Adsorption behavior of copper ions on graphene oxide–chitosan aerogel

•Graphene oxide–chitosan aerogel was prepared by lyophilization for heavy metal removal.•Graphene oxide–chitosan aerogel had a huge adsorption capacity for Cu2+, higher than that of graphene oxide aerogel.•Graphene oxide–chitosan aerogel was stable and not dispersible in water, thus, could be easily separated from environment after adsorbing pollutants.

Graphene oxide (GO)–chitosan (CS) composite was lyophilized to prepare GO–CS aerogel for Cu2+ removal, then the separation of adsorbents after adsorption was easily achieved by filtration or low speed centrifugation. GO–CS was a good adsorbent of Cu2+ with a large adsorption capacity of 2.54 × 101 mg/g according to the Langmuir model. The adsorption kinetics was well described by the pseudo-second-order model with a k2 of 4.14 × 10−3 min−1. The intraparticle diffusion model was adopted to reveal the diffusion mechanism. Higher pH, lower ionic strength and higher temperature benefited the adsorption. The thermodynamics parameters at 303 K were calculated as ΔG of −3.89 kJ/mol, ΔH of 3.46 kJ/mol and ΔS of 2.42 × 101 J/mol/K. The adsorption identity was physisorption and apparently driven by the increase of randomness. The implications to the application of graphene adsorbents in the decontamination of heavy metals are discussed.

Graphical abstractGraphene oxide–chitosan aerogel (GO–CS) was stable in water and could be easily separated from environment after adsorbing copper ions, where the adsorption capacity of GO–CS aerogel was higher than that of GO aerogel.Figure optionsDownload full-size imageDownload as PowerPoint slide