Research On Preparation Of Gaphene And Its Adsorptive Properties

Graphene, as a novel carbon nanomaterial, owned unique phisicochemical properties and huge application prospects. In order to study the adsoption of organic contaminant on graphene, a facial oxidation-reduction method was used to prepare graphene. The graphene samples were characterized by transmission electron microscope(TEM), X-ray diffraction(XRD), X-ray photoelectron spectroscopy analysis(XPS), Zeta potential and specific surface area. The static adsorption experiment was carried out to study the adsorption of methylene blue and tetracycline on graphene. The effects of temperature、pH and adsorption contact time on the adsorption were also investigated. And the results provided theoretical basis for the environmental application of graphene. The main contents of this paper were:(1) Graphene was prepared from flake graphite via a facial oxidation-reduction method. The produced graphene was dried through freeze-drying. The specific surface area of graphene obtained through nitrogen adsorption-desorption was210.6m2/g. The TEM image of graphene showed that the samples were rippled with each other and the edge was transparent, indicating that the graphene had less layers. As shown in XRD pattern, graphene owned the graphitic crystalline structure. The results of Ranman and XPS analysis showed that the oxygen groups imported during the preparation process had been removed through the reduction reaction. The isoelectric point value of graphene was about3.9.(2) Adsorption of methylene blue on graphene reached balance in900minutes, and the adsorption process could be well described by pseudo second order model. The maximum adsorption capacity was respectively171.31mg/g,200.08mg/g and232.07mg/g at293K,303K and313K. The adsorption isotherm could be described well by Langmuir isotherm, indicating that the adsorption was monalayer adsorption. The alkaline solution environment was in favour of the adsorption. Based on the solution adsorption method, the specific surface area values of graphene, graphene oxide, carbon nanotube and graphite were respectively222.7m2/g,1225m2/g,122m2/g,23.6m2/g.(3) Adsorption of tetraceclinc on graphene reached balance in20minutes, and the adsorption process could be well described by pseudo second order model. The maximum tetracycline adsorption capacity of graphene was respectively172.1mg/g,278.2mg/g and467.6mg/g at293K,303K and313K. The adsorption process was spontaneous and endothermic in nature which could be described well by Frcundlich isotherm. The optimal pH condition for the adsorption process was at4-7. The highest occupied molecular orbital energy of graphite surface, graphene oxide surface and tetracycline molecule, which calculated based on the density functional theory, was respectively-80.063Kcal/mol,-91.692Kcal/mol and-129.210Kcal/mol. This indicated that the electron donating ability followed an order of graphite surface>graphene oxide surface>tetracycline molecule. Electrostatic interaction, van der Waals forces and π-based interaction might be the adsorption mechanisms of tetracycline adsorption on graphene.