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DETERMINATION OF THE RATES AND PRODUCTS OF FERROUS IRON OXIDATION IN ARSENIC-CONTAMINATED POND WATER.
Hernandez, G. AND R Ford*. DETERMINATION OF THE RATES AND PRODUCTS OF FERROUS IRON OXIDATION IN ARSENIC-CONTAMINATED POND WATER. Presented at 3rd Annual Research Day for Regional Universities, Univ. of Central OK, Edmond, OK, 11/09/2002.
Dissolved ferrous iron and arsenic in the presence of insufficient oxygenated ground water is released into a pond. When the mixing of ferrous iron and oxygenated water within the pond occurs, the ferrous iron is oxidized and precipitated as an iron oxide. Groups of experiments with pond water samples and prepared synthetic water samples were used to estimate the ferrous iron oxidation and precipitation rates. The pond water samples were initially purged with air to oxidize and precipitate naturally occurring ferrous iron. Iron oxidation experiments were then initiated through addition of known amounts of ferrous iron. The pH, temperature, and conductivity were measured at each sampling. Suspension aliquots were collected at each sampling interval to assess changes in the concentration of ferrous iron and soluble total iron. The overall rate of Fe2+ oxidation of shallow, deep, and synthetic water was compared at the 50% conversion point. The fraction of Fe that converted to a precipitate in the experiments was based on the difference between the total iron content and the value measured by the Ferrover method. Identification of precipitates was performed by X-ray diffraction analysis. Overall, the rate of ferrous iron oxidation was greater in deep pond water. Results from experiments with shallow pond water and synthetic water indicated slower oxidation rates, but greater production of iron oxide precipitates. The pond water solids were poorly crystalline in contrast to the synthetic water, which was more crystalline. It was suspected that the presence of interfering ions in both shallow and deep pond waters prevented the production of crystalline material.