Mechanism and microstructure of Eu(III) interaction with γ-MnOOH by a combination of batch and high resolution EXAFS investigation

Abstract

In this paper, the macroscopic interaction method and high resolution EXAFS technique with a bent crystal analyzer were combined to study Eu(III) interaction mechanism and microstructure with gamma-MnOOH as a function of pH. The results indicated that Eu(III) interaction with gamma-MnOOH was apparently dependent on pH but independent of ionic strength, suggesting the formation of inner-sphere surface complexation for Eu(III) onto gamma-MnOOH. Results of EXAFS analysis indicated that Eu was surrounded by similar to 9.0 O atoms in first coordination shell at R (Eu-O) a parts per thousand 2.40 , and second shell of Mn atoms at R (Eu-Mn) a parts per thousand 3.60 was observed for the three adsorption samples. These findings suggested formation of a bidentate surface complex with Eu(III) bonding by edge sharing to MnO6-octahedron on gamma-MnOOH surface. Both the macroscopic interaction data and the molecular level evidence of Eu(III) microstructure at the gamma-MnOOH-water interface should be factored into better understanding the fate and mobility of Eu(III) and related radionuclides in the natural soil and water environment.