The protection of environment is an important issue of societies. Industrial developments lead to releasing of contaminants into the environment and so the destructive effects of these pollutants are increasing. Dyes which have long been used in different industrial fields such as paper, textile, leather, and cosmetics industries are considered as an important group of contaminants. Colour stuff discharged from industries possesses certain hazards and environmental problems due to their complex composition, toxicity, poor degradability, and high solubility [1,2]. Therefore, removal of azo dyes from colored effluents of industries is necessary. Among various physicochemical methods of dye removal, adsorption is widely used for water purification. Adsorption is superior to other techniques due to its initial cost, flexibility, simplicity of design, and ease of operation [3]. Among different adsorbents which were applied for azo dye removal, graphene, a two dimensional sp2 carbon networks with a honeycomb structure, is a new and attractive one with extraordinary properties. Some amazing properties of graphene can be listed as high electron mobility, high transparency due to an atomic monolayer, and high thermal conductivity [4]. Additional unique features of graphene are ultra-large specific surface area, flat structure, and the ability of formation π-π stacking interaction with the benzene ring of dyes which provide ideal characteristics of an excellent adsorbent [5]. In this work, graphene nanosheets were synthesized by green, cost effective, and simple procedure. Six methods such as X-ray diffraction, transmission electron microscopy (TEM), high resolution TEM, Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy, and N2 adsorption-desorption technique (BET) were used to characterize the prepared graphene nanosheets. The ability of the synthesized graphene nanosheets as a novel and efficient adsorbent for removal of an azo dye, Reactive Black 5 (RB5), was investigated. The influence of different factors including adsorbent dosage, pH, temperature, and dye concentration on the dye removal efficiency were investigated. The experimental data obey the pseudo-second order kinetic model (R2=0.997). The adsorption isotherm is described well by Freundlich isotherm. The high value of Freundlich constant (191.9 mg g-1) shows the high capacity of graphene for the RB5 adsorption from aqueous solutions. The thermodynamic parameters confirm that the RB5 adsorption on graphene surface is spontaneous and endothermic. References: [1] T. A. Nguyen, R. S. Juang, Chem. Eng. J. 219 (2013) 109-117. [2] E. Forgacs, T. Cserháti, G. Oros, Environ. Int. 30 (2004) 953-971. [3] M. A. M. Salleh, D. K. Mahmoud, W. A. W. A. Karim, A. Idris, Desalination 280 (2011) 1-13. [4] X. Huang, Z. Yin, S. Wu, X. Qi, Q. He, Q. Zhang, Q. Yan, F. Boey, H. Zhang, Small 7 (2011) 1876-1902. [5] G. K. Ramesha, A. Vijaya Kumara, H. B. Muralidhara, S. Sampath, J. Colloid Int. Sci. 361 (2011) 270-277.

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