【作者】 陈洁；

【导师】 董浩然； 曾炜；

【作者基本信息】 湖南大学 ， 环境工程（专业学位）， 2021， 硕士

【摘要】 众所周知,在推进工业快速发展的过程中,造成我们赖以生存的地下水环境急剧恶化。三氯乙烯（TCE）和磺胺二甲嘧啶（SMT）在有机合成、燃料制造、农药生产和养殖业等领域应用广泛,是环境中较难降解、检出率高、毒性较强的两类典型污染物,会对人体造成极大的危害。针对TCE和SMT两种污染物,开发高效、经济和适应性强的的稳定的新型材料以防止二次污染在大规模实际废水处理中起着至关重要的作用。近年来,硫化铁基纳米材料由于自身的优异性能（铁是自然界丰度较大的过渡金属元素）引起了广泛的关注,为当前的环境修复领域提供新的思路,故本文采用了环境友好的硫化铁基纳米材料用于还原/氧化反应体系以去除地下水体中的有机污染物。另外,根据这两种典型的纳米颗粒的特性,深入研究了反应过程的各种影响因素的影响、催化氧化剂的途径、不同自由基降解污染物的贡献以及污染物降解的机制。本论文具体内容分为以下两部分:第一部分:本文探讨了在地下水修复的情况下,生物炭上负载硫化物修饰的纳米级零价铁（S-n ZVI@BC）去除三氯乙烯的可行性和机理。具体来说,主要研究了一些外在影响因素,如生物炭的裂解温度,S-n ZVI和BC的质量比,初始p H,典型的地下水成分,共存污染物及纳米颗粒老化时间对污染物去除的影响,结果显示不同的热解温度会改变BC的理化性质,从而影响S-n ZVI@BC对TCE的吸附和降解。另外,质量比为3:1的S-n ZVI@BC较质量比为1:1和1:3的S-n ZVI@BC表现出更好的污染物去除性能。初始p H（3.0–9.0）对TCE的总去除率没有显著影响,但是在较高p H下,TCE的降解效率会明显增强。值得注意的是,地下水中的典型阴离子(SO₄^2-、HCO₃^-和HPO₄^2-),腐殖酸和共污染物（Cr（VI）和NO₃^-）均对TCE的总去除有轻微影响,但大大地抑制了污染物的降解。此外,随着在空气中暴露时间的增加（5天、10天、20天和30天）,材料表面会发生钝化,S-n ZVI@BC复合材料的反应活性明显降低,然而随着反应时间延长时,老化的S-n ZVI@BC复合材料仍然保持相对较高的TCE去除率和降解率。总体而言,由于BC的高吸附能力和S-n ZVI的高还原能力的协调作用,S-n ZVI@BC的性能要比单一S-n ZVI或BC优越,这表明S-n ZVI@BC是一种有前景的材料,可广泛应用于修复TCE污染的地下水。第二部分:除了人工硫化纳米材料外,自然界中存在着许多硫化的铁基纳米材料,这对水体中污染物的迁移转化有着重要的影响。因此,我们开发了一种简单的溶剂热法合成了具有3D花状结构的纯相Fe₃S₄纳米颗粒（NPs）,研究其作为非均相催化剂活化过硫酸盐降解SMT的效果,并通过扫描电子显微镜和X射线光电子能谱的结构研究了Fe₃S₄ NPs的结构和组成变化。结果表明,Fe₃S₄纳米材料具有最优异的催化活性,p H的应用范围也较广且在不同的p H条件下,金属离子的浸出率较低。此外,结合了ESR,化学分子探针和ROS淬灭实验进一步阐明了Fe₃S₄NPs降解污染物的潜在机理,SO₄·^-、·OH、O₂·^-和¹O₂在催化过程中产生,其中SO₄·^-和¹O₂被证明是有机物降解的主要活性氧物种（ROSs）。此外,在金属硫化物活化PS的过程中,纳米颗粒表面的还原的硫物种可以增强Fe（III）/Fe（II）的氧化还原循环,进而促进氧化剂的分解产生更多的ROSs以提高SMT的降解效率。以上这些发现,表明了Fe₃S₄纳米颗粒出色的催化性能将有助于增强硫化铁基纳米材料在类Fenton废水中的实际应用。更多还原

【Abstract】 As we all know,the groundwater environment on which we depend to survive has deteriorated sharply in the process of advancing the rapid development of industry.Trichloroethylene（TCE）and Sulfamethazine（SMT）are widely used in the fields of organic synthesis,fuel manufacturing,pesticide production and aquaculture.They are two typical pollutants that are difficult to degrade,have a high detection rate and strong toxicity in the environment.At the same time,long-term exposure to this environment may cause great harm to human body.Therefore,In response to the pollution of TCE and SMT,the development of new heterogeneous catalysts with stable catalytic activity to prevent secondary pollution plays a vital role in large-scale actual wastewater treatment.In recent years,more and more scientists are keen to explore efficient and green water pollution control technologies.At the same time,sulfurized iron-based nanomaterials have attracted widespread attention due to their excellent properties（iron is a relatively abundant transition metal element in nature）,providing new ideas for the current environmental remediation field.Therefore,this article uses environmentally friendly sulfurized iron-based nanomaterials for the reduction/oxidation reaction system to remove persistent organic pollutants in water.In addition,according to the characteristics of these two typical nanoparticles,the influence of various influencing factors of the reaction process,the pathway of catalytic oxidant,the contribution of different free radicals to degrade pollutants,and the mechanism of pollutant degradation are deeply studied.The specific content of this paper is divided into the following two parts:Part one:This study surveyed the practicability and mechanism of sulfide-modified nanoscale zero-valent iron supported on biochar（S-n ZVI@BC）for the removal of TCE in the scenario of groundwater remediation.The effects of some critical factors,including pyrolysis temperature of biochar,the mass ratio of S-n ZVI to BC,initial p H,typical groundwater compositions,co-contaminants,and particle aging time,on the TCE removal were examined.The results revealed that the different pyrolysis temperatures could change the physicochemical properties of BC,which influenced the TCE adsorption and degradation by S-n ZVI@BC.In addition,S-n ZVI@BC with a mass ratio of 3:1 showed better pollutant removal performance than S-n ZVI@BC with a mass ratio of 1:1 and 1:3.The total removal of TCE was not significantly influenced by the initial p H（3.0–9.0）,but the degradation of TCE was enhanced at higher p H.Notably,the typical anions(SO₄^2-,HCO₃^-,and HPO₄^2-),humic acid,and co-contaminants（Cr（VI）and NO₃^-）in groundwater all slightly influenced the total removal of TCE,but markedly inhibited its degradation.Additionally,after exposure to air over different times（5 days,10 days,20 days,and 30 days）,the reactivity of S-n ZVI@BC composites was apparently decreased due to surface passivation.Nevertheless,the aged S-n ZVI@BC composites still maintained relatively high removal and degradation of TCE when the reaction time prolonged.Overall,the results showed that the S-n ZVI@BC,combining the high adsorption capacity of BC and the high reductive capacity of S-n ZVI,had a much better performance than the single S-n ZVI or BC,suggesting that S-n ZVI@BC is one promising material for the remediation of TCE-contaminated groundwater.Part two:The second part:In addition to artificial vulcanized nanomaterials,there are many vulcanized iron-based nanomaterials in nature,which have an important impact on the migration and transformation of pollutants in water.Therefore,we developed a simple solvothermal method to synthesize pure phase Fe₃S₄ nanoparticles（NPs）with a 3D flower-like structure,and studied its effect as a heterogeneous catalyst to activate persulfate to degrade SMT.The structure and composition changes of Fe₃S₄ NPs were also studied by scanning electron microscope and X-ray photoelectron spectroscopy.The results show that Fe₃S₄ nanospheres have the best catalytic activity,and the application range of p H is also wider.Under different p H conditions,the leaching rate of metal ions is lower.At the same time,the combination of ESR,chemical molecular probes and ROS quenching experiments further clarified the potential mechanism of Fe₃S₄ NPs degrading pollutants.SO₄·^-、·OH、O₂·^-和¹O₂were determined to be produced in the catalytic process,Among them,SO₄·^-and ¹O₂are proven to be the main reactive oxygen species（ROSs）for the degradation of organic matter.In addition,the reduced sulfur species on the surface of the nanoparticles can enhance the Fe（III）/Fe（II）redox cycle in the process of activating PS by metal sulfides,thereby promoting the decomposition of oxidants to generate more ROSs to improve the degradation efficiency of SMT.The above findings indicate that the excellent catalytic performance of Fe₃S₄ nanoparticles will help to enhance the practical application of sulfurized iron-based nanomaterials in Fenton-like wastewater.更多还原