Oxidation of aqueous hydrogen sulfide by peroxymonosulfate

This paper summarizes the results of an experimental investigation of the stoichiometry and kinetics of the oxidation of aqueous hydrogen sulfide by the inorganic peroxide, peroxymonosulfate (HSO_5-). Peroxymonosulfate is a powerful oxidant¹ (E₀ = +1.82 V) that is commercially available as a free-flowing powder known by the trade name Oxone. The latter is a triple salt with the composition 2KHSO₅·KHSO₄·K₂SO₄. It is shown that peroxymonosulfate oxidizes aqueous H₂S 3-4 orders of magnitude faster than H₂O₂ at a given pH, and therefore in applications where the rate of oxidation of H₂S is of prime concern or where high concentrations of oxidant cannot be tolerated peroxymonosulfate may be an attractive alternative to H₂O₂. However comparison of eq 3 with eq 5, and eq 4 with eq 6 shows that the use of peroxymonsulfate inevitably results in higher sulfate yields and higher acid production. The quantity of sulfate introduced would in fact be even more than eq 4 and 6 indicate since Oxone is a triple salt that contains 1 mole of sulfate per mole of peroxymonsulfate.