Preparation of Graphene-Oxide/Polyamidoamine Dendrimers and Their Adsorption Properties toward Some Heavy Metal Ions

Graphene oxide/polyamidoamine dendrimers (GO/PAMAMs) were prepared via a "grafting to" method. The adsorption behavior of the GO/PAMAMs for Pb(II), Cd(II), Cu(II), and Mn(II) was studied, and the effects of solution pH, adsorption time, and initial metal ion concentration on adsorption capacity of the adsorbent were also investigated. The pseudo-first-order and pseudo-second-order kinetic models were used to describe the kinetic processes, and the results indicated that the adsorption of Pb(II), Cd(II), Cu(II), and Mn(II) followed a second-order type reaction kinetics and the adsorption of Pb(II), Cd(II), Cu(II), and Mn(II) onto GO/PAMAMs is a chemical adsorption. The adsorption capacities of GO/PAMAMs were found to be 568.18, 253.81, 68.68, and 18.29 mg/g for Pb(II), Cd(II), Cu(II), and Mn(II), respectively. The adsorption reached equilibrium within 60 min and characteristics of the adsorption process were evaluated by using the Langmuir and Freundlich isotherm models. The adsorption processes fit better with the Langmuir model for Cu(II) and Mn(II) than for Pb(II) and Cd(II); the adsorption of Cu(II) and Mn(II) on GO/PAMAMs was a typical monomolecular layer adsorption.