OXIDATION OF NITRITE IONS AND CHLORINE-CONTAINING COMPOUNDS BY POTASSIUM FERRATE(VI)

Potassium ferrate(VI) was shown to easily oxidize aqueous nitrite ions to nitrate over the pH range of 2.5 to 6.8. Stopped-flow and conventional spectroscopy were used to monitor the rate of disappearance of the purple solution color of potassium ferrate(VI) at 505nm. The parallel oxidation of solvent water was also monitored using a calibrated dissolved oxygen probe. A selective nitrate electrode was used to potentiometrically determine product formation. The overall reaction was determined to be mixed-order with a hydronium ion dependency of 0.58. The rate of the reaction was also shown to depend on the fraction of species of diprotonated ferrate(VI). Potassium ferrate(VI) was also able to oxidize chlorite ions to chlorate and hypochlorite to chlorite. Evidence is also presented showing, to a slight extent, the oxidation of chlorate to perchlorate. Attempts were made to oxidize chloride to higher states, but no successful oxidation was detected. Chlorate oxidation rates were studied at pH\u27s from 2.5 to 6.8. Chlorite rates were determined from pH 8.0 to 10.1. Hypochlorite oxidation was investigated over the pH range 6.4 to 8.4. Possible chloride oxidation was investigated from a pH of 3.5 to 8.2. Identification of possible solute oxidation products was accomplished via ion chromatography of stock solutions that had been reacted with potassium ferrate(VI). The parallel oxidation of solvent water to oxygen was also monitored with a dissolved oxygen probe. Investigation of chlorate containing solutions showed the water oxidation pathway of potassium ferrate(VI) to be much more favorable than the chlorate oxidation pathway. The same result was obtained when chloride was in solution. However, when chlorite was in solution, the solvent oxidation pathway was less favored. The rate of water oxidation was shown to be inversely related to chlorite concentration. When hypochlorite was in solution with potassium ferrate(VI) the amount of water being oxidized increased with increased hypochlorite. This was explained by the oxidation of hypochlorite to chlorite with a subsequent reaction that produces chlorine dioxide