【作者】 刘莹；

【导师】 靳健； 朱玉长；

【作者基本信息】 苏州大学 ， 化学， 2025， 博士

【摘要】 随着全球水资源短缺与能源转型需求的加剧,膜分离技术在海水淡化和战略资源回收领域的重要性日益凸显。当前,应用于海水淡化及分盐过程的主流分离膜材料主要通过界面聚合（IP）工艺制备,其核心组分为胺类水相单体与均苯三甲酰氯（TMC）有机相单体的聚合产物。其中,间苯二胺（MPD）是目前制备反渗透膜（RO）唯一可用的有效单体,该物质具有急性毒性且易挥发,在膜制备环节释放的MPD蒸汽,对操作人员呼吸系统易构成潜在危害,而在膜清洗过程中,其从膜中的浸出将对环境包括水体和土壤造成二次污染。尽管MPD存在诸多风险,但由于界面聚合反应所需的条件极为严苛,这使得寻找MPD替代品的研究面临严峻挑战,也在很大程度上限制了更安全单体材料的探索与开发进程。利用环保且无毒的天然提取物进行膜的合成与修饰,为解决上述问题提供了一种替代方案。然而,天然提取物的化学成分主要包含低反应活性的酚羟基和醇羟基类化合物,其难以通过聚合反应形成均匀致密的薄膜。尽管有研究者尝试在含天然提取物的界面聚合反应体系中引入催化剂,以加速反应、增强交联度,但仍无法满足反渗透膜对盐截留的极高要求。本论文针对传统反渗透膜制备中依赖于有毒胺类单体的难点问题,创新性地提出了一种新的界面催化聚合（ICP）策略,采用天然植物提取物（如单宁酸等）替代传统的有毒胺类单体,成功开发出无毒且环保的聚酯反渗透膜。与传统的聚酰胺反渗透膜相比,该类材料不仅具有较好的盐分去除性能,更彻底解决了成膜原料高毒性、高环境污染性的关键难题,推动了膜分离技术向更加绿色环保、可持续性和安全性方向发展。具体研究内容如下:1.界面催化聚合机制研究及聚酯反渗透膜的制备。反渗透膜技术作为海水淡化与废水回用的核心手段,其界面聚合工艺依赖的胺类单体（如MPD）因毒性和环境风险制约了技术可持续性。本研究针对天然提取物（如多酚）在界面聚合中反应活性低、成膜质量差的关键瓶颈,提出界面催化聚合（ICP）策略,首次利用天然提取物单宁酸（TA）制备高性能聚酯基反渗透膜,系统探究了ICP反应机制实现了高性能聚酯基RO膜的绿色制备。通过引入十六烷基三甲基氯化铵（CTAC）作为水溶性界面催化剂,其季铵基团与TA酚羟基形成离子对,通过双重作用机制（促进TA单体于界面处富集、扩散并活化酚羟基降低反应能垒）显著提升反应效率。结果表明,ICP策略制备的聚酯RO膜展现出优异的脱盐性能,其NaCl截留率达99.2%,通量为31.7 L m^-2 h^-1（15 bar）,与商业BW30膜性能相当。此外,TA衍生的聚酯膜表面更光滑,荷负电性更强,表现出更佳的抗污染能力。通过中试规模验证,卷对卷涂布工艺制备的螺旋卷式组件（0.32 m²有效面积）对市政自来水脱盐率达90.5%,主要离子去除率超95%。稳定性测试表明,TA膜连续运行18天性能无衰减,且单体渗出量较MPD基膜降低80%。以上结果验证了ICP策略制备的TA基聚酯薄膜复合膜在实际水处理中的高效脱盐能力和稳定性。与传统MPD基膜相比,TA基膜在环保性和安全性方面更具优势,不仅为反渗透膜的绿色制备提供了新思路,也为膜分离技术的可持续发展奠定了基础。2.不同催化剂和单体结构对聚酯膜分离性能的影响。在解决传统胺类单体毒性与天然材料反应活性不足的双重挑战中,ICP策略通过引入水溶性界面催化剂,成功实现了天然多酚（如单宁酸）在反渗透膜中的高效应用。然而,该策略应用于不同界面催化剂及天然单体时所制备聚酯膜的分离性能仍需系统探讨。本章通过拓展天然单体类型与界面催化剂结构,并基于ICP策略深入探究了催化剂与单体结构对聚酯膜分离性能的影响,旨在验证该策略在不同界面催化剂和天然提取物中的应用潜力。首先,在TA水相中通过引入一系列不同烷基链长的季铵盐界面催化剂（包括十二烷基三甲基氯化铵,DTAC;十四烷基三甲基氯化铵,TTAC;十六烷基三甲基氯化铵,CTAC;十八烷基三甲基氯化铵,OTAC;二十二烷基三甲基氯化铵,BTAC）,系统研究了它们对聚酯薄膜复合膜结构与性能的影响,揭示了界面催化剂的构效关系。结果表明,界面催化剂烷基链长度的最优值（16个碳原子）,并证实了不同界面催化剂均能有效调控界面聚合过程。其次,本章节还扩展了ICP策略的应用范围,考察了多种天然来源的酚类和醇羟基类单体（如表没食子儿茶素没食子酸酯、没食子酸、花青素、葡萄糖等）在ICP过程中的反应行为。实验结果发现,CTAC作为水溶性界面催化剂能显著促进这些天然单体的聚合反应,形成均匀致密的聚酯薄膜。酚类单体因多个酚羟基而表现出更高的反应活性,以（-）-表没食子儿茶素没食子酸酯（EGCG）为例,ICP策略将成膜时间从IP的180 s缩短至10 s,NaCl截留率从2.3%提升至98.2%,平均孔径减小至0.39 nm;醇羟基类单体虽反应活性较低,但在CTAC催化下仍能形成具有一定分离性能的聚酯膜（如葡萄糖基膜Na₂SO₄截留率89.8%）,证实了ICP策略对羟基功能化化合物的普适性。以上结果表明,通过系统研究不同催化剂和天然单体结构对聚酯膜分离性能的影响,验证了ICP策略在多种界面催化剂和天然提取物中的适用性,为绿色膜材料的设计和制备提供了广泛的理论依据和技术支持。3.双相界面催化聚合制备耐高盐高压聚酯反渗透膜。前面章节通过ICP策略,利用天然提取物TA成功制备了高性能聚酯反渗透膜（15 bar操作压力下对2000 ppm NaCl的截留率高达99%）。然而,通过TA与TMC交联制备的聚酯反渗透膜在高盐高压下（如55 bar操作压力、32,000 ppm NaCl）聚合物网络溶胀使膜孔结构松弛导致截留率显著下降（低至80%左右）,且该酯键在酸性环境中受到质子攻击易水解断裂（p H范围较窄,仅为3～8）,从而限制了其工业化应用潜力。为了解决这个问题,本章以1,3-苯二磺酰氯（BDSC）替代TMC作为有机相单体,同时在有机相中添加双十八烷基二甲基氯化铵（DDAC）提升交联度,通过双相界面催化聚合（BICP）策略实现了耐高盐高压且耐酸的聚磺酸酯反渗透膜。实验结果表明,优化后的聚磺酸酯反渗透膜（M3）在低压（15 bar,2000 ppm NaCl）和高压（55 bar,32000 ppm NaCl）条件下对NaCl的截留率分别达98.5%和97.4%,与商业SW30膜性能接近。M3膜在20%H₂SO₄中浸泡24 h后性能无显著衰减,为其在海水淡化和酸洗处理中的应用提供了重要保障。本研究不仅攻克了聚酯膜本征缺陷,更为开发兼具高性能与环境耐受性的绿色海水淡化膜提供了新范本。该成果拓展了天然多酚在高性能分离材料中的应用边界,对推动反渗透技术向更广阔场景延伸具有重要工程价值。4.聚酯膜孔径精准调控实现锂硼分离。本章基于ICP策略,通过CTAC浓度机制,控制TA酚羟基的电离程度及参与反应的单体量,从而影响聚合反应的交联度,进而实现对聚酯膜孔直径从0.4 nm至1 nm精准调控。通过优化CTAC浓度,构建了具有亚埃（（?））级筛分能力的聚酯基锂硼分离膜（ICP-LB膜）,实现膜孔半径（0.245 nm）与锂离子（水合半径0.38 nm）、硼酸分子（Stokes半径0.16 nm）的精准匹配,构建了尺寸筛分的分离机制,突破了传统聚酰胺离子分离膜难以实现锂硼分离的瓶颈。实验结果表明,ICP-LB膜对Li⁺截留率达95.5%,硼酸截留率<25%,分离因子高达19.5,首次通过膜技术实现了锂硼的高选择性分离。基于ICP-LB膜设计的多级压力驱动分离工艺,可实现锂硼的高效回收与纯化:一级分离后锂纯度提升至75%,经二级分离可进一步提纯至90%,同时硼产品纯度超过90%。该过程不仅有效提高了锂和硼的回收纯度,同时通过物料循环利用实现了工艺的可持续性,为锂硼混合溶液的分离与提纯提供了一种高效且经济可行的解决方案。更多还原

【Abstract】 With the intensification of global water scarcity and energy transition,the importance of membrane separation technology in the field of seawater desalination and strategic resource recovery is becoming more and more prominent.Currently,the mainstream separation membrane materials applied in desalination and salt separation processes are mainly prepared by interfacial polymerization（IP）process,whose core components are the polymerization products of amine aqueous monomers and 1,3,5-Benzenetricarboxylic acid chloride（TMC）organic phase monomers.Among them,m-phenylenediamine（MPD）is currently the only effective monomer available for the preparation of reverse osmosis membranes.The substance is acutely toxic and volatile,and the MPD vapors released in the membrane preparation process are potentially hazardous to the respiratory system of the operators,while its leaching from the membrane will cause secondary pollution to the environment,including water bodies and soil.Despite these risks,finding alternatives to MPD has been challenging due to the stringent conditions of the interfacial polymerization reaction,which has largely hindered the exploration and development of safer monomer materials.Synthesis and modification of membranes using environmentally friendly and non-toxic natural extracts provide an alternative solution to the above problem.However,the chemical composition of natural extracts mainly contains polyphenols and hydroxyl compounds with low reactivity,which make it difficult to form uniform and dense membranes.Although some researchers have attempted to introduce catalysts into the interfacial polymerization reaction system containing natural extracts in order to accelerate the reaction and enhance the degree of cross-linking,they still fail to satisfy the extremely high requirements of reverse osmosis（RO）membranes in terms of salt retention.Aiming at the difficult problem of relying on toxic amine monomers in the preparation of traditional reverse osmosis membranes,this thesis innovatively proposes a new interfacial catalytic polymerization（ICP）strategy,which employs natural plant extracts（e.g.,tannic acid,etc.）to replace traditional toxic amine monomers,and successfully develops non-toxic and environmentally friendly polyester reverse osmosis membranes.Compared with the traditional polyamide reverse osmosis membrane,this kind of material not only has better salt removal performance,but also completely solves the key problem of high toxicity and environmental pollution of membrane-forming raw materials,and promotes the development of membrane separation technology in the direction of greener,more sustainable and safer.Specific research content is as follows:1.Research on the mechanism of interfacial catalytic polymerization and preparation of polyester reverse osmosis membranes.Reverse osmosis（RO）membrane technology,as a core tool for seawater desalination and wastewater reuse,relies on amine monomers（e.g.,MPD）for its interfacial polymerization process,which constrains the sustainability of the technology due to toxicity and environmental risks.In this study,we propose an interfacial catalytic polymerization（ICP）strategy to address the key bottlenecks of low reactivity and poor film-forming quality of natural extracts（e.g.,polyphenols）in interfacial polymerization,and for the first time,we utilize natural extracts such as tannins（TA）to prepare high-performance polyester-based reverse osmosis（RO）membranes,and systematically investigate the ICP reaction mechanism to realize the green preparation of high-performance polyester-based RO membranes.By introducing cetyltrimethylammonium chloride（CTAC）as a water-soluble interfacial catalyst,its quaternary ammonium group formed ion-pair with the phenolic hydroxyl group of TA,which significantly enhanced the reaction efficiency through the dual-action mechanism（to promote the enrichment and diffusion of TA monomer at the interface and to activate the phenolic hydroxyl group to lower the reaction energy barrier）.The results showed that the polyester RO membranes prepared by the ICP strategy exhibited excellent desalination performance with 99.2%NaCl retention and a flux of 31.7 L m^-2 h^-1（15 bar）,which was comparable to that of commercial BW30 membranes.In addition,the TA-derived polyester membrane has a smoother surface and stronger charge-negativity,showing better resistance to contamination.Through pilot-scale validation,the spiral rolled module（0.32 m²effective area）prepared by roll-to-roll coating process achieved a desalination rate of90.5%for municipal tap water,with a major ion removal rate of over 95%.The stability test showed that the TA membrane operated continuously for 18 days without performance degradation,and the monomer exudation was 80%lower than that of the MPD-based membrane.The above results verified the efficient desalination capability and stability of TA-based polyester film composite membranes prepared by ICP strategy in practical water treatment.Compared with the traditional MPD-based membrane,the TA-based membrane has more advantages in environmental protection and safety,which not only provides a new idea for the green preparation of reverse osmosis membrane,but also lays a foundation for the sustainable development of membrane separation technology.2.Effects of different catalysts and monomer structures on the separation performance of polyester membranes.In addressing the dual challenges of toxicity of traditional amine monomers and insufficient reactivity of natural materials,the ICP strategy has successfully realized the efficient application of natural polyphenols（e.g.,tannins）in reverse osmosis（RO）membranes through the introduction of water-soluble interfacial catalysts.However,the separation performance of polyester membranes prepared when this strategy is applied to different interfacial catalysts and natural monomers still needs to be systematically explored.In this chapter,the effects of catalyst and monomer structures on the separation performance of polyester membranes were investigated in depth by expanding the types of natural monomers and interfacial catalyst structures and based on the ICP strategy,aiming to validate the potential application of this strategy to different interfacial catalysts and natural extracts.Firstly,a series of quaternary interfacial catalysts with different alkyl chain lengths（including DTAC,TTAC,CTAC,OTAC and BTAC）were systematically investigated in the aqueous phase of TA,and their effects on the structure and properties of polyester membrane composites were investigated,which revealed the conformational relationships of interfacial catalysts.The results show the optimal value of alkyl chain length（16 carbon atoms）for the interfacial catalysts and confirm that all the different interfacial catalysts can effectively regulate the interfacial polymerization process.Secondly,this chapter also extends the application of the ICP strategy by examining the reaction behavior of a variety of phenolic and alcoholic monomers of natural origin（e.g.,epigallocatechin gallate,gallic acid,anthocyanin,glucose,etc.）in the ICP process.It was found that CTAC as a water-soluble interfacial catalyst significantly promoted the polymerization reaction of these natural monomers to form uniform and dense polyester films.Phenolic monomers showed higher reactivity due to multiple phenolic hydroxyl groups,and the ICP strategy shortened the film formation time from 180 s to10 s for EGCG,increased the NaCl retention rate from 2.3%to 98.2%,and reduced the average pore size to 0.39 nm,for example.Alcohol monomers,although with lower reactivity,were still able to form polyester membranes with certain separation properties catalyzed by CTAC（e.g.Glucose-based membrane Na₂SO₄ retention rate of89.8%）,confirming the universality of the ICP strategy for hydroxyl-functionalized compounds.The above results indicate that the applicability of the ICP strategy in a variety of interfacial catalysts and natural extracts has been verified by systematically investigating the effects of different catalysts and natural monomer structures on the separation performance of polyester membranes,which provides a broad theoretical basis and technical support for the design and preparation of green membrane materials.3.Preparation of high salt and high-pressure resistant polyester reverse osmosis membranes by catalytic polymerization at biphasic interfaces.In the previous section,high-performance polyester reverse osmosis membranes（99%retention of 2000 ppm NaCl at 15 bar operating pressure）were successfully prepared by the ICP strategy using the natural extract TA.However,the polyester RO membranes prepared by cross-linking TA with TMC showed a significant decrease in the retention rate（down to about 80%）due to the relaxation of the membrane pore structure by swelling of the polymer network under high salt pressures（e.g.,55 bar,32,000 ppm NaCl）,and the ester bond was susceptible to hydrolysis and rupture by proton attack in acidic environments（narrow pH range of pH 3～8）,thus this limits its industrialization potential.In order to solve this problem,in this chapter,1,3-benzenedisulfonyl chloride（BDSC）was used to replace TMC as the monomer in the organic phase,and dioctadecyl dimethyl ammonium chloride（DDAC）was added to the organic phase to enhance the cross-linking degree,so that poly（sulfonic ester）reverse osmosis membranes resistant to high salt and high pressure as well as acid were realized by the strategy of biphasic interfacial catalytic polymerization（BICP）.The optimized polysulfonate reverse osmosis membrane（M3）was found to retain 98.5%and 97.4%of NaCl at low pressure（15 bar,2000 ppm NaCl）and high pressure（55 bar,32000 ppm NaCl）,respectively,which is close to the performance of the commercial SW30 membrane,and no significant degradation of the performance of the M3 membrane was found after immersion in 20%H₂SO₄ for 24 h,which is a good solution for its application in high salinity and high pressure.The performance of M3 membrane after immersion in 20%H₂SO₄ for 24 h has no significant attenuation,which provides an important guarantee for its application in seawater desalination and pickling treatment.This study not only overcomes the intrinsic defects of polyester membranes,but also provides a new paradigm for the development of green seawater desalination membranes with both high performance and environmental tolerance.This achievement expands the application boundary of natural polyphenols in high-performance separation materials,which is of great engineering value to promote the extension of reverse osmosis technology to a wider scenario.4.Precise regulation of polyester membrane pore size for lithium-boron separation.In this chapter,based on the ICP strategy,the ionization degree of TA phenolic hydroxyl group and the amount of monomer involved in the reaction were controlled through the mechanism of CTAC concentration,thus affecting the cross-linking degree of the polymerization reaction,and thus realizing the precise regulation of the pore size of polyester membranes from 0.4 nm to 1 nm.By optimizing the concentration of CTAC,the polyester-based lithium-boron separation membrane（ICP-LB membrane）with sub-（?）screening ability was constructed,and the precise matching of the membrane pore size（0.245 nm）with lithium ions（hydration radius of 0.38 nm）and boron（stokes radius of 0.16 nm）was achieved,so as to construct a separation mechanism of size screening,and break through the bottleneck of the lithium-boron separation that is difficult to be realized by the traditional polyamide ion separation membrane.The experimental results show that the ICP-LB membrane has a retention rate of 95.5%for Li⁺and<25%for boric acid,and the separation factor is as high as19.5,which is the first time to realize the highly selective separation of lithium and boron by membrane technology.The multi-stage pressure-driven separation process based on ICP-LB membrane design can realize the efficient recovery and purification of lithium and boron:the purity of lithium can be increased to 75%after the first stage of separation,and can be further purified to 90%after the second stage of separation,while the purity of boron product is more than 90%.This process not only effectively improves the recovery purity of lithium and boron,but also realizes the sustainability of the process through material recycling,providing a highly efficient and economically feasible solution for the separation and purification of lithium and boron mixed solutions.更多还原