【作者】 赵先辉；

【导师】 储金宇； 李华明；

【作者基本信息】 江苏大学 ， 环境工程， 2007， 硕士

【摘要】 自1972年Fujishima和Honda报道了TiO₂电极光分解水以来，因半导体光催化剂转换太阳能净化环境方面有广泛的应用，大多数研究都集中在这方面。在众多的光催化剂中，Bi_WO₆已被证实具有合适的价带和良好的物理性能，如铁电性、热电性、非线性传导磁化性、催化活性，被认为是能有效光解水和降解有机污染物的可见光型催化剂。实验分别采用共沉淀法和固相法合成催化剂Bi₂WO₆，并利用浸渍法对合成的Bi₂WO₆催化剂进行改性，形成金属（Ag，Cu等）掺杂型光催化剂。并以亚甲基蓝（Methylene Blue，MB）为模型化合物，在可见光条件下研究Bi₂WO₆催化剂用量、pH值、光照强度、空气流量、光照时间、初始浓度等因素对亚甲基蓝降解率的影响，并初步探讨了可见光下Bi₂WO₆光催化降解亚甲基蓝的动力学特征。实验结果表明：共沉淀法合成的催化剂在可见光照射下光催化降解亚甲基蓝的效果远远好于固相法合成的催化剂。当共沉淀法合成的催化剂用量为0.2g／L，pH值为9.30，亚甲基蓝的初始浓度为10 mg／L时，对亚甲基蓝降解的效果最佳，4 h后亚甲基蓝的降解率达到80％。同时还研究了光催化降解亚甲基蓝的动力学特征，发现该降解反应符合一级反应动力学特征。实验还研究了采用共沉淀法合成的Bi₂WO₆光催化剂对亚甲基蓝的吸附性能。结果表明：Bi₂WO₆对亚甲基蓝的最大吸附量达16.46 mg／g，其吸附规律较好的符合Langmuir吸附等温式；Bi₂WO₆对亚甲基蓝吸附速率较快，在25℃条件下0.02 g Bi₂WO₆对100.0 ml含10.0 mg／L的亚甲基蓝溶液吸附时间为30 min时，亚甲基蓝的吸附达到平衡；Bi₂WO₆对亚甲基蓝的吸附率随着温度和Bi₂WO₆用量增加而增大。研究表明，金属掺杂型Bi₂WO₆催化剂的光催化活性有所降低，这可能是因为金属离子的介入导致了催化剂晶体结构的变化。其中Ag离子的掺杂效果较好，同时，还考察了Ag掺杂量对催化剂活性的影响，发现在3wt．％时降解效果最佳。实验中通过XRD、SEM、TG-DSC等表征分析发现：在600℃热处理条件下，XRD谱图中Bi₂WO₆的衍射峰出现；热分析表明当温度升高到450℃左右，催化剂中所含的硝酸盐等大部分杂质被去除，800℃以上Bi₂WO₆处于热稳定状态。更多还原

【Abstract】 In recent years, a large number of investigations have focused on the semiconductor photocatalyst for its wide applications in solar energy conversion and environmental purification since Fujishima and Honda discovered the photocatalytic splitting of water on the TiO₂ electrodes in 1972．Among various oxide photocatalyst, Bi₂WO₆ was reported that it had a suitable valence band and possessed interesting physical properties, such as ferroelectric piezoelectricity, pyroelectricity, a nonlinear dielectric susceptibility and catalytic behavior. It has been recognized as a photocatalst for water splitting and pollutant degradation under visible light irradiation.The Bi₂WO₆ photocatalyst were prepared by simple co-precipiation process and solid-state reaction method, metal particles were loaded on the Bi₂WO₆ catalyst by deposition method. The photocatalytic activity of Bi₂WO₆ was evaluated by methylene blue under visible light irradiation （λ>400 nm）.The MB degradation was examined to assess the pH value, initial concentration of MB , illumination intension, air flux, illumination times, the dosage of catalyst and metal particles loaded. The results demonstrated that the activity of catalyst which were prepared by co-precipiation process much better than prepared by solid-state reaction method. In the former MB/Bi₂WO₆ system, MB was effectively degraded by about 80% within 4 h, when the dosage of catalyst was 0．2 g/L, the initial concentration of MB was 10 mg /L and pH was 9．30．Results of kinetic study show that the degradation of MB using Bi₂WO₆ followed the first-order reaction kinetic model.In the present study the adsorptive properties of Bi₂WO₆ to MB were studied. The results include the following: the maximum MB adsorption capacity was 16．46 mg/g and the adsorption accord with Langmuir adsorption isotherm preferable; the adsorption velocity of menthylene blue executed by B₂WO₆ is comparable high. The adsorption rate could reach adsorption balance within 30 min at 25℃when we added 0．02 g Bi₂WO₆ to 100 mL 10 mg/L menthylene blue solution. To sum up, Bi₂WO₆ could rapidly and effectively adsorb menthylene blue in solution; the adsorption of menthylene blue increases alongside the rise of temperature and augment of the Bi₂WO₆ usage.But the activity of catalyst was decreased when Bi₂WO₆ catalyst loaded metal particles. It maybe because of the variation of crystal structure after metal ions entered. Among the metal-Bi₂WO₆, Ag-loaded photocatalyst had a better effect, and also found that when the content of Ag was 3 wt.%, the best photocatalytic degradation efficiency of MB was obtained. The samples were characterized with XRD, SEM, TG-DSC. It was found that the diffraction peaks of Bi₂WO₆ catalyst appeared at 600℃. TG-DSC analysis indicated that NO₃ had been removed at 450℃, and Bi₂WO₆ had been in steady state after 800℃.更多还原