How can peroxide remove hydrogen sulfide and sulfur dioxide from wastes?

Would hydrogen sulfide and sulfur dioxide both be oxidized by hydrogen peroxide? (if the gases were bubbled through a solution of hydrogen peroxide). Would the result result be an acidic solution because of sulfuric acid formation.

Hydrogen sulfide and sulfur dioxide are waste products of several manufacturing processes, and reaction with peroxide is one fairly cost-effective method of removing them from industrial wastes.

The sulfur in hydrogen sulfide (H₂S) is in the -2 state. In a neutral solution, hydrogen peroxide will oxidize hydrogen sulfide to elemental sulfur via the following reaction:

8 H₂S(g) + 8 H₂O₂(aq) = S₈(s) + 16 H₂O(l)

No acid is produced. The reaction takes a while, so if you're bubbling the hydrogen sulfide through the peroxide solution, you need to recycle the gas stream through the peroxide solution. Metal ions catalyze the reaction.

In alkaline solution, you get a completely different reaction. The hydrogen sulfide is present as sulfide ion, and you'll get sulfate after oxidation:

S^2-(aq) + 4 H₂O₂(aq) = SO₄^2- (aq) + 4 H₂O(l)

The reaction is exothermic and much more rapid than the neutral pH reaction above, but again, no acid is produced.

Acid is produced when SO₂ is bubbled through a hydrogen peroxide solution, though. First the SO₂ dissolves and reacts with water to form sulfurous acid:

SO₂(g) + H₂O(l) = H₂SO₃

The sulfurous acid is then oxidized to sulfuric acid by the peroxide:

H₂SO₃(aq) + H₂O₂(aq) = H₂SO₄(aq) + H₂O(l)

Author: Fred Senese senese@antoine.frostburg.edu

General Chemistry Online! How can peroxide remove hydrogen sulfide and sulfur dioxide from wastes?