The sorption of Eu(III) from aqueous solutions by magnetic graphene oxides: A combined experimental and modeling studies

The sorption of Eu(III) on magnetic graphene oxides (GOs) was investigated by batch techniques and surface complexation modeling. The pH-dependent sorption results indicated that sorption of Eu(III) on GOs and magnetic GOs significantly increased with increasing of pH values ranging from 2.0 to 6.0, and then high-level sorption was observed at pH > 7.0. No effect of ionic strength on Eu(III) sorption revealed that inner-sphere surface complexation dominated the sorption of Eu(III) on magnetic GOs over wide range of pH. The maximum sorption capacity of Eu(III) on magnetic GOs calculated from Langmuir model at pH 4.5 and 298 K was 70.15 mg/g, which was much higher than that of natural adsorbents. Thermodynamic parameters calculated from temperature-dependent sorption isotherms showed that the sorption of Eu(III) on magnetic GOs was a spontaneous and exothermic process. The results of surface complexation modeling showed that the sorption mechanism of Eu(III) on magnetic GOs was mainly monodentate and multidentate inner-sphere surface complexation at circumneutral and high pH conditions, respectively. The results indicated that magnetic GOs can be considered as a candidate for the removal and sequestration of Eu(III) in aqueous solutions in environmental remediation.