pH/Temperature tuning selective generation of SO/HO/Fe in Fe-activated peroxide water systems.

Active species (AS) are key in Fenton/Fenton-like reactions. The unclear AS category and generation order of SO and HO in the reaction of peroxymonosulfate (PMS) and Fe, as well as the quantity of SO produced in the Fe/peroxydisulfate (PDS) system, limiting the practical application of selective AS generation for targeted pollutant degradation. Understanding the pathway of PMS/PDS/HO activated by Fe for SO, HO, and Fe generation is critical for the selective generation of AS by adjusting reaction conditions of pH or temperature. Results suggested that SO was the sole PMS active product at T < 340 K and pH < 12, subsequently driving HO generation from HO, while FeO was rapidly generated due to the chemical interaction between Fe and PMS. In Fe/PDS system, one SO instead of reputed two SO was generated since the coactions of Fe and SO moiety, while FeO is generated when HO acts as reactant at pH 0 -7. In Fe/HO system, FeO can only be formed stem from the pre-reaction of HO generation. Furthermore, Tuning the reactant concentration could convert the AS category. This work advances the cognition of Fenton/Fenton-like microcosmic reactions, and is positive to the future design of experimental and industrial processes.