Amide-functionalized graphene-assembled monoliths with high adsorption capacity of Cd2+

Three-dimensional graphene-assembled monoliths (GAs) are emerging materials used in supercapacitors, catalysis, etc. However, GAs prepared by mainstream reduction methods (reduced GAs, RGAs) have fewer functional groups and display poor adsorption capacity of heavy metals. In this paper, we developed a new method of preparing amide-functionalized GAs (AGAs) with high degree of modification by the reaction of carboxyl-functionalized graphene oxides and ethylenediamine. AGAs contained multiple functional groups and exhibited dendritic structure at micron scale. Benefiting from these properties, the maximum adsorption capacities Cd 2 + on AGAs at T = 303 K were about 56.6 mg/g, which was twice that of RGAs and higher than that of graphene ( ∼ 10 mg/g) and biochar ( ∼ 18 mg/g) at the same conditions. By calculating the Gibbs free energies ( Δ G), the adsorption of Cd 2 + on AGAs was proved a spontaneous process, while the adsorption of Cd 2 + on RGAs was not spontaneous X-ray photoelectron spectroscopy analysis demonstrated that AGAs contained more adsorption sites and Cd 2 + adsorbed on AGAs through coordination bond. Thus, AGAs exhibited good application potentials as adsorbents for the removal of Cd 2 + from contaminated water.