title: Fe(II) uptake on natural montmorillonites. II. Surface complexation modeling.
abstract: Fe(II) sorption edges and isotherms have been measured on low structural Fe-content montmorillonite (STx) and high structural Fe-content montmorillonite (SWy) under anoxic (O2 < 0.1 ppm) and strongly reducing conditions (Eh = -0.64 V). Under anoxic conditions Fe(II) sorption on SWy was significantly higher than on STx, whereas the sorption under reducing conditions was essentially the same. The uptake behavior of Fe(II) on STx under all redox conditions (Eh = +0.28 to -0.64 V) and SWy under reducing conditions (Eh = -0.64 V) was consistent with previous measurements made on other divalent transition metals. All of the sorption data could be modeled with the two-site protolysis nonelectrostatic surface complexation and cation exchange (2SPNE SC/CE) sorption model including an additional surface complexation reaction for Fe(II) which involved the surface oxidation of ferrous iron surface complexes (≡S(S,W)OFe(+)) to ferric iron surface complexes (≡S(S,W)OFe(2+)) on both the strong and weak sites. The electron acceptor sites on the montmorillonite are postulated to be the structural Fe(III).
authors.affiliation: Laboratory for Waste Management, Paul Scherrer Institut , 5232 Villigen PSI, Switzerland.
authors.forename: Daniela
authors.initials: D
authors.lastname: Soltermann
authors.forename: Bart
authors.initials: B
authors.lastname: Baeyens
authors.forename: Michael H
authors.initials: MH
authors.lastname: Bradbury
authors.forename: Maria
authors.initials: M
authors.lastname: Marques Fernandes
mesh_terms: D000327:Adsorption; D001546:Bentonite / Q000737:chemistry*; D055664:Electrochemical Techniques; D005290:Ferric Compounds / Q000737:chemistry*; D005296:Ferrous Compounds / Q000737:chemistry*; D007501:Iron / Q000737:chemistry; D008956:Models, Chemical; D010084:Oxidation-Reduction
chemical_list: D005290:Ferric Compounds; D005296:Ferrous Compounds; D001546:Bentonite; D007501:Iron