【作者】 杨莉；

【导师】 关卫省；

【作者基本信息】 长安大学 ， 地质工程， 2010， 博士

【摘要】 印染废水是水体污染中主要的有害、难处理工业废水之一。半导体光催化氧化法具有反应条件温和、净化彻底、绿色环保、经济高效等优点,是一种比较理想的印染废水治理技术。本论文利用酵母细胞作为生物模板和生物载体,分别制备了钨酸锌空心球和酵母-硫化锌(YC-ZnS)两种新型光催化剂,运用多种表征手段和测试方法阐明了两种材料的主要物理化学性能和制备机理,并在此基础上考察了两种新型光催化剂对模拟印染废水的处理工艺条件。主要结果概括为：(1)选用酵母细胞作为模板制备了ZnWO4空心微球。多种表征结果表明：ZnWO4空心微球系闪锌矿ZnWO4晶体；颗粒分散度良好,形貌较为一致,较好地保持了酵母细胞椭圆形的形貌,大小约为3.7x2.0gm。机理分析证实ZnWO4空心微球光催化剂的形成机理可分为4步：酵母表面功能性基团的活化—生物吸附实现细胞表面水合锌离子层的形成—ZnWO4纳米颗粒在酵母细胞表面的逐步成长—煅烧去除酵母细胞。(2)以低浓度罗丹明B (RhB)模拟染料废水为目标降解物,对ZnWO4空心微球的光催化性能进行研究,实验证实影响降解率的主要因素是pH、染料初始浓度和催化剂用量。ZnWO4空心微球光催化处理罗丹明B模拟染料废水的最佳工艺条件为：催化剂用量2g/L,pH为6,染料浓度为0.5×10-5mol/L。ZnWO4空心微球在光催化循环实验中表现出较稳定的光催化活性。(3)成功地以酵母细胞为载体制备了负载型光催化剂酵母-硫化锌(YC-ZnS),表征结果表明：产物颗粒分散度良好,形貌一致,很好地保持了酵母细胞的基本形态,大小为2-3×3-5μm；颗粒结构为一层厚度为450-500nm的纳米ZnS粒子负载于酵母细胞表面；负载态ZnS为闪锌矿p-ZnS;荧光特性研究证实了颗粒表面的负载物为具有荧光性能的ZnS。YC-ZnS的制备机理研究证实：光催化剂ZnS在酵母上的成功负载在很大程度上依赖于酵母细胞壁所提供的反应表面。(4)对YC—ZnS的沉降性及其对染料亚甲基蓝(MB)的吸附性能进行了测定和探讨。吸附实验表明：YC-ZnS对亚甲基蓝的吸附规律较好地符合Freundlich等温吸附模型。优化后吸附实验条件为：23℃、pH7及YC—ZnS用量为4.5g/L,最大吸附量可达471.2μg/g。通过YC-ZnS与ZnS微球和酵母细胞的沉降性能的比较研究表明：YC—ZnS具有较好的悬浮性能,其在水溶液中的悬浮性能略差于酵母细胞,但远远强于所制备的ZnS微球。(5)以低浓度亚甲基蓝模拟染料废水为降解物,对YC-ZnS的光催化性能进行优化研究,主要考察了溶液初始pH值、催化剂用量、染料浓度,辐射距离和反应温度对YC—ZnS光催化降解亚甲基蓝模拟染料废水的影响,得到了优化后的光催化处理体系条件参数是：pH为8,辐射距离5cm,YC-ZnS用量3g/L。本文制备的两种新型光催化剂在材料设计中实现了生物细胞和纳米材料各自优势的巧妙结合,制备过程绿色环保,工艺简单,所制备的产物对印染废水的催化效率高,可以较好地达到改善环境和资源利用生态化的目的。本研究在纳米技术、生物科学和环境工程的交叉研究领域中做出了一些尝试,对其他生物相关的新型材料在环境工程领域的研究有一定参考价值。更多还原

【Abstract】 As a harmful industrial water body, printing and dyeing wastewater has been a technically refractory pollution. Semiconductor photocatalytic oxidation process is deemed as an ideal treatment technology for printing and dyeing wastewater as it exhibits outstanding superiority such as mild reaction conditions, thorough purification, environmental protection, high economic efficiency, and etc. In this thesis, employing yeast cells as bio-templates and biological carriers, we prepared ZnWO4 hollow microspheres and yeast—zinc sulfide (YC-ZnS).And new photocatalysts were characterized by various means and methods to learn their main physical and chemical properties and to propose probable formation mechanisms. On this basis, we obtained the parameters of photocatalytic process of two photocatalysts in the treatment of low concentrations dyeing wastewater. Main results were summarized as follows:(1) We used yeast cells as biotemplates in the synthesis of ZnWO4 hollow microspheres. Results from characterizations indicated that ZnWO4 hollow microspheres were sphalerite ZnWO4 crystal; particles were in good dispersion which faithfully retained the morphology of yeast templates; and the size was approximate 3.7×2.0μm. Based on the experimental results, the formation mechanism of the ZnWO4 hollow microspheres was proposed into four steps:activation of functional groups on yeast cells—hydration zinc ion level formation on the cell surface through biological adsorption—growth of ZnWO4 nanoparticles on the yeast cellwall—calcinations to elimination yeast templates to form hollow microspheres.(2) Rhodamine B was taken as the degradation goal in the photocatalytic examination of ZnWO4 hollow microspheres. The dye photodecolorization process was studied considering the influence of experimental parameters such as pH、the initial dye concentration and catalyst amount used. The conditions when ZnWO4 with the best photocatalytic activity towards the Rhodamine B wastewater were 2g/L catalyst used, pH 6 and the dye concentration 0.5×10-5mol/L. And the ZnWO4 hollow microspheres displayed stable photocatalytic activity in the photocatalytic circulation experiments.(3) Employing yeast cells as carriers, a novel loaded photocatalyst YC-ZnS was successfully synthesized. Results from characterizations showed that the product particles were in good dispersion with consistent appearance; YC-ZnS particles maintained the morphology of yeast cells fairly well and the size was about 2-3×3-5μm; structurally the particle was consisted of a yeast cell inside covered with nanometer ZnS granule layer of 450-500nm thickness. The loaded ZnS was the sphaleriteβ-ZnS, and fluorescence characterization confirmed the loaded ZnS with fluorescence properties. The study on the preparation mechanism of YC-ZnS proved the successful loading of ZnS onto yeasts relied greatly on the reactive surface provided from the yeast cells.(4) Both the settling property of YC-ZnS in solution and its adsorption performance to the dye methylene blue were studied. Isotherm modeling revealed that Freundlich equations described well the adsorption of methylene blue onto YC-ZnS. The optimized adsorption conditions were:23℃, pH7 and the YC-ZnS amount used was 4.5g/L. Under these conditions, the adsorption capacity of YC-ZnS may reach 471.2μg/g. Compared with ZnS microspheres and yeast cells, the settling properties of YC-ZnS were also examined and simulated. It was found that the suspending performance of YC-ZnS was slightly less than yeast cell, but by far better than the ZnS microspheres.(5) Taking methylene blue as the degradation goal, we studied the photocatalytic process conditions of YC-ZnS. Factors affecting the photocatalysis of YC-ZnS were evaluated in details, such as the pH value, the catalyst amount used, the initial dye concentration, the illumination distance and the reaction temperature. Then we obtained the optimized conditions of photochemical catalysis system as followed:pH 8, the illumination distance is 5cm, and the yeast-ZnS amount used was 3g/LIn this article we prepared two new photocatalysts, blending together both the superiorities of the biological cells and the nanomaterials in the material design. It was proved that the preparation processes were simple and environmentally friendly, and the synthesized products exhibited high photocatalytic efficiency in the treatment of the printing and dyeing wastewater. Hence we might achieve goals in the green solution of environmental pollution and the ecological development of resources as well. This paper has made some attempts in the multidiscipline among nanotechnology, biological science and environmental engineering. And it may be of reference value to the application of other organism-related new material in the research of environmental engineering.更多还原