Fabrication of hyperbranched polyamine functionalized graphene for high-efficiency removal of Pb(II) and methylene blue

• HPA-GO was firstly prepared for Pb(II) and methylene blue removal.
• The pseudo-second-order model and Langmuir model fitted the adsorption process.
• The thermodynamics implied the adsorption was endothermic and spontaneous.
• The adsorption mechanisms were discussed.
• HPA-GO could be recycled efficiently in the adsorption–desorption cycles.

Multifunctional hyperbranched polyamine modified graphene oxide (HPA-GO) was successfully prepared and characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), X-ray diffraction (XRD), zeta potential and scanning electron microscope (SEM) analyses. HPA-GO exhibited excellent adsorption performance for the removal of a heavy metal (Pb(II)) and a dye (methylene blue (MB)). The equilibrium adsorption capacity was 819.7 mg g−1 for Pb(II) and 740.7 mg g−1 for MB under the optimal conditions. The pseudo-second order equation and the Langmuir model exhibited good correlation with the adsorption kinetic and isotherm data, respectively, for these two pollutants. The thermodynamic results (ΔG < 0, ΔH > 0, ΔS > 0) implied that the adsorption process of Pb(II) and MB was feasible, endothermic and spontaneous in nature. A possible adsorption mechanism has been proposed where chelation and electrostatic attraction dominated the adsorption of Pb(II) and π–π stacking interactions and electrostatic attraction dominated the adsorption of MB. In addition, the excellent reproducibility endowed HPA-GO with the potential for application in water treatment.

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