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国内外的饮用水中均检测出医药品污染物,其浓度通常处于ng·L−1或更低水平. 风险评价研究显示,饮用水中微量的医药品污染物对于健康的成年人影响较小,但是敏感性人群特别是孕妇及新生儿暴露于环境中的风险需要加以考虑[1]. 布洛芬(IBU)属于抗炎药物,据估计全球年产量达数千吨,其在地表水和废水中检测到的浓度范围为ng·L−1至低μg·L−1水平[2];传统的水处理技术无法对持久性污染物IBU有效去除,研究发现IBU能对淡水环境中的无尾类动物的胚胎发育产生影响[3]. 非均相催化臭氧氧化技术是一种能够在室温和常压下,将那些难以通过臭氧单独氧化的有机污染物高效分解的方法[4-5]. 臭氧在催化剂表面有效分解产生羟基自由基等活性氧来降解水中有机污染物[6-7]. 由于不同催化剂的属性差异较大,其促进臭氧有效分解的机理还不清楚,需要深入研究催化臭氧氧化水中有机污染物的作用机制[8-9].
本文采用固体酸γ-Al2O3和多价态的钛活性组份负载法制备了TiO2/γ-Al2O3介孔催化剂. 由于TiO2的Lewis酸性强于Al2O3,通过调节钛的负载量来控制γ-Al2O3的酸量,从而更深入的研究Lewis酸性位对布洛芬去除的影响,并通过吡啶红外光谱、电子自旋共振和原位激光显微拉曼光谱等测试手段来探究催化反应机理.
TiO2/γ-Al2O3催化臭氧氧化水中布洛芬
Catalytic ozonation of ibuprofen by TiO2/γ-Al2O3 in water
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摘要: 以葡萄糖为模板,采用蒸发诱导自组装法合成了γ-Al2O3介孔催化剂,以钛酸四正丁酯(TBOT)为原料制备TiO2/γ-Al2O3催化剂,并将其用于催化臭氧氧化水中布洛芬(IBU). X射线衍射、扫描电子显微镜、氮气吸附-脱附和吡啶红外光谱表征结果表明,TiO2均匀负载于γ-Al2O3表面,保持γ-Al2O3有序的介孔结构,具有较大的比表面积和更多的Lewis酸性位. 不同催化剂活性评价结果表明,TiO2的负载显著提高γ-Al2O3催化臭氧氧化水中布洛芬的活性,反应60 min,TiO2/γ-Al2O3催化剂的TOC去除率达到80%,而γ-Al2O3、TiO2及单独臭氧氧化过程中TOC去除率则分别达到62%、32%及26%. 电子顺磁共振和原位激光显微拉曼光谱实验结果表明,Lewis酸性位为臭氧高效分解的活性位,活性原子氧和过氧物种是TiO2/γ-Al2O3催化臭氧氧化反应的活性氧物种,有利于有机物的矿化,从而表现出最高的催化活性. 重复利用实验结果表明,TiO2/γ-Al2O3催化剂具有较长的使用寿命.
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关键词:
- TiO2/γ-Al2O3 /
- 催化臭氧氧化 /
- 活性原子氧 /
- 布洛芬.
Abstract: The γ-Al2O3 mesoporous catalyst was synthesized by evaporation-induced self-assembly method using glucose as template. TiO2/γ-Al2O3 catalyst was prepared from tetrabn-butyl titanate (TBOT) as raw material, and was used to catalytic ozonation of ibuprofen (IBU) in water. The results of X-ray diffraction, scanning electron microscopy, nitrogen adsorption-desorption and pyridine infrared spectroscopy showed that titanium dioxide was uniformly loaded on the surface of γ-Al2O3, maintaining the ordered mesoporous structure of γ-Al2O3, with larger specific surface area and more Lewis acidic sites. The evaluation results of different catalyst activities showed that TiO2 support significantly improved the activity of γ-Al2O3 catalytic ozonation of ibuprofen in water, and the TOC removal rate of TiO2/γ-Al2O3 catalyst reached 80% after 60 min reaction. The TOC removal rates of γ-Al2O3, TiO2 and ozonation alone reached 62%, 32% and 26%, respectively. The results of electron paramagnetic resonance (EPR) and in-situ laser micro-Raman spectroscopy showed that Lewis acid sites were the active site for effective decomposition of ozone, while active atomic oxygen and peroxy species were the active oxygen species of TiO2/γ-Al2O3 catalytic ozonation reaction, which was conducive to the mineralization of organic matter and showed the highest catalytic activity. The reuse experiment results showed that the TiO2/γ-Al2O3 catalyst had a long service life.-
Key words:
- TiO2/γ-Al2O3 /
- catalytic ozonation /
- active atomic oxygen /
- ibuprofen.
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表 1 催化剂的比表面、孔径、孔容和孔壁
Table 1. Specific surface area, pore diameter, pore volume, and pore wall of catalysts
催化剂
Catalyst比表面积/ (m2·g−1)
S BET孔径/ nm
Pore diameter孔容/(cm3·g−1)
Pore volumeγ-Al2O3 252.81 0.50 6.13 TiO2/γ-Al2O3 221.97 0.47 5.86 表 2 吡啶-红外光谱测定的不同催化剂的Lewis酸量
Table 2. Amount of Lewis acid sites of different catalysts determined by Pyridine-FTIR
催化剂
Catalyst总酸量/(μmol·g−1)
Total acid中强酸量/(μmol·g−1)
Medium acid强酸量/(μmol·g−1)
Strong acidγ-Al2O3 540.1 197.4 61.1 TiO2/γ-Al2O3 653.8 222.9 85.4 -
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