Adsorption of Eu(III) on sulfonated graphene oxide: Combined macroscopic and modeling techniques

Abstract The sulfonated graphene oxide (GO-OSO 3 H) was synthesized by the oxidation of GO under concentrated H 2 SO 4 conditions. It is demonstrated based on characterization results that sulfonated groups was satisfactorily grafted on the surface of GO. Macroscopic investigation indicated that the adsorption of Eu(III) on GO-OSO 3 H can be better fitted by pseudo-second-order kinetic model with high correlation coefficient (R 2  > 0.999) compared to pseudo-first-order kinetic model (R 2 3 H was independent of ionic strength, revealing that inner-sphere surface complexation dominated the Eu(III) adsorption at pH from 2.0 to 11.0. The maximum adsorption capacity of GO-OSO 3 H for Eu(III) calculated from Langmuir model was 125.0 mg/g at pH 5.5 and T  = 293 K conditions. The calculation of thermodynamic parameters showed that the adsorption of Eu(III) on GO-OSO 3 H was an exothermal and spontaneous processes. According to fitting of surface complexation modeling, the adsorption of Eu(III) on GO-OSO 3 H can be satisfactorily simulated by diffuse layer model with monodentate and mononuclear complexes (SOEu 2 + species) and bidentate and mononuclear complexes ((SO) 2 Eu (OH) 3 − species) at pH 2.0–11.0 conditions.