CAS OpenIR
GO及Co/rGO磁性复合材料的制备及其离子吸附性能研究
张晶晶
Thesis Advisor齐涛
2020-07-01
Degree Grantor中国科学院大学
Degree Name硕士
Degree Discipline化学工艺
Keyword还原氧化石墨烯,磁性复合材料,吸附,碱金属离子,铜离子
Abstract

本文在深入调研氧化石墨烯及其复合材料的制备技术、在吸附领域的应用研究的基础上,首次系统地研究GO对碱金属离子的吸附特性并成功利用吸附-原位还原法制备了金属/还原氧化石墨烯新型磁性吸附复合材料,该材料显示了优异的对Cu2+吸附性能。首先采用改进Hummers法制备氧化石墨,水溶液中超声剥离处理获得氧化石墨烯分散液,通过多种手段对氧化石墨烯材料进行了表征,并考察了氧化石墨烯对不同碱金属离子的吸附特性。然后利用吸附-原位还原法制备不同形貌Co/rGO磁性复合材料。考察了Co/rGO复合材料对铜离子的吸附性能及其吸附热力学、动力学。(1)鳞片石墨为原料,利用改进Hummers法制备氧化石墨,后超声分散剥离成氧化石墨烯纳米片。利用SEM、FT-IR、Raman、XRD和TG-MS对氧化石墨烯的结构和热稳定性。研究表明,氧化石墨烯为层状结构,表面存在大量褶皱;氧含量高达42.66%,—COOH所占含氧基团含量最高,有利于发生离子交换反应。(2)针对氧化石墨烯对于碱金属离子的吸附机理,采用改进Hummers法制备氧化石墨烯纳米片,并用作吸附剂从溶液中去除Li+、Na+、K+、Rb+和Cs+。结果表明,碱金属离子在氧化石墨烯上的吸附强烈依赖于溶液初始pH和氧化石墨烯表面丰富的含氧官能团。Li+、Na+、Rb+和Cs+吸附过程符合Langmuir等温模型,K+的吸附符合Freundlich等温模型且均符合准二级动力学,热力学参数ΔG<0,ΔH>0,即氧化石墨烯对碱金属离子的吸附是自发吸热且为化学控制的过程。在单一或者混合碱金属溶液中,氧化石墨烯均对K+具有更高的吸附容量和比例。氧化石墨烯对K/Na的分离系数为2.11,对K/Rb的分离系数为2.53。(3)以氧化石墨烯为模板制备了Co/rGO磁性复合材料。Co/rGO复合材料具有超顺磁性,能够很方便的使用磁铁进行分离并在无磁场情况下振荡分散。系统考察了NaOH加入量、络合剂种类、溶剂种类等关键因素对Co粒子在rGO载体上形貌和分布特性,并对优选条件下制备的Co/rGO复合材料进行了FT-IR、XRD、SEM表征。结果表明:利用原位还原法所制Co/rGO复合材料,钴粒子粒径主要受到NaOH加入量的影响,添加的柠檬酸则对钴纳米粒子起到了很好的分散作用,而丙醇环境下钴纳米颗粒多为花瓣状球形,显著增加了复合材料的吸附性能。通过不同条件合成的Co/rGO复合材料对溶液中Cu2+的吸附效果研究发现,最优条件为OH-/Co2+=8,溶剂为丙醇,络合剂为柠檬酸。最有利条件下制备的Co/rGO复合材料呈褶皱状平面,石墨烯C=C结构得到了明显的恢复,但由于Co的保护作用,仍然残留较多的C—OH等含氧活性基团。小于100 nm的菜花状金属钴颗粒较为均匀地分散在表面。(4)探究溶液初始pH值、吸附时间、初始Cu2+浓度和反应温度对吸附性能的影响,及吸附热力学和复合材料重复利用的问题。结果显示,Co/rGO复合材料对Cu2+具有稳定的吸/脱附性能,最佳实验条件下对Cu2+的最大吸附容量达到117.5 mg/g且5 min内实现吸附平衡,远优于其原料氧化石墨烯的60 min吸附容量27.5 mg/g。纳米Co/rGO磁性材料对Cu2+的吸附过程更符合Freundlich模型,属于多层吸附。室温下吸附焓ΔH=17.81 kJ/mol,吸附反应平衡常数K0=3.65。当初始Cu2+浓度为10 mg/L时,脱附率超过93%,五次吸/脱附循环后吸附容量仍保持在初始值的94%,每次吸附后溶液中残余Cu2+浓度均满足钴电解液对杂质铜离子的浓度去除要求(5 mg/L)或者GB 8978—1996污水综合排放标准3级(2 mg/L),可望在相关领域发挥作用。;After in-depth research on the preparation technology of graphene oxide and its composite materials, as well as the application of graphene oxide and its composite materials in the field of adsorption, this paper firstly and systematically studies the adsorption characteristics of graphene oxide for the alkali metal ions,proposes and successfully uses the adsorption-in-situ reduction method to prepare metal/rGO composite materials, which has excellent adsorption properties for Cu2+. First, this paper uses modified Hummers method to prepare graphite oxide, which is ultrasonically stripped in aqueous solution to obtain graphene oxide dispersion. The graphene oxide material is characterized by various means, and the adsorption characteristics of graphene oxide to different alkali metal ions are investigated. Then, this paper uses adsorption-in-situ reduction method to prepare Co/rGO magnetic composites with different morphologies, and studies the adsorption performance, reusability, adsorption thermodynamics, kinetics and adsorption mechanism of Co/rGO composites for Cu2+.(1) Using flake graphite as the raw material, this paper uses the modified Hummers method to prepare graphite oxide, and then disperses and peels it into graphene oxide nanosheets under ultrasound. The structure and thermal stability of graphene oxide were characterized by SEM, FT-IR, Raman, XRD and TG-MS. Studies have shown that graphene oxide is a layered structure with a large number of folds on the surface; the oxygen content is as high as 42.66%, and —COOH has the highest content of oxygen-containing groups, which is conducive to ion exchange reactions.(2) Aiming at the adsorption mechanism of graphene oxide for alkali metal ions, this paper adopts the modified Hummers method to prepare graphene oxide nanosheet and it is used as an adsorbent to adsorb Li+, Na+, K+, Rb+ and Cs+ in the solution. The experimental results show that the adsorption of graphene oxide to alkali metal ionsstrongly depends on the initial pH of the solution and the rich oxygen-containing groups on the graphene oxide surface. The adsorption process of graphene oxide to Li+, Na+, K+, Rb+ and Cs+ conforms to the Langmuir isotherm model, and the adsorption of graphene oxide to K+ conforms to the Freundlich isotherm model and they all conform to the pseudo-second-order kinetics. The thermodynamic parameters show ΔG<0, ΔH>0, which shows adsorption is a spontaneous endothermic process and is a chemically controlled process. In this paper, in single or mixed alkali metal solutions, graphene oxide has higher adsorption capacity and ratio of K+. The separation factor of graphene oxide for K/Na is 2.11 and the separation factor of K/Rb is 2.53.(3) At room temperature, this paper prepared Co/rGO composites from graphene oxide. Using propanol as a solvent, the cobalt nanoparticles have been further functionalized to prepare magnetic Co/rGO composite materials.Co/rGO composites have superparamagnetic properties, which can be easily separated using magnets, and oscillate and disperse Co/rGO composites without magnetic field. This paper systematically investigated the influence of key factors including the amount of NaOH added, the type of complexing agent, and the type of solvent on the morphology and distribution characteristics of Co particles on the rGO. The Co/rGO composites prepared under the optimal conditions are characterized by FT-IR, XRD, and SEM. The results show that for the Co/rGO composite material prepared by in-situ reduction method, the particle size of cobalt particles is mainly affected by the amount of NaOH added, the added citric acid is beneficial to disperse the cobalt nanoparticles, while in the propanol solution, the cobalt nanoparticles are petal-shaped spherical, which significantly increases the adsorption performance of the composite. Research on the adsorption effect of Co/rGO composites synthesized by different conditions on Cu2+ in solution, the optimal reaction condition is OH-/Co2+=8, the solvent is propanol, and the complexing agent is citric acid. The Co/rGO composites prepared under optimal conditions are fold-shaped planes, and the graphene C=C structure has been obviously restored, but due to the protective effect of Co, more oxygen-containing active groups such as C—OH remain group are remaining. Cauliflower-like metallic cobalt particles smaller than 100 nm are more uniformly dispersed on the surface. (4) This paper also explores the effects of initial pH value, adsorption time, initial Cu2+ concentration and reaction temperature on the adsorption performance of the solution, as well as adsorption thermodynamics and the reuse of compound materials. The results show that the Co/rGO composite has stable adsorption/desorption performance for Cu2+. Under the experimental conditions, its maximum adsorption capacity for Cu2+ reaches 117.5 mg/g and the adsorption equilibrium can be achieved within 5 minutes, which is far superior to that of the raw material graphene oxide (the adsorption capacity of graphene oxide is 27.5 mg/g within 60 min). The adsorption process of nano-Co/rGO magnetic materials for Cu2+ is in line with the Freundlich model and belongs to the multilayer adsorption. At room temperature, the enthalpy of adsorption is ΔH=17.81 kJ/mol, and the equilibrium constant of adsorption is K0=3.65. When the initial concentration of Cu2+ is 10 mg/L, the desorption rate exceeds 93%. After five adsorption/desorption cycles, the adsorption capacity remains at 94% of the initial value, and the residual Cu2+ concentration in the solution after each adsorption meets the cobalt electrolyte's requirement for the concentration of impurity copper ions (5 mg/L) and meets the level 3 of GB 8978—1996 comprehensive sewage discharge standard (2 mg/L), and it is expected to play a important role in related fields. 

Language中文
Document Type学位论文
Identifierhttp://ir.ipe.ac.cn/handle/122111/49628
Collection中国科学院过程工程研究所
Recommended Citation
GB/T 7714
张晶晶. GO及Co/rGO磁性复合材料的制备及其离子吸附性能研究[D]. 中国科学院大学,2020.
Files in This Item:
File Name/Size DocType Version Access License
GO及Co-rGO磁性复合材料的制备及其(3139KB)学位论文 限制开放CC BY-NC-SAApplication Full Text
Related Services
Recommend this item
Bookmark
Usage statistics
Export to Endnote
Google Scholar
Similar articles in Google Scholar
[张晶晶]'s Articles
Baidu academic
Similar articles in Baidu academic
[张晶晶]'s Articles
Bing Scholar
Similar articles in Bing Scholar
[张晶晶]'s Articles
Terms of Use
No data!
Social Bookmark/Share
All comments (0)
No comment.
 

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