title: Competition between selenium (IV) and silicic acid on the hematite surface.
abstract: Competition between selenium (IV) and silicic acid for the hematite (alpha-Fe(2)O(3)) surface has been studied during this work. Single batch experiments have been performed to study separately the sorption of selenium (IV) and silicic acid as a function of the pH. With the help of the 2-pK surface complexation model, experimental data have been fitted using the FITEQL 4.0 program. Two monodentate inner-sphere surface complexes have been used to fit selenite ions retention, triple bond FeSeO(3)(-) and triple bond FeHSeO(3). In order to fit sorption of silicic acid, the two following surface complexes, namely triple bond FeH(3)SiO(4), and triple bond FeH(2)SiO(4)(-), have been used. Using the surface complexation constants coming from these two binary systems, prediction curves of the effect of silicic acid on the retention of selenium (IV) onto hematite have been obtained. Finally, performed experiments showed a competition between selenium (IV) and silicic acid for the surface sites of hematite. Experimental data matched DDLM predictions, confirming the ability of the surface complexation model to predict quantitatively and qualitatively the ternary system selenium (IV)/H(4)SiO(4)/hematite.
authors.affiliation: Université de Nice-Sophia-Antipolis, Laboratoire de Radiochimie, Sciences Analytiques et Environnement, 28 Avenue Valrose, 06108 Nice Cedex 2, France. jordan@unice.fr
authors.forename: Norbert
authors.initials: N
authors.lastname: Jordan
authors.forename: Nicolas
authors.initials: N
authors.lastname: Marmier
authors.forename: Claire
authors.initials: C
authors.lastname: Lomenech
authors.forename: Eric
authors.initials: E
authors.lastname: Giffaut
authors.forename: Jean-Jacques
authors.initials: JJ
authors.lastname: Ehrhardt
mesh_terms: D000327:Adsorption; D005290:Ferric Compounds / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D011850:Radioactive Waste / Q000517:prevention & control; D012643:Selenium / Q000737:chemistry*; D012824:Silicic Acid / Q000737:chemistry*; D013499:Surface Properties; D013997:Time Factors
chemical_list: D005290:Ferric Compounds; D011850:Radioactive Waste; D012824:Silicic Acid; C000499:ferric oxide; D012643:Selenium