Synthesis of graphene oxide nanosheets for the removal of Cd(II) ions from acidic aqueous solutions

In this study, graphene oxide nanosheets were synthesized and employed to adsorb Cd(II) in acidic aqueous solutions. Characterization techniques, such as AFM, TEM, XRD, FT-IR, Raman and Zeta potential were used to investigate the adsorbent properties. Results demonstrated that the Cd(II) removal efficiency was found to increase from 6.29% to 96.72% with the increase of adsorbent dosage from 0.02 to 2.00 g/L. The removal efficiency remained constant with further increase of the adsorbent dosage. Cd(II) adsorption was greatly enhanced with the increase of solution pH from 2.02 to 4.01. In addition, the adsorption equilibrium was attained within 120 min, and a slight decrease in solution pH was observed after the adsorption of Cd(II). The adsorption data were revealed to fit well in pseudo-second-order kinetics and Langmuir isotherm model, and the maximum Cd(II) adsorption capacity was recorded to be about 44.64 mg/g with 0.50 g/L of adsorbent dosage. Ion-exchange, electrostatic attraction and physical adsorption were found to be involved in the adsorption mechanisms of this process. Findings from this study suggested that the synthesized adsorbent could be highly effective for Cd(II) removal from acidic water environments.