【作者】 白雪；

【导师】 潘建明；

【作者基本信息】 江苏大学 ， 环境科学与工程， 2023， 博士

【摘要】 控制化石能源的使用,促进可替代新能源和清洁能源的发展符合资源开发与环境保护协同发展的主题。核能作为一种能量密度高的绿色能源,其广泛应用可以极大地缓解我国的能源短缺问题。海水中已探明的铀资源含量比陆地铀矿中高出1000倍以上,从海水中提铀是可以确保铀资源长期供应及核能可持续发展的潜在方法,是提高能源安全的战略性策略。吸附法因其吸附效率高、操作简单、成本低和绿色环保等优点成为海水中铀酰离子提取的有效方法之一。但吸附法用于海水中铀酰离子提取时面临诸多挑战,例如海水中铀酰离子的浓度极低（仅3.3 ppb）且以Ca₂UO₂（CO₃）₃或[UO₂（CO₃）₃]^4-的形式稳定存在、共存离子种类和数量多等。因此,制备高性能吸附剂以实现海水中铀酰离子的高效选择性分离富集具有战略意义,是环境科学领域的重要研究课题之一。偕胺肟功能化吸附剂因对铀酰离子的高特异性吸附性能而备受关注,随后偕胺肟功能化中空或多孔吸附剂和偕胺肟功能化水凝胶吸附剂等应运而生。但现有的上述海水提铀功能化吸附剂仍存在以下问题没有解决:（1）吸附剂制备和洗涤过程复杂,易产生二次污染,不符合绿色化学发展理念;（2）吸附剂对铀酰离子的吸附速率和吸附容量还有待进一步提高;（3）吸附剂对铀酰离子的辨识活性还需要强化,相应的机制需要深入研究。基于此,本工作以液气液滴反应器制备中空/多孔偕胺肟功能化吸附剂为主线,设计合成了三类用于选择性提铀的吸附剂,阐明了吸附剂结构调控和性能强化的机制,为推动吸附提铀研究提供了理论和技术支撑。本论文主要研究内容如下:1、溶剂混合诱导的液气液滴反应器制备功能化中空吸附剂及其选择性提铀研究（1）首先,利用溶剂混合诱导生成的液气液滴反应器,基于多巴胺的黏附效应和自聚制备了聚多巴胺（PDA）纳米碗,探索了转速、醇的种类、醇的用量及混合醇的使用等对PDA纳米颗粒形貌的影响。其次,选择2-氨基-3,5-二乙烯基苯腈为功能单体,利用PDA纳米碗的光热纳米约束效应和自身的自由基,经光引发自由基聚合（FRP）制备了氨基-偕胺肟功能化碗状纳米吸附剂（NH₂-AO-PDAbawl）,并用于铀酰离子的选择性提取。最后,通过静态吸附实验探讨了NH₂-AO-PDAbawl对铀酰离子的吸附行为。结果表明,在p H为6.0时NH₂-AO-PDAbawl对铀酰离子具有最大的吸附容量,在30 min内即可达到吸附平衡,吸附动力学数据符合准二级动力学模型,Langmuir吸附模型拟合计算在298 K时其对铀酰离子的最大单层吸附容量为507.0 mg/g。此外,NH₂-AO-PDAbawl在竞争离子存在下对铀酰离子具有优异的吸附选择性,且在六次吸附-脱附循环后仍具有高的吸附效率,表明NH₂-AO-PDAbawl对铀酰离子具有吸附再生性。（2）以氧化石墨烯（GO）纳米片为载体,利用溶剂混合诱导生成的液气液滴反应器在纳米片上的黏附原位生成中空模板,基于多巴胺的自聚及其氨基与GO纳米片表面的羧基形成的共价键,制备了结构稳定的纳米片原位生长纳米颗粒的复合材料。利用Schiff碱反应和自由基聚合反应制备了双偕胺肟功能化的吸附剂（ad AO-HPDA/RGO）,并通过静态吸附实验考察了其对铀酰离子的吸附性能。结果表明,吸附过程符合Langmuir等温吸附模型和准二级动力学模型,说明ad AO-HPDA/RGO对铀酰离子吸附以单层的化学吸附为主,吸附热力学结果说明该吸附过程是熵增、吸热的自发过程。在298 K和p H=6.0条件下,ad AO-HPDA/RGO在35 min内的最大吸附容量为581.3 mg/g,在模拟海水条件下对铀酰离子具有吸附选择性,七次吸附-脱附循环后吸附剂对铀酰离子的吸附容量较第一次循环中吸附容量仅降低7.4%,且其结构保持不变,说明该吸附剂具有良好的吸附再生性和稳定性。XPS结果表明,吸附机理是吸附剂中含O和含N官能团与铀酰离子的配位作用。2、水包CO₂ Pickering液气液滴反应器制备功能化多孔中空吸附剂及其选择性提铀的研究（1）基于水包CO₂Pickering液气液滴反应器和两步接枝聚合制备了具有高密度偕胺肟位点的功能化多孔中空聚合物微球吸附剂（AO-HP-MF）,并用于铀酰离子的选择性分离富集。在本工作中,经化学反应原位生成的CO₂气泡被用作制备中空结构的模板,二氧化硅纳米颗粒作为液气液滴反应器的稳定剂和多孔聚合物的成孔模板。同时,接枝的聚乙烯亚胺（PEA）链为偕胺肟官能团的后修饰提供了大量位点。AO-HP-MF具有质量密度小、尺寸均一、功能位点密度高等优点,同时还具有吸附速率快、吸附容量高和优异的吸附选择性等性能,298 K条件下的吸附平衡时间和最大吸附容量分别为1.0 h和162.6 mg/g。基于铀酰离子和偕胺肟官能团螯合的单层化学吸附是选择性吸附铀酰离子的主要机制。更重要的是,即使模拟溶液中存在大量Ca²⁺、Mg²⁺、Na⁺和Zn²⁺离子,AO-HP-MF对铀酰离子也具有显著的选择性。此外,经七次吸附-脱附循环后,AO-HP-MF对铀酰离子仍具有高的吸附容量和脱附效率,表明具有良好的吸附再生性。（2）利用二氧化硅纳米颗粒稳定的水包CO₂ Pickering液气液滴反应器和随后的两步接枝聚合制备了氨基-偕胺肟功能化“莲藕”型多孔中空聚合物微球吸附剂（NH₂@AO-PLRMS）。证实了二氧化硅纳米粒子作为Pickering乳化剂、表面成孔剂和内部“莲藕”结构调节剂的重要作用。“莲藕”型孔道取决于水包CO₂Pickering液气液滴反应器中压缩CO₂气泡的界面强度和渗透率。得益于“莲藕”型结构和丰富的亲和位点,NH₂@AO-PLRMS在298 K下的最大吸附容量为1214.5 mg/g,并且在30 min内即可完成超快的吸附过程。静态吸附实验研究表明,该过程是一个自发、熵增和吸热的化学过程,偕胺肟和氨基的协同作用可以提高吸附剂对铀酰离子的吸附选择性。特别地,NH₂@AO-PLRMS在七次吸附-脱附循环后仍显示高的铀酰离子吸附能力和脱附效率。3、水包空气液气液滴反应器制备偕胺肟功能化多孔水凝胶基吸附剂及其选择性提铀研究（1）报道了一种基于自乳化水包空气高内相液气液滴反应器构建偕胺肟（AO）功能化多孔水凝胶吸附剂（GMPAO）的新方法,并将其用于水溶液中铀酰离子的高效提取。卷曲的、具有两亲性的甲基丙烯酰明胶（Gel MA）链同时发挥Pickering乳化剂和分子表面活性剂的作用,具有稳定水/空气界面和自乳化的能力。所制备的GMPAO表现出具有内部交联孔道（尺寸分布在55μm到75μm之间的大约占70%）的开孔结构（直径在200μm到300μm之间约占80%）,聚偕胺肟（PAO）通过与Gel MA之间的链缠绕固定在水凝胶基质中,同时还可增强水凝胶的机械强度。得益于具有内部交联孔道的多孔结构和丰富的亲和位点,GMPAO在298 K下的最大铀酰离子吸附容量为386.6 mg/g,且在60 min内即可达到吸附平衡,这优于先前报道的水凝胶基吸附剂。此外,在竞争离子存在的情况下,GMPAO水凝胶吸附剂可以实现对铀酰离子的选择性吸附,且吸附效率几乎达到100%。对吸附剂进行五次吸附-脱附循环之后仍有较高的铀酰离子吸附容量,说明该吸附剂具有良好的吸附再生性。此外,除了铀酰离子与偕胺肟官能团的配位外,Gel MA中的羧基可通过电荷相互作用协同吸附铀酰离子,增强了吸附剂与铀酰离子结合的亲和力。（2）首先,通过对亲水微凝胶接枝双键的疏水化改性,制备了具有稳定液气界面能力的、可聚合的微凝胶纳米颗粒,并将其作为Pickering粒子,基于水包空气Pickering高内相液气液滴反应器制备了一种具有丰富活性位点的新型多孔水凝胶基吸附剂,经多巴胺溶液浸泡处理得到了具有水下黏附特性的多孔水凝胶吸附剂（PAOmgel）。该吸附剂的水下黏附性基于在较高温度时微凝胶的疏水性实现,而在较低温度时微凝胶呈现亲水性,避免了对吸附性能的影响。利用聚合形成的链与聚偕胺肟（PAO）链的缠绕实现了功能化水凝胶的制备,同时有利于增强水凝胶吸附剂的机械性能。所制备的吸附剂对溶液中铀酰离子具有快速（<50 min）、高效（97.8%）和高吸附容量（475.3 mg/g）的吸附,这远快于其他偕胺肟功能化水凝胶基吸附剂的吸附速率。此外,PAOmgel还表现出对铀酰离子高的吸附选择性和吸附再生性。更多还原

【Abstract】 Controlling the use of fossil fuels and promoting the development of alternative new and clean energy are in line with the theme of coordinated development of resource development and environmental protection.Nuclear energy,as a green energy with high energy density,its wide application can greatly alleviate the energy shortage in our chuntry.The proven uranium resource content in seawater is more than 1000 times higher than that in uranium mines.Extracting uranium from seawater is a potential method to ensure long-term uranium resource supply and sustainable development of nuclear energy,and is a strategic enrichment to improve energy security.Adsorption has become one of the effective methods for extracting uranium from seawater due to its advantages of high adsorption efficiency,simple operation,low cost,and environmentally friendly.However,the adsorption method faces many challenges when extracting uranium from seawater,such as extremely low concentrations of uranium in seawater（only 3.3 ppb）and stable existence in the form of Ca₂UO₂（CO₃）₃or[UO₂（CO₃）₃]^4-,as well as a large variety and quantity of coexisting ions.Therefore,the preparation of high-performance adsorbents to achieve efficient and selective separation and enrichment of uranium in seawater is of great strategic significance and is one of the important research topics in the field of environmental science.Amidoxime functionalized adsorbents have attracted much attention due to their highly specific adsorption performance for uranum.The resulting amidoxime functionalized hollow or porous adsorbents and amidoxime functionalized hydrogel adsorbents have emerged.However,the existing functional adsorbents for uranium extraction from seawater still have the following problems unsolved:（1）The preparation and washing process of the adsorbent is complex,which is easy to cause secondary pollution and does not conform to the development concept of green chemistry;（2）The adsorption rate and capacity of the adsorbent for uranium still need to be further improved;（3）The recognition activity of adsorbents for uranium still needs to be strengthened,and the corresponding mechanisms need to be further studied.Based on this,this work focuses on the preparation of hollow or porous amidoxime functionalized adsorbents in a gas in liquid droplet reactor.Three types of adsorbents for selective uranium extraction were designed and synthesized,elucidating the mechanisms of adsorbent structure regulation and performance enhancement,providing theoretical and technical support for promoting research on uranium extraction.The main research contents of this thesis are as follows:1、Preparation of functionalized hollow adsorbents based on a gas in liquid droplet reactor induced by solvent mixing and its selective adsorption of uranium（1）Firstly,polydopamine（PDA）nanobowls were prepared using a gas in liquid droplet reactor induced by solvent mixing based on the adhesion effect and self-polymerization of dopamine.The effects of homogeneous speed,types of alcohols,amount of alcohols,and use of mixed alcohols on the morphology of PDA nanoparticles were explored.Secondly,2-amino-3,5-divinylbenzonitrile was selected as the functional monomer,and amino-amidoxime functionalized bowl shaped nano-adsorbent（NH₂-AO-PDAbawl）was prepared through photoinitiated free radical polymerization（FRP）using the photothermal nano confinement effect of PDA nanobowl and its own free radicals,and was used for selective extraction of uranium.Finally,the adsorption behavior of NH₂-AO-PDAbawl on uranium was investigated through static adsorption experiments,including the effect of p H,adsorption kinetics,adsorption equilibrium,adsorption thermodynamics,adsorption selectivity,and adsorption regeneration.The results showed that NH₂-AO-PDAbawl had the maximum adsorption capacity for uranium at a p H of 6.0,and the adsorption equilibrium could be achieved within 30 min.The adsorption kinetics data followed a pseudo-second-order kinetic model,and the Langmuir adsorption model showed that its maximum single-layer adsorption capacity for uranium was 507.0 mg/g at 298 K.In addition,NH₂-AO-PDAbawl exhibits excellent adsorption selectivity for uranium in the presence of competitive ions,and still exhibits high adsorption efficiency after 6 adsorption-desorption cycles,indicating that NH₂-AO-PDAbawl has good adsorption regeneration ability for uranium.（2）Graphite oxide（GO）nanosheets were used as carriers,and hollow templates were generated on the nanosheets in situ by the adhesion of gas in liquid droplet reactor induced by solvent mixing.Based on the self-polymerization of dopamine and the covalent bond formed by the amino group and the carboxyl group on the surface of GO,a composite material with stable structure was prepared for in situ growth of nanoparticles on nanosheet.A functionalized adsorbent（ad AO-HPDA/RGO）was prepared using Schiff base reaction and FRP,and its adsorption performance for uranium was investigated through static adsorption experiments.The results show that the adsorption process conforms to Langmuir model and pseudo-second-order model,indicating that the adsorption of uranium by ad AO-HPDA/RGO is dominated by single-layer chemisorption,and the adsorption thermodynamic results indicate that the adsorption process is a spontaneous endothermic process with entropy increase.At 298K and p H=6.0,the maximum adsorption capacity of ad AO-HPDA/RGO was 581.25mg/g within 35 min.Under simulated seawater conditions,ad AO-HPDA/RGO exhibited adsorption selectivity for uranium.After 7 adsorption-desorption cycles,the adsorption capacity of the adsorbent for uranium decreased by only 7.4%compared to the first cycle,and its structure remained unchanged,indicating that the adsorbent has good adsorption regeneration and stability.The XPS results indicate that the adsorption mechanism is the coordination between the O-containing and N-containing functional groups of the adsorbent and uranium.2、Preparation of functionalized hollow porous adsorbent based on CO₂ in water Pickering dropper reactor and its selective uranium extraction（1）Conventional methods for preparing amidoxime-based hollow porous sorbents（HPS）for uranium extraction usually use a solution or emulsion process with surfactant and expensive pore template,so they cannot meet requirements of economic and environmentally friendly evaluation.Here,hollow porous microspheres functionalized with abundant amidoxime（AO-HP-MF）are prepared via CO₂ in water Pickering dropper reactor interfacial polymerization and assembly of site chains for highly efficient uranium extraction.For this strategy,in situ generated CO₂ bubbles are utilized as a core template,and Si O₂ nanoparticles serve dual roles of an emulsion stabilizer and pore template for polymer shell.Meanwhile,assembled polyvinyl polyamine（PEA）chains provide lots of sites for post-modification with amidoxime.Taking the advantages of well-defined hollow porous morphology,uniform size,and high density of amidoxime,AO-HP-MF is expected to possess excellent adsorption capacity,fast equilibrium rate,and high selectivity.The equilibrium time and maximum adsorption capacity are 1.0 h and 162.6 mg/g at 298 K,respectively,and the monolayer chemisorption based on chelation between uranium and amidoxime is the main mechanism of selective uranium extraction.Their uniform size may be associated with the pressure-dependent formation condition of in situ generated CO₂ bubbles,which is different from traditional emulsion-templated microspheres with fairly irregular sizes.Most importantly,AO-HP-MF has remarkable selectivity for uranium,even if massive amounts of Ca²⁺,Mg²⁺,Na⁺,Zn²⁺,and other ions exist in the simulated solution.Therefore,this work not only presents a new clue to fabricating high-performance sorbents via a simple gas in liquid dropper reactor but also provides a novel platform for uranium extraction.（2）Simultaneous construction of porous and hollow adsorbent,especially from gas in water Pickering dropper reactor,is vital for improving mass transfer kinetics and uptake amount.Inspired by the formation process of stalagmites in karst cave,amino,and amidoxime bi-functionalized lotus root-type microsphere with the porous surface（NH₂@AO-PLRMS）is prepared by the silica nanoparticles stabilized CO₂-in-water Pickering dropper reactor and subsequent two-step grafting polymerization.The important roles of silica nanoparticles acting as Pickering emulsifiers,surface pore-forming agents,and adjusting internal lotus root structure are confirmed.Lotus root-type pores are dependent on the interface intensity and the permeability of compressed CO₂bubbles in the CO₂-in-water Pickering dropper reactor.Benefitting from the lotus root-type structure and abundant affinity sites,the maximum uranium adsorption capacity of NH₂@AO-PLRMS is 1214.5 mg/g at 298 K,and an ultrafast uptake process can be achieved in the first 30 min.Both thermodynamic and kinetic studies indicate a spontaneous,entropy-increased,and endothermic chemisorption process,and the synergies of amidoxime and amino groups can enhance the adsorption selectivity.Remarkably,NH₂@AO-PLRMS displays a high uranium adsorption capacity and desorption efficiency after seven cycles.3、Preparation of porous hydrogel-based adsorbent functionalized with amidoxime and its selective uranium extraction in air-in-water droplet reactor（1）A convenient design of amidoxime（AO）functionalized hydrogel-based adsorbent containing interconnected pores is critical for facilitating fast and selective uranium extraction.To address this,the AO functionalized macroporous hydrogel sorbents（GMPAO）are constructed by air-in-water high internal phase dropper reactor（HIPEs）,and used for highly efficient extraction of uranium from aqueous solution.Curled gelatin methacryloyl（Gel MA）chains,as amphiphilic Pickering emulsifier and molecular surfactant,endow self-emulsifying ability to stabilize the air/water interface.GMPAO exhibits an open-cell structure（diameter is about 80%between 200μm and300μm）with interconnecting pores（distribution is about 70%between 55μm and 75μm）,and the chain entanglement between polyamidoxime（PAO）and Gel MA enhances mechanical strength.Benefitting from the macroporous structure and abundant affinity sites,GMPAO displays a spontaneous uranium adsorption capacity of 386.6 mg/g at298 K and faster uptake within 60 min,which are superior to better than the previously reported hydrogel-based adsorbent.In addition,GMPAO still achieves the highest capacity and remarkable removal rate of almost 100%towards uranium in the presence of competitive ions,as well as excellent recyclability toward uranium capture.Except for the coordination between uranium with amidoxime groups,the carboxylates from Gel MA also cooperate as a synergistic effect for uranium uptake by charge interaction,which enhances the binding affinity of the adsorbent to uranium.Most importantly,this work demonstrates a new strategy for preparing macroporous hydrogel-based adsorbent with enough stability and provides a new perspective for recovering uranium from an aqueous solution.（2）Firstly,this work prepared the polymerizable microgel nanoparticles with the ability to stabilize the liquid/gas interface by hydrophobic modification of hydrophilic microgel and grafting double bonds,which were used as Pickering particles,and a novel porous hydrogel-based adsorbent with abundant active sites was prepared based on the air in water Pickering high internal phase droplet reactor.The porous hydrogel-based adsorbent（PAOmgel）with underwater adhesion characteristics was obtained by dopamine immersion.The underwater adhesion of the adsorbent is based on the hydrophobicity of the microgel at a higher temperature,while the microgel is hydrophilic at a lower temperature,which avoids the influence on the adsorption performance.The functionalized hydrogel was prepared by winding the polymerized chain with the PAO chain,which also was conducive to enhancing the mechanical properties of the hydrogel-based adsorbent.The prepared adsorbent can quickly（<50min）achieve high adsorption efficiency（97.8%）and high adsorption capacity（475.3mg/g）for uranium,which is much faster than the adsorption kinetic of other amidoxime functionalized hydrogel-based adsorbents.In addition,PAOmgel also exhibits high adsorption selectivity and adsorption regeneration for uranium.更多还原