Study On The Preparation Of Functionalized Graphene And Adsorption Of Heavy Metal And Methylene Blue

Graphene which is 2D carbon nanomaterial with SP2 carbon atoms has attracted enormous scientific attentions in chemical and physical domains since it was detected in 2004. It has many excellent properties, its theoretical specific area is 2630 m2g-1, and its excellent mobility of charge carriers and high thermal conductivity are 15 000 cm2V-1s-1 and 5300 W/mK respectively, it also has high values of its Young's modulus (1100 GPa) and fracture strength (125 GPa). Graphene has many potential applications in computer, solar cells, super capacitors, biological technology, catalysis, composite materials and so on due to its excellent properties. There are many synthesis methods of graphene, the main methods are micromechanical cleavage, chemical vapour deposition (CVD), epitaxial growth and graphite redox methods.In this paper, the functionalized graphene (GNSPF6) was fabricated by simple and fast method of electrolysis with potassium hexafluorophosphate solution as electrolyte under the static potential of 15 V. The characterization results of transmission electron microscopy, atom force microscopy, X-ray photoelectron spectroscopy, X-ray powder diffraction, Raman spectroscopy and Thermogravimetric analysis indicate that graphite rod was exfoliated completely to graphene layer containing 30 wt % PF6~- with the average thickness is ca. 1.0 nm.Our sample of GNSPF6 was developed for the removal of Pb(Ⅱ) or Cd(Ⅱ) ions from water, and the determined adsorption capacities are 406.6 mg/g (pH=5.1) for Pb(Ⅱ) and 73.42 mg/g (pH=6.2) for Cd(Ⅱ), which is much higher than that by our previous sample of GNSC8P and carbon nanotube. The adsorption processes reach equilibrium in just forty minutes and the adsorption data are described well by Langmuir and Freundlich classical isotherms models.The adsorption property of methylene blue (MB) onto functionalized graphene (GNSPF6) is investigated as well. The researches show that the adsorption amount increases with the increase of pH, as well as temperature which suggesting that the adsorption process is endothermic in our investigation. The adsorption process reaches equilibrium in 60 min, and the regression results show that pseudo-second-order kinetic model provides a better correlation than pseudo-first-order. The typical Langmuir and Freundlich models describe the experiment data well. Meanwhile, the maximum adsorption capacity of MB onto GNSPF6 is 374.4 mg/g obtained from Langmuir model at 20 oC.