【作者】 王震；

【导师】 史惠祥；

【作者基本信息】 浙江大学 ， 环境工程， 2014， 博士

【摘要】 染料废水是目前最难降解的工业废水之一,随着染料工业的蓬勃发展,对水体等环境的危害日趋严重。如何绿色经济地处理染料废水逐渐受到人们重视。半导体光催化技术具有速度快、无选择性、降解完全等优点,在处理染料废水方面备受关注。但是,目前传统的光催化材料存在只能利用紫外光、光生载流子复合率高、粉体催化剂难以分离回收等难题而大大限制了其应用。具有高催化活性的可见光响应催化剂的制备与应用,已成为研究人员广泛关注和研究的热点课题。本论文围绕Ti02和Ag3PO4等潜力光催化剂,从催化剂的合成和改性入手,制备了Ti-Cr-MCM-48、Ag3PO4/MWCNT、AgBr/Ag3PO4/Fe3O4等一系列可见光催化剂,通过多种表征手段考察其结构、形貌、光吸收性质及可见光条件下对甲基橙染料的降解性能。本论文的主要研究内容如下：1、采用十六烷基三甲基溴化铵为模板剂,钛酸异丙酯为钛源、正硅酸乙酯为硅源,硝酸铬为金属前驱体,结合超声-水解合成工艺,一步法制备了具有可见光活性的Ti-Cr-MCM-48钛硅分子筛催化剂。结果表明,Ti-Cr-MCM-48具有良好的可见光活性,5h内对甲基橙的降解效率达到81%,远高于Cr-MCM-48相同时间内45%的甲基橙降解效率,而MCM-48几乎无可见光催化活性。Ti-Cr-MCM-48的高催化活性这主要归因于Ti-O-Cr异质结间良好的电子传递作用。2、通过沉淀法比较分析了三种沉淀剂(Na3PC、Na2HPO4和NaH2PO4)对Ag3PO4形貌和催化活性的影响。通过简单的控制溶剂pH值来寻求制备高效Ag3PO4光催化剂。结果表明,酸性条件下制备的Ag3PO4具有最佳的光催化活性,40min就可以使甲基橙完全褪色,其表观反应速率常数是碱性条件下制备的Ag3PO4的5.2倍。3、以十二烷基硫酸钠为辅助剂,采用原位沉淀法制备合成了Ag3PO4/MWCNT复合催化剂。结果表明,MWCNTs提高了与Ag3PO4的光催化降解效率和稳定性。Ag3PO4/1.4wt%MWCNT光照反应12min后即可完全降解甲基橙,其表观化学反应速率达到0.258min-1,是纯Ag3PO4的5.84倍。并且循环三次后Ag3PO4/1.4wt%MWCNT的光催化活性依然保持有最初的85.6%。4、针对粉体Ag3PO4难回收利用的问题,利用磁性Fe304固定Ag3PO4,增强磁分离能力,并通过在Ag3PO4的表面复合AgBr纳米颗粒,提高Ag3PO4光催化剂的稳定性。制备的AgBr-80/Ag3PO4/Fe3O4复合催化剂光照反应15min后可完全降解甲基橙,远高于纯Ag3PO4相同时间内不到50%的甲基橙降解效率,并且循环反应三次后,其光催化活性仍然保持在95%以上。光催化效率和稳定性相对Ag3PO4得到很大提高。同时,AgBr/Ag3PO4/Fe3O4复合催化剂具有良好的磁分离能力,在外加磁场的作用下180s内就可以从反应液中分离。更多还原

【Abstract】 Dye wastewater is among the largest groups of water pollutants in the world. With the rapid development of the dye industry, the removal of these non-biodegradable dye molecules from the environment is a crucial ecological problem due to their toxicity and potential carcinogenicity. It has drawn much attention to the vital need for ecologically clean chemical technologies. Over the past few decades, semiconductor-based photocatalysis for its high efficiency and promising economy has been extensively developed to treat dye wastewater. However, it should be noted that the traditional photocatalyst can only utilize the ultraviolet light (about4%solar spectrum). Moreover, due to its low quantum efficiency as well as the difficulty in separation and reuse of the powder catalysts, the practical application of the photocatalyst is greatly limited. Thus, it is urgently required to develop effective strategies to explore novel, highly efficient visible light driven photocatalysts to the environmental pollution control.In the present work, based on the two excellent photocatalyst of TiO2and Ag3PO4, we try to synthesize a series of visible light driven photocatalysts such as Ti-Cr-MCM-48、Ag3PO4/MWCNT. AgBr/Ag3PO4/Fe3O4with various structures and morphology. The morphology and photocatalytic activity of the as prepared photocatalysts were characterized through a variety of characterization methods and the degradation of methyl orange dye under visible light.The main results of the present work were summarized as follows:1. Ti-Cr-MCM-48photocatalyst was successfully synthesized via a facile and rapid one-step approach at room temperature, which takes CTAB as a template, Cr(NO3)3·9H2O and titanium isopropoxide as metallic precursors, and TEOS as source of silicon. The results shows that the Ti-Cr-MCM-48exhibits good visible light activity. The degradation of MO over Ti-Cr-MCM-48was reached to81%in5h, which is much higher than that of Cr-MCM-48(45%in5h). The high activity of Ti-Cr-MCM-48was closely associated with the formation of Ti-O-Cr structure.2. A high-performance Ag3PO4photocatalyst was prepared with different phosphate salts (Na3PO4, Na2HPO4, and NaH2PO4) through a precipitation method. Due to the different pH in preparation system, the type of phosphate salt used as a precipitating agent can affect the purity, morphology, particle size, and photocatalytic activity of the prepared Ag3PO4powder. The results indicate that the Ag3PO4sampled prepared from NaH2PO4showed better photocatalytic efficiency of MO under visible light (100%in40min), compared with those prepared from Na2HPO4andNa3PO4. The degradation rate of MO over the Ag3PO4sampled prepared from NaH2PO4was about5.2times faster than that of the Ag3PO4sampled prepared from Na3PO4.3. Ag3PO4/MWCNT composite was successfully synthesized via in-situ precipitation method. The MWCNTs play a key role for the enhanced pho-tocatalytic activity and stability of Ag3PO4. The Ag3PO4/1.4wt%MWCNT sample shows optimal photocatalytic ability over MO (100%in12min), which improved by nearly55%compared with pure Ag3PO4. The rate constant of MO degradation over Ag3PO4/1.4wt%MWCNT is5.84times that of pure Ag3PO4. Moreover, The photocatalytic activity of Ag3PO4/MWCNT sample decreased slowly in three successive experimental runs.4. A novel magnetically recoverable AgBr/Ag3PO4/Fe3O4hybrid was successfully synthesized via in-situ precipitation method. Because of the magnetism of Fe3O4and the matching band between AgBr and Ag3pO4, the as-synthesized AgBr/Ag3PO4/Fe3O4nanoparticles exhibited efficient photocatalytic activity, good stability and recyclability toward decomposition of methyl orange (MO) dye under visible light irradiation. The AgBr-80/Ag3PO4/Fe3O4sample shows optimal photocatalytic ability over MO (100%in15min), which is much higher than that of pure Ag3PO4(50%in15min). Moreover, after three successive experimental runs, the photocatalytic activity of AgBr/Ag3PO4/Fe3O4still reached to95%of the initial efficiency. Besides, the as-prepared AgBr/Ag3PO4/Fe3O4can be conveniently collected from the solution by applying an external magnetic field within3min.更多还原