Ultrafast activation of peroxymonosulfate by reduction of trace Fe3+ with Ti3C2 MXene under neutral and alkaline conditions: Reducibility and confinement effect

Ultrafast activation of peroxymonosulfate (PMS) by reduction of trace Fe3+ at the μg L-1 level with the ecofriendly Ti3C2 MXene under neutral and alkaline conditions was achieved for the first time. Complete removal of model pollutant sulfamethoxazole (SMX) was accomplished within about 5 min and 10 min at pH 7.0 and 9.0, respectively. The degradation rate of SMX in Fe3+/PMS/MXene process was increased by 72 times compared with that in the absence of Ti3C2 MXene (pH = 7). Methanol/tert-butanol quenching experiment and electron spin resonance (ESR) measurement demonstrated that hydroxyl radical (•OH) and sulfate radical (SO4•–) were the primary reactive species. The strong reducibility of Ti3C2 MXene played the key role in triggering the Fe(III)/Fe(II) cycle and accelerating PMS activation. The reducibility of Ti3C2 MXene towards Fe3+ was measured to be 3.35:1–5.03:1 (mol:mol), far higher than that of hydroxylamine (1:1). Because the confinement effect of MXene inhibited the hydrolysis of iron ions, Fe3+/PMS/MXene process exhibited excellent performance even under neutral and alkaline conditions. This study improved the understanding of MXene in Fenton-like reaction and provided an ideal Fenton-like process with ultra-low metal consumption, high efficiency and broad pH range.