title: Sb(III) oxidation by iodate in seawater: a cautionary tale.
abstract: Knowledge of antimony redox kinetics is crucial in understanding the impact and fate of antimony in the environment. The oxidation of Sb(III) with iodate was measured in 0.5 mol L(-1) NaCl solutions as a function of pH at environmentally significant concentrations of antimony and iodate. The oxidation of Sb(III) with iodate is pH dependent: no measurable oxidation is observed below pH 9. The undissociated Sb(OH)3 does not react with iodate and the formation of significant amounts of Sb(OH)4- is needed for the reaction to take place. It is thus unlikely that iodate oxidizes Sb(III) in seawater. Our results support that the observed presence of the thermodynamically unstable Sb(III) in oxic waters can be due to the kinetic stabilization of the trivalent state vis-à-vis some common abiotic oxidants at natural pH values. However, caution must be exercised because the presence of iodate in seawater favours fast oxidation of Sb(III) if water samples are acidified, as is the case in many analytical procedures.
authors.affiliation: Laboratoire de Chimie Analytique, UMR-CNRS 6521, Université de Bretagne Occidentale, 6, Avenue V. Le Gorgeu, BP 809, F-29285 Brest, France.
authors.forename: François
authors.initials: F
authors.lastname: Quentel
authors.forename: Montserrat
authors.initials: M
authors.lastname: Filella
authors.forename: Catherine
authors.initials: C
authors.lastname: Elleouet
authors.forename: Christian-Louis
authors.initials: CL
authors.lastname: Madec
mesh_terms: D000965:Antimony / Q000737:chemistry*; D007452:Iodates / Q000737:chemistry*; D010084:Oxidation-Reduction; D012623:Seawater / Q000737:chemistry*; D014874:Water Pollutants, Chemical
chemical_list: D007452:Iodates; D014874:Water Pollutants, Chemical; D000965:Antimony