【作者】 常春；

【导师】 祝凌燕；

【作者基本信息】 南开大学 ， 环境科学， 2013， 博士

【摘要】 双酚A(BPA,2,2-bis(4-hydroxyphenyl)propane)是一种化工原料,主要用于聚碳酸酯和环氧树脂等产品的合成。由于广泛的生产和使用,大量的BPA被释放到自然水体中。同时,研究发现BPA具有内分泌干扰效应,可诱导女性乳腺癌,男性前列腺炎等疾病的发生,还可以导致婴幼儿性早熟。因此关于BPA有效降解技术(包括物理、化学和生物)的研究受到了普遍关注。TiO2光催化技术由于操作简便、能耗低、反应条件温和、高效而又无毒等优点而具有较好的应用前景。但是由于TiO2吸收的紫外光仅占太阳光谱的不到5%,为了更好的利用太阳能,开发具有可见光响应的光催化剂具有重要的意义。本文首先使用热缩合联合液相还原法合成了具有可见光响应的光催化剂——金属钯掺杂介孔石墨相氮化碳,并将其应用于水中BPA的降解。金属钯的掺杂增强了材料对光的吸收,抑制了光生电子和空穴的复合,从而促进催化剂对BPA的光催化降解,最佳掺杂量为1.5%。研究结果显示：0.5g L-1的1.5%-Pd/mpg-C3N4在模拟太阳光照射下,经过6h将20mg L-1的BPA全部降解；金属钯的掺杂同时也增强了催化剂的光电性能,1.5%-Pd/mpg-C3N4的光电流强度是mpg-C3N4的2倍；1.5%-Pd/mpg-C3N4光催化剂在较宽的pH值范围(3.08-11.00)内保持良好的光催化降解效果；并具有很好的抗光腐蚀性,循环反应十次依然具有很好的光催化活性。通过ESR-DMPO捕获以及各种捕获剂的验证实验,表明在1.5%-Pd/mpg-C3N4光催化降解BPA起作用的活性物种为羟基自由基,空穴和超氧自由基,并且以超氧自由基为主。其次,通过一步溶剂热反应合成了一种新的复合材料Bi/BiOI,并采用XRD、 FE-SEM、HR-TEM、FT-IR、UV-vis DRS、XPS、比表面积及孔径分布等测试手段对合成材料进行表征。实验结果显示通过控制溶剂热反应温度和时间可以调控产物的化学组成、结晶度以及形貌。在180℃溶剂热反应24h合成出的催化剂(金属铋含量约12.5%)在模拟太阳光照射下对BPA具有最好的光催化降解活性,对40mg L-1的BPA光催化降解90min后,去除率可以达到92.8%,在同样实验条件下,TOC去除率可以达到79.0%。光催化剂的用量、污染物初始浓度以及溶液初始pH值等实验条件均对BOI-180-24降解BPA产生不同程度的影响。通过向反应体系投加不同活性基团捕获剂,确定在BOI-180-24光催化降解BPA过程中起主要作用的活性物种为：光生空穴、超氧自由基以及单线态氧。通过LC/MS/MS检测降解中间产物(m/z=133),推测BPA的降解历程为：BPA经活性物种氧化分解成4-异丙基苯酚以及对苯二酚或苯酚,进一步被矿化为C02和H2O。最后,通过溶剂热法合成了n型有机聚合物半导体MCN/p型无机半导体BiOI异质结光催化剂,通过XRD, FE-SEM, HR-TEM, FT-IR, UV-vis DRS, XPS,比表面积测试等对合成样品的晶体结构,形貌,组成,光吸收性能等进行了相关表征。MCN和BiOI两种半导体形成异质结后伴随着产生从n-MCN到p-BiOI的内电场,它促进了光生电子和空穴的有效分离。这使得所合成MCN/BiOI复合材料的光催化和光电化学性能都比单独的MCN和BiOI要好,且在MCN掺入量为10%时所合成催化剂具有最佳的活性。1.0g L-1的10%-MCN/BiOI经可见光照射240min能够对20mg L-1BPA去除率可达90%；所合成MCN, BiOI以及MCN/BiOI复合光催化剂,在可见光激发下都可以产生光电流,10%-MCN/BiOI产生的光电流是纯BiOI的1.5倍,是纯MCN的2倍。实验结果表明MCN/BiOI光催化降解机理以光生电子与表面氧反应生成的超氧自由基有关,超氧自由基在降解过程中其主要作用。更多还原

【Abstract】 Bisphenol A (BPA,2,2-bis(4-hydroxyphenyl)propane) is an important building block material and used extensively as the monomer to manufacture polycarbonate plastic and epoxy resins. Due to its large production and wide application, a large amount of BPA has been released into the aquatic environment. Unfortunately, it could cause adverse effects to human beings, such as the occurrence of breast cancer for female and prostatitis for male and so on. It could also result in the sexual precocity of infants. Thus, a great concern has been raised to remove BPA from water by different techniques, such as physical absorption, chemical remediation, and microbial degradation. Among these methods, photocatalytic degradation with TiO2is attracting widespread attention due to its simplicity, low energy consumption, mild reactive conditions, effective activity and low toxicity. However, TiO2could only use <5%solar energy for photodegradation due to its large bandgap energy, and this restricts its application. It is of significance to develop new photocatalysts to utilize solar energy efficiently.Firstly, palladium modified mesoporous graphitic carbon nitride polymer (Pd/mpg-C3N4) was fabricated by thermal condensation coupled with liquid phase reduction and used for the degradation of bisphenol A (BPA) in water. Doping Pd on the surface of mpg-C3N4enhanced the light absorbance in the range of UV-Vis region. Most of the embedded Pd was present as Pd0and could act as electron traps and reduce the recombination of photogenerated holes and electron pairs. As a result, the photocatalytic performance was improved significantly. The reaction rate constant (Kobs) increased with the Pd loading on the surface of mpg-C3N4and the maximum was achieved with1.50%Pd. Almost100%of BPA (20mg·L-1) was photodegraded by the solids of0.5g·L-1Pd/mpg-C3N4after irradiation with simulated solar light for360min, meanwhile, the photocurrent intensity generated by1.5%-Pd/mpg-C3N4electrode was also enhanced and was about2.0times of that induced by mpg-C3N4under visible light irradiation. The Pd/mpg-C3N4exhibited very stable and high efficient photocatalytic activity to BPA in a wide range of pH (3.08-11.00). It also displayed high photocatalytic activity without photocorrosion after reuse for many times. Hydroxyl radicals, photogenerated holes, and superoxide radical species were responsible for the photodegradation while the superoxide radical species were more predominant in the Pd/mpg-C3N4reaction system.Secondly, a novel3D Bi/BiOI composite was synthesized by a facile one-step solvothermal method. The resultant catalysts were comprehensively characterized by means of XRD、FE-SEM、HR-TEM、FT-IR、UV-vis DRS、XPS、and N2adsorption/desorption. The solvothermal temperature and reaction time affected the chemical compositions, crystallinity and morphology of the prepared materials. The photocatalyst prepared at180℃for24h (BOI-180-24) contained approximate12.5%metallic Bi and displayed the best photocatalytic performance to BPA under simulated solar light irradiation. About92.8%of40mg L-1BPA was degraded after90min reaction using1g L-1BOI-180-24as catalyst under simulated solar irradiation, while79.0%of TOC was removed at the same time. The photocatalytic efficiency was affected by many factors, such as the amount of photocatalyst, the initial concentration of BPA and pH and so on. Photogenerated holes, superoxide radical species and singlet oxygen were responsible for the photodegradation while the superoxide radical species were more predominant in the Bi/BiOI photocatalytic reaction system. Only one intermediate (m/z133) was observed by LC-MS/MS and a simple degradation pathway of BPA was proposed:BPA was first oxidized to4-isopropenyphenol and hydroquinone or phenol which was further transfer to CO2and H2O.Finally, a novel organic-inorganic3D mesoporous graphite carbon nitrogen/BiOI (MCN/BiOI) heterojunction photocatalyst was synthesized by a facile solvothermal method. The crystal phase, morphology, constituent and light absorbance of the resultant was characterized by XRD, FE-SEM, HR-TEM, FT-IR, UV-vis DRS, XPS, and N2adsorption/desorption. After hybridization with MCN, a heterojunction would be formed and then photogenerated carriers could be effectively separated by the internal electric field built at the heterojunction interface. The photocatalytic and photoelectrochemical performance of BiOI was improved and was much higher than pure BiOI and MCN. The composite with10%MCN displayed the highest photocatalytic performance, and about90%of BPA (20mg-L-1) was photodegraded by the solids of1.0g·L-110%-MCN/BiOI after irradiation with visible light for240min. The photocurrent intensity generated by10%-MCN/BiOI electrode was about1.5and2.0times of those induced by BiOI and MCN under visible light irradiation, respectively. The superoxide radical species were predominant in the reaction system.更多还原