Ozone oxidation-precipitation reaction was investigated in strongly acidified solutions of MnSO4 with/without added sulfate.
The rate of the oveall reaction was determined by chemical analysis on manganese ion species in the solution and the variation of oxidation-reduction potential (ORP) was continuously measured to follow the ozonation process in MnSO4 solutions of initial Mn concentration of 0.10 mol/l and sulfuric acid concentration of 1.0 to 5.0mol/l over a temperature range between 25 and 80°.
The behavior of 15 elements (18 ionic species of metal ions and oxonium complex ions) added to the MnSO4 solution (0.1mol/l in Mn and 1.0mol/l in acid) during ozone oxidation at 25 and 70° was examined by ORP measurement and chemical analysis of the precipitates.
The results are summarised as follows: 1) The rate of ozone oxidation-precipitation is strongly affected by acid concentration. An increase in acid concentration resulted in elongated induction period for the precipitation of MnO2, the reduced overall reaction rate and also higher minimum concentration of manganese remaining in the solution.
2) A rise in reaction temperature favors the ozonation reaction. At 70°, precipitation of MnO2 took place even at sulfuric acid concentration of 4 or 5.0mol/l.
3) Li, Na, K, Al and Mg ions added to the solutions caused only a little change in ORP during ozonation and the content of these ions of the precipitates was fairly low.
4) Co, Ni and Cu in the solution were incorporated at about 2% in the precipitate without a significant change in ORP.
5) ORP measurement showed that As (III), V (IV) and Fe (II) were oxidized prior to the oxidation of Mn (II). These ions and Ti (IV) are incorporated in the precipitates to a considerable extent of 7 to 10 wt % of the dried samples. None of the added metal ions is precipitated alone from their single acidic solution.
6) Zn and Cd were incorporated in the precipitate at about 1 wt %. More than 70% of the added mercury was eliminated with manganese from the solution of an initial mercury concentration of 0.001mol/l.
