Kinetics and mechanism of Sr(II) adsorption by Al-Fe2O3: Evidence from XPS analysis

Abstract The Al-Fe 2 O 3 with different aluminum contents were synthesized by heating Al-substituted goethite and were characterized by FESEM, XRD, FT-IR and XPS techniques. The characteristic results showed that the Fe 3 + ion in hematite was partly substituted by Al 3 + ion, leading to the change of crystal structure. The batch experiments indicated that the adsorptions of Sr(II) on Al-Fe 2 O 3 slowly increased with increasing pH starting from 2 to 11. The pseudo-second-order kinetic and the Langmuir model gave the better fits to the adsorption kinetics and isotherms, respectively. The thermodynamic parameters indicated that the adsorption of Sr(II) on Fe 2 O 3 was an endothermic and spontaneous process. The XPS analysis demonstrated that the oxygen-containing functional groups were responsible for the Sr(II) adsorption. These findings indicated that Al-Fe 2 O 3 may be a valuable candidate for pre-concentration and solidification of radionuclides from aqueous solutions.