【作者】 胡晓丹；

【导师】 张海黔；

【作者基本信息】 南京航空航天大学 ， 材料加工工程， 2012， 博士

【摘要】 作为治疗各种细菌感染或以致病微生物感染的药物，氟喹诺酮类抗生素在医药业、畜牧养殖业得到广泛使用。然而，绝大部分抗生素不能完全被机体吸收，以原型药物或者代谢物形式排入环境，特别是水体环境，虽然环境中抗生素的浓度普遍较低，但仍可能对环境和人体造成生物冲击和潜在危害。随着世界经济的发展，环境问题成为人类可持续发展的首要问题，本论文通过探讨第三代氟喹诺酮类抗生素左氧氟沙星（LVFX）在环境中的降解来寻求降低环境中抗生素污染的方法。本着以上研究目的，采用半导体纳米材料光催化氧化技术降解LVFX。本文主要制备了CdS纳米晶体，选用二硫化四甲基秋兰姆（TMTD）作为特殊结构的有机硫源，采用溶剂热方法，分别在水－苯、水、乙二胺、苯四种不同的反应介质中，成功制备出花簇状、冰锥状、线状、粒子状CdS晶体，系统地从热力学和动力学两方面研究了反应介质、反应温度、反应时间等条件对CdS纳米晶体形貌、结构、光学性能的影响。采用紫外－可见光谱（UV-Vis）和阴极射线发光光谱（CL）研究了CdS纳米晶体的光学性能。研究结果表明，温度是影响晶体生长的主要因素，反应介质的物化性质也从动力学方面影响了CdS纳米晶体的成核生长过程，从而影响晶体的形貌和尺寸。晶体的形貌不同，导致光学性能有所不同，良好的光学性能，在光催化的应用上具有潜在优势。CdS纳米线、纳米粒子得到了紫外－可见光谱，由于量子尺寸效应，与体相CdS材料比较，发生了蓝移，但花簇状、冰锥状没有得到UV-Vis光谱。花簇状、冰锥状、线状CdS晶体在可见光区均有阴极射线发光，得到了CL谱，但没有得到纳米粒子的CL谱。为了对比CdS的光催化效果，本论文还分别以聚乙二醇（PEG）、聚乙烯吡咯烷酮（PVP）作分散剂，采用共沉淀法、共沉淀—γ辐射法、溶剂热法制备了Fe₃O₄纳米晶体，并以透射电镜（TEM）、XRD粉末衍射、傅立叶红外光谱（FT-IR）、振动样品磁强计（VSM）对晶体进行表征和分析。与传统的共沉淀方法比较，引入γ射线，可改善纳米粒子的结晶性和分散性。溶剂热方法制备了球形单分散的立方晶型Fe₃O₄晶体，与聚乙二醇分散剂比较，聚乙烯吡咯烷酮作分散剂得到的晶体尺寸更小、结晶性和分散性更好。本论文以紫外光为光源，分别选用0.005g自制的CdS、Fe₃O₄作光催化剂，对100mL浓度为10mg/L的左氧氟沙星水溶液进行光催化降解。与LVFX溶液的直接光降解比较，光催化氧化技术具有更好的降解效果。以花簇状、粒子状、冰锥状、线状四种形貌的CdS晶体作光催化剂降解LVFX水溶液，较短时间光照，纳米粒子和纳米线的催化降解速率明显优于花簇状和冰锥状晶体；当紫外照射时间延长至60min时，以四种形貌的CdS晶体作催化剂，LVFX的降解百分率分别达到99％、99％、89％、97%，而LVFX的直接光解百分率为85%，说明以整体形貌为亚微米/纳米级的CdS晶体作光催化剂，小尺寸效应、晶体的表面粗糙度均有利于提高CdS光催化活性，而小尺寸效应是影响CdS光催化剂的主要因素。在UV－Fe₃O₄的高级氧化技术中，当紫外照射时间60min时，以PVP作分散剂溶剂热法制备的Fe₃O₄作光催化剂，LVFX的降解百分率为95%，以PEG作分散剂溶剂热法制备的Fe₃O₄作光催化剂，LVFX的降解百分率为98%，以PVP作分散剂共沉淀－γ辐射法制备的Fe₃O₄作光催化剂的LVFX降解百分率为89%，而LVFX的直接降解百分率仍为85%。溶剂热法制备的Fe₃O₄具有更佳的催化效果，说明在UV－Fe₃O₄的高级氧化技术中，尺寸效应并不一定占主导地位，Fe₃O₄中的铁能否进入水中，即形成配合物的趋势，以及晶体生长完善与否也是LVFX降解的重要影响因素。更多还原

【Abstract】 Fluorinated quinolone-type antibiotics are widely used in human and veterinary systems for infectiousdisease prevention and growth promotion. However, most of them are only partially metabolized andexcreted into the environment with parent compounds and metabolites. Although there is the presenceof antibiotics at low concentration in the aquatic systems, their occurrence has become a concern asbiological impacts and potential risks to the environment and human health. With the development ofworld economy, environmental problems have become the primary problem for the sustainabledevelopment of mankind. In this dissertation, we want to seek the method of reducing antibioticpollution in environment by studying the degradation of the third generation fluoquinolones-levofloxacin lactate （LVFX） in aquatic environment.In the above purpose, LVFX was degradated applying semiconductor photocatalytic oxidationtechnique. Flower-like, ice-piton, wire-like and particle-like CdS nanocrystals were successfullysynthesized using solvothermal route in water-benzene, water, ethylenediamine and benzenerespectively, which took tetramethyl thiuram disulfide （TMTD） as a special structured organic sulphursource. The influence of reaction medium, temperatures and time on microstructure and opticalproperties of CdS nanocrystals was systematically investigated from thermodynamics and kinetics. Theoptical properties of CdS crystals were investigated by ultraviolet-visible spectroscopy （UV-Vis） andcathodoluminescence （CL）. The results indicated that the solvothermal temperature played a moreimportant role in the formation of crystal morphology, and the physical and chemical properties ofsolvent also affected the structure and formation of CdS nanocrystals from kinetics. Furthermore，It wasthus evident that different synthesis conditions and crystal morphologies led to different opticalproperties, and excellent optical property implied potential applications for the CdS nanocrystals asphotocatalysts. UV-Vis spectra of CdS nanowire and namoparticles were obtained. Quantumconfinement effects were revealed by blue shifts at the onset of absorption, compared with theabsorption of the bulk CdS, but UV-Vis spectra of flower-like and ice-piton CdS weren’t obtained. CLspectra of flower-like, ice-piton, wire-like CdS crystals were acquired in the visible region, whereasspectra of CdS nanoparticles weren’t obtained.In order to contrast the photocatalytic effect of CdS, Fe₃O₄nanocrystals were also synthesized withpolyethylene glycol （PEG） and polyvinyl pyrrolidone （PVP） as dispersant respectively bycoprecipitation, coprecipitation-gamma radiation and solvothermal process. Nanocrystals werecharacterized by transmission electron microscopy（TEM），X-ray diffraction（XRD）, fourier transform infrared spectroscopy（FT-IR） and vibrating sample magnetometer（VSM） respectively. The crystallinityand dispersity of nano-particles were improved by gamma radiation，compared with the particlesobtained by traditional coprecipitation. Globular and monodisperse Fe₃O₄nanocrystals synthesized bysolvothermal method had cubic phase no matter what dispersant was. However, the crystals had smallerdiameter, better dispersibility and crystallinity with PVP as dispersant.Photocatalytic degradation experiments were carried out with UV radiation as the energy source, and0.005g CdS or Fe₃O₄, which were catalysts, were put into a100mL LVFX aqueous solution with aconcentration of10mg/L. Compared with direct photolysis, the photocatalytic degradation effect ofLVFX is better. As the UV radiation time was short, the catalytic rate of particle-shape and wire-likeCdS was good to flower-like and ice-piton CdS crystals. As the UV radiation time was60min, thephotocatalytic degradation percentage of LVFX was about99%，99%，89%and97%respectively withflower-like, particle-shape, ice-piton, wire-like CdS crystals as photocatalyst. However, the directphotolysis percentage of LVFX was about85%. Thus, size effects and surface roughness of crystalsfavored increasing catalytic activity with submicron/nano grade CdS crystals as photocatalysts,nevertheless quantum size effect was more prominent. As the UV radiation time was60min, thephotocatalytic degradation percentage of LVFX with Fe₃O₄as catalyst, which were synthesized withPEG and PVP as dispersant respectively by solvothermal process, was about98%and95%respectively.When Fe₃O₄nanocrystals were synthesized by coprecipitation-γ with PVP as dispersant, thephotocatalytic degradation percentage of LVFX was89%. However, the direct photolysis percentage ofLVFX was about85%. It’s indicated that Fe₃O₄nanocrystals prepared by solvothermal process werebetter photocatalyst. Size effects don’t necessarily dominates AOPs of UV－magnetite, and moreover,crystal growth and the tendency of iron ions in solution to form complexes are also consideredimportant in mechanistic studies.更多还原