Competitive adsorption of Sr(II) and U(VI) on graphene oxide investigated by batch and modeling techniques

In this studies, the effect of reaction time, pH, ionic strength and initial U(VI) concentration on the competitive adsorption of U(VI) and Sr(II) onto graphene oxide (GO) was investigated by batch techniques. Adsorption tests showed that the GO presented higher adsorption capacity for U(VI) than Sr(II) in single and binary-solute systems, revealing that electrostatic interaction was the main driving force responsible for the competitive adsorption of U(VI) and Sr(II) on GO. The adsorption kinetics and isotherms of U(VI)/Sr(II) on GO at single- and multi-solute systems can be simulated by pseudo-second-order kinetic model and Langmuir model, respectively. No effect of ionic strength on competitive adsorption of U(VI) and Sr(II) onto GO indicated the inner-sphere surface complexation predominately. The competitive adsorption of U(VI) and Sr(II) on GO can be satisfactorily fitted with two inner-sphere surface complexes using surface complexation modeling by extended triply layer modeling when two surface acidity constants are considered.