【作者】 王琦；

【导师】 周明华；

【作者基本信息】 南开大学 ， 环境工程， 2022， 硕士

【摘要】 基于零价铁的高级氧化法具有污染物去除效率高、反应迅速及污染物降解彻底等优点被广泛用于去除各种有害物质和废水中难降解的有机污染物。但体系中存在着氧化剂反应利用率低、环境友好性差等缺点。寻找更为经济、绿色的氧化剂是十分必要的。利用氧气（O₂）替代常规氧化剂的分子氧活化高级氧化技术已成为目前研究的热点。研究表明Fe⁰可以活化分子氧产生活性自由基。但该体系中活性自由基的产效很低、反应时间长、处理效率低,现有研究表明络合剂的存在能提高Fe⁰/O₂体系中Fe⁰的利用率,促进产生氧化物种,提高有机污染物的处理效率。本文研究了在次氮基三乙酸（NTA）、乙二胺-N,N′-二琥珀酸（EDDS）和乙二胺四乙酸（EDTA）三种胺基聚羧酸（CAs）存在下Fe⁰活化O₂对磺胺二甲嘧啶（SMT）的降解。在最佳条件下,Fe⁰/EDDS/O₂、Fe⁰/EDTA/O₂和Fe⁰/NTA/O₂体系对SMT的去除率分别为58.2%、75.3%和93.8%,远高于Fe⁰/O₂体系（1.36%）。Fe⁰/NTA/O₂体系扩大了p H的应用范围,在p H=3-7均有88.8%以上的降解率。且在三种CAs体系中检测到SMT被降解为小分子物质。CAs促进了Fe⁰/O₂体系的H₂O₂产生和分解,其中Fe⁰/NTA/O₂体系的H₂O₂的产生和分解能力最强。CAs也促进了表面Fe²⁺和溶解铁离子的生成。为了进一步探究?O₂^-在Fe⁰/CAs/O₂体系的作用,本文研究了Fe⁰/CAs/O₂体系对对硝基苯酚（PNP）的降解。三种CAs增强了Fe⁰对O₂活化和对PNP的降解,在p H=5时PNP的降解率均能达到91.8%以上,且Fe⁰/NTA/O₂体系扩大p H的应用范围,在p H=3-7均有83.7%以上的降解率。Cl^-对Fe⁰/CAs/O₂降解PNP没有影响。O₂对Fe⁰/CAs/O₂体系活性物质的产生有着重要的作用,但O₂的浓度在反应体系中需要适量。在SMT降解过程中,Fe⁰/NTA/O₂和Fe⁰/EDTA/O₂体系中的H₂O₂主要是通过双电子氧还原转移途径产生的,Fe⁰/EDDS/O₂体系中的H₂O₂主要是单电子氧还原转移途径产生的。Fe²⁺和H₂O₂均相反应产生的?OH是SMT降解的主要活性物质。Fe⁰/EDDS/O₂比Fe⁰/EDTA/O₂和Fe⁰/NTA/O₂体系产生更多的¹O₂,然而¹O₂对SMT去除的贡献很小。Fe⁰/EDDS/O₂体系和Fe⁰/EDTA/O₂体系对PNP降解的主要自由基是?O₂^-,且?O₂^-是通过单电子氧还原途径生成的。Fe⁰/NTA/O₂体系对PNP降解的主要自由基是?OH和?O₂^-,且?OH和?O₂^-均是单电子氧还原途径生成的。CAs的络合效应是影响Fe²⁺和O₂的反应速率的主要因素。CAs通过提供质子来加速电子转移和表面Fe²⁺的生成从而促进污染物的去除。本研究对揭示Fe⁰/CAs/O₂体系的氧还原机理具有重要意义。更多还原

【Abstract】 Advanced Oxidation Processes based on zero-valent iron had been widely used to treat harmful substances and organic pollutants in wastewater,which contributed to the advantages of high removal efficiency.However,there was the disadvantage in the system,like the low utilization efficiency and poor environmental issues.Hence,the economic and green oxidizing agent was essential for zero-valent iron system.The previous research demonstrated that Fe⁰ could activate the oxygen to generate free radical,which was the research focus nowadays.Whereas,the low production of free radical,long reaction time and low degradation efficiency were the disadvantage in the system.Hence,complexing agent combined the system of Fe⁰/O₂ could increase the production of free radical and pollution removal efficiency.This study combined several aminepolycarboxylic acids（CAs）,amine triacetic acid（NTA）,ethylenediamine-N,N’-disuccinic acid（EDDS）and ethylene-diaminetetraacetic acid（EDTA）,with Fe⁰ to activate the oxygen to degrade sulfamethazine（SMT）.The SMT removal efficiency in the system of Fe⁰/EDDS/O₂,Fe⁰/EDTA/O₂ and Fe⁰/NTA/O₂ was 58.2%,75.3%and 93.8%under optimal conditions,which was significantly higher than Fe⁰/O₂ system（1.36%）.The aminepolycarboxylic acids promoted the generation of surface-bound Fe²⁺and dissolved iron ions.Meanwhile,The degradation of SMT into small molecules was detected in three CAs systems.Also,p-nitrophenol（PNP）was selected as targeted pollutant to explore the role of?O₂^-in the Fe⁰/CAs/O₂ system.In the presence of three kinds of CAs,Fe⁰enhanced the activation of O₂ and degradation of PNP,and the degradation rate of PNP could reach more than 91.8%at p H=5.Moreover,Fe⁰/NTA/O₂ system expanded the application range of p H,and the degradation rate of PNP was more than 83.7%at p H=3-7.Cl^-had no effect on Fe⁰/CAs/O₂ degradation of PNP.O₂ plays an important role in the production of active substances in Fe⁰/CAs/O₂ system,but the concentration of O₂ in the reaction system needs to be appropriate.In the process of SMT degradation,H₂O₂ in Fe⁰/NTA/O₂ and Fe⁰/EDTA/O₂systems is mainly generated by the two-electron ORR transfer pathway,while H₂O₂ in Fe⁰/EDDS/O₂ system is mainly generated by the single-electron ORR transfer pathway.?OH,produced by the reaction of Both Fe²⁺and H₂O₂,is the main substance of SMT degradation.Fe⁰/EDDS/O₂ produced more ¹O₂ than Fe⁰/EDTA/O₂ and Fe⁰/NTA/O₂,but ¹O₂ contributed little to SMT removal.The·O₂^-generating through single-electron ORR pathway was the main free radical for PNP degradation in the Fe⁰/EDDS/O₂system and Fe⁰/EDTA/O₂ system.Meanwhile,·OH and·O₂^-were the main free radicals for degradation in the Fe⁰/NTA/O₂ system,and·OH was mainly generated by single-electron ORR pathway.The complexation effect of CAs is the main factor affecting the reaction rates of Fe²⁺and O₂.CAs facilitates pollutant removal by providing protons to accelerate electron transfer and surface Fe²⁺formation.This study is of great significance to reveal the ORR mechanism of Fe⁰complex system.更多还原