Sb(III) oxidation by iodate in seawater : a cautionary tale

Francois Quentel (1) , Montserrat Filella (2) , Catherine Elleouet (1) , Christian-Louis Madec (1)

1 CEMCA - Chimie, Electrochimie Moléculaires et Chimie Analytique
2 D I A A C - Department of Inorganic Analytical and Applied Chemistry

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 L1 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-a`-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.

Mots clés: Antimony; Oxidation; Iodate; Seawater

Domaines: Chimie analytique

Francois Quentel, Montserrat Filella, Catherine Elleouet, Christian-Louis Madec. Sb(III) oxidation by iodate in seawater : a cautionary tale. Science of the Total Environment, 2006, 355, pp.259-263. ⟨10.1016/j.scitotenv.2005.01.048⟩. ⟨hal-00457272⟩