Experimental determination of iron(II) oxidation rate constants in natural waters

CHED 1136

Michael J. Pullin, mpullin@nmt.edu, Andrea Higdon, higdona@nmt.edu, and Eric Osantowski, eosantow@nmt.edu. Department of Chemistry, New Mexico Institute of Mining and Technology, 801 Leroy Place, Socorro, NM 87801
The iron chemistry in natural waters is dominated by redox reactions that convert iron(II) to iron(III) and visa versa. One major reaction of this type is the oxidation of iron(II) to iron(III) by dissolved oxygen. The most currently available and detailed iron(II) oxidation model has had only limited success in predicting the rate of this reaction. While this model is able to calculate the oxidation rates for solutions containing carbonic acid, it is does not accurately predict the rates for solutions that exclude it. This research presents an iron redox model that can accurate predict the oxidation rates of iron in a wider range of natural waters. The greater success of this model is in part due to new, experimentally-determined rate constants for the iron(II) hydrolysis species. These rate constants were determined using a novel iron(II)-specific flow injection analysis system.