石墨烯负载零价纳米铁去除有机污染物的研究

发布时间：2019-05-09 07:36

【摘要】：自2004年石墨烯发现以来,就以其独特结构与性能引起人们的重视,并迅速成为诸多学科前沿研究的热点。石墨烯具有独特的二维平面结构和极大的比表面积,使其成为负载无机纳米粒子的理想载体,目前,已有一系列报道将石墨烯与功能性粒子结合起来制备出石墨烯复合材料。此外,零价纳米铁(nZVI)在环境修复中表现出非常明显的优势,但在实际应用中仍存在一些问题,如易氧化,易团聚、制备成本高等,这些都限制了nZVI对环境污染物的去除效率。若将两者结合起来,制备石墨烯负载零价纳米铁(nZVI/rGO)复合材料,不仅能抑制nZVI的团聚提高其反应活性,还拓展了石墨烯在环境修复领域的潜在应用价值。本文主要以nZVI/rGO复合材料为研究对象,研究该材料去除有机污染物(罗丹明B、多溴二苯醚)的可行性,能够为nZVI/rGO的实际应用提供一定的参考价值。主要研究内容如下:采用液相还原法制备nZVI;通过改进的Hummers方法制备氧化石墨(GO),以硼氢化钠为还原剂制备nZVI/rGO复合材料。之后对所制备的材料进行分析表征,主要包括:扫描电镜、X射线衍射、拉曼光谱、BET比表面积以及X射线光电子能谱。利用石墨烯负载零价纳米铁复合材料去除罗丹明B(Rh B),并采用RSM和ANN-GA建模的方法,优化罗丹明B去除率的影响因素(pH、初始浓度、温度以及反应时间)。结果表明,两个模型的预测值都能较好的与实验值吻合,相比而言,ANN-GA模型的预测结果更为准确。RSM通过方差分析得出初始浓度是最重要的影响因素。另外,通过拟合nZVI/rGO去除罗丹明B的吸附等温线和动力学方程发现,Freundlich方程和伪二级动力学能更好地描述nZVI/rGO对罗丹明B的吸附过程。研究并比较nZVI和nZVI/rGO对BDE-47、BDE-100、BDE-154降解效果。在反应初级阶段两种材料对PBDEs降解速度较快,随着吸附作用及还原能力的减弱其降解速率也随之下降。另外,由于BDE-154含有较多的溴原子,与BDE-47和BDE-100相比更容易降解,因此BDE-154不仅降解速度快,还具有较高降解率。通过对动力学模型的研究分析发现,nZVI和nZVI/rGO对PBDEs的降解效果为伪一级反应动力学或伪二级反应动力学。另外,根据课题组实际情况,通过理论计算,对PBDEs的实验结果进行补充。采用B3PW91/6-311+G(d,p)和PBE/TZ2P/ZORA方法对BDE-28、BDE-30、BDE-32、BDE-51、BDE-116与BDE-166进行结构优化,并将C-Br与C-O键键长与其实验值进行比较;利用QST2的方法研究了BDE-7和BDE-12构型过渡态以及阴离子态之间的转换关系;研究了溶剂化条件下BDE-47、BDE-17、BDE-15、BDE-8、BDE-7和BDE-4阴离子的脱卤路径;通过建立定量构效关系模型对所选择的14种BDE同系物的脱溴速率常数进行预测。
[Abstract]:Since graphene was discovered in 2004, it has attracted people's attention because of its unique structure and properties, and has rapidly become the focus of frontier research in many disciplines. Graphene has a unique two-dimensional plane structure and large specific surface area, which makes it an ideal carrier for loading inorganic nanoparticles. At present, there have been a series of reports that graphene and functional particles are combined to prepare graphene composites. In addition, zero-valent nano-iron (nZVI) shows a very obvious advantage in environmental remediation, but there are still some problems in practical application, such as easy oxidation, easy agglomeration and high preparation cost. These limit the removal efficiency of environmental pollutants by nZVI. The preparation of graphene-supported zero-valent iron nanocomposites (nZVI/rGO) can not only inhibit the aggregation of nZVI and improve its reactivity, but also expand the potential application value of graphene in the field of environmental remediation. In this paper, the feasibility of removing organic pollutants (rhodamine B, polybrominated diphenyl ether) from nZVI/rGO composites was studied, which can provide some reference value for the practical application of nZVI/rGO. The main contents are as follows: nZVI; was prepared by liquid phase reduction method and graphite oxide (GO), was prepared by modified Hummers method. NZVI/rGO composite was prepared by using sodium borohydride as reducing agent. The prepared materials were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy (Raman), BET specific surface area (BET) and X-ray photoelectron spectroscopy (XPS). The removal of Rhodamine B (Rh B), by graphene-loaded zero-valent iron nanocomposites was studied by using RSM and ANN-GA modeling methods to optimize the influencing factors of Rhodamine B removal rate (initial pH, concentration, temperature and reaction time). The results show that the predicted values of the two models are in good agreement with the experimental values. Compared with the experimental values, the prediction results of the ANN-GA model are more accurate, and the initial concentration of RSM is the most important influencing factor by ANOVA. In addition, by fitting the adsorption isotherms and kinetic equations of Rhodamine B removal by nZVI/rGO, it is found that the Freundlich equation and pseudo-second order kinetics can better describe the adsorption process of Rhodamine B by nZVI/rGO. The degradation effects of nZVI and nZVI/rGO on BDE-47,BDE-100,BDE-154 were studied and compared. In the primary stage of the reaction, the degradation rate of PBDEs by the two materials was faster, and the degradation rate decreased with the decrease of adsorption and reduction ability. In addition, because BDE-154 contains more bromine atoms, it is easier to degrade than BDE-47 and BDE-100, so BDE-154 not only degrades faster, but also has higher degradation rate. Through the study and analysis of the kinetic model, it is found that the degradation effect of nZVI and nZVI/rGO on PBDEs is pseudo-first-order reaction kinetics or pseudo-second-order reaction kinetics. In addition, according to the actual situation of the research group, the experimental results of PBDEs are supplemented by theoretical calculation. The B3PW91/6-311 G (d, p) and PBE/TZ2P/ZORA methods were used to optimize the structure of BDE-28,BDE-30,BDE-32,BDE-51,BDE-116 and BDE-166, and the bond lengths of C-Br and CNO were compared with their experimental values. The transition relations between BDE-7 and BDE-12 configuration transition states and anionic states were studied by QST2 method, and the dehalogenation paths of BDE-47,BDE-17,BDE-15,BDE-8,BDE-7 and BDE-4 anions under solvation condition were studied. The debromination rate constant of 14 kinds of BDE homologues was predicted by establishing a quantitative structure-activity relationship model.
【学位授予单位】：贵州师范大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X505;TB33

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