High-efficiency removal of cationic dye and heavy metal ions from aqueous solution using amino-functionalized graphene oxide, adsorption isotherms, kinetics studies, and mechanism

GO-NH2 (amino functionalized graphene oxide) was synthesized by grafting (3-aminopropyl) triethoxysilane onto the surface GO (graphene oxide). The GO-NH2 with a higher surface area and many active sites was characterized and its effectiveness in removing Rhod B dye and Ni(II) ions from wastewater by adsorption was observed. The effects of pH, time, and strange ions on the adsorption efficiency were investigated. The equilibrium isotherm data confirmed that it fits the Langmuir and Freundlich isotherm models. GO and GO-NH2 exhibited high adsorption capacity (QM); 2500 (mg L-1) and 3333 (mg L-1) for Rhod B dye, and 312.5 (mg L-1), and 714.28 (mg L-1) for Ni(II) ions, respectively. The kinetics of adsorption was studied using pseudo-first-order, pseudo-second-order, intraparticle diffusion, and the Boyd model. It was found that the adsorption followed pseudo-second-order and film diffusion model are effective in this adsorption process. Adsorption mechanisms have been attributed to possible electrostatic attractions, hydrogen bonding, and interactions. In summary, the experimental results showed the synthesized GO and GO-NH2 would be promising adsorbents to remove aqueous solutions contaminated with Rhod B dye and Ni(II) ions.