Kinetics of CH3S− reaction with in situ ferrate(VI) in aqueous alkaline solution

• A new treatment process named “in situ ferrate(VI) oxidation (IFO)” was developed.
• Two kinetic models to describe the IFO system were established.
• The kinetic models were successfully validated by fitting the experimental data.
• An optimum NaOH concentration at 10 M was found in such an IFO system.

This study introduced a new treatment process named “in situ ferrate(VI) oxidation (IFO)” in which odorous compounds such as CH3S− can be quickly degraded by in situ freshly generated ferrate(VI) through electrolysis in aqueous alkaline solution. Two kinetic models to describe the in situ ferrate(VI) generation and its reaction with CH3S− were established mathematically by considering three main reaction mechanisms of ferrate(VI) electrochemical generation, ferrate(VI) self-decomposition and CH3S− degradation in aqueous strong alkaline solution. The effects of three key factors: (i) NaOH concentration, (ii) applied current density, and (iii) initial CH3S− concentration on the performance of the IFO process were investigated by conducting three sets of experiments and the kinetic models were validated by fitting the experimental data. The goodness of the fittings demonstrated that the new models could well describe both the kinetics of ferrate(VI) generation reaction and CH3S− degradation reaction. The experimental results confirmed that the higher NaOH concentration and current density applied would be beneficial to the electrochemical generation of ferrate(VI) and also elimination of its self-decomposition, but the experiments also demonstrated an optimum NaOH concentration at 10 M to achieve the best performance of CH3S− degradation reaction in such an IFO system.