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间甲酚是酚类化合物中具有代表性的一种物质,广泛存在于煤化工、石油化工、制药废水等工业废水中,它的存在是造成工业废水难被生物降解的原因之一,具有腐蚀性和强烈刺激性,已被美国环保署列为11种难降解酚类化合物之一,同时也是我国水污染优先控制污染物黑名单中的一类。间甲酚的处理技术一般采用高级氧化法,可以在较短的时间内使间甲酚转化为其他小分子脂肪族化合物或完全矿化,为煤气化废水的治理奠定了基础[1-3]。
催化臭氧氧化法利用O3,在催化剂的作用下,产生了氧化能力极强的 · OH,以降解水中的有机物,具有反应速度快、不产生污泥和二次污染、显著提高废水可生化性等优点[4-6],但其O3转化率较低,工艺成本比较高。在此体系中加入H2O2后,H2O2和O3协同作用,可以显著加快O3分解产生 · OH的速率,既能提高处理效果,又能帮助降低经济成本。为了获得这一优势,可以将O3和H2O2进行联用。催化臭氧氧化技术常选用非均相氧化法,催化剂多以金属氧化物、金属负载于载体上及经金属改进的沸石、活性炭为主 [7]。与均相催化剂相比,非均相催化剂具有活性高、流失少、便于回收等优点,因此,选用非均相催化剂投入到O3/H2O2体系中考察其处理效果。
本研究采用等体积浸渍法制备了Fe-Mn/γ-Al2O3催化剂,考察O3氧化法、催化O3氧化法、催化H2O2氧化法以及催化O3-H2O2氧化法对间甲酚的降解效果,系统分析了pH、空速等对催化O3-H2O2氧化间甲酚的影响,同时表征了催化剂的性能,并对比了4种催化氧化条件下的氧化产物,为2种技术联用降解煤化工废水提供了参考。
Fe-Mn/γ-Al2O3催化O3-H2O2协同氧化间甲酚
Catalytic peroxide and ozone co-oxidation of m-cresol by Fe-Mn/γ-Al2O3
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摘要: 为提高臭氧氧化法对难降解有机污染物的降解效率,采用在催化臭氧氧化体系中引入H2O2的方法,建立催化O3-H2O2联合氧化体系,使O3与H2O2在体系中起协同作用。采用等体积浸渍法筛选制备了具有高催化性能的 Fe-Mn/γ-Al2O3 催化剂,应用于O3/Fe-Mn/γ-Al2O3/H2O2 复合体系协同催化臭氧氧化处理间甲酚模型废水。通过扫描电子显微镜(SEM)、物理吸附、X射线衍射(XRD)、X射线荧光光谱(XRF)、X射线光电子波谱(XPS)对催化剂的物理化学性质进行表征。考察了O3 投加量、H2O2 投加量、初始pH、空速等因素对Fe-Mn/γ-Al2O3催化O3-H2O2氧化间甲酚处理效果的影响,并采用GC-MS和LC-OCD,对Fe-Mn/γ-Al2O3催化O3-H2O2氧化间甲酚的中间产物的类型及相对分子质量进行分析。结果表明,当以Fe-Mn/γ-Al2O3为催化剂时,协同催化氧化体系的最优处理参数为:间甲酚浓度100 mg·L−1,O3 投加量481 mg·L−1,反应时间10 min,空速6 h−1,H2O2投加量211 mg·L−1,进水pH 6.7。在此条件下,TOC去除率可达68.37%,间甲酚转化率可达100%。以上研究结果可为2种技术联用降解煤化工废水提供参考。Abstract: In order to improve the degradation efficiency of ozone oxidation for refractory organic pollutants, a method of introducing H2O2 into the catalytic ozone oxidation system is uesd to establish a catalytic O3-H2O2 combined oxidation system, so that O3 and H2O2 have a synergistic effect in the system. A type of Fe-Mn/γ-Al2O3 catalyst which was selected because of the high catalytic performance was prepared by incipient impregnation method, and was applied in the O3/Fe-Mn/γ-Al2O3/H2O2 composite system to catalytic co-oxidation of m-cresol simulated wastewater. Scanning electron microscope (SEM), physical adsorption, X-ray diffraction (XRD), X-ray fluorescence spectrometry (XRF), X-ray photoelectron spectroscopy (XPS) were used to determine the physical and chemical characteristics of the catalyst. The effect of catalytic O3-H2O2 oxidation with Fe-Mn/γ-Al2O3 were investigated, namely O3 dosage, H2O2 dosage, initial pH and space velocity. The intermediate types and molecular weight of products from the m-cresol catalytic oxidation degradation process by Fe-Mn/γ-Al2O3 were also analyzed using GC-MS and LC-OCD. The result by optimized experimental analysis shows that when Fe-Mn/γ-Al2O3 is selected as the catalyst, the highest m-cresol conversion rate of 100% and the highest TOC removal of 68.37% were obtained with the O3 dosage of 481 mg·L−1 of water and H2O2 dosage of 211 mg·L−1 water when the concentration of m-cresol was 100 mg·L−1, reaction time is 10 min, space velocity is 6 h−1 and initial pH is 6.7. The results of this study provide a reference for the combination of two technologies to degrade coal chemical wastewater.
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Key words:
- O3-H2O2 /
- catalytic oxidation /
- m-cresol
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表 1 γ-Al2O3及Fe-Mn/γ-Al2O3的物理吸附测试
Table 1. Physical adsorption test of γ-Al2O3 and Fe-Mn/γ-Al2O3
材料种类 比表面积/ (m2·g−1) 平均孔径/ nm γ-Al2O3 189.59 7.95 Fe-Mn/γ-Al2O3 181.08 9.77 表 2 Fe-Mn/γ-Al2O3催化剂表面的O1s XPS图谱分析
Table 2. Analysis of O1s XPS spectra on the surface of Fe-Mn/γ-Al2O3 catalyst
催化剂 电子结合能/eV 峰面积占比/% Oad OL Oad OL 新鲜催化剂 531.37 530.57 84.56 15.44 反应后的催化剂 532.03 530.87 83.08 16.92 -
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