【作者】 唐敏；

【导师】 万金泉；

【作者基本信息】 华南理工大学 ， 环境科学与工程， 2024， 博士

【摘要】 水体中的有机微污染物（Organic micropollutants,OMPs）具有浓度低、持久性强和难生物降解特性,其大量积累会对生态系统构成威胁。非均相高级氧化技术（Advanced oxidation processes,AOPs）可彻底去除水中OMPs。目前,非均相AOPs存在催化性能有限、活性物种利用率低和降解反应速率慢等问题。针对这些问题,本文提出构建基于限域效应的高级氧化体系,实现OMPs特异性吸附、氧化传质强化以及催化降解反应能垒降低,从而提高OMPs降解效率。本文研究内容和主要结论如下:通过表面聚合的方法在铁基金属有机框架上构建分子印迹层,制备了具有分子印迹孔穴的核壳结构MIC（Molecular imprinting catalyst）催化剂。MIC在多污染物混合体系中对目标污染物磺胺甲恶唑（Sulfamethoxazole,SMX）表现出吸附选择性。MIC活化过硫酸盐（Persulfate,PS）对SMX的降解率高达95%,与NIC（Non-imprinting catalyst）/PS体系相比,MIC/PS体系的降解率提高了5倍以上,MIC/PS体系在自来水和污染河水中对SMX的去除率达到90%以上。MIC通过印迹孔穴的形状识别以及氢键、π-π堆叠等弱相互作用选择性吸附SMX,形成的表面限域效应缩短了自由基到污染物的传质距离,既提高了活性氧物种（Reactive oxygen species,ROS）SO₄^-·和·OH的利用率,因此强化催化氧化过程。此外,该催化体系降解产物的毒性降低。MIC表现出良好的稳定性,在p H3.0～9.0范围内实现高效降解,对制药废水COD降解率可达66.67%。为进一步促进ROS的传质,在MIC催化剂中引入了纳米孔道制备了一种具有纳米印迹孔道的MIC-#催化剂。MIC-#对SMX的最大吸附容量达到276.71 mg/g,印迹因子大于2.04,降解效率达到97%,表现出吸附选择性和高效降解性。此外,MIC-#/PS体系对模拟废水、自来水和污染河水中SMX的去除率保持在91%以上。孔道限域效应通过加速传质将SMX富集在孔道中,催化体系产生的SO₄^-·、·OH和¹O₂会持续地多位点攻击SMX及其中间产物,使TOC矿化率达到78%,实现了污染物的高效降解。MIC-#在5次循环实验中对SMX的吸附和降解效率仍然保持稳定,且Fe离子的溶出量低。进一步将MIC-#填充在连续流反应器中,对水中SMX的去除率高达97%以上。为缩短PS的活化传距离,合成了分子印迹聚合物MI-PDA,MI-PDA在多污染物共存环境中对SMX表现出良好的选择性吸附性能（印迹因子大于1）,MI-PDA/PS体系对SMX的降解率达到95%以上,降解速率常数相比于非印迹的NI-PDA/PS体系提高了9.23倍。PS活化和SMX降解发生在同一界面形成界面限域效应,使得SMX倾向于吸附在MI-PDA的N位点上,N原子上的电子会重新分布到PS的O原子上,导致PS的S–O键断裂而生成¹O₂。同时,MI-PDA原位催化缩短了PS传质距离,加快了传质和降解。MI-PDA具有良好的催化稳定性,其降解过程不受水体中Cl^–、NO₃^–和腐殖酸的影响,MI-PDA/PS体系在自来水、河水和制药废水中对SMX的降解率均达到80%以上。通过将Fe₂O₃负载在中空碳球的纳米孔道中制备了一种具有中空-纳米限域结构的NC-IN催化剂,进一步探究限域效应对催化中心电子结构的影响。实验表明,NC-IN/PS体系对SMX的降解率为100%,降解速率常数可达6.25 min^-1,比非限域催化体系的降解速率提高了3个数量级,表现出超快的降解速率。由于中空碳球曲率改变了孔道内的电子结构,导致纳米孔道内外电子电位差增大,加速催化过程的电子传递,PS被快速的分解并生成¹O₂,孔道内的SMX的降解反应能垒降低了31 kcal/mol,因此加速了SMX的降解。同时中空-纳米限域效应使SMX、PS和水分子的均方根位移明显减小,实现了超快扩散传质。NC-IN/PS体系也可100%去除药品及个人护理用品、阻燃剂和染料等多种污染物,6次循环实验仍保持100%的SMX去除率和快速的降解速率(k_app超过4.0 min^-1),表现出优异的催化稳定性。为了进一步探究限域空间原位产生的限域能对降解过程的影响,制备了具有不同孔径大小的纳米限域印迹孔道催化剂MIC-x（x=5、10、40、70）。其中,MIC-5表现出最强的吸附性能和最好的吸附选择性,随着催化剂孔道的增大,污染物的降解效率逐步降低,其中MIC-5/PS体系表现出最佳降解效率,MIC-5/PS体系的TOC去除率较非限域体系提高了46.2%。MIC-5/PS体系中的主要ROS为SO₄^-·、·OH和¹O₂。随着孔道减小,催化体系产生的限域能增大。其中,MIC-5/PS体系产生的限域能最大,为143.6 kcal/mol,导致SMX降解反应的焓变效能提高了6.5×10⁴倍。MIC-5原位产生的限域能通过形成不完全热平衡,导致孔道内能量场的重分布,调控SMX向低能垒方向降解,加速降解速率。影响因素探究实验表明MIC-5具有选择性、抗干扰性、广泛的p H范围适用性和实际应用可行性。更多还原

【Abstract】 Organic micropollutants（OMPs）have posed threats to ecosystems in water due to their low concentration and persistence.Heterogeneous advanced oxidation processes（AOPs）are a promising technology to efficient remove OMPs from water.However,current heterogeneous AOPs face challenges such as low reactive species utilization,limited catalytic performance,and slow degradation rates.To address these issues,this study proposed the construction of an AOPs based on the confinement effect,aiming to achieve specific adsorption of OMPs,enhanced oxidation mass transfer,and reduced energy barriers for pollutant degradation.These improvements significantly enhance the degradation efficiency of OMPs.The key content and conclusions of this study are presented as follows:A molecularly imprinted core-shell（MIC）catalyst with molecular imprinting cavities was prepared on Fe-MOF through surface polymerization.The results showed that MIC exhibited selective adsorption performance towards the target pollutant sulfamethoxazole（SMX）in a mixed pollutant system.MIC activated persulfate（PS）achieved a degradation rate of 95%for SMX.Compared with NIC/PS system,the degradation rate of MIC/PS system was increased by more than 5 times.The MIC/PS system achieved a removal rate of over 90%for SMX in both tap water and polluted river water,demonstrating efficient degradation performance.Through shape recognition of the imprinting cavities,as well as weak interactions such as hydrogen bonding,π-πstacking,and electrostatic interactions,MIC selectively adsorbed SMX and formed a surface confinement effect,which shortened the mass transfer distance between the reactive oxygen species（ROS）of SO₄^-·and·OH with the pollutants,thereby enhancing the catalytic oxidation process by improving both the utilization of ROS and overcoming the rate-limiting step of Fe（III）reduction.Furthermore,the radical degradation pathway reduced the toxicity of degradation products.Finally,MIC showed excellent stability and achieved high efficiency degradation in the p H 3.0～9.0 range,and the COD degradation rate of pharmaceutical wastewater reached 66.67%.In order to further promote the mass transfer of ROS,a MIC-#catalyst with imprinted nano-channels was prepared by introducing nano-pore channels into the MIC catalyst.MIC-#exhibited a maximum adsorption capacity for SMX of 276.71 mg/g,an imprinting factor greater than 2.04,and a degradation efficiency of 97%,demonstrating both selective adsorption and efficient degradation.Moreover,the MIC-#/PS system maintained a removal rate of over 91%for SMX in simulated wastewater,tap water,and polluted river water.The confinement effect accelerated the mass transfer,enriching SMX within the channels.The generated SO₄^-·,·OH,and ¹O₂ in the catalytic system continuously attacked SMX and its intermediates at multiple sites,resulting in a TOC mineralization rate of 78%and achieving efficient degradation of pollutants.MIC-#maintained stable adsorption and degradation efficiencies for SMX after 5cycle experiments,with low leaching of Fe ions.Furthermore,when packed into a continuous flow reactor,MIC-#achieved a removal rate of over 97%for SMX in wate.To shorten the mass transfer distance of PS in the molecularly imprinted layer,a molecularly imprinted polymer（MI-PDA）was synthesized.MI-PDA exhibited excellent selective adsorption performance for SMX in a multi-pollutant coexistence environment（imprinting factor greater than 1）.The degradation rate of SMX reached over 95%in the MI-PDA/PS system,and the degradation rate constant was 9.23 times higher compared to the non-imprinted NI-PDA/PS system.PS activation and SMX degradation occur at the same interface,resulting in an interfacial limiting effect,which makes SMX tend to adsorb at the N site of MI-PDA,and electrons on the N atom will be redistributed to the O atom of PS,leading to the cleavage of the S-O bond in PS and the generation of ¹O₂.Additionally,the in-situ activation of PS by MI-PDA shortened the mass transfer distance and accelerated the degradation process.The catalytic performance of MI-PDA remained above 80%after 4 cycles.Furthermore,the catalytic process of MI-PDA was not affected by Cl^-,NO₃^-,and humic acid in the water.The MI-PDA/PS system achieved a degradation rate of over 80%for SMX in tap water,river water,and pharmaceutical wastewater.A hollow-nanoconfinement catalyst（NC-IN）was prepared by loading Fe₂O₃ into the nanochannels of hollow carbon spheres to investigate the influence of confinement effect on the electronic structure of catalytic centers.The NC-IN/PS system could completely degrade SMX within 1 min,and the degradation rate constant reached 6.25 min^-1,which was three orders of magnitude higher than that of the non-confined catalyst system,demonstrating an ultra-fast degradation rate.The increased curvature of the hollow carbon spheres led to a larger potential difference between the inner and outer regions of the nanochannel,accelerating electron transfer.PS was rapidly decomposed to generate ¹O₂,and the reaction barrier for the degradation of SMX within the nanochannels was reduced by 31 kcal/mol,thereby speeding up the degradation process.Additionally,the hollow-nanoconfinement effect reduced the root mean square displacement of SMX,PS,and water molecules,achieving ultra-fast diffusion and mass transfer.The NC-IN/PS system also achieved 100%removal of various pollutants,including pharmaceuticals and personal care products,flame retardants,and dyes.After 6 cycle experiments,the NC-IN/PS system maintained 100%SMX removal and a fast degradation rate(k_app exceeding 4.0 min^-1),demonstrating excellent catalytic stability.To investigate the influence of confinement effect generated by in-situ formation of confined spaces on the degradation process,a nanoconfined catalysts with different imprinting channels,MIC-x（x=5,10,40,70）,were prepared.MIC-5 exhibited the strongest adsorption performance and the outstanding adsorption selectivity.As the catalyst channel size increased,the degradation efficiency of pollutants gradually decreased.Among the catalysts,the MIC-5/PS system demonstrated the optimal degradation efficiency,with a 46.2%higher TOC removal rate compared to the non-confined catalytic system.The main ROS in the MIC-5/PS system were SO₄^-·,·OH,and ¹O₂.As the channel size decreased,the confinement effect generated by the catalytic system increased.The MIC-5/PS system exhibited the highest confinement effect,with a value of 143.6 kcal/mol,leading to a 6.5×10⁴-fold increase in the enthalpy change efficiency of the SMX degradation reaction.The confinement effect generated by MIC-5,through the formation of incomplete thermal equilibrium,caused the redistribution of the energy field within the nanochannel,regulating the degradation of SMX towards lower energy barriers and accelerating the degradation rate.Exploratory experiments on influencing factors demonstrated that MIC-5 had selectivity,resistance to interference,wide p H range applicability,and feasibility for practical applications.更多还原