69 D32. Geochemistry (Posters)

Sunday, 22 October 2017
9:00 AM - 5:30 PM
Halls 4EF

FLUME SIMULATIONS TO DETERMINE FE2+ AND FE3+ KINETICS OF THE COLLOIDAL AND DISSOLVED FRACTIONS IN ABANDONED MINE DRAINAGE

Paper number: 69-22
Program: Technical Sessions
Time: 9:00 AM – 5:30 PM

Authors

Abstract

To examine the processes that control the formation and transportation of iron oxyhydroxide minerals in abandoned mine drainage (AMD), we used an annular flume to conduct mixing studies. Sediments at AMD sites have been the focus of research for many years, but the formation and transportation of the precipitates in these streams, particularly in the colloidal fraction, are still not well understood. The annular flume, with an 18 cm wide channel and 170 cm diameter, simulated AMD stream conditions while we examined the effect of flow rate on the kinetics associated with iron (oxidation of Fe2+ and loss of Fe3+ from the colloidal fraction through deposition) in the system.

We synthesized AMD water using ferrous sulfate heptahydrate (FeSO4.7H2O), sodium sulfate (Na2SO4), and sodium metasilicate (Na2SiO3) to match known aqueous concentrations of iron, sulfate, and silicon in anthracite region AMD field sites. We sampled the synthetic water at specific intervals, centrifuged to separate the suspended sediment from the colloidal and dissolved fractions, and analyzed the samples for concentrations of Fe2+ and total Fe using a spectrophotometric method. Between trials, we altered the rate of flow as well as the bed material in the channel. For bed trials, goethite-coated quartz sand more closely approximated AMD streambed conditions. Increasing the flow rate in no-bed trials resulted in faster rates of Fe2+ oxidation and Fe3+ loss from the colloidal and dissolved fractions. Preliminary data from bed trials suggest that including the bed material, while maintaining flow rate, also produces faster rates of Fe2+ oxidation and Fe3+ loss.

Geological Society of America Abstracts with Programs. Vol. 49, No. 6

doi: 10.1130/abs/2017AM-303936

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