【作者】 段芳；

【导师】 谢毅； 陈明清；

【作者基本信息】 江南大学 ， 应用化学， 2011， 博士

【摘要】 目前,环境污染日趋严重,已成为一个直接威胁人类生存,亟需解决的焦点问题。其中,有机染料因其结构复杂、毒性大、对环境污染重及难降解等特性,已成为环境治理中的一个难点。传统的吸附技术和近年来发展的光催化技术都是目前处理有机染料污染问题的重要手段,已成为环境保护、化学合成和新材料等领域的研究热点。本论文利用和发展了液相化学合成的方法,得到了新型复合氧化物纳米结构的吸附剂（ZnV₂O₄）和可见光催化剂(CHBiO₃, Bi₂WO₆, PtCl4/Bi₂WO₆, Bi_3.64Mo_0.36O_6.55, C/Bi_3.64Mo_0.36O_6.55),并系统的研究了它们在有机染料处理方面的应用。本论文的主要内容归纳如下:1.作者利用一种简单有效的溶剂热法一步合成了高产量的ZnV₂O₄空心球。该合成方法简单易操作、可重复,避免了传统模板法的繁琐合成过程。并对空心球的生成机理进行了研究,提出了自生成的花状中间产物支撑下还原-溶解-聚集的生成过程。通过氮气吸附-脱附测试分析空心球结构ZnV₂O₄的比表面积为105.1 m²/g,总的孔体积为0.1563 cm³/g。利用空心球结构ZnV₂O₄较大的比表面积和多孔特性,将所得ZnV₂O₄空球对有机染料亚甲基蓝（MB）进行吸附,结果发现ZnV₂O₄对MB具有很好的吸附效果,能在40min内基本都达到吸附平衡,说明该吸附剂具有很高的吸附速率。并且发现ZnV₂O₄吸附剂对低浓度的MB溶液吸附达到平衡的时间要比对高浓度的MB溶液吸附达到平衡的时间短。在吸附剂浓度一定时,染料的去除效率是随着染料初始浓度的下降而增加的。此外,研究了ZnV₂O₄对有机染料MB的吸附动力学和吸附等温线,结果表明,ZnV₂O₄对MB的吸附都符合准二级动力学方程。吸附等温线用Langmuir和Freundlich等温方程对其实验数值进行拟和,结果发现Freundlich方程的拟和结果更接近实验数值。2.基于对甲酸氧铋晶体结构的分析,首先预测了甲酸氧铋应该具有光催化性质的可能。于是通过简单经济的液相化学合成方法,在没有添加任何的表面活性剂和模板的条件下成功合成了三维花状结构的甲酸氧铋,并对其反应过程和生长机理进行了分析。认为这种花状结构的形成与甲酸氧铋自身的层状结构有关,层与层之间的相互作用相对比较微弱,而在（001）面内原子间的相互作用比较强,导致甲酸氧铋容易长成二维片状结构,在降低系统表面能的驱动下,这些片状结构自组装成最终的花状甲酸氧铋。通过对罗丹明B（RhB）溶液的降解作用,评价了制备的三维花状结构甲酸氧铋的光催化性质,发现合成的三维花状结构甲酸氧铋对RhB溶液具有显著的降解效果,能在60分钟内完全降解RhB溶液。因此这种花状结构的甲酸氧铋具有优越的光催化性能,有望在环境污染治理中得到应用,同时也验证了之前的预测。3.采用水热法一步得到花状等级制结构Bi₂WO₆材料,通过考察反应时间、醋酸的加入量、硝酸的加入等对反应的影响,提出了花状等级制结构Bi₂WO₆的形成机理。认为这种花状等级制结构的形成经过了非晶颗粒聚集成微米球,由于Bi₂WO₆自身层状结构特点导致组成微米球的非晶颗粒溶解重结晶形成片状结构Bi₂WO₆,同时这些纳米片在醋酸羧基的作用下以及羧基之间形成的氢键作用下紧密排列形成花状等级制结构。由于花状等级制结构Bi₂WO₆特殊的形貌和层状结构,在光催化领域具有潜在的应用价值。因此对得到的花状等级制结构Bi₂WO₆光催化降解RhB进行了研究,结果表明这种花状等级制结构的Bi₂WO₆对RhB具有显著的降解效果,能在60分钟内完全降解RhB,比商业TiO₂（P25）和Bi₂WO₆块材降解RhB性质优越。并对降解RhB的过程进行了分析,认为Bi₂WO₆光降解RhB的过程分为两个过程:催化降解过程和RhB的敏化降解过程,这两个过程同时进行,但主要以Bi₂WO₆光催化降解RhB过程为主。4.通过对铋基光催化剂表面的修饰作用,进一步提高了铋基光催化剂的可见光催化性质。其中以PtCl4修饰对Bi₂WO₆光催化剂以及碳修饰对Bi_3.64Mo_0.36O_6.55颗粒光催化性质的影响为研究对象,分析了这两种修饰对光催化剂性能提高的原因和机理。（1）通过将氯铂酸溶液与花状等级制结构Bi₂WO₆充分接触,煅烧得到PtCl4/Bi₂WO₆复合光催化剂。并且该处理过程对Bi₂WO₆的形貌和晶体结构都没有产生明显的影响,PtCl4的修饰能显著提高Bi₂WO₆在可见光区的光吸收性能,并且使Bi₂WO₆的光学吸收边发生了红移。对掺杂不同PtCl4量的Bi₂WO₆样品光催化性质进行了系统的研究,发现PtCl4的修饰显著提高了Bi₂WO₆样品的光催化性能,并且PtCl4存在最佳修饰量。PtCl4/Bi₂WO₆样品光催化性质的提高可以归纳为两个方面的原因:一方面是PtCl4的修饰增强了Bi₂WO₆样品对可见光的吸收性能;另一方面是PtCl4的修饰在Bi₂WO₆样品表面提高了电荷的转移效率和抑制了电子-空穴的再结合。（2）利用微波辐射法合成了Bi_3.64Mo_0.36O_6.55 （BMO）八面体颗粒,通过葡萄糖水热碳化修饰在BMO表面,再于280°C高温下煅烧使残余的有机物进一步碳化,从而得到了碳修饰的BMO样品。对修饰前后BMO样品的形貌、晶体结构以及光学性质进行了测试,得出碳的修饰对BMO样品的形貌和晶体结构没有发生明显的影响,但显著提高了BMO样品在可见光区的光吸收性质。通过对不同碳修饰量的BMO样品进行光催化性能测试发现碳的修饰也存在一个最佳值。并分析了碳修饰的BMO样品光催化性质提高的原因是碳在染料的吸附作用方面、碳在载流子的迁移速率影响方面以及碳在光催化剂对可见光的吸收这三方面协同作用的结果。更多还原

【Abstract】 Nowadays, environmental problems have become a global concern because of their impact on public health. Among them, organic dyes removal has recently attracted considerable attention because of their complex structure, poor biodegradability, and long-term environmental toxicity. Various methods have been developed to remove organic dyes from aqueous environment, while the adsorption technique and photocatalytic degradation of organic dyes have been extensively considered as effective methods. Furthermore, the preparing methods and property investigations for the adsorbents and photocatalysts are of much significance in the chemical synthesis, new materials and environmental protection areas. In this dissertation, a series of new bismuth based photocatalysts (CHBiO₃, Bi₂WO₆, PtCl4/Bi₂WO₆, Bi_3.64Mo_0.36O_6.55, C/Bi_3.64Mo_0.36O_6.55) and adsorbent （ZnV₂O₄） were obtained through the developed solution-based chemical synthesized methods. Besides, their applications in organic dye removal were also systematically studied. The details are summarized briefly as follows:1. Hollow ZnV₂O₄ spheres aggregated by small nanoparticles were successfully synthesized through a facile one-pot template-free solvothermal method. The formation of ZnV₂O₄ hollow spheres was based on a flowerlike intermediate product supported reduction-dissolution-aggregation process at the expense of consumption of all the flowerlike intermediate products. The obtained ZnV₂O₄ hollow spheres exhibited Brunauer-Emmett-Teller （BET） specific surface areas of 105.1 m²/g and total pore volume of 0.1563 cm³/g. Their novel structures resulted in a high surface to bulk ratio and a large surface area, contributing to high adsorption capacities and faster adsorption rates. In fact, they showed a good adsorption capacity of MB organic dye, and a faste adsorption rate within 40 min, which might be attributed to their special structural feature with large surface area. The adsorption kinetics and isotherm of MB on ZnV₂O₄ hollow spheres were also studied.2. By virtue of structural understanding, bismuth oxide formate （CHBiO₃） was first put forward to be a novel photocatalyst candidate. 3D flowerlike architectures have been successfully synthesized through a facile and economical route, which was free from any surfactant and template. Besides, the formation mechanism of the CHBiO₃ flowerlike architectures was also discussed. It was believed that the formation of the flowerlike CHBiO₃ was related to its crystal structure. There was a weak nonbonding interlayer vander Waals interaction along the c axis and strong intralayer bonding in the （001） plane. Therefore, it tended to form layered structures, e.g. flakes or platelets with a high aspect ratio. Then, the flowelike CHBiO₃ was formed by self-assembly of the nanoplate in order to decrease the surface energy. From the results of photocatalytic tests, the synthesized CHBiO₃ architectures exhibited excellent photocatalytic activity for rhodamine-B （RhB） degradation under the simulated solar light irradiation. Therefore, this novel 3D flowerlike CHBiO₃ architectures show significance of potential application in environment protection problems.3. The flowerlike hierarchical Bi₂WO₆ was successfully synthesized through a facile template-free hydrothermal method. The reaction time, the amount of HAc, and the addition of HNO₃ were systematically refined, and the formation mechanism of the flowerlike hierarchical Bi₂WO₆ was also discussed. Based on the morphology evolution as a function of hydrothermal time, the formation mechanism was proposed to be as follows: First, the aggregation of the noncrystal nanoparticles; Then, the formation of crystalline nanoplates by dissolution of the noncrystal nanoparticles; Finally, organization of the formed nanoplates into flowerlike hierarchical structure in the assistant of HAc adsorption on the surface of nanoplates and the hydrogen bonds formed between carboxyls. For its special flowerlike hierarchical structure, Bi₂WO₆ can be used as photocatalyst for potential application in environment protection problems. In this work, the obtained flowerlike hierarchical Bi₂WO₆ exhibited excellent visible-light-driven photocatalytic efficiencies for the degradation of RhB within 60 minutes, which were much higher than those of TiO₂ （P25） and Bi₂WO₆ sample prepared by solid-state reaction （SSR- Bi₂WO₆）. Besides, we concluded the photodegradation of RhB with two competitive processes: a photocatalytic process and a photosensitized process. Both the photocatalytic process and the photosensitized process would work concurrently under visible light irradiation, but the former was the predominant process.4. In order to further improve the photocatalytic activity of bismuth based photocatalysts, several materials were introduced to modify the surface of the photocatalysts. We modified Bi₂WO₆ with PtCl4 and Bi_3.64Mo_0.36O_6.55 with carbon, and systematically studied their influences on photocatalytic activity of bismuth based photocatalysts. （1） Flowerlike PtCl4/Bi₂WO₆ composite photocatalyst was successfully synthesized through a simple two-step method involving a template-free hydrothermal process and the following impregnation treatment. The results indicated that the introducing of PtCl4 did not affect the crystal structure and the morphology of Bi₂WO₆ photocatalyst, but it had great influences on the photocatalytic activity of Bi₂WO₆ towards RhB degradation, and also an optimal Pt species content on the surface of Bi₂WO₆ photocatalyst was discovered with the highest photocatalytic ability. The improved photocatalytic performance could be ascribed to the increased photoabsorption ability, the enhanced interfacial charge transfer and the inhibited recombination of electron-hole pairs by modified with PtCl₄. Meanwhile, a possible mechanism for RhB photocatalytic degradation over PtCl4/Bi₂WO₆ catalyst was also proposed. （2） The bismuth molybdate Bi_3.64Mo_0.36O_6.55 （BMO） was successfully synthesized by a rapid and convenient microwave-assisted method. Carbon was introduced to hybridize with BMO material through the simple combination of hydrothermal process in the presence of glucose and subsequent calcination treatment in N₂ gas at 280°C. The results indicated that carbon did not affect the final crystalline structure and morphology of BMO, but it had great influences on the photocatalytic activity of BMO towards RhB degradation. The improved photocatalytic performance could be ascribed to the synergetic effects of increased photoabsorption ability, enhanced photogenerated electron-hole separation and more RhB adsorption associated with carbon.更多还原