【作者】 李博；

【导师】 黄丹莲；

【作者基本信息】 湖南大学 ， 环境科学与工程， 2021， 硕士

【摘要】 抗生素具有可以挑战微生物种群的特性,因此在临床医疗,水产及畜牧养殖业被广泛应用。当抗生素被排放到自然界后,其被视为影响环境中微生物群的结构和活性,并使得具有多重耐药性的“超级细菌”逐步产生的重要污染物。所以,寻找一种绿色高效的去除环境中抗生素的方法和技术就显得尤为重要。半导体光催化作为一种能在温和条件下,拥有着卓越的太阳能捕获和转换能力的技术,在有机污染物降解、全水分解、析氢析氧、有机合成等诸多领域得到青睐。近些年来,苝二酰亚胺有机超分子（PDI）在光催化降解领域引起了广泛的关注,但其存在着电子-空穴重组速度快,降解效率不理想等问题。因此,为充分解决上述问题,本文将PDI与单斜相钒酸铋（BiVO₄）进行结合,并对其光催化性能进行了深入的探索和分析。随后,在实验室中模拟和研究了上述光催化剂对水体中以四环素（TC）为代表的广谱抗生素的降解效率、反应动力学、循环稳定性、光催化降解机理和路径以及电子转移机制等内容。最后证实了该催化剂应用于实际水体中抗生素治理的可行性,并分析了光降解过程中的主要影响因素,具体内容如下:（1）通过原位静电自组装的方法,将软体有机材料PDI包裹在3D BiVO₄表面,成功构建了BiVO₄/PDIsa无机-有机Z型光催化剂。其中,20%BiVO₄负载量的样品（BP-2）光催化活性最强,在30 min内可降解81.75%的TC,分别比单体自组装的PDI（PDIsa）和BiVO₄高出19.16%和43.31%。BP-2的降解速率常数(K_t=0.0545 min^-1)则分别是PDIsa和BiVO₄的1.69倍和3.61倍。循环实验、粉末X射线衍射谱图（PXRD）分析和傅里叶变换红外（FTIR）光谱表征证明了本研究中所制备的最佳催化剂BP-2具有很好的稳定性。通过自由基捕获实验和ESR表征结果显示在TC降解过程中起主导作用的是¹O₂,^·O₂^-和h⁺。此外,^·O₂^-定量检测实验表明BP-2的^·O₂^-产生速率(2.26μmol L^-1 mg^-1)分别是单体PDIsa和BiVO₄的1.19倍和1.37倍。总有机碳（TOC）测试表明,BP-2对TC的矿化效率为24.95%,并利用液相色谱-串联质谱联用系统,分析和推测了4条TC的可能降解路径。（2）通过实验研究、多种表征手段和密度泛函理论（DFT）计算分析了BP-2光催化性能的提升的原因。窄带隙半导体PDIsa的引入拓宽了BiVO₄对可见光的吸收范围。而两种直接带隙半导体的结合则增强复合材料对可见光的利用率。在Z型异质结和内建电场（IEF）的协同下,界面处实现了高效的光生载流子的分离和转移。更有趣的是,PDIsa分子的极性结构和π-π堆积方式,以及直接Z型异质结的形成,通过构建高效的载流子定向分离通道,延长了光生电子和空穴的寿命。（3）本研究还将催化剂应用于实际水体中TC的降解。结果发现在河流水、湖泊水、自来水和工业废水中TC的降解效率分别为59.14%,62.60%,68.04%和71.46%,这证实了该催化剂用于实际的可行性。另外,通过研究影响光催化降解TC过程中的因素发现,当溶液的pH值处于4.01-6.99范围时,对BP-2光催化性能的负面影响较小。而溶液中共存阴离子对TC光降解的影响顺序为:SO₄^2-<NO₃^-<Cl^-。简而言之,本研究成功设计了一种无机-有机Z型光催化剂,并对废水中的TC有着较高的去除效率。这项工作将为光催化剂的降解机理和电子转移机制的研究提供理论基础,还为光催化剂应用于实际水体中难降解抗生素的去除提供实践参考价值。更多还原

【Abstract】 Antibiotics are widely used in clinical care,aquaculture,and livestock farming due to their ability to challenge microbial populations.It is worth noting that antibiotics must also be considered as an important pollutant that affects the structure and activity of microbiota in the environment and allows the progressive production of multi-drug resistant"superbugs"when they are released into the natural environment.Therefore,it is particularly important to find a green and efficient method and technology to remove antibiotics from the environment.Semiconductor photocatalysis,as a technology with excellent solar energy capture and conversion capability under mild conditions,is favored in many fields such as organic pollutant degradation,water aplitting,hrdrogen/oxygen evolution,organic synthesis.In recent years,perylene diimide organic supermolecule（PDI）has attracted significant interest in the field of photocatalytic degradation,but it suffers from rapid electron-hole recombination and unsatisfactory degradation efficiency.To adequately solve the above problems,herein,PDI was combined with monoclinic bismuth vanadate（BiVO₄）,and its photocatalytic performance was thoroughly explored and analyzed.Subsequently,the degradation efficiency,reaction kinetics,cycling stability,photocatalytic degradation mechanism and pathway,and electron transfer mechanism of the above photocatalysts for broad-spectrum antibiotics represented by tetracycline（TC）in water were simulated and studied in the laboratory.Finally,the feasibility of utilizing the catalyst in the treatment of antibiotics in real water was confirmed,and the main influencing factors in the photodegradation process were analyzed.The detailed contents are as follows.（1）The inorganic-organic Z-scheme BiVO₄/PDIsa photocatalysts were successfully constructed by wrapping the soft organic material PDI on the surface of 3D BiVO₄ through an in situ electrostatic self-assembly method.The optimized sample with 20%BiVO₄ loading（BP-2）exhibited excellent photocatalytic activity towards TC removal,with the highest degradation efficiency of 81.75%within 30 min,which was 19.16%and 43.31%higher than that of monomeric self-assembled PDI（PDIsa）and BiVO₄,respectively.The degradation rate constant(K_t=0.0545 min^-1)of BP-2 was 1.69 and 3.61 times higher than that of PDIsa and BiVO₄,respectively.Cycling experiments,powder X-ray diffraction spectroscopy（PXRD）analysis and Fourier transform infrared（FTIR）characterization demonstrated the good stability of the as-prepared BP-2.The radical trapping experiments and electron spin response（ESR）technique revealed that ¹O₂,^·O₂^-and h⁺played a dominant role in the TC degradation process.In addition,the^·O₂^-quantification assay showed that the^·O₂^-production rate of BP-2(2.26μmol L^-1 mg^-1)was 1.19 and 1.37 times higher than that of monomeric PDIsa and BiVO₄,respectively.The total organic carbon（TOC）test revealed that the mineralization efficiency of BP-2 for TC was 24.95%,and four possible degradation pathways of TC were analyzed and speculated utilizing a liquid chromatography coupled with tandem mass spectrometry（LC-MS）system.（2）The reasons for the enhanced photocatalytic performance of BP-2 were analyzed by experimental studies,various characterization tools and density functional theory（DFT）calculations.The introduction of the narrow bandgap semiconductor PDIsa broadens the absorption range of visible light for BiVO₄,while the combination of two direct bandgap semiconductors enhances the utilization of visible light for the composite material.The separation and transfer of photogenerated charge carriers at the interface is greatly enhanced by the synergistic effect of the Z-scheme heterojunction and the built-in electric field（IEF）.More interestingly,the polar structure andπ-πstacking mode of PDIsa molecules and the formation of direct Z-scheme heterojunction prolong the lifetimes of photogenerated electrons and holes by constructing efficient carrier-directed separation channels.（3）In this study,the catalysts were also applied to the degradation of TC in actual water bodies.It was found that the degradation efficiency of TC in river water,lake water,tap water and industrial wastewater was 59.14%,62.60%,68.04%and 71.46%,respectively,which confirmed the feasibility of the catalysts for practical use.Furthermore,through studying the factors affecting the process of photocatalytic degradation,it was found that no significant decline in TC removal efficiency was observed when the pH of the solution was in the range of 4.01-6.99,while the order of the effects of coexisting anions in solution on TC photodegradation was:SO₄^2-<NO₃^-<Cl^-.In conclusion,an inorganic-organic Z-scheme photocatalyst has been successfully designed in this study,which has a high removal efficiency for TC in wastewater.This work will provide a theoretical basis for the study of the degradation mechanism and electron transfer mechanism of the photocatalyst,and also provide a practical reference value for the application of photocatalyst in the removal of refractory antibiotics in real water bodies.更多还原