Adsorption of Cu2+, Cd2+ and Ni2+ from aqueous single metal solutions on graphene oxide membranes

Novel, highly ordered layered graphene oxide (GO) membranes with larger interlayer spacing were prepared by induced directional flow and were used as adsorbents for the removal of Cu2+, Cd2+ and Ni2+ from aqueous solutions. The effects of pH, ionic strength, contact time, metal ion concentration and cycle time on Cu2+, Cd2+ and Ni2+ sorption were investigated. The results indicated that the adsorption of Cu2+, Cd2+ and Ni2+ onto GO membranes was greatly influenced by the pH and weakly affected by the ionic strength. The adsorption isotherms for Cu2+, Cd2+ and Ni2+ were well fitted by the Langmuir model. The maximum adsorption capacities of the GO membranes for Cu2+, Cd2+ and Ni2+ were approximately 72.6, 83.8 and 62.3 mg/g, respectively. The adsorption kinetics of Cu2+, Cd2+ and Ni2+ onto GO membranes followed the pseudo-second-order model. The adsorption equilibrium was reached in a shorter time. The GO membranes can be regenerated more than six times based on their adsorption/desorption cycles, with a slight loss in the adsorption capacity. The results demonstrated that the GO membranes can be used as effective adsorbents for heavy metal removal from water.