title: Nitrate reduction by mixed iron(II-III) hydroxycarbonate green rust in the presence of phosphate anions: the key parameters influencing the ammonium selectivity.
abstract: The reduction of nitrate anions by a mixed Fe(II)-Fe(III) carbonated green rust (GR) in aqueous medium is studied as a function of the initial pH and the initial concentrations of iron, phosphate and nitrate. The influence of these parameters on the fraction of nitrate removed and the production of ammonium is investigated by the help of statistical experimental designs. The goal is to determine experimental conditions that maximize the fraction of NO3(-) removed and concomitantly minimize the production of NH4(+). Increasing the phosphate concentration relatively to the initial Fe(II) concentration inhibits the reduction of nitrate probably due to a surface saturation of the lateral sites of the GR crystals. The kinetics of the reaction is greatly enhanced by increasing the initial pH at 10.5, however it leads to a global increase of the NH4(+) production. A partial saturation of the surface sites by phosphate leads to a global decrease of selectivity of the reaction towards ammonium. The evolution of the ratio of the NH4(+) concentration to the Fe(II) concentration confirms that the NO3(-) species are only partially transformed into ammonium. Interestingly at an initial pH of 7.5, the selectivity of the reaction towards NH4(+) is often lower than ∼30%. The reduction of nitrate by carbonated GR differs from the behavior of other GRs incorporating Cl(-), F(-) and SO4(2-) anions that fully transform nitrate into ammonium. Finally, if GR is intended to be used during a passive water denitrification process, complementary dephosphatation and ammonium treatments should be considered.
authors.affiliation: Université de Lorraine, Laboratoire de Chimie Physique et Microbiologie pour l'Environnement, LCPME, UMR 7564, 405 rue de Vandœuvre, F-54600 Villers-lès-Nancy, France; CNRS, Laboratoire de Chimie Physique et Microbiologie pour l'Environnement, LCPME, UMR 7564, 405 rue de Vandœuvre, F-54600 Villers-lès-Nancy, France.
authors.forename: Marjorie
authors.initials: M
authors.lastname: Etique
authors.affiliation: Université de Lorraine, Laboratoire de Chimie Physique et Microbiologie pour l'Environnement, LCPME, UMR 7564, 405 rue de Vandœuvre, F-54600 Villers-lès-Nancy, France; CNRS, Laboratoire de Chimie Physique et Microbiologie pour l'Environnement, LCPME, UMR 7564, 405 rue de Vandœuvre, F-54600 Villers-lès-Nancy, France.
authors.forename: Asfaw
authors.initials: A
authors.lastname: Zegeye
authors.affiliation: Université de Lorraine, Laboratoire de Chimie Physique et Microbiologie pour l'Environnement, LCPME, UMR 7564, 405 rue de Vandœuvre, F-54600 Villers-lès-Nancy, France; CNRS, Laboratoire de Chimie Physique et Microbiologie pour l'Environnement, LCPME, UMR 7564, 405 rue de Vandœuvre, F-54600 Villers-lès-Nancy, France.
authors.forename: Brian
authors.initials: B
authors.lastname: Grégoire
authors.affiliation: Université de Lorraine, Laboratoire de Chimie Physique et Microbiologie pour l'Environnement, LCPME, UMR 7564, 405 rue de Vandœuvre, F-54600 Villers-lès-Nancy, France; CNRS, Laboratoire de Chimie Physique et Microbiologie pour l'Environnement, LCPME, UMR 7564, 405 rue de Vandœuvre, F-54600 Villers-lès-Nancy, France.
authors.forename: Cédric
authors.initials: C
authors.lastname: Carteret
authors.affiliation: Université de Lorraine, Laboratoire de Chimie Physique et Microbiologie pour l'Environnement, LCPME, UMR 7564, 405 rue de Vandœuvre, F-54600 Villers-lès-Nancy, France; CNRS, Laboratoire de Chimie Physique et Microbiologie pour l'Environnement, LCPME, UMR 7564, 405 rue de Vandœuvre, F-54600 Villers-lès-Nancy, France. Electronic address: christian.ruby@lcpme.cnrs-nancy.fr.
authors.forename: Christian
authors.initials: C
authors.lastname: Ruby
mesh_terms: D064751:Ammonium Compounds / Q000737:chemistry*; D000838:Anions; D002254:Carbonates / Q000737:chemistry*; D007501:Iron / Q000737:chemistry*; D007700:Kinetics; D009566:Nitrates / Q000302:isolation & purification*; D010084:Oxidation-Reduction; D010710:Phosphates / Q000737:chemistry*
chemical_list: D064751:Ammonium Compounds; D000838:Anions; D002254:Carbonates; D009566:Nitrates; D010710:Phosphates; D007501:Iron
keywords: Denitrification; Green rust; Iron; Layered double hydroxide; Passive treatment