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石墨烯基功能材料的设计及其去除有机污染物的研究
王朋磊
学位类型硕士
导师张亚刚
2017-05-29
学位授予单位中国科学院大学
学位授予地点北京
学位专业材料工程
关键词石墨烯 还原程度 吸附 类fenton 催化 酚类有机污染物
摘要

石墨烯材料具有独特的物理和化学性质,在能源、催化和环境等领域有广阔的应用前景。本论文设计和制备了两类不同功能的石墨烯基材料,分别将其用于吸附和催化降解水相中有机污染物。1)为了探究石墨烯基材料表面含氧官能团对其吸附有机酚类污染物过程中的影响,通过控制氧化石墨烯的还原过程,制备不同还原程度的磁性还原氧化石墨烯材料并将其应用于吸附水相中的双酚A污染物,探究了还原过程对其吸附容量的影响及其吸附机制。2)针对传统的非均相Fenton反应中,Fe2+/Fe3+循环速率较慢,严重制约羟基自由基(?OH)的产生等问题。将Fe0和Fe3O4均匀的纳米分散在还原氧化石墨烯(RGO)上,作为非均相Fenton催化剂用于降解水相中苯酚污染物。主要研究结果如下:(1)不同还原程度的磁性氧化石墨烯(MRGO)用于去除水相中的双酚A污染物,其吸附动力学较好地符合准二级动力学方程,吸附等温线符合朗格缪尔吸附等温方程。MRGO-1和MRGO-2在298 K下对双酚A的最大吸附容量分别为93.0 mg/g和71.77 mg/g。与其他已报道的吸附材料相比,MRGO-1和MRGO-2具有较高的吸附容量和吸附速率。热力学研究表明双酚A在MRGO-1上的吸附是一个自发且放热的过程。较低的温度和中性或酸性的环境有利于吸附的发生。使用过的MRGO-1可以通过外加磁场快速回收并重复使用。MRGO-2的比表面积要低于MRGO-1,归结于在深度还原过程中石墨烯片层的聚合,MRGO-1具有比MRGO-2更大的表观吸附量,这表明深度还原过程也许是不必须的。然而如果可以避免在深度还原过程中石墨烯片层的聚合,深度还原过程对提高其对双酚A的吸附容量是有益的。基于所有的实验结果,π-π作用很有可能是双酚A在MRGO吸附的主要机制。(2) Fe0/Fe3O4/RGO纳米复合材料的制备、表征及其催化性能研究。 研究结果显示:Fe0/Fe3O4-RGO 作为类芬顿催化剂在30 min内可将苯酚100%催化降解去除。催化剂具有优异稳定性和可再生性,五次催化循环后其对苯酚的去除效率依然可以达到93% 以上。此外,该催化剂具有优异的还磁分离性能。该催化剂具有独特≡Fe2+再生机理,Fe0 和Fe3O4 纳米粒子被均匀的分散在RGO上,使更多的活性位点暴露,同时借助RGO为电子转移介质促进电子由Fe0转移给Fe3O4使得≡Fe2+ 得到再生。苯酚分子与RGO之间的π-π作用使得苯酚分子可以有效的吸附在催化剂表面,增加了苯酚分子与?OH接触的几率。基于这些因素,使得Fe0/Fe3O4-RGO具有优异的类Fenton催化活性。 关键词:石墨烯;还原程度;吸附;类Fenton催化;酚类有机污染物

其他摘要

Graphene has been widely applied in energy, catalysis and environment fields due to its unique physical and chemical properties. In this dissertation, two type of function materials based graphene were designed and synthesized. The prepared materials were used for organic pollutant absorption and Fenton-like catalytic degradation of phenol type pollutants. 1) In order to reveal the influence of surface oxygen-containing functional groups of graphene based materials on adsorption of phenol type pollutants , the effects of the reduction degree of graphene oxide on the adsorption kinetics and adsorption capacity of bisphenol A on magnetic reduced graphene oxides (MRGO) were investigated systematically. 2) In order to overcome the slow conversion of ≡Fe3+ to ≡Fe2+ and to help regenerating Fe2+ in Fenton-like catalytic process, nano-dispersed Fe0 and Fe3O4 on reduced graphene oxide (Fe0/Fe3O4-RGO) was prepared and used as magnetically separable Fenton-like catalyst for the catalytic degradation of phenol .The key results and major conclusions are summarized as follows:(1) Two kinds of MRGO namely MRGO-1 and MRGO-2 with different reduction degree were synthesized by a in situ chemical co-precipitation method. MRGO-2 was obtained by further reduction of MRGO-1 using hydrazine to obtain a relatively deeper reduction degree. Removal of bisphenol A (BPA) from aqueous solution using MRGO-1 and MRGO-2 was investigated. The kinetics and isotherm data of BPA absorbed by MRGO-1 and MRGO-2 were both well fitted with the pseudo-second-order kinetic model and the Langmuir isotherm, respectively. The maximum adsorption capacity of MRGO-1 and MRGO-2 for BPA obtained from the Langmuir isotherm was 92.98 mg.g-1 and 71.66 mg.g-1 at 298.15 K, respectively. Furthermore, the used MRGO-1 and MRGO-2 could be collected and recycled efficiently via an external magnet. The BPA adsorption capacity of the MRGO-1 remained greater than 86% of the initial adsorption capacity after nine repeated absorption–desorption cycles. The thermodynamic study showed that the adsorption was spontaneous and exothermic. The maximum adsorption capacity of MRGO-1 for BPA was higher than that of MRGO-2, implying a deeper reduction process to MRGO-2 from MRGO-1 was not necessary for the removal of BPA from aqueous solution. It was also found that if severe aggregation of graphene sheets in the deep reduction process to MRGO-2 from MRGO-1 could be alleviated, the corresponding absorption capacity of MRGO-2 for BPA may be greatly improved.(2) The prepared Fe0/Fe3O4-RGO was used as magnetically separable Fenton-like catalyst and showed superior catalytic activity compared to Fe3O4-RGO and Fe3O4 as well as other Fenton-like catalysts for the removal of phenol. The Fe0/Fe3O4-RGO achieved 100 % removal efficiency for phenol within 30 min. Free radical inhibition experiments and Electron Paramagnetic Resonance (EPR) showed that main reactive species was ?OH rather than FeIV. High resolution TEM results revealed that nanoscale Fe0 and Fe3O4 were uniformly dispersed and distributed on RGO without agglomeration, furnishing more active sites. The catalyst featured a unique mechanism of electron transfer facilitated regeneration of active Fe2+ by nano-dispersed iron/graphene. RGO served as an effective mediator to facilitate the electron transfer from Fe0 to ≡Fe3+ for the regeneration of ≡Fe2+, which was critical in catalytic process. This electron transfer facilitated regeneration of active Fe2+ resulted in reusable catalyst with high catalytic activity for removal of phenol. The Nano-dispersed Fe0/Fe3O4-RGO could be easily separated and recovered by magnetic field. The Fe0/Fe3O4-RGO catalyst was reusable and removal efficiency of phenol after 5 catalytic cycles was as high as 93 %. The Fe0/Fe3O4-RGO could be effective Fenton-like catalyst for the treatment of waste water containing refractory phenol and phenol type pollutants. Keywords: Graphene, Degree of Reduction, Absorption, Fenton Catalysis, Phenol Type Pollutants

文献类型学位论文
条目标识符http://ir.xjipc.cas.cn/handle/365002/4946
专题资源化学研究室
作者单位中国科学院新疆理化技术研究所
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王朋磊. 石墨烯基功能材料的设计及其去除有机污染物的研究[D]. 北京. 中国科学院大学,2017.
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