Abstract
Wet oxidation of hypophosphite and phosphite was conducted at a fixed temperature of 453 K under a partial oxygen pressure of 0.5-5 MPa, with the initial hypophosphite and phosphite concentrations of 0.1 mol/dm3.
As a result, it was found that hypophosphite was only slightly oxidized under an N2 atmosphere, but that hypophosphite was decreased to 5% after 180 minutes of reaction time under an O2 atmosphere of 1 MPa. For the wet oxidation of phosphite under an O2 pressure of 0.5-5 MPa, the conversion of phosphite to phosphate was increased with an increase in the partial pressure of O2. It was also found that the conversion of phosphite to phosphate was increased with a decrease in the initial pH value from 6.05 to 1.04. In the pH range between pH6.05 and 7.01, the conversion of phosphite to phosphate after 180 minutes of reaction time increased from 9.2% to 78%, which was further increased with an increase in the pH value.
Furthermore, when Ca(OH)2 was added to phosphite during wet oxidation, the concentration of phosphorus at 360 minutes was decreased to 6 mg/dm3, which was less than 8 mg/dm3 of the daily phosphorus emission standard.
