【作者】 安俊健；

【导师】 朱丽华；

【作者基本信息】 华中科技大学 ， 材料物理与化学， 2013， 博士

【摘要】 高级氧化技术主要利用H₂O₂和O₂为代表的绿色氧化剂，通过产生氧化性活化物种实现对有机污染物的降解。在H₂O₂和O₂的应用过程中，如何有效活化其分子中的O-O键非常关键。目前，对于O-O键的活化方案有两种：一种是引入外来能量的方式；另一种是开发有效的催化剂。在引入外来能量方面的研究中，引入太阳光中所占比例较大的可见光成本极低、条件温和，因此具有较强的竞争力。关于开发催化剂催化活化O-O键方面的研究主要集中均相Fenton反应和多相类Fenton反应两类。其中多相类Fenton反应中的催化剂能回收利用，但催化活性还需提高。因此，如何提高多相Fenton反应的降解效率是当前的研究热点之一。另外，由于多相催化中污染物在催化剂上的吸附对于其后续降解十分关键，因此，开发具有较强吸附能力和催化能力的双功能材料对于实现高浓度污染物的降解具有非常重要的意义。本论文的研究主要集中在以下几方面：一是利用配体改性和引入可见光照射的方式来提高含铁多相催化剂活化H₂O₂的能力，进而提高多相类Fenton反应降解污染物的效率。；二是利用石墨烯材料负载的方式提高含铁多相催化剂的吸附和催化能力，将其应用于催化降解新型有机污染物；三是将含铁催化剂负载在吸附材料活性碳上，制备吸附-降解双功能材料，进一步拓宽该催化剂的应用范围。本文主要研究内容包括：（1）建立了可见光催化的类Fenton高效催化氧化反应体系。该体系基于纳米BiFeO₃具有一定的类Fenton和可见光催化能力，将其化学催化能力和可见光催化活性有机结合，在H₂O₂和可见光照射条件下BiFeO₃MNPs可高效地催化氧化降解有机污染物。在优化条件下，BiFeO₃-H₂O₂-可见光体系中甲基紫（30μmol/L）、罗丹宁B（10μmol/L）和苯酚（3mmol/L）降解的一级动力学常数（k）分别为2.21×10^-2,5.56×10^-2和2.01×10^-2min^-1。与暗反应相比，该反应体系对甲基紫、罗丹宁B和苯酚的降解速率常数分别是暗反应的3.47、1.95和2.07倍。一般而言，BiFeO₃-H₂O₂-Vis反应体系中污染物的降解速率常数k随着催化剂用量和H₂O₂的增加而增加，但随着污染物初始浓度的增加而下降。采用EDTA和NTA配体对BiFeO₃进行表面修饰，可进一步提高高浓度污染物的降解速率。加入0.4mmol/L的EDTA后，甲基紫（60μmol/L）降解的速率常数从1.01×10^-2min^-1提高到1.30min^-1，增加了128倍。最后，提出了该催化体系的羟基自由基产生的反应机理。（2）采用溶胶-凝胶法合成了纳米BiFeO₃-石墨烯的新型可见光-类Fenton催化剂。由于石墨烯具有良好的负载性能，多相催化剂BiFeO₃在石墨烯上的负载显著地减少了纳米BiFeO₃的团聚，提高复合催化剂的比表面积，BiFeO₃-石墨烯复合物的比表面积为35.07m²g^-1，比BiFeO₃的(7.50m²g^-1)大得多。该复合物具有优异的可见光-类Fenton催化性能。将煅烧温度、石墨烯含量及溶液pH值等因素优化后，利用该复合物实现了四溴双酚A的光-Fenton催化降解，其表观降解速率常数为1.19min^-1，分别是BiFeO₃及BiFeO₃-石墨烯简单混合物的5.43和3.68倍。该复合物可见光-类Fenton催化性能的提高主要是由于其相对于BiFeO₃具有较大的比表面积，更强的吸附能力及复合物中石墨烯较强的电子传导能力，这些都有利于促进氧化活性物种的产生及增加其与污染物的接触机会，从而高效降解和矿化难降解有机污染物。（3）采用水热法合成了同时具有吸附和降解催化功能的BiFeO₃基双功能材料。为了进一步拓宽BiFeO₃的应用范围，本部分工作将BiFeO₃和氧化活性碳复合制成吸附-降解双功能材料。利用活性碳独特的多孔结构，提高该复合物的比表面积。研究结果表明，该复合物的比表面积为119.61m²g^-1，比水热法合成的BiFeO₃的比表面积(26.50m²g^-1)要高得多。另外，将纳米级的BiFeO₃负载微米级的氧化活性碳上，可减少BiFeO₃纳米颗粒的团聚几率，这一方面提高了其比表面积和吸附能力；另一方面还提高了BiFeO₃纳米颗粒和污染物的接触机会，从而提高其催化降解污染物能力。在优化条件下，该复合物对高浓度亚甲基蓝的降解速率是BiFeO₃的6.25倍，且矿化效果也比BiFeO₃高得多。研究结果表明，该复合物具有良好的吸附和催化性能，能够高效去除高浓度有机污染物。更多还原

【Abstract】 The environmentally friendly oxidants （such as H₂O₂and O₂） are activated togenerate oxydic species, which are utilized to degrade organic pollutants in advancedoxidation technology. During the activation of H₂O₂and O₂, it is a key problem whetherthe O-O band existed in these molecules could be activated effectively. At present, theactivated approaches of O-O band are included two aspects: the first one is to introduceadditional energy; the second one is to develop effective catalysts. In the reasearch aboutthe introduction of additional energy, the utilization of visible light which has a largeproportion in sunlight possesses the superiority of lower cost and mild condition.Therefore, it processes strong competitiveness. The study of developing catalysts with theability of activating O-O band is focus on homogeneous Fenton calalysts andheterogeneous Fenton calalysts. Among them, the heterogeneous Fenton-like catalystscould be recycled and reutilized. However, the catalytic activity of these catalysts needs tobe improved furtherly. Hence, it is very important to improve the degraded efficiency ofpollutants in heterogeneous Fenton-like process. In addition, many researchers have foundthat the adsorption of pollutants on catalysts is very important to their subsuquentdegradation in heterogeneous Fenton process. Therefore, the development of newmaterials with both stronger adsorped and catalytic ablility is very significance to removepollutants at higer concentration in the environment. Therefore, the study of this paper isfocus on these aspects: the first one was to improve the degradation efficiency of organicpollutants in heterogeneous Fenton process. The methods which includ the in-situ surfacemodification to catalysts by ligands and introducing visible light are utilized, which toimprove the catalytic ability of heterogeneous catalyst; the second one was focus onenhancing the adsorption and catalytic ability of Fe-contained heterogeneous catalystthrough load it on graphene material. And the compound catalyst is used to degrade neworganic pollutant; the third one was to load Fe-contained catalyst on activated carbon anddevolp the adsorption-degradation double function materials, which expanded theapplication scope of the catalyst. The main research contants about this paper are showed as follows:（1） The new effective catalytic oxidation system which is coupled with Fenton-likeand visible light catalytic reaction was established. This was based on the Fenton-like andvisible light catalytic ability of nano-BiFeO₃. The degradation of organic pollutants inBiFeO₃-H₂O₂-visible light （Vis） system was investigated. Under optimum conditions, thepseudo-first-order rate constant （k） was determined to be2.21×10^-2,5.56×10^-2and2.01×10^-2min^-1for the degradation of MV （30μmol/L）, RhB （10μmol/L） and phenol （3mmol/L）, respectively, in the system. The introduction of visible light irradiation increasedthe k values of MV, RhB and phenol degradation3.47,1.95and2.07times in comparisonwith those in dark. Generally, the k values in the BiFeO₃-H₂O₂-Vis system wereaccelerated by increasing BiFeO₃load and H₂O₂concentration, but decreased withincreasing initial pollutant concentration. To further enhance the degradation of pollutantsat high concentrations, BiFeO₃was modified with the addition of surface modifiers. Theaddition of ethylenediamineteraacetic acid （EDTA,0.4mmol/L） increased the k value ofMV degradation （60μmol/L） from1.01×10^-2min^-1in the BiFeO₃-H₂O₂-Vis system to1.30min^-1in the EDTA-BiFeO₃-H₂O₂-Vis system, a factor of128. This suggests that in situsurface modification can enable BiFeO₃nano-particles to be a promising visible lightphoto-Fenton-like catalyst for the degradation of organic pollutants. At last, themechanism for OH radical generation in EDTA-BiFeO₃-H₂O₂-Vis system was proposed.（2） Graphene-BiFeO₃nanoscaled composites were prepared with a sol-gel methodand evaluated as highly efficient photo-Fenton like catalyst under visible light irradiation.In the preparation of the compound, the nanoscaled particles of BiFeO₃were loaded on thesheets of graphene. Due to the good load performance of graphene, the aggregation ofBiFeO₃nano-particles was avoided greatly. Thus, the specific surface area of thecompound was increased. The experiment result showed that the graphene-BiFeO₃composite had a specific surface area of35.07m²g^-1, being considerably larger than thatof BiFeO₃nanoparticles (7.50m²g^-1). The composite exhibited excellent visiblelight-Fenton like catalysis activity, being influenced by calcination temperature, graphenecontent and solution pH value. Under optimal conditions with visible light irradiation, thegraphene-BiFeO₃composite yielded fast degradation of tetrabromobisphenol A with a apparent rate constant of1.19min^-1, which was5.43and3.68folds of that achieved byusing BiFeO₃and the mixture of BiFeO₃and graphene, respectively. The significantlyenhanced visible light-Fenton like catalytic properties of the graphene-BiFeO₃compositein comparison with that of BiFeO₃was attributed to a large surface area, much increasedadsorption capacity and the strong electron transfer ability of graphene in the composite.（3） The double-function materials with adsorption and catalysis based on BiFeO₃wasprepared with hydrothermal process. To expand the application scope of BiFeO₃, BiFeO₃and oxidated activate carbon （OAC） were combined as both adsorbent and catalyst. Thespecific surface area of the compound was increased due to the porous structure of OAC.And the experiment result indicated that the specific surface area of the compound was119.61m²g^-1, which was much higher than that of BiFeO₃prepared with hydrothermalprocess (26.50m²g^-1). Moreover, the loading of BiFeO₃nano-particles on OAC hinderedthe aggregation of BiFeO₃nano-particles greatly, which increased the specific surface area;On the other hand, the contact chances between BiFeO₃and pollutants were increased,which increased the catalytic ability of the compound. Under optimum conditions, thedegraded rate constant of methylene blue with high concentration （0.4mmol L） was6.25folds compare with that of BiFeO₃. And the TOC removal was much higher than that ofBiFeO₃. The study result showed that the compound possess good adsorption and catalyticperformance, which could be utilized to remove pollutants at high concerntration.更多还原