The stoichiometry and mechanism of the oxidation of aqueous S(−II) by HSO5− is similar to the oxidation of S(−II) by H2o2, but the rate of oxidation by HSO5− is 3-4 orders of magnitude faster than the corresponding reaction with H2O2. A two-term rate law of the following form is found to be valid for the pH range of 2.0-6.3: −d[S(−II)]/dt = k1[H2S][HSO5−] + k2Ka1 [H2S] [HSO5−]/ [H+], where k1 = 1.98 × 101 M−1 s−1, k2 = 1.22 × 104 M−1 s−1, and Ka1 = [H+][HS−]/[H2S] = 2.84 × 10−8 M at 4.9 °C, μ = 0.2 M, and [S(−II)] = [H2S] + [HS−] + [S2−]. At high pH and high [HSO5−]/[S(−II)] ratios SO42− and H+ formation are favored, whereas at low pH and low [HSO5−]/[S(−II)] ratios elemental sulfur (S8) is favored as the principal reaction product. Peroxymonosulfate is a monosubstituted derivative of hydrogen peroxide that is thermodynamically more powerful as an oxidant than H2O2 and kinetically more reactive. These properties make HSO5− a potentially important oxidant in natural systems such as remote tropospheric clouds and also a viable alternative to H2O2 for the control of malodorous sulfur compounds and for the control of sulfide-induced corrosion in concrete sewers.
ASJC Scopus subject areas
- Environmental Chemistry