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题名: 铁铝金属氧化物活性材料对多氯萘的降解研究
作者: 芦会杰
学位类别: 硕士
答辩日期: 2015-05
授予单位: 中国科学院研究生院
授予地点: 北京
导师: 苏贵金
关键词: 氧化铁,氧化铝,铁铝复合氧化物,多氯萘,降解,iron oxide, alumina, iron and aluminum composite oxide, polychlorinated naphthalenes, degradation
其他题名: Study on Degradation of Polychlorinated Naphthalenes by Iron Oxides and Aluminum Oxides
学位专业: 分析化学
中文摘要:     氯代芳烃是一种难降解的持久性有机污染物,由于其高毒性、难降解及在食物链中富集,对环境和人类健康具有极大的危害。因此,对氯代芳烃进行消减处理具有十分重要的意义。
金属氧化物尤其是一些复合金属氧化物因具有活性高、热稳定性好、来源丰富以及价格低廉等一系列的优点,在催化领域得到了广泛应用。多氯萘(PCNs)作为一种新型的持久性污染物,具有和二恶英相似的结构和毒性,在环境中广泛存在且不易降解,对环境和人体健康具有极大的危害。多氯萘常伴随非故意生产而排放,因此对非故意产生的多氯萘废弃物的处置问题一直存在。在此基础上,迫切需要开发能耗低、经济、绿色、高效的处理新方法。本研究以多氯萘为降解的目标污染物,利用气相色谱-质谱联用仪、红外光谱仪等手段,系统研究了氧化铁、氧化铝及铁铝复合氧化物对多氯萘的降解,获得的主要研究结果有:
1. 深入研究了通过乙二醇介导法合成的Fe2O3微/纳米材料对八氯萘(CN-75)在300 °C的热催化降解。结果表明,Fe2O3微/纳米材料对CN-75具有高效的降解活性,反应时间为60 min时,降解效率高达99.94%,降解过程满足准一级动力学,速率常数为0.075 min-1。根据加氢脱氯降解产物的定性定量结果推测出CN-75在Fe2O3上的主要加氢脱氯反应历程:CN-75→CN-73→CN-66/67→PeCNs→TeCNs→CN-20→CN-8/11。检测到部分的开环产物甲酸和乙酸,说明CN-75在Fe2O3上的降解,除加氢脱氯反应外,还存在氧化降解。
2. 采用水热法制备了形貌为棒状纤维形的α-Al2O3、η-Al2O3和γ-Al2O3。γ-Al2O3具有最小的颗粒直径。自制的α-Al2O3、η-Al2O3和γ-Al2O3对1-氯萘(CN-1)的降解的实验结果表明,在相同的反应条件下,降解效率的大小关系:γ-Al2O3>η-Al2O3>α-Al2O3。这是因为γ-Al2O3具有最大的比表面积(135.0 m2/g),γ-Al2O3表面具有最多的活性氧物种,γ-Al2O3表面存在强Lewis酸和Bronsted酸。
3.利用气相色谱-质谱联用仪检测到的主要产物是萘和1,4-二氯萘(CN-5),说明CN-1在Al2O3表面发生反应时,加氢脱氯反应与反加氢脱氯反应同时存在。在三种晶型的Al2O3催化反应体系中检测到的萘和1,4-二氯萘两种产物的生成量不同,γ-Al2O3催化反应体系中萘和1,4-二氯萘的含量都高于其他两种晶体。在线红外分析结果显示,α-Al2O3和η-Al2O3催化反应体系中,反应物芳香环中碳的红外振动峰的响应随温度变化不明显;γ-Al2O3催化反应体系中,反应物芳香环中碳的红外振动峰的响应随温度变化明显。
4. 通过浸渍法制备出形貌为棒状纤维形的铁铝复合氧化物材料(FeAlxOy)。FeAlxOy对1,2,3,4-四氯萘(CN-27)降解的实验结果显示,随Fe所占比重的增加,FeAlxOy的活性先增大后减小。摩尔配比的不同,加氢脱氯产物也随之改变。在铁、铝摩尔配比为5:100的FeAlxOy和CN-27反应后的产物中检测到了1,2,7,8-TeCN(CN-41)、1,2,7-TrCN(CN-17)、1,4-DiCN(CN-5)和1,5-DiCN(CN-6)。产物以二氯萘为主,在总产物中占的摩尔百分比为86.2%。检测到的二氯萘的两种单体CN-5与CN-6的摩尔比为2.5:1,说明CN-5是主要的二氯萘的产物。在铁、铝摩尔配比为10:100的FeAlxOy和CN-27反应后的产物中只检测到了1,2,4/1,4,6-TrCN(CN-14/24)和1,2,3-TrCN(CN-13)。CN-14/24占的摩尔百分比为72.7%。
英文摘要:     Chlorinated aromatic compounds (CACs) are ubiquitous environmental pollutants, with the potential for high toxicity, bioaccumulation, persistence, recalcitrance toward degradation and accumulation in food sources. These compounds can cause serious harm to human health and to the environment and thus the remediation of CAC pollutants is a matter of public concern. Polychlorinated naphthalenes (PCNs) are CACs that represent a newly recognized class of persistent organic pollutants. They are widely present in the environment and are not readily degraded, and are also known to exhibit dioxin-like toxicity effects. PCNs are always released unintentionally, and thus it is important to have a means of remediating waste PCNs. For this reason, there is an urgent need to develop an energy efficient, economic and green method for the degradation of PCNs.
    Metal oxides and their composites offer a number of advantages when applied as catalysts, such as high activity, good thermal stability, ready availability and low cost, and thus are widely used. In the present work, PCNs were selected as a model compound for destruction over several catalysts: Fe2O3 micro/nano materials, three types of crystalline Al2O3, and FeAlxOy composite metal oxides. Gas chromatography/mass spectrometry (GC-MS), GC/electronic capture detector (GC-ECD), Fourier transform infrared spectroscopy (FTIR) and ion chromatography (IC) were all employed to assess the decomposition of PCNs in an attempt to understand this process and its mechanism. The primary results obtained were as follows.
1. Fe2O3 with flower-like three dimensional micro or nanostructures was successfully synthesized by an ethylene glycol-mediated process and was applied to the degradation of octachloronaphthalene (CN-75) at 300 °C. This material exhibited a high degradation efficiency (DE) value of 99.94% within a short reaction time span of 60 min. The destruction of CN-75 over Fe2O3 was found to conform to pseudo-first-order kinetics with a reaction rate constant of 0.075 min−1. Based on qualitative and quantitative assessments of the hydrodechlorinated products, the hydrodechlorination of CN-75 over Fe2O3 was determined to proceed in the following sequence: CN-75 → CN-73 →CN-66/67 → PeCNs → TeCNs → CN-20 → CN-8/11. The detection of formate and acetate products demonstrated that, during CN-75 degradation over micro/nano Fe2O3, the hydrodechlorination and oxygen attack mechanisms occur simultaneously.
2. Three crystal forms of Al2O3 (α-Al2O3, η-Al2O3 and γ-Al2O3) were prepared using a hydrothermal method with a morphology of rod-shaped fibers. XRD results showed that γ-Al2O3 has the shortest particle diameter. Each of the three crystal forms of Al2O3 were used to degrade 1-chloronaphthalene at 300 °C. The γ-Al2O3 generated a degradation efficiency (DE) of more than 92.2% over 30 min, compared with a DE of 65.7% for the η-Al2O3 and a DE of 26.6% for the α-Al2O3. The largest surface area of 135.0 m2/g, the highest concentration of oxygen species, strong Bronsted acids and more Lewis acids on its surface contributed to the better catalytic activity of γ-Al2O3.
3. Naphthalene and 1,4-dichloronaphthalene were identified as the main degradation products based on the GC/MS results. However, higher concentrations of these two products were observed when employing the γ-Al2O3, suggesting that hydrodechlorination and inverse-hydrodechlorination proceed to a greater extent on the γ-Al2O3 compared to the other two forms. On-line FTIR was used to follow changes in the carbons in the 1-chloronaphthalene aromatic ring along with temperature, and the carbon peak intensity was found to be reduced significantly when employing γ-Al2O3, with the peak exhibiting an obvious loss of intensity with variations in the reaction temperature.
4. Three different iron and aluminum composite oxides (FeAlxOy), distinguished by variations in the ratio between iron and aluminum (1:100, 5:100 and 10:100) were obtained by impregnation method with a morphology of rod-shaped fibers. Three different iron and aluminum composite oxides were used to degrade 1,2,3,4-tetrachloronaphthalene (CN-27) at 300 °C for 60 min. The results demonstrated that the activity of FeAlxOy first increased then decreased with the increase of proportion of Fe. The increase of proportion of Fe also had an influence on the distribution of degradation products. When using the 5:100 composite, the main degradation products were 1,2,7,8-tetrachloronaphthalene (CN-41), 1,2,7-trichloronaphthalene (CN-17), 1,4-dichloronaphthalene (CN-5) and 1,5-dichloronaphthalene (CN-6), with the dichlorinated products accounting for approximately 86.2% of the total. The ratio between CN-5 and CN-6 was 2.5:1, and so the CN-5 accounted for the majority of the dichlorinated isomers. In contrast, 1,2,3-trichloronaphthalene (CN-13), 1,2,4-trichloronaphthalene (CN-14) and 1,4,6-trichloronaphthalene (CN-24) were the main products of the reaction between the 10:100 composite and 1,2,3,4-tetrachloronaphthalene. In this case, CN-14 and CN-24 accounted for approximately 72.7% of the total products.
内容类型: 学位论文
URI标识: http://ir.rcees.ac.cn/handle/311016/34351
Appears in Collections:环境化学与生态毒理学国家重点实验室_学位论文

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Recommended Citation:
芦会杰. 铁铝金属氧化物活性材料对多氯萘的降解研究[D]. 北京. 中国科学院研究生院. 2015.
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