载银抗菌分离膜的制备及动态微生物污染评价

	载银抗菌分离膜的制备及动态微生物污染评价
	戚龙斌
学位类型	硕士
导师	胡云霞 ; 杨世传
	2011-05-23
学位授予单位	中国科学院大学
学位授予地点	北京
关键词	分离膜微生物污染银纳米颗粒多巴胺抗菌
摘要	淡水是人类生存不可或缺的资源，随着经济发展和人口增长，人类对淡水需求量显著增加，同时水污染日益恶化导致可利用的淡化资源总量减少，淡水资源短缺正成为全球可持续发展的重要瓶颈。开发淡水资源和治理水污染成为当今全球迫切所需研究的关键科学问题。膜分离技术因其高效和节能等优点，在海水淡化和污水处理等领域得到广泛应用。然而，膜生物污染一直以来都是膜分离技术大规模工程应用过程中所面临的最棘手难题。开发简便高效的膜生物污染防控策略，正成为膜领域的研究热点。本研究利用银纳米颗粒（Ag NPs）高效广谱的抗菌性能，结合贻贝仿生多巴胺表面修饰方法，以膜表面形成的聚多巴胺层为中间层和结合位点，实现Ag NPs在膜表面原位生长，直接赋予膜本身抗生物污染能力。实验以聚酰胺正渗透复合膜（TFC FO膜）为模板，通过浸泡多巴胺溶液，在膜表面生成聚多巴胺层，随后浸泡硝酸银溶液，进而在膜表面生成Ag NPs，赋予膜抗菌性能。采用扫描电子显微镜（SEM）、X-ray光电子能谱（XPS）、原子力显微镜（AFM）、静态接触角测试仪和电感耦合等离子体质谱仪（ICP-MS）对膜的表面形貌、表面元素、粗糙度、亲水性和银负载量进行表征，探究了Ag NPs对膜性能的影响。研究结果表明，该方法能够同时在正渗透复合膜的聚砜支撑层和聚酰胺活性层生成Ag NPs，膜表面银负载量可达23.8 μg/cm²。银离子释放实验表明，银释放速率缓慢，一个月内的释放总量仅为膜表面银含量的1.58 %。同时，实验还发现，该方法可以实现Ag NPs在膜表面的多次重复生长，重复生长1次和2次后银的负载量分别为10.1 μg/cm²和6.5 μg/cm²。进一步采用克隆计数法（CFU）和荧光染色法评价载银膜的抗菌性能，发现载银膜对大肠杆菌的抗菌率高达95.6 %，同时具有杀菌和抗粘附的双重抗微生物效果。为了考察载银膜的动态微生物污染，以载银TFC FO膜为研究对象，采用富含铜绿假单胞菌的模拟废水为原料液，以模拟海水为汲取液，在正渗透错流系统中测试评价载银膜的长期通量变化，进而考察微生物污染对膜性能的影响。实验结果表明，载银膜在聚酰胺活性层面向富含微生物原料液的测试模式下，与原始膜相比，其水通量提高了8 %；在聚砜支撑层面向富含微生物原料液的测试模式下，其水通量提高了28 %。随后，采用总有机碳分析仪和BCA蛋白定量方法对膜表面的生物污染层进行定量分析，对比载银膜和原始膜的抗微生物污染效果。实验结果发现，原始膜和载银膜表面微生物的总有机碳含量分别为223.1 μg/cm²和91.0 μg/cm²，总蛋白含量分别为93.8 μg/cm²和10.2 μg/cm²。这说明负载Ag NPs后，膜表面微生物污染层的生物量显著减少。更为重要的是，在错流系统中测试后的载银膜对铜绿假单胞菌的抗菌率仍然高达96.1 %，说明载银膜能够耐受错流测试条件，并展现出持久的抗菌性能。为了简化抗菌膜的制备过程，开发一步在膜表面生成银纳米颗粒的方法。本研究以多巴胺为还原剂，巯基聚乙二醇为稳定剂，在膜表面一步还原银离子生成Ag NPs。采用扫描电子显微镜、X-ray光电子能谱和电感耦合等离子体质谱仪等表征膜的形貌、表面元素和银负载量。实验结果表明，该一步负载Ag NPs的方法可适用于多种材质的膜表面，包括有机、无机非金属和金属膜。采用抑菌圈法和克隆计数法，以金黄色葡萄球菌和大肠杆菌分别为革兰氏阳性菌和革兰氏阴性菌的代表菌株，评价载银膜的抗菌性能。实验结果表明，载银聚砜超滤膜、载银玻璃纤维膜和载银不锈钢网膜具有良好的抗菌效果，对金黄色葡萄球菌的抑菌率分别高达91.6 %，94.0 %和95.4 %，对大肠杆菌的抑菌率分别高达93.9 %，95.1 % 和96.8 %。此课题通过开发两种不同的载银膜的制备方法，并系统评价了载银膜的抗菌性能和动态抗污染性能，旨在开发过程简单，条件温和，并易于大规模应用推广的膜表面抗菌改性方法，并建立一套系统评价抗菌膜的静态和动态微生物污染的方法和手段，为分离膜微生物污染研究提供新思路和新方法，推动分离膜更广泛地应用到淡水资源的获取和水污染的治理等领域。
其他摘要	Fresh water is an essential element for life on earth. The human demand for fresh water has increased significantly with the development of economic and the growth of population, while, water pollution has worsened to reduce the amount of available fresh water resources. Thus, the fresh water shortage is becoming an important bottleneck for the global sustainable development of our society. Membrane separation technology has been widely used in the desalination and wastewater treatment to obtain clean and fresh water because of its high efficiency and energy saving advantages. However, membrane biofouling has always been the most challenging issue in the large-scale applications of filtration membranes. The research of developing highly-efficient and cost-effective antibacterial membranes is a hot topic to mitigate biofouling in the membrane fields. In this work, silver nanoparticles (Ag NPs), an excellent broad-spectrum bactericide, were in situ generated on the surfaces of thin-film-composite forward osmosis (TFC FO) membranes via mussel-inspired dopamine chemistry to endow membranes with antibacterial properties. To fabricate silver-loaded membrane, a TFC FO membrane coupon was immersed in dopamine solution in pH 8.5 Tris buffer to grow polydopamine coating on the membrane surfaces, and then immersed in silver nitrate solution to generate Ag NPs upon the reduction of silver ions by the polydopamine. Scanning electron microscope (SEM) was used to observe dense populate small bright nanoparticles on the membrane surface upon the growth of Ag NPs, and Energy Dispersive X-Ray Spectroscopy (EDX) was used to confirm that the small bright nanoparticles observed in SEM images were composed of silver. The silver loading amount on the membranes were quantified by inductively coupled plasma mass spectrometry (ICP-MS) after completely dissolving the Ag NPs of TFC FO membranes in 3.5 % nitric acid. The effects of Ag NPs generation were investigated on the water flux and salt permeability of TFC FO membranes as well. Results show that Ag NPs were generated simultaneously on both surfaces of membranes including polysulfone surface and polyamide surface. The silver loading amount was 23.8 μg/cm² on membrane surfaces and the Ag NPs have a slow release rate with only 1.58 % of original silver mass released in a month. The rechargability of Ag NPs has been demonstrated on the polydopamine modified membrane. After one and two cycles of depletion and regeneration, the silver loading mass was still as high as 10.1μg/cm² and 6.5 μg/cm² respectively. The colony forming unit method was employed to find that the numbers of live E. coli attached on the silver-loaded membrane was decreased by 95.6 % compared to pristine membrane. Confocal laser scanning microscope (CLSM) was used to observe the live and dead Pseudomonas aeruginosa attached on the TFC FO membranes with and without Ag NPs, and results present that the silver-loaded membrane exhibited great anti-adhesion and bacterial killing properties. To investigate the dynamic anti-biofouling performances of silver-loaded TFC FO membranes, a lab-scale cross-flow set-up was used to monitor their long-term water flux using synthetic wastewater containing P. aeruginosa and artificial seawater as feed and draw solutions, respectively. Results show that the water flux of silver-loaded TFC FO membranes increased by 8 %, compared to pristine, when running under the operation mode of polysulfone support facing microbial-containing feed solution; and their water flux increased by 28 % when running under the operation mode of polyamide layer facing microbial-containing feed solution. Moreover, total organic carbon biomass was 223.1 μg/cm² and 91.0 μg/cm² for pristine and silver-loaded TFC FO membranes, respectively. The total protein biomass was quantified by BCA method to be 93.8 μg/cm² and 10.2 μg/cm² for pristine and silver-loaded TFC FO membranes, respectively. Furthermore, the confocal laser scanning microscopic (CLSM) results show that the biofilm growth was strongly inhibited on silver-loaded TFC FO membranes. More importantly, the numbers of live P. aeruginosa attached on silver-loaded TFC FO membranes were still decreased by 96.1 % even after the 24 h cross-flow test, which indicates that the silver-loaded TFC FO membranes has sustainable antibacterial properties. In order to simplify the surface functionalization process of fabricating silver-containing membranes, one-step method was developed to grow Ag NPs on the membrane surfaces upon immersing the membrane coupons in a mixture solution having silver nitrate, poly (ethylene glycol) methyl ether thiol and dopamine. The surface morphology, surface elements and silver loading amount of the functionalized membranes were characterized by SEM, XPS and ICP-MS respectively. Results show that Ag NPs were successfully generated on various membranes, made of organic, inorganic, or metal materials. The inhibition zone method and colony forming unit method were employed to evaluate the antibacterial properties of silver-loaded membranes. Results show that the numbers of live S. aureus cells attached on Ag NPs modified polysulfone ultrafiltration membrane, glass fiber membrane and steel mesh membrane were decreased by 91.6 %, 94.0 % and 95.4 % respectively, and the numbers of live E. coli cells attached on Ag NPs modified polysulfone ultrafiltration membrane, glass fiber membrane and steel mesh membrane were decreased by 93.9 %, 95.1 % and 96.8 %, respectively. Thus, this silver-loaded membranes show great bactericidal efficacy against both Gram-negative and Gram-positive bacteria. Above all, two methods of fabricating silver-loaded membranes were developed in this work, and the static and dynamic biofouling tests of the membranes were operated to evaluate their antibacterial performances. Our study aims to develop a simple, universal and applicable approach for fabricating biofouling-resistant membranes on a large scale, and to build a set of systemic characterization methods for membrane biofouling evaluation in both static condition and dynamic conditions. Our findings provide new insights on the membrane biofouling control and promote the extensive applications of the filtration membranes in water purification, desalination and wastewater treatment.
文献类型	学位论文
条目标识符	http://ir.yic.ac.cn/handle/133337/22443
专题	中国科学院烟台海岸带研究所知识产出_学位论文
作者单位	中国科学院大学
推荐引用方式 GB/T 7714	戚龙斌. 载银抗菌分离膜的制备及动态微生物污染评价[D]. 北京. 中国科学院大学,2011.

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