工程， 2012， 硕士

【摘要】 膜生物反应器(Membrane Bioreactor, MBR)技术以其突出的优点在城市生活污水和工业废水的处理与回用领域得到广泛的应用,但是,在其进一步推广的过程中,膜污染问题成为瓶颈,膜污染会导致膜阻力增大及膜通量下降,因而需要加大曝气量、频繁清洗,提高了能耗、降低了膜寿命,加大了污水处理成本。因此,开发抗污染、高通量的分离膜具有重要意义。本研究用新型材料氧化石墨烯(Graphene Oxide, GO)作为改性剂,对PVDF膜和聚丙烯无纺布两种重要的分离膜进行表面改性,使其具有良好的亲水性和通透性。用改进的Hummers法制备出氧化石墨,超声剥离得到GO,将制得的GO分别分散于去离子水和乙醇中,配置成不同浓度的分散液,通过压电式喷墨打印法和直接浸没涂覆法将GO分布在膜表面。(1)用l mg／mL的GO水相分散液对PVDF膜进行直接浸没涂覆,分散液无法有效润湿膜表面,改性剂也无法在膜表面均匀分布。相比之下,喷墨打印法无论改性剂的分散液和膜表面极性如何,都可以完成改性,应用范围广,且对膜表面改性十分均匀,另外还有极其节省改性剂、改性范围和形状可以任意设置等优点。GO能够大大改善PVDF膜表面的亲水性,使其表面的静态接触角从76.0。降低至21.90,降低幅度达到71.2%,打印次数越多,分布在膜表面的GO越多,亲水性越好,打印遍数大于9遍,膜亲水性不再继续增加。但改性膜的纯水通量并没有增加,反而迅速下降,打印遍数大于3遍合浸没涂覆的膜纯水通量都降为0,而且GO片层在PVDF膜表面的存在并不稳固,超声5min可以使膜表面的GO部分剥落,其中打印1-3遍的膜GO剥落不明显,打印遍数更多的膜则剥落明显。另外,N,N-二甲基乙酰胺(DMAc)可以进一步增强膜的亲水性,其浓度大于5g／L后亲水效果不再继续增加,DMAc不能增强GO在PVDF膜表面的稳固程度。(2)通过喷墨打印法和直接浸没涂覆法都可以将GO分布在聚丙烯无纺布分离膜表面,且分布效果都很均匀,其中喷墨打印法只能将GO片层分布于无纺布的表面纤维间隙,浸没涂覆法可以将GO片层紧致地镶嵌在无纺布深处的纤维间隙,因此用浸没涂覆法改性更有效率,也可以使GO片层更稳固地存在于膜表面。GO不能明显提高无纺布表面的静态接触角,但可以使无纺布的纯水通量得到十分显著的提高,其中打印20遍可以使纯水通量提高55.9%,而用1mg／mL的GO溶液涂覆后膜的纯水通量提高了177.5%,浸没涂覆法可以使无纺布对纯水的渗透性能提高更多,且操作更为方便。更多还原

【Abstract】 Membrane Bioreactor (MBR) has been widely used within wastewater treatment and reuse field for its outstanding advantages. However, the promotion of MBR has been drawn back by membrane fouling, which increased membrane resisitance and reduces flux, so more aeration and frequent cleaning was needed. Membrane fouling increased energy consumption and reduced membrane life, leading to more cost to the sewage treatment. Therefore, it is of great significance to develop anti-fouling and high flux membrane.In this study, a new material-graphene oxide(GO) was used as modifier to make PVDF membrane and non-woven polypropylene membrane(NWF) gain more hydrophilicity and permeability by surface modification.Graphite oxide was prepared with improved Hummers method, then treated by ultrasound and dispersed into deionized water and ethanol respectively. The dispersion was then used to modificate the membranes with inkjet printing and direct immersion method.(1) PVDF membrane surface cannot be wetted effectively by GO water dispersion because of different polarity when direct immersion modification method was used, while inkjet printing method could be successful to make the dispersion distributed on the membrane evenly. GO could improve the hydrophilicity of PVDF membrane surface obviously, which decreased the static cantact angle from76.0°to21.9°with a71.2%drop. The hydrophilicity of the membrane increased with growing printing times, and when the membrane was printed more than9times, its hydrophilicity was no longer changed. On the other hand, pure water flux of the modified membrane declined rapidly with the growing printing times. Pure water almost could not get through the membrane when it was printed more than3times. A5-minute ultrasound treatment could make the GO get off the membrane surface. Furthermore, DMAc could also increase the membrane hydrophilicity while it did not influence the stability of GO on membrane surface.(2) GO could be distributed evenly on the membrane by both inkjet printing and direct immersion method, among which the former one could only make GO exisit within the fiber gap on surface part of the membrane, while the latter one could distribute GO in the depths of NWF fiber gap. The static contact angle of modified membrane was not improved obviously, but the membtane’s pure water flux increased significantly. Printing20times increased the membrane flux by55.9%, while the immersion method could make the flux improved by177.5%.更多还原