【作者】 杨静；

【导师】 练鸿振；

【作者基本信息】 南京大学 ， 分析化学， 2014， 博士

【摘要】 采用现代分析测试技术直接测定环境有机污染物往往存在一定的难度,这是由于环境样品中的有机污染物浓度低、基质复杂、干扰物质多,因此发展快速、高效的样品前处理方法对环境样品中有机污染物的分析有着重要的意义。在诸多分离富集技术中,固相萃取(Solid phase extraction, SPE)因分离能力强、富集倍数高、样品和溶剂消耗少、价格低廉且易于自动化等优点,已成为有机污染物分析中主流的样品前处理方法,而将不同功能化的磁性纳米粒子用作磁固相萃取(Magnetic solid-phase extraction, MSPE)材料还具有比表面积大、磁性强、修饰方便、分离效率高、操作简便、可重复利用和环境友好等优点,逐渐受到人们的广泛重视。光催化降解是目前关注度较高的一种有机污染物降解技术,基于纳米二氧化钛(TiO2)的光催化降解以反应条件温和、无选择性、环境友好、成本低廉等特点已得到普遍的认可,过渡金属掺杂可提高TiO2的光催化效率,正越来越受到青睐。另外,磁载光催化剂集光催化和磁分离的特点于一身,能够实现催化剂的回收和重复使用,且操作简单、环境友好,有望成为有机污染物废水处理中一种非常有前途的新型催化剂。本论文结合纳米材料对有机污染物的磁固相萃取和光催化降解开展了以下工作：1、用水热法合成了碳包裹的四氧化三铁(Fe3O4/C)磁性纳米材料,结合各种谱学表征,系统研究了Fe3O4/C纳米粒子作为MSPE萃取剂对分析物的作用机理：一是通过比较Fe3O4/C和活性炭对多环芳烃(PAHs)的吸附-解吸现象,探讨两者的差异；二是把Fe3O4/C纳米粒子直接作为液相色谱固定相,研究其对典型分析物的保留行为；三是研究Fe3O4/C纳米粒子对具有不同疏水性、氢键作用力和极性的化合物的富集效果。结果表明,在Fe3O4/C纳米粒子和分析物之间存在着疏水相互作用和氢键或偶极-偶极相互作用。2、建立了Fe3O4/C纳米粒子MSPE结合高效液相色谱(HPLC)分析环境样品中的溴代阻燃剂(BFRs)和五氯苯酚(PCP)的方法,优化了吸附剂用量、重复使用次数、溶液pH和富集因子等萃取条件,并探讨了Fe3O4/C的水热法合成条件对萃取效率的影响。同时,用X-射线光电子能谱法(XPS)和热分析-质谱联用技术(TG-MS)深入研究了Fe304表面包裹碳的化学组成,进一步证实Fe3O4/C与分析物之间不仅有疏水相互作用还有氢键或偶极-偶极作用。3、用溶剂热法合成了石墨烯包裹的Fe3O4(Fe3O4/G)磁性纳米材料,建立了Fe3O4/G纳米粒子MSPE结合HPLC分析环境样品中BFRs的方法,优化了吸附剂用量、溶液pH和重复使用次数等萃取条件。结合对Fe3O4/G的形貌和谱学表征,讨论了Fe3O4/G与BFRs之间的相互作用机理,结果表明,两者之间主要存在π-π：堆积作用,还可能有疏水相互作用。4、用超声辅助水热法合成了钴掺杂的TiO2(TiO2/Co)纳米粒子,并用于氯酚(CP)和溴酚(BP)的降解,得到了10种氯酚和溴酚的光催化降解速率,通过比较CP和BP的降解动力学发现它们的光催化降解都符合假一级反应方程,且BP比CP更容易降解。进而,基于对降解产物的准确定量,研究了2,4,6-三氯酚(2,4,6-TCP)和2,4,6-三溴酚(2,4,6-TBP)的降解机理,发现两者都经历了脱卤路径,实验中还对Co的掺杂量进行了优化。5、用水热法制备了磁载光催化剂Fe3O4/C/TiO2,对其形貌和物相等进行了表征。研究了该催化剂对2,4,6-TCP的光降解性能,探讨了其重复使用的可能性,并用荧光光谱法推测了可能的反应机理。结果表明该材料结合了光催化与可再生的优点,对2,4,6-TCP有较高的降解效率,降解过程中有羟基自由基(·OH)生成。更多还原

【Abstract】 Current analytical technologies determining organic pollutants in environmental samples are challenged by extremely low level of the target analytes and very complex matrix with many interfering substances in samples. So, the preliminary separation and preconcentration prior to their determination are often required in real-world analysis. Solid-phase extraction (SPE) is one of the most commonly used separation/preconcentration techniques due to its strong separation capacity, high enrichment factor, minimal sample and solvent consumption, low cost and easy automation. Nowadays, a new mode of SPE, magnetic solid-phase extraction (MSPE) based on magnetic nanomaterials has gained more attention because the adsorbents combine numerous advantages such as large surface area, unique magnetic property, convenient functional modification, high separation efficiency, easy operation, high reusability and environmental friendliness.Photocatalic degradation is one of the most important degradation technologies of organic pollutants in environment. Photocatalytic degradation by TiO2nanoparticles has attracted continuous attention because of mild reaction conditions, non-selectivity, environmental friendliness and low cost. Transition metal doped TiO2is more and more frequently used to improve photocatalytic effect. Furthermore, magnetic separation technology has been exploited in the treatment of waste waters because the magnetic photocatalyst not only has excellent photocatalytic property but also can be easily isolated and reused. In addition, magnetic photocatalyt is very potential in the photodegradation of organic pollutants in waste waters for its simple operation and environmental friendliness. The nanomaterials used in MSPE and photodegradation of some organic pollutants have been studied in this paper. The major contents are described as follows:1. The carbon doped Fe3O4nanoparticles (Fe3O4/C) have been prepared by hydrothermal method. The interaction mechanism of Fe3O4/C to analytes has been elucidated by comparison in adsorption/desorption property of polycyclic aromatic hydrocarbons (PAHs) with activated carbon, retention behavior of the nanoparticles directly used as liquid chromatographic stationary phase, the outcome of related MSPE experiments for several typical compounds, as well as various spectroscopic characterizations. It is found that there is hydrophobic interaction coupled with hydrogen bonding or dipole-dipole interaction between Fe3O4/C nanoparticles and analytes.2. The magnetic Fe3O4/C nanoparticles have been used as adsorbents for effective MSPE of some brominated flame retardants (BFRs) and pentachlorophenol (PCP) from environmental waters followed by HPLC. Extraction conditions including sorbent dosage, reusage times, pH and enrichment ability were optimized comprehensively. The influence of hydrothermal synthesis conditions of Fe3O/C nanoparticles on the MSPE performance was also discussed. Moreover, the chemical components of coated carbon layer on the surface of Fe3O4nanoparticles were more exactly identified by X-ray photoelectron spectroscopy (XPS) and thermogravimetry-mass spectrometry (TG-MS). This finding adequately supported the proposed adsorption/desorption mechanism of Fe3O4/C to the analytes that there are hydrophobic interaction coupled with hydrogen bonding or dipole-dipole interaction between Fe3O4/C nanoparticles and analytes.3. The graphene based on Fe3O4(Fe3O4/G) nanoparticles have been prepared by solvothermal method and used as adsorbents for effective MSPE of some BFRs. Extraction conditions including sorbent dosage, solution pH and reusage times were optimized. Combing the morphology and spectroscopy of the nanoparticles, the interactions of Fe3O4/G and BFRs have been discussed and the MSPE mechanism of Fe3O4/G to analysts has been speculated. There are π-π stacking interaction and probable hydrophobic interaction.4. Cobalt doped Fe3O4nanoparticles (TiO2/Co) were prepared by ultrasonic-assisted hydrothermal method and used as catalyst for photodegradation of chlorophenols (CPs) and bromophenols (BPs). The degradation rates of10 halophenols were carefully estimated and compared. It was demonstrated that the degradation of CPs and BPs mainly underwent dehalogenation process with pseudo-first-order kinetics. Moreover, the dehalogenation behaviors of2,4,6-tribromophenol (2,4,6-TCP) and2,4,6-tribromophenol (2,4,6-TBP) were compared in the process of photocatalytic degradation based on the reliable determination of the degradation products. In addition, the doping content of cobalt in TiO2/Co nanoparticles was optimized.5. A separable magnetic photocatalyst (Fe3O4/C/TiO2) was prepared by a hydrothermal reaction. The catalyst Fe3O4/C/TiO2was characterized in terms of morphology and phase. The catalytic activity and mechanism were evaluated by degradation of2,4,6-TCP aqueous solution. The reaction mechanism was investigated by the fluorescence measurement. The results indicate that the catalyst have high degradation ability to2,4,6-TCP and can be easily reused. Moreover, the hydroxyl radicals (OH) have been detected in the reaction.更多还原