Oxidation of ethanethiol in aqueous alkaline solution by ferrate(VI): Kinetics, stoichiometry and mechanism

The oxidation of ethanethiol (C2H5SH), as a representative odorous pollutant, by ferrate (Fe(VI)) in aqueous alkaline solution was investigated to understand its kinetics, stoichiometry, and reaction pathways. The reaction kinetics and fraction of different intermediates were found highly dependent on pH. The reaction behaved as a 5/2-order reaction in a pH range of 8.0-10.0, and a second-order reaction in a pH range of 10.5-12.0. The rate constants decreased with increased pH, and the speciation of Fe(VI) and C2H5SH during the reaction were further discussed. C2H5SH was finally oxidized to nonvolatile and odorless sulfonic acid (C2H5SO3H) with the intermediates of sulfinic acid (C2H5SO2H) and disulphide (C2H5SSC2H5). A plausible mechanism involving two competing reactions for C2H5S% radicals was proposed to explain the pH-dependent reaction order. In addition, kinetics and products of C2H5SH degradation by Fe(VI) were compared with other oxidants (O-3, chlorine, ClO2, KMnO4, H2O2, and (OH)-O-center dot). Our results provided a deep understanding of C2H5SH degradation by Fe(VI) in aqueous alkaline solution.