INSOLUBILIZATION OF ARSENITE IN WATER AND SOIL SAMPLES USING POTASSIUM FERRATE

Abstract

 In this study, the insolubilization of arsenate in water and soil samples was investigated using potassium ferrate (K₂FeO₄) produced by a wet chemical method. In water samples, the addition of K₂FeO₄ decreased the dissolved As(III) concentration, while the dissolved As(V) concentration was increased, suggesting the oxidation of As(III) to As(V) with K₂FeO₄. The As(V) concentration was decreased to less than 10 μg/L with a further increase in Fe dosage due to coprecipitation with ferric hydroxide produced via reduction of ferrate ion. In soil samples, the total dissolved As concentration was about 50 μg/L in the leaching test using pure water before iron addition, and the As(III) concentration was much greater than the As(V) concentration. The addition of K₂FeO₄ decreased the concentration of As(III) leachable from the soil to less than 10 µg/L at less iron dosage compared to that of FeCl₃. However, a larger amount of K₂FeO₄ was required to lower the total concentration of dissolved arsenic to less than 10 μg/L. Selective extraction of As from the treated soil samples based on the modified BCR method showed that the addition of K₂FeO₄ transformed reducing agent-extractable As into less extractable form. This finding suggests that K₂FeO₄ would be useful for reducing the potential leachability of arsenic from treated soil after being returned to the underground.