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The Investigation of Photocatalysts and Iron Based Materials in the Oxidation and the Adsorption of Toxic Organic and Chromium Materials

机译:光催化剂和铁基材料在有毒有机铬材料氧化和吸附中的研究

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摘要

The presences of heavy metals, organic contaminants and natural toxins in natural water bodies pose a serious threat to the environment and the health of living organisms. Therefore, there is a critical need to identify sustainable and environmentally friendly water treatment processes. In this dissertation, I focus on the fundamental studies of advanced oxidation processes and magnetic nano-materials as promising new technologies for water treatments.Advanced oxidation processes employ reactive oxygen species (ROS) which can lead to the mineralization of a number of pollutants and toxins. The rates of formation, steady-state concentrations, and kinetic parameters of hydroxyl radical and singlet oxygen produced by various TiO2 photocatalysts under UV or visible irradiations were measured using selective chemical probes. Hydroxyl radical is the dominant ROS, and its generation is dependent on experimental conditions. The optimal condition for generation of hydroxyl radical by of TiO2 coated glass microspheres is studied by response surface methodology, and the optimal conditions are applied for the degradation of dimethyl phthalate. Singlet oxygen (1O2) also plays an important role for advanced processes, so the degradation of microcystin-LR by rose bengal, an 1O2 sensitizer was studied. The measured bimolecular reaction rate constant between MC-LR and 1O2 is ~ 106 M-1 s-1 based on competition kinetics with furfuryl alcohol.The typical adsorbent needs separation after the treatment, while magnetic iron oxides can be easily removed by a magnetic field. Maghemite and humic acid coated magnetite (HA-Fe3O4) were synthesized, characterized and applied for chromium(VI) removal. The adsorption of chromium(VI) by maghemite and HA-Fe3O4 follow a pseudo-second-order kinetic process. The adsorption of chromium(VI) by maghemite is accurately modeled using adsorption isotherms, and solution pH and presence of humic acid influence adsorption. Humic acid coated magnetite can adsorb and reduce chromium(VI) to non-toxic chromium (III), and the reaction is not highly dependent on solution pH. The functional groups associated with humic acid act as ligands lead to the Cr(III) complex via a coupled reduction-complexation mechanism. Extended X-ray absorption fine structure spectroscopy demonstrates the Cr(III) in the Cr-loaded HA-Fe3O4 materials has six neighboring oxygen atoms in an octahedral geometry with average bond lengths of 1.98 Å.
机译:天然水体中重金属,有机污染物和天然毒素的存在对环境和生物的健康构成了严重威胁。因此,迫切需要确定可持续和环保的水处理工艺。本文主要研究高级氧化工艺和磁性纳米材料的基础研究,作为有前途的水处理新技术。高级氧化工艺利用活性氧(ROS)导致多种污染物和毒素的矿化。 。使用选择性化学探针测量了各种TiO2光催化剂在紫外线或可见光照射下生成的羟基自由基和单线态氧的形成速率,稳态浓度和动力学参数。羟基自由基是主要的ROS,其生成取决于实验条件。采用响应面法研究了TiO2包覆玻璃微球产生羟基自由基的最佳条件,并将其应用于邻苯二甲酸二甲酯的降解。单线态氧(1O2)在先进工艺中也起着重要作用,因此,研究了玫瑰红(一种1O2敏化剂)对微囊藻毒素LR的降解作用。根据与糠醇的竞争动力学,测得的MC-LR与1O2之间的双分子反应速率常数为〜106 M-1 s-1。典型吸附剂在处理后需要分离,而磁性氧化铁可以很容易地被磁场去除。合成了磁赤铁矿和腐殖酸涂层的磁铁矿(HA-Fe3O4),进行了表征并用于去除铬(VI)。磁赤铁矿和HA-Fe3O4对铬(VI)的吸附遵循拟二级动力学过程。使用吸附等温线准确地模拟了磁赤铁矿对铬(VI)的吸附,并且溶液的pH值和腐殖酸的存在会影响吸附。腐殖酸涂层磁铁矿可以吸附铬并将其还原为无毒的铬(III),并且反应高度不依赖于溶液的pH值。与腐殖酸相关的官能团作为配体,通过偶联的还原-络合机理形成Cr(III)络合物。扩展的X射线吸收精细结构光谱表明,在八面体几何结构中,Cr负载的HA-Fe3O4材料中的Cr(III)具有六个相邻的氧原子,平均键长为1.98Å。

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    Jiang Wenjun;

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  • 年度 2013
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