Calcium sulphite oxidn. to sulphate - in neutral aq. suspension contg. alkali(ne earth) metal-and/or ammonium sulphate, suppressing dithionate formation

摘要

The oxidn. of CaSO3 to CaSO4 is improved by carrying out oxidn. in the presence of 0.5-10 wt.% soluble alkali(ne earth) sulphates (pref. Na2SO4 and/or MgSO4) and/or (NH4)2SO4 at pH 5-7. The sec. formation of dithionate is suppressed. In an example, 65 l/h fine air bubbles are passed into a suspension of 200 g CaSO3 in 680 g water contg. 5 (0) wt.% Na2SO4 and 1 (0) wt.% MgSO4 at 60 degrees C. The rate of dithionate formation in mole/h kg was 0.002 at pH 6 (0.026 at pH 4) and the rate of oxidn. of CaSO3 was 0.3 at pH 6 (0.3 at pH 4 and 0.02 at pH 6).