MXene-supported Co3Ti and single-atom Co catalyst activated PMS for efficient removal of Pb-EDTA: The involvement of Co (Ⅳ)

Activation of peroxymonosulfate (PMS) by MXene-supported Co 3 Ti and single-atom Co catalyst (Co@MXene) achieved the efficient decomplexation of lead-ethylenediaminetetraacetic acid (Pb-EDTA) and the recovery of lead (Pb) over the pH range of 3.0–9.0. The removal efficiency of Pb-EDTA reached up to 93.6 % within 30 min and total Pb was completely removed within 15 min. The coordination structure differences between Co 3 Ti and single-atom Co induced their various electron transfer pathways with PMS, in which Co 3 Ti brought key effect to the generation of Co (Ⅳ), while single-atom Co and regenerative Co (II) were responsible for the generation of HO and SO 4 − and 1 O 2 , More importantly, the oxygen transfer reaction from O-Co 3 Ti to Co 3 Ti-O and the reducibility of MXene triggered the regeneration of low-valent Co. This study proposed a novel mechanism of Co (Ⅳ) generation and low-valent Co regeneration, which improved the understanding of the electron transfer pathways of Co@MXene/PMS oxidation process.