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基于聚多巴胺仿生涂层的分离、吸附、催化多功能膜的制备、优化及应用
曹晓彤
学位类型硕士
导师万印华  
2017-07
学位授予单位中国科学院研究生院
学位授予地点北京
学位专业生物化工
关键词多巴胺 漆酶 多功能膜 共沉淀 微量污染物 水处理
摘要

生物催化膜将物质选择性传递与化学反应结合,可以极大地提高反应效率,在医药、食品、水处理等领域应用前景广泛。然而目前生物催化膜制备过程中存在的载酶率不高、酶活保持低和膜本身性能下降等问题限制了其应用。针对上述问题,本论文重点研究了同时具备分离、吸附、催化功能的多功能膜的制备及其在水处理过程的应用。研究内容和成果主要分为以下两个部分:(1)受到贻贝粘蛋白和细胞膜结构的启发,将漆酶通过逆向过滤的方式包埋在纳滤膜支撑层内,再利用聚多巴胺(PDA)仿生涂层将漆酶封装在膜内,制备了同时具有截留、催化、吸附三种功能的多功能膜,并将其应用于水中微量污染物的去除。以去除水中双酚A(BPA)为例(原料液中BPA浓度为10 mg?L-1),NF270多功能膜对BPA的去除率达到84.3±7.3%,远远高于传统的芬顿氧化(BPA去除率55%)。对其多功能协同作用机制的研究表明,纳滤膜本身具有的截留功能截留部分污染物,减少了酶催化负荷;而膜以及PDA涂层的吸附功能将未被截留的微量污染物在膜内富集并且延长了底物与酶分子的反应时间,进而大大提高酶促反应效率;同时生物酶的催化功能打破了膜材料“吸附饱和”的限制,使得“吸附-催化”过程连续进行,且协同效应的存在大大提高了整体效果。(2)为了解决多功能膜在长期使用过程中由于PDA涂层不够致密导致的酶泄露问题,进一步提高载酶量和酶活力,分别利用多巴胺/聚乙烯亚胺(DA/PEI)和多巴胺/铜离子(DA/Cu2+)共沉淀方法在载酶纳滤膜支撑层内形成新型仿生涂层。研究结果表明共沉淀不仅缩短DA自聚时间,增强PDA涂层的均一性和稳定性,还极大地降低酶泄露,增加封装效率,提高酶活性。此外,采用该种方法制备的多功能膜,其特殊的“分离层-漆酶-支撑层/封装层”三明治结构使得该多功能膜两面均具有催化活性,可以利用其构建双面酶膜反应器(EMR),高效去除水中污染物,其中以DA/Cu2+共沉淀制备的多功能膜构建的EMR具有最高的BPA去除率,且由于流通模式下的强制对流有效移除产物,打破膜稳定性与去除率之间平衡,EMR的使用稳定性得以大幅度提高。研究表明通过调控多功能膜的载酶量、固定化酶位置、酶活性以及底物/产物传质,可以优化EMR对微量污染物的去除效率和稳定性。本研究不仅提出了一种新的生物催化膜制备方法和多功能膜新概念,解决了传统分离膜对水中微量污染物去除效率不高、生物催化膜稳定性不佳等问题,为生物催化膜的制备和应用打开了新思路,而且制备的多功能膜和双面EMR在深度尾水处理及家用净水器上具有较大的应用潜力。

其他摘要

Biocatalytic membrane which could combine mass transfer with biochemical reaction and improve enzymatic catalysis efficiency, is promising in biochemical engineering. However, due to the lack of efficient enzyme immobilization technologies, biocatalytic membrane suffers from low enzyme loading, low activity and low stability, which limits its further application. Aiming at these problems, this thesis focused on the construction and optimization of a multifunctional membrane based on polydopamine (PDA) coatings, and also investigated its application in water purification. The main research contents and results were summarized as follows: (1) Based on mussel-inspired chemistry and biological membrane properties, a multifunctional membrane was firstly proposed and prepared by applying ‘reverse filtration’ of a laccase solution and subsequent ‘dopamine coating’ on a nanofiltration (NF) membrane support, which was applied on bis-phenol A (BPA) removal. The BPA removal efficiency of NF270 multifunctional membrane was 84.3±7.3% when initial BPA concentration was 10 mg?L-1, outperforming the conventional Fenton treatment (55%). The super performance of the multifunctional membrane was due to a combination of separation (reducing the enzymatic burden), adsorption (enriching the substrate concentration as well as prolonging the residence time) and finally, catalysis (oxidizing the pollutants and breaking the ‘adsorption saturation limits’), and the synergistic effect enhanced the micro-pollutant removal efficiency.(2) To further improve the performance of the multifunctional membrane (i.e. enzyme loading, activity and stability), three multifunctional membranes were prepared by ‘reverse filtration’ of laccase and subsequently different coating strategies: single dopamine (DA) coating, DA/polyethyleneimine(PEI) co-depostion, and DA/Cu2+ co-deposition on NF270 membrane support. Compared with the single DA coating, two co-deposition methods not only accelerated the process of DA self-polymerization, improving its uniformity and stability, but also exhibited much better performances in terms of enzyme loading, activity and permeability as well as the stability of immobilized enzyme. The sandwich structure (skin layer-laccase-support/coating layer) of these biocatalytic membranes endowed their both sides with catalytic ability, which was used to construct a bifacial enzymatic membrane reactor (EMR) for highly efficient micro-pollutant removal (taking BPA as an example), and it was highest for the EMR with the DA/Cu2+ coated membrane. Besides, the stability of the bifacial EMR could be well maintained by in situ product removal, which was achieved by pressure-driven convective mass transfer. This work clearly confirmed the benefits of the mussel-inspired co-deposition for biocatalytic membrane fabrication, and demonstrated the potential to achieve a high and stable micro-pollutant removal by manipulating the enzyme loading, location and activity as well as substrate/product mass transfer of the biocatalytic membrane.In summary, this thesis not only proposes a novel strategy for biocatalytic membrane preparation and a new concept of multifunctional membrane, but also solves some application problems, such as the low removal efficiency of micro-pollutant by the traditional membrane filtration and the low operation stability of biocatalytic membrane. Moreover, this work provides a new methodology for the preparation and application of biocatalytic membrane, and the obtained multifunctional membrane and bifacial EMR are promising in tertiary wastewater treatment or household water purifier.

语种中文
文献类型学位论文
条目标识符http://ir.ipe.ac.cn/handle/122111/24205
专题研究所(批量导入)
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曹晓彤. 基于聚多巴胺仿生涂层的分离、吸附、催化多功能膜的制备、优化及应用[D]. 北京. 中国科学院研究生院,2017.
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