The rates of oxidation of hydrogen sulfide with Fe(VI) were made anaerobically as a function of pH (7-12) and temperature (5-15 °C). The reaction was found to be first order for each reactant. The rates decrease with an increase in pH. The energy of activation was found to be 30.1 ± 4.9 kJ mol-1 at pH = 12. When the concentrations of [H2S]T ([H2S] + [HS-]) are in excess, the ratio of [H2S]T consumed to [Fe(VI)] consumed was 1.51 ± 0.14 at pH = 70 and 2.50 ± 0.13 at pH = 9.0 and 11.3. Thiosulfate was the main product at pH = 7.0; sulfite, thiosulfate, and sulfate were identified as the products of the reactions at pH = 9.0 and 11.3. In an excess of [Fe(VI)] over [H2S](T), the hydrogen sulfide is fully oxidized to sulfate. A mechanism in which Fe(VI) oxidizes H2S by a one-electron process is proposed. Experiments were conducted to test the Fe(VI) removal efficiency of sulfide in groundwater and waste-water. The results indicate that Fe(VI) can be used as an effective oxidant to remove hydrogen sulfide from wastewaters.
ASJC Scopus subject areas
- Environmental Chemistry