Rapid and highly efficient removal of Eu(III) from aqueous solutions using graphene oxide

In this work, the use of graphene oxide (GO), a high efficiency and low-risk adsorbent, has been studied for the removal of Eu(III) from aqueous solutions. A series of experiments was conducted in a batch system to assess the effect of the system variables, i.e. contact time, initial pH, ionic strength, temperature, coexistent electrolyte ions and humic substances. The results indicated that the adsorption is strongly dependent on pH but independent of ionic strength and the effects of coexistent electrolyte ions can be negligible. A positive effect of HA/FA on Eu(III) adsorption was found at pH < 7.5, whereas a negative effect was observed at pH> 7.5. The adsorption kinetic can be described more favorably by the pseudo-second-order kinetic model and the adsorption isotherms can be described well by Langmuir isotherm model, Freundlich isotherm model and D-R isotherm, model, but Langmuir is the best. The thermodynamic data calculated from the temperature-dependent adsorption isotherms suggested that the adsorption was spontaneous and enhanced at higher temperature. Results of this work suggest that GO may be a promising candidate for the removal of Eu(III) from aqueous solutions. (C) 2016 Published by Elsevier B.V.