Application of three surface complexation models on U(VI) adsorption onto graphene oxide

• Maximum adsorption capacity of GO for U(VI) at pH 4.5 and 333 K was 142.86 mg/g.
• Inner-sphere surface complexation dominated U(VI) adsorption on GO.
• Three surface complexation models give the better fits for U(VI) adsorption on GOs.

The effect of environmental factors (i.e., reaction time, pH, ionic strength, temperature and initial U(VI) concentration) on the adsorption of U(VI) on graphene oxide (GO) had been investigated by batch techniques. The macroscopic experiments indicated that the adsorption kinetics and adsorption isotherms of U(VI) on GO can be satisfactorily fitted by the pseudo-second-order kinetic model and Langmuir model, respectively. No change of ionic strength indicated that the inner-sphere surface complexation dominated the adsorption of U(VI) on GO over the wide pH range. Three surface complexation models (SCMs), including constant capacitance model (CCM), diffuse layer model (DLM) and triple layer model (TLM), had been given an excellent fits for the adsorption of U(VI) on GO with two inner-sphere surface complexes such as SOUO2+ and (SO)2UO2(OH)22− species.