Synthesis Of Magnetic Activated Carbon Nanocomposites And Their Properties

Activated carbon(AC) is a kind of specially treated carbon, with numerous small pore and a huge specific surface area(about 500-1500m2/g). Therefore, the activated carbon has strong physical adsorption and chemical adsorption ability and can be used as a good carrier. It has been widely used in foodstuff, medicine, industry, environmental protection and all aspects of human life, especially in water treatment and air cleaning. However, the problem is that the powder AC cannot be efficiently recovered from treated water by traditional methods. But, in this case, if the AC possesses magnetic properties, it can be readily separated from the treated water with an external magnetic field, which is an effective way to solve the separation and recycling after the activated carbon used. With this goal in mind, in this paper,magnetic activated carbon nanocomposites were synthesized through several methods, and a comparation study has been done for these materials.(1) γ-Fe2O3@activated carbon was prepared by thermal decomposition method using the Fe(NO3)3·9H2O as the iron source、activited carbon as carrier, and it was characterized by XRD、N2 adsorption-desorption、XPS、FT-IR and VSM. The result shows that, nanocomposites containing pure γ-Fe2O3 phase can be obtained, when the Fe2O3 content is less than 30 wt%. When the Fe2O3 content is greater than 30 wt%, α-Fe2O3 phase also appears in the final product. 30 wt% γ-Fe2O3@AC composite BET surface area is about 293.5 m2/g,the average pore size is 3.49 nm and the saturation magnetization is 10.2 emu/g.(2) Fe3O4@activated carbon(I) nanocomposite was prepared by Ultrasonic method, using self-made Fe3O4 nano-powder as raw materials, activated carbon as support material, and it was characterized by XRD、N2 adsorption-desorption and VSM. XRD and VSM result show that, the average crystallite and saturarion magnetization of compsites increases with the increasing of Fe3O4 content. The specific surface area and the saturation magnetization of 30 wt% Fe3O4@AC(I) are measured to be 880.6 m2/g and 22.7 emu/g, respectively.(3) Fe3O4@activated carbon(II) nanocomposite was synthesized by ultrasonic method using Fe3O4 magnetic fluid as raw material, activated carbon as support, and it was characterized by XRD and N2 adsorption-desorption measurements and VSM. XRD result shows that the nanocomposite only contains Fe3O4 phase. VSM result shows that nanocomposite was superparamagnetic material. The obtained Fe3O4@activated carbon(II) can be recycle from water by using a magnet. 25.6% Fe3O4@AC composite possesses a mesoporous structure with a BET surface area of 890.4 m2/g and the saturation magnetization is as large as 17.9 emu/g, respectively.(4) The adsorption abilities of above-mentioned three kinds of nanocomposites for cationic dye(e.g., methylene blue) have been investigated. The adsorption of methylene blue was very fast and can reach the adsorption equilibrium within 20 min. The adsorbed percentages of methylene blue on three adsorbents were as high as ? 98%. For three adsorbents, the adsorption capacity increases with the increasing of methylene blue concentration. Langmuir adsorption model and Freundlich adsorption model were used for the analysis of experimental data. The result shows that the adsorption data fit well with Langmuir adsorption model. The maximum adsorption capacities of γ-Fe2O3@AC 、 Fe3O4@AC(I) and Fe3O4@AC(II) nanocomposites for methylene blue are determined to be 198.8 mg/g、404.9 mg/g and 384.6 mg/g, respectively.(5) This chapter was based on γ-Fe2O3@AC 、 Fe3O4@AC(I) and Fe3O4@AC(II) composites as adsorbent adsorbed the anionic dye(e.g., methyl orange). The results show that the adsorption were all consistent with pseudo-second-order kinetics equation, which belongs to chemical adsorption, and the adsorption rate is about 98%. When the pH of Methyl orange 2 to 12, it was no influence on the adsorption and the adsorption rate was very high. The adsorption capacity increases and adsorption rate decreases with the increasing of methyl orange concentration. Langmuir adsorption model and Freundlich adsorption model were used for the analysis of experimental data. The result shows that the adsorption data fit well with Langmuir adsorption model, illustrate the adsorption mainly is the monolayer adsorption. The maximum adsorption capacities of γ-Fe2O3@AC 、 Fe3O4@AC(I) and Fe3O4@AC(II) nanocomposites for methyl orange are determined to be 312.5 mg/ g、392.2 mg/g and 357.1 mg/g.