Fe(III) Reduction in the Presence of Catechol in Seawater
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Fe(II)-Fe(III) redox behavior has been studied in the presence of catechol under different pH, ionic media, and organic compound concentrations. Catechol undergoes oxidation in oxic conditions producing semiquinone and quinone and reduces Fe(III) in natural solutions including seawater (SW). It is a pH-dependent process. Under darkness, the amount of Fe(II) generated is smaller and is related to less oxidation of catechol. The Fe(II) regeneration is higher at lower pH values both in SW with log k = 1.86 (M−1 s−1) at pH 7.3 and 0.26 (M−1 s−1) at pH 8.0, and in NaCl solutions with log k of 1.54 (M−1 s−1) at pH 7.3 and 0.57 (M−1 s−1) at pH 8.0. At higher pH values, rate constants are higher in NaCl solutions than in SW. This is due to the complexation of Mg(II) present in the media with the semiquinone that inhibits the formation of a second Fe(II) through the reaction of this intermediate with other center Fe(Cat)+.
KeywordsIron Catechol Oxidation Reduction Kinetics Seawater
This study was supported by the Project CTM2006-09857 of Ministerio de Ciencia y Tecnología from Spain. F.J. Millero wishes to acknowledge the support of the Oceanographic Section of the National Science Foundation and the National Oceanic and Atmospheric Administration for supporting his marine physical chemistry studies.
- Harrington JM, Crumbliss AL (2009) The redox hypothesis in siderophore-mediated iron uptake. Biometals doi: 10.1007/s10534-009-9233-4
- Kuma K, Nishioka J, Matsunaga K (1996) Controls on iron(III) hydroxide solubility in seawater: the influence of pH and natural organic chelators. Limnol Oceanogr 41:396–407Google Scholar
- Millero FJ (1986) The pH of estuarine waters. Limnol Oceanogr 31:839–847Google Scholar
- Takeda S, Kamatani A (1989) Photoreduction of Fe(III)-EDTA complex and its availability to the coastal diatom Thalassiosira weissflogii, Red Tides. Biol Environ Sci Toxicol 349–352Google Scholar
- Waite TD (2001) Thermodynamics of the iron system in seawater. In: Turner DR, Hunter KA (eds) The biochemistry of iron in seawater. Wiley, New York, pp 291–342Google Scholar
- Winkelmann G (1991) Handbook of microbial iron chelates. CRC Press, Boca RatonGoogle Scholar