A surface complexation model for sulfate and selenate on iron oxides consistent with spectroscopic and theoretical molecular evidence |
| |
| Authors: | Keisuke Fukushi Dimitri A Sverjensky |
| |
| Institution: | Department of Earth and Planetary Sciences, Johns Hopkins University, Baltimore, MD 21218, USA |
| |
| Abstract: | Sulfate and selenate adsorption on iron oxides are important reactions in natural systems under a very wide range of pH values, ionic strengths, and electrolyte compositions. Under such conditions, spectroscopic and theoretical calculations have demonstrated the potential importance of a variety of surface species. Understanding the variations in the surface speciation of these oxyanions is fundamental to prediction of their partitioning between minerals and aqueous solutions. In the present study, published experimental spectroscopic and theoretical molecular evidence of the identity of sulfate/selenate surface species are integrated with a surface complexation model consistent with a wide variety of experimental adsorption, surface titration, and proton coadsorption data to define the surface speciation of sulfate and selenate on iron oxides under a wide range of conditions. The analysis was carried out with the extended triple layer model (ETLM) taking into account the electrostatics of water dipole desorption during ligand exchange reactions. On seven out of eight goethites studied, sulfate and selenate surface reactions can be represented by the formation of a monodentate-mononuclear inner-sphere and a bidentate-binuclear outer-sphere (or H-bonded) species according to |
| |
| Keywords: | |
| 本文献已被 ScienceDirect 等数据库收录！ |
|
