中国科学院生态环境研究中心机构知识库
Advanced  
RCEES OpenIR  > 环境化学与生态毒理学国家重点实验室  > 学位论文
题名: 多元铁基复合金属氧化物材料的制备与多氯联苯的降解研究
作者: 黄林艳
学位类别: 博士
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: 郑明辉 ; 苏贵金
关键词: 多氯联苯,氯代芳烃,铁基复合氧化物,催化降解,纳米材料,Polychlorinated biphenyls, Chlorinated aromatic hydrocarbons, Iron-based composite oxide, Catalytic degadation, Nano-material
其他题名: Preparation of iron-based composite oxides and their applications in degradation of polychlorinated biphenyls
学位专业: 环境科学
中文摘要:     多氯联苯(PCBs)为一类持久性有机污染物,虽然目前已禁止生产和使用,然而仍然有大量的  PCBs赋存于封闭工业设备容器中或已逸散到周围环境中,这些  PCBs将会对人类健康和生态环境造成极大的潜在危害。由于受经济、技术、社会舆论等的影响,目前  PCBs的各处理处置方法在实际应用中都受到一定的限制。因此,迫切需要开发能耗低、经济、绿色高效的处理新方法。利用新型多元复合金属氧化物材料对  PCBs进行降解为这类物质的处置提供了新的思路。
    本论文分别利用共沉淀法、多元醇介导法和水热法合成了系列二元和三元铁基复合金属氧化物材料,研究了合成的材料对选定的  PCBs模型化合物的催化降解活性,并初步探讨了降解反应机制。本论文的主要研究成果有:
1.采用共沉淀法合成了一系列NiFe复合氧化物材料,并对材料进行了物化性质表征。同时考察了不同灼烧温度得到的材料对十氯联苯( CB-209)的降解活性,并与多元醇介导法合成的 Fe3O4进行比较。结果表明,灼烧温度为400°C得到的NiFe2O4材料具有最高的表面活性氧量和比表面积。材料对CB-209降解活性评价结果表明,制备的NiFe2O4对CB-209降解表现出最高的反应活性,Fe3O4次之,这可能与  NiFe2O4丰富的表面活性氧及Ni-Fe间存在协同作用有关。
2.通过检测分析 NiFe2O4催化降解  CB-209过程中的中间产物和超氧自由基,并结合理论计算探讨了 CB-209热催化降解反应路径,且与  Fe3O4反应体系进行比较。结果显示,在 NiFe2O4和  Fe3O4降解  CB-209两种反应体系中均有低氯代联苯、氯苯、羟基化合物和有机酸中间产物的生成,说明  CB-209存在四种竞争性发生的反应路径,即加氢脱氯、C–C桥键断裂、氧化和结合反应。且 CB-209的氧化降解路径在  NiFe2O4体系中比在  Fe3O4体系中更易发生,而其加氢脱氯降解路径在Fe3O4体系中更易发生。这与NiFe2O4降解 CB-209过程中产生的  O2−•有关,而 Fe3O4在反应过程中会部分转变为Fe2O3,为CB-209的加氢脱氯反应提供更多的电子。生成的九氯联苯(NoCB)同分异构体相对含量关系为:CB-207>CB-208>CB-206,表明不同取代位上 Cl的活性相对大小为:间位>对位>邻位,推测这与不同取代位上 C-Cl键解离能和产物的稳定性有关。
3.研究了NiFe2O4催化降解  CB-209过程中对二恶英类(PCDD/Fs)副产物生成的影响,并与 Fe2O3反应体系和  CB-209空白加热体系进行比较。结果显示,各反应体系中2,3,7,8-PCDFs的生成均显著高于2,3,7,8-PCDDs。在30-120 min内,NiFe2O4体系中生成的   2,3,7,8-PCDFs的总浓度和WHO-TEQ比CB-209空白加热体系分别减少了  75.9-99.7%和86-98.4%,且均低于Fe2O3反应体系。NiFe2O4对  PCBs降解过程中  PCDD/Fs副产物生成的阻滞作用与其对 PCBs这一前生体表现出的高降解活性及其本身稳定的化学性质有关。
NiFe2O4对生成的  PCDFs还具有降解作用,其中  OCDF的主要加氢脱氯路径为:OCDF→1,2,3,4,6,7,8-HpCDF→1,2,3,6,7,8-HxCDF→1,2,3,7,8-PeCDF→2,3,7,8-TCDF,加氢脱氯优先发生在 1-和 9-取代位上。
4.通过水热法合成了三元铁基复合氧化物材料,并对材料进行了一系列表征。结果显示,合成的材料为具有高比表面积、高表面活性氧量和丰富表面 B酸、L酸性位的磁性纳米材料。合成的材料在  300 °C下对一氯联苯(CB-1)表现出非常高的降解活性和稳定性,连续反应 10  h后   CB-1的降解效率仍维持在  98%左右,这与材料稳定的物理化学性质及丰富的表面活性氧和酸性位有关。CB-1在三元铁基复合氧化物催化下能发生加氢脱氯、C-C桥键断裂、矿化和氯化反应,且可能以矿化反应为主。
英文摘要:     Polychlorinated   biphenyls   (PCBs)   are   persistent   organic   pollutants.   The production and  use of PCBs  have been  prohibited, but  large amounts of  PCBs still exist in  closed industrial equipment  and large  amounts of  PCBs have been  emitted into the  environment. In the  environment, PCBs have  harmful effects  on the health
of humans and  other biota. Because of  the costs involved,  the technology available,and  public  opinion,  practical  ways  of  disposing  of   PCBs  are  currently  limited.Therefore, there  is an urgent  need for the  development of  PCB disposal techniques that  are  economic, safe,  effective,  and  energy  efficient.  Degradation using  novel multicomponent metal oxides might be a new way of disposing of PCBs.
    In this  study, a  series of binary  and ternary  iron-based composite oxides  were prepared using oprecipitation, polyol-mediated, and  hydrothermal methods, and the PCB degradation  activities of the  materials produced and  the mechanisms  involved were studied. The methods used and the main results are described below.
1.   A series of NiFe  composite oxides, synthesized by  coprecipitation, were used to degrade   decachlorobiphenyl  (CB-209),   which   was  used   as   a  model   PCB compound. The results were compared with those found using Fe3O4 prepared by a polyol-mediated  process. NiFe2O4 had  a larger specific  surface area and  more abundant surface  active  oxygen than  did the  other NiFe  composite  oxides that were synthesized. Of the materials  that were tested, NiFe2O4 had the highest  and Fe3O4 had  the second highest  CB-209 degradation activity.  The high activity  of NiFe2O4  was attributed  to  the  physicochemical  properties of  the  material  and synergistic effects between Ni and Fe in the material.
2.   The degradation pathways involved in the thermal catalytic  destruction of CB-209 by NiFe2O4 were  studied by identifying the intermediate  products and superoxide radicals  and using  theoretical  calculations. The  results  were compared  with the results found when CB-209 was degraded using Fe3O4. Less-chlorinated biphenyls, chlorobenzenes,  hydroxyl   species,  and   organic  compounds  were   found  after performing the  degradation  tests. This  suggested  that hydrodechlorination,  C–C bridge  bond  cleavage,  and oxidation,  accompanied  by  a  combination  reaction,occurred competitively  during CB-209  degradation by  both NiFe2O4  and  Fe3O4. The  oxidation  reaction was  more  favored  when  NiFe2O4  was  used  than when Fe3O4 was used, while the hydrodechlorination was  more favored over Fe3O4. The reason would  be that the NiFe2O4  reaction system  contained highly reactive O2−•species,   whereas   the   Fe3O4   reaction   system   provided   more   electrons   for hydrodechlorination  by  the  transformation  of  Fe3O4  into  Fe2O3.  The  amounts produced nonachlorobiphenyl congeners decreased in the order CB-207>CB-208>CB-206, indicating that  the activities of the  substituent chlorine atoms in  CB-209 decreased in the order meta  > para > ortho. These activities will have been  related to the energy required to break the C–Cl bonds at the different positions.
3.   The  amounts of  PCDD/F byproducts  formed  during the  thermal  degradation of CB-209 by NiFe2O4  and Fe2O3 and  in a catalyst-free system  were evaluated. The total   2,3,7,8-substituted   PCDF    concentrations   and   toxic   equivalents    were 75.9–99.7% and  86–98.4% lower,  respectively, after  CB-209 had  been degraded for 30–120  min in  the NiFe2O4  catalyst system  than in the  catalyst-free reaction system, and  were  lower than  those  in the  Fe2O3 catalytic  system.  These results indicate that NiFe2O4  suppressed the formation of PCDFs,  and this was attributed to  the stability  of  the chemical  structure  of  NiFe2O4 and  the  strong activity  of NiFe2O4  for  degrading  biphenyl-like constituents  in  PCB  mixtures.  The  initial hydrodechlorination of  octachlorodibenzofuran formed  during the degradation  of CB-209 was  found to occur  at the  1- and 9-positions  in preference to  the 4-  and 6-positions.    This   initial    step    will    have   been    followed    by   subsequent hydrodechlorination  steps,   the   main  pathway   being  1,2,3,4,6,7,8-HpCDF   →1,2,3,6,7,8-HxCDF → 1,2,3,7,8-PeCDF → 2,3,7,8-TCDF.
4.   A ternary iron-based composite oxide was prepared using a hydrothermal method and characterized using  a number of techniques. The  material synthesized was a magnetic nanomaterial with a high  surface area, abundant surface active oxygen, and Lewis  and Brønsted acid sites.  The ternary iron-based  composite oxide that was prepared had an
excellent activity for the degradation of monochlorobiphenyl (CB-1)  at  300 °C  and was  stable through  the degradation process. The activity  of the material could  be attributed to its  stability, abundant surface active oxygen, and acid  sites. CB-1 could have been degraded during the thermal  catalytic   process  through  hydrodechlorination,   C–C  bond   cleavage,mineralization, and  chlorination, and mineralization  appears likely to have  been the dominant pathway.
内容类型: 学位论文
URI标识: http://ir.rcees.ac.cn/handle/311016/34332
Appears in Collections:环境化学与生态毒理学国家重点实验室_学位论文

Files in This Item:
File Name/ File Size Content Type Version Access License
黄林艳--多元铁基复合金属氧化物材料的制备与多氯联苯的降解研究.pdf(3442KB)学位论文--限制开放 联系获取全文

Recommended Citation:
黄林艳. 多元铁基复合金属氧化物材料的制备与多氯联苯的降解研究[D]. 北京. 中国科学院研究生院. 2015.
Service
Recommend this item
Sava as my favorate item
Show this item's statistics
Export Endnote File
Google Scholar
Similar articles in Google Scholar
[黄林艳]'s Articles
CSDL cross search
Similar articles in CSDL Cross Search
[黄林艳]‘s Articles
Related Copyright Policies
Null
Social Bookmarking
Add to CiteULike Add to Connotea Add to Del.icio.us Add to Digg Add to Reddit
所有评论 (0)
暂无评论
 
评注功能仅针对注册用户开放,请您登录
您对该条目有什么异议,请填写以下表单,管理员会尽快联系您。
内 容:
Email:  *
单位:
验证码:   刷新
您在IR的使用过程中有什么好的想法或者建议可以反馈给我们。
标 题:
 *
内 容:
Email:  *
验证码:   刷新

Items in IR are protected by copyright, with all rights reserved, unless otherwise indicated.

 

 

Valid XHTML 1.0!
Copyright © 2007-2018  中国科学院生态环境研究中心 - Feedback
Powered by CSpace