The Behaviors of Inorganic Sulfur Compounds during Oxygen Bleaching

抄録

Oxidized white liquor is commonly used as alkali in oxygen delignification. This is the reason that using the oxidized white liquor in this stage helps to maintain the sodium and sulfur balance in the pulp mill. The most regularly, sulfide in white liquor is oxidized to thiosulfate with air in an open reactor. In previous perception, thiosulfate does not change during oxygen delignification. However, some researchers found that thiosulfate was oxidized to sulfate during oxygen delignification recently.
In the mill study, we found that thiosulfate was oxidized to sulfate during oxygen delignification. In the laboratory experiment, we confirmed that the existence of pulp was needed by oxidation of thiosulfate. Thiosulfate was oxidized by oxygen and this reaction was intermediated by lignin and pulp.
S₂O₃^2-+2 O₂+H₂O→2 SO₄^2-+2 H⁺
This oxidation scheme suggested that, thiosulfate oxidation consumed not only oxygen but also alkali. That is, the oxidation of thiosulfate which was derived from oxidizing white liquor consumed by the addition of 15% of oxygen and by the addition of 20% of alkali.