氧化石墨烯的制备、改性及对水中镉的去除研究

发布时间：2018-05-01 02:15

本文选题：氧化石墨烯 + 巯基改性氧化石墨烯　；参考：《浙江大学》2015年硕士论文

【摘要】：石墨烯是由单层碳原子以六元环形式紧密堆积而成的二维片状碳纳米材料,因其完美的二维晶体结构和独特的光学、电学、力学和热学等性质,引起学者的广泛关注。氧化石墨烯作为化学法制备石墨烯的前驱物,具有比表面积大、电子迁移率高和化学稳定性强等特性。与石墨烯相比,氧化石墨烯表面及边缘上含有大量的含氧基团,使其对重金属、有机物等污染物质具有较好的吸附能力,并易于被修饰与功能化。本文采用改性Hummers法制备出氧化石墨烯,并将其应用于水中Cd(Ⅱ)的去除。考察了温度、初始pH、投加量等因素对Cd(Ⅱ)吸附效果的影响,并探究了其对Cd(Ⅱ)的去除机理。同时针对氧化石墨烯不易从水溶液中分离,难以实现循环利用的缺点对其进行巯基化改性,制备出巯基功能化氧化石墨烯,研究了其对水中Cd(Ⅱ)的吸附性能和再生循环效果。且通过AFM、TEM、XRD、FITR、Zeta电位、XPS、Raman等技术对氧化石墨烯和巯基改性氧化石墨烯进行了表征。实验结果表明：氧化石墨烯与巯基改性氧化石墨烯均为半透明状的片层结构,其表面都具有丝绸一样的褶皱与折叠,并且在边缘部位存在明显的多层结构,但是氧化石墨烯的表面褶皱较巯基改性氧化石墨烯更多一些。氧化石墨烯表面具有大量的羟基、羧基、羰基等含氧官能团,采用巯基乙酸对其进行改性后,巯基乙酸的羧基可以与氧化石墨烯的羟基发生酯化反应,将巯基枝连到氧化石墨烯的表面。温度对氧化石墨烯和巯基改性氧化石墨烯去除水中Cd(Ⅱ)的影响均较小。当温度为293.15 K,300.15 K,313.15 K时,氧化石墨烯对Cd(Ⅱ)的去除率分别为90.94%,91.64%,92.67%；而巯基改性氧化石墨烯对Cd(Ⅱ)的去除率有所下降,但较氧化石墨烯更易分离、再生和循环使用。当氧化石墨烯和巯基改性氧化石墨烯投加量逐渐增加时,其对Cd(Ⅱ)的去除率先有一个快速的增大阶段,然后上升趋势减弱,最后逐渐趋于平缓。对其进行吸附等温线拟合发现,氧化石墨烯和巯基改性氧化石墨烯对Cd(Ⅱ)的去除均能较好的用Langmuir等温式拟合。初始pH对氧化石墨烯和巯基改性氧化石墨烯去除水中Cd(Ⅱ)均有显著影响。随着溶液pH的增加,氧化石墨烯对Cd(Ⅱ)的去除率逐渐增大,且当初始pH由2.00升高到5.00时,Cd(Ⅱ)的去除率急剧增大,当pH继续升高,Cd(Ⅱ)的去除率趋于平稳。氧化石墨烯表现出较好的酸碱适应性,在pH=4时,去除率就已达到90.05%。而巯基氧化石墨烯对Cd(Ⅱ)的去除率的总趋势随着溶液初始pH的升高而增大。当pH从2增大至6时,Cd(Ⅱ)的去除率从7.32%升高至73.97%,当pH=9和10时,Cd(Ⅱ)去除率增大至88.09%和96.86%。随着反应时间的增加氧化石墨烯及巯基改性氧化石墨烯对Cd(Ⅱ)的总去除率均呈现先逐渐增大后趋于平衡稳定的趋势。氧化石墨烯的反应速率较快,在1 min时Cd(Ⅱ)去除率就已达到77.32%,巯基氧化石墨烯的反应速率相对要慢一些,在1 min时Cd(Ⅱ)去除率仅为27.56%,但是两者均在反应2 h内达到平衡。通过对吸附反应进行动力学方程拟合发现,氧化石墨烯体系及巯基改性氧化石墨烯体系对Cd(Ⅱ)的吸附均符合准二级动力学模型。
[Abstract]:Graphene is a two-dimensional sheet carbon nanomaterial formed by the compact accumulation of single carbon atoms in the form of six membered rings. Because of its perfect two-dimensional crystal structure and unique optical, electrical, mechanical and thermal properties, graphene has attracted wide attention of scholars. As a precursor to the preparation of graphene by chemical method, graphene has a large specific surface area and electron migration. Compared with graphene, the surface and edge of graphene oxide contain a large number of oxygen containing groups, so that they have good adsorption capacity for heavy metals, organic substances and other pollutants, and are easy to be modified and functionalized. In this paper, the modified Hummers method was used to prepare graphene oxide and applied it to water. The removal of Cd (II). The effects of temperature, initial pH, dosage and other factors on the adsorption of Cd (II) were investigated, and the mechanism for the removal of Cd (II) was explored. At the same time, the mercapto modification of graphite oxide was difficult to be separated from aqueous solution, and the sulfhydryl functionalized graphene oxide was prepared. The adsorption properties and regenerative cycle effect of Cd (II) in water were characterized by AFM, TEM, XRD, FITR, Zeta potential, XPS, Raman and other techniques. The results showed that graphene oxide and Mercapto modified graphene oxide were all semitransparent lamellar structure with silks on the surface. The surface folds of graphene oxide are more than that of mercapto modified graphene. The surface of graphene oxide has a large number of hydroxyl, carboxyl, carbonyl and other oxygen-containing functional groups. The carboxyl group of mercapto acetic acid can be modified with Qiu Jiyi acid. The hydroxyl group of graphene oxide is esterified to connect the mercapto branch to the surface of graphene oxide. The temperature has little effect on the removal of Cd (II) in water by graphene oxide and Mercapto modified graphene oxide. When the temperature is 293.15 K, 300.15 K, and 313.15 K, the removal rates of graphene oxide to Cd (II) are 90.94%, 91.64%, 92.67%, and the sulfhydryl group, respectively. The removal rate of modified graphene oxide has a decrease in the removal rate of Cd (II), but it is more easily separated, regenerated and recycled than graphene oxide. When the dosage of graphene oxide and Mercapto modified graphene oxide gradually increases, the removal of Cd (II) first has a rapid increase stage, then the rising trend is weakened, and finally gradually tends to flat. The adsorption isotherm fitting shows that the removal of Cd (II) by graphene oxide and Mercapto modified graphene oxide can be better fitted with Langmuir isothermal fitting. Initial pH has significant influence on the removal of Cd (II) in water by graphene oxide and Mercapto modified graphene oxide. With the increase of pH, the removal rate of graphene oxide to Cd (II) When the initial pH increased from 2 to 5, the removal rate of Cd (II) increased rapidly. When pH continued to increase, the removal rate of Cd (II) tended to be stable. The removal rate of graphene oxide was better than that of 90.05%. while the removal rate of the mercapto oxygen fossil to Cd (II) was the general trend with the initial pH of solution at pH=4. When the pH increased from 2 to 6, the removal rate of Cd (II) increased from 7.32% to 73.97%. When pH=9 and 10, the removal rate of Cd (II) increased to 88.09% and 96.86%., with the increase of the total removal rate of graphene oxide and Mercapto modified graphene oxide as the reaction time increased, and then the total removal rate of Cd (II) gradually increased and then tended to be stable and stable. The reaction rate of the fossil graphene is faster, the removal rate of Cd (II) has reached 77.32% at 1 min, and the reaction rate of mercapto graphene oxide is relatively slow, and the removal rate of Cd (II) is only 27.56% at 1 min, but both of them balance within the reaction of 2 h. The adsorption of Cd (II) by sulfhydryl modified graphene oxide accords with the quasi two level kinetic model.

【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ127.11;X703

【参考文献】