title: Modeling iron binding to organic matter.
abstract: The aim of the present work is to model iron speciation during its interaction with natural organic matter. Experimental data for iron speciation were achieved with an insolubilised humic acid used as an organic matter analogue for 30microM to 1.8 mM total iron concentrations and 2< or = pH< or = 5.5. IHA was found to be able to impose its redox potential to the solution and therefore the Fe(ll)/Fe(lll) ratio. Model VI and the NICA-Donnan model have been adjusted to experimental results of acid-base titrations, total iron measurements, and redox speciation in solution. They both describe well pH and concentration dependence of iron adsorption. For high iron concentration, Fe(lll) solution activity is limited by precipitation of a poorly ordered Fe oxyhydroxide with a higher solubility (log Ks = 5.6-5.7) than ferryhydrite described in the litterature.
authors.affiliation: Institut de Minéralogie et Physique des Milieux Condensés, Universités Paris 6 et 7, UMR 7590 CNRS and IPGP, 140 rue de Lourmel, 75015 Paris, France. weber@ipgp.jussieu.fr
authors.forename: Tiphaine
authors.initials: T
authors.lastname: Weber
authors.forename: Thierry
authors.initials: T
authors.lastname: Allard
authors.forename: Edward
authors.initials: E
authors.lastname: Tipping
authors.forename: Marc F
authors.initials: MF
authors.lastname: Benedetti
mesh_terms: D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000737:chemistry*; D008956:Models, Chemical; D009930:Organic Chemicals; D010084:Oxidation-Reduction
chemical_list: D009930:Organic Chemicals; D007501:Iron