【作者】 王凯；

【导师】 梁英； 沈军；

【作者基本信息】 四川大学 ， 建筑与土木工程（专业学位）， 2021， 硕士

【摘要】 工业生产、家庭活动产生的含油废水、有机溶剂排放和日益增多的海洋溢油事故,对生态环境和人类健康造成了巨大威胁。因此,含油污水的处理是一个亟待解决的问题。传统油水分离技术虽然可有效分离油和水,但往往耗时较长、分离效率低、能耗高和易造成二次污染等。因此,迫切需要开发高效且经济的新型油水分离功能材料。近年来,静电纺纳米纤维材料因其具有大比表面积、高孔隙率和易于调节的结构等特点,已成为低驱动压力下实现高通量油水分离的理想材料。然而,静电纺有机聚合物纤维材料的纤维强度和结合性较差,导致其机械强度往往较低。无机材料往往表现出优异的强度和特殊的浸润性。基于此,本文通过采用不同的无机材料和处理方法强化有机聚合物静电纺丝纳米纤维膜的性质,从简单的碳纳米管（CNTs）混纺到径向互穿的自锁Ti O₂纳米棒涂层的合理制备,再到多功能ZIF-8@Zn O纳米涂层的原位巧妙构建,实现了复合膜的机械强度和防污能力的极大提升,从仅增强纤维强度到同时增强纤维强度和结合性,润湿性从单一超浸润性到可逆的液下超双疏性,自清洁能力从无到紫外光自清洁再到可见光自清洁,含油污水处理能力从简单的油水混合物分离到含水溶性有机污染物的高度乳化复杂油水乳液的处理。本文工作主要分为3个部分,考察了无机材料改性对膜的力学性能和润湿性的影响,重点研究了超浸润复合膜对不同类型含油污水的分离,并探索了含水溶性有机污染物的高度乳化的复杂油水乳液的处理策略。根据复合膜的机械强度和含油污水处理难度,所制备的复合膜性能是逐步提升的,论文主要研究成果总结如下:（1）为改善纤维膜的强度和浸润性,通过共混静电纺丝法一步制备了一种碳纳米管（CNTs）强化的超疏水聚偏氟乙烯（PVDF）纳米纤维膜。研究了CNTs含量对油水选择润湿性和油水分离性能的影响,重点探究了对复合膜力学性能和稳定性的影响。研究结果表明,高机械强度的疏水CNTs与PVDF聚合物分子链间很强的相容相互作用,强化了复合膜的纤维强度、疏水性和稳定性;当CNTs浓度为2.55 mg g^-1时,复合膜具有良好的分离性能和循环稳定性,且仅在重力驱动下即可获得较高的油水分离通量。（2）为同时提高纤维的强度、结合性和膜的防污性能,通过结合同轴静电纺丝、萃取相分离和水热合成方法,制备出具有径向互穿的Ti O₂纳米棒涂层的纤维膜。该亲水纳米棒涂层由于自锁效应增强了纤维的强度和结合性,并同时赋予复合膜超亲水/水下超疏油性、紫外光驱动自清洁性能和提高抗污染能力。所得复合膜可实现对16种不同类水包油（O/W）型（包括无表面活性剂和阴离子型、阳离子型、非离子型）乳液的高效分离,兼具有良好的自清洁和重复利用性能,并对机理进行了分析。进一步探索了“分离-富集-消除”策略对含水溶性有机污染物的复杂乳液的处理,结果表明该序批式处理有利于在不同条件下充分利用复合膜的性能。（3）为进一步提高膜的防污性能和处理能力,将静电纺丝技术、浸渍涂敷和水热合成技术相结合,在PVDF纤维膜上构建了多功能ZIF-8@Zn O纳米棒涂层,这增强了纤维的强度和结合性。考察了复合膜的油水选择润湿性并分析了机理。测试表明,液体环境和ZIF-8的协同作用使得界面相互作用发生转变,导致该复合膜具有可逆的液下超双疏性。复合膜对O/W和油包水（W/O）型乳液的依次切换高分离结果表明其具有良好的切换分离效果和重复利用性能。进一步探索了“分离-富集-消除”策略对含水溶性有机污染物的复杂乳液的处理,测试表明,在连续150 min的处理中,复合膜可获得稳定的通量和污染物去除率,且在可见光照射下可实现膜的完全/无损修复。更多还原

【Abstract】 The increasing oily wastewater and discharge of organic solvents generated from industrial factory,domestic activities,and marine oil spills accidents has led to a great threat to global ecosystems and human health.Therefore,it is urgent to treat the oily wastewater.Various traditional oil-water separation technologies can effectively separate oil-water.However,significant disadvantages exist for these methods,including time-consuming,low efficiency,high energy cost,and secondary pollution,etc.Thus,an efficient and economical novel oil-water separation functional material is in urgent demand.Recently,electrospun nanofibrous materials have become an exceptional candidate for high-flux oil-water separation under low driving pressure due to their large specific surface area,high porosity and easy tunable structure.However,the electrospun organic polymer fibrous materials generally exhibit relatively low mechanical strength because of the low strength of its fiber and the weak bonding between fibers.The inorganic materials often possess excellent mechanical strength and special wettability.Based on the above analysis,various inorganic materials and modification methods are applied to reinforce the properties of electrospun organic polymer fibrous materials.There are successful efforts in reinforcing the electrospun nanofibrous membrane,from simply blend-electrospinning carbon nanotubes（CNTs）to in-situ growth of self-locked interpenetrating Ti O₂ nanorods with radial structure,and then to multifunctional ZIF-8@Zn O nanocoating.The mechanical strength and anti-fouling ability of the composite membrane have been greatly improved,from strengthening only fibers’strength to both strength and bonding.The wettability ranges from single irreversible superwettability to reversible under-liquid dual superlyophobicity.The self-cleaning capability ranges from zero to UV-driven and then visible-light-driven.The oily wastewater treatment capacity ranges from simple oil-water mixtures to highly emulsified complex oil-water emulsion with water-soluble organic pollutants in water.This work could be divided into three parts.The effects of inorganics modification on the mechanical properties,and wettability of the membrane were investigated.The separation of different types of oily wastewater by using composite membrane was studied,and the treatment strategy of complex oil-water emulsion with water-soluble organic pollutants in water was explored.According to the mechanical properties of the composite membranes and treatment difficulty,the performance of membranes are gradually improved.The main works are concluded as follows:（i）To enhance the strength and hydrophobicity of the membrane,a CNTs reinforced superhydrophobic nanofibrous membrane was successfully developed via one-step blend-electrospun.The effects of different CNTs concentrations on the oil/water selective wettability and separation performance,mechanical properties and stability of the composite membranes were investigated.Due to the good mechanical strength of CNTs,the significant chemical resistance and thermal stability for both PVDF and CNTs,and the strong compatible interaction between CNTs molecules and PVDF polymer molecules,the composite membranes exhibited enhanced hydrophobicity,excellent mechanical properties and stability.The results showed that the composite membrane exhibited good separation performance and recyclability as the concentration of CNTs was 0.15 wt%(2.55 mg g^-1).A high oil/water separation flux with good reusability was obtained only under the driving of gravity.（ii）To improve both the strength and bonding of the fibers and anti-fouling capacity of electrospinning fibrous membrane,a self-locked structured membrane with interpenetrating Ti O₂ nanorods nanocoating with radial structure was prepared by combining coaxial electrospinning,extraction phase separation and hydrothermal synthesis.This hydrophilic nanocoating improved both the fibers’strength and bonding for its self-locked structure,and endowed the composite membrane with excellent superhydrophilicity/under-water superhydrophobicity,UV-light-induced self-cleaning and improved anti-fouling performance.The composite membrane achieved the efficient separation of 16 types of oil-in-water emulsions,including surfactant-free emulsion and cationic,anion and non-ionic surfactant stabilized emulsions,and the membrane exhibited good self-cleaning performance and reusability.The separation mechanism was also analyzed.The“bait-hook-destroy”strategy was further explored to treat the composite emulsions.The results showed that the sequential batch treatment is beneficial to make full use of the properties of the composite membrane in different conditions.（iii）To further improve the anti-fouling and treatment capacity of the membrane,an in-situ growth of high-quality ZIF-8 nanocoating on porous PVDF membranes was achieved by the combination of electrospinning,dip-coating and hydrothermal synthesis.The hybrid nanocoating reinforced both the fibers’strength and bonding.The oil-water selective wettability of the composite membrane was investigated and its mechanism was analyzed.The interfacial interaction transition would occur because of the synergetic effect liquid environment and ZIF-8.The membrane exhibited switchable under-liquid dual superlyophobicity.The excellent switchable on-demand separation performance toward highly emulsified water-in-oil and oil-in-water emulsions indicated that the membrane possessed good switchable separation performance and reusability.The“bait-hook-destroy”strategy was further explored for the treatment of complex emulsion with water-soluble organic pollutants in water.As a proof-of-concept,a stable flux with high removal efficiencies（>99%）was obtained and the membrane could be completely/non-destructively reinstated by visible light irradiation during the continuous 150 min treatment process.更多还原