The role of Fe(II) species on the oxidation of Fe(II) in natural waters in the presence of O2 and H2O2

✍ Scribed by J.M. Santana-Casiano; M. González-Dávila; F.J. Millero

• Publisher: Elsevier Science
• Year: 2006
• Tongue: English
• Weight: 227 KB
• Volume: 99
• Category: Article
• ISSN: 0304-4203
• DOI: 10.1016/j.marchem.2005.03.010

✦ Synopsis

The oxidation of Fe(II) at nanomolar levels with O 2 , H 2 O 2 and their mixtures has been studied and a kinetic model has been applied to describe the experimental results. A first order pH dependence is obtained when the H 2 O 2 controls the oxidation, due to the large contributions of FeOH + and FeCO 3 to the overall rate constant. The second order pH dependence for the oxidation of Fe(II) with O 2 is due to the contributions of Fe(OH) 2 and Fe(CO 3 ) 2 2À species. Trace amounts of H 2 O 2 or O 2 in the solutions radically affect the observed oxidation rates, and the presence of these two oxidants at the same time can explain some deviations obtained from the expected behavior when one of the oxidants is in excess. The experimental data and model results indicate that the oxidation of Fe(II) with H 2 O 2 plays a relatively major role in most natural waters. At the pH of seawater, O 2 is the most important oxidant when [H 2 O 2 ] is below 200 nM and [Fe(II)] is at nanomolar levels.