Enhanced peroxymonosulfate activation by δ-MnO2 nanocatalyst enriched with oxygen vacancies for phenolic pollutants polymerization

Heterogeneous advanced oxidation processes technology holds great potential for the removal of toxic phenolic molecules in water, but is currently challenged by overuse of oxidation agents and undesirable carbon emissions during the mineralization process. The present work demonstrates that with an oxygen-vacancy-rich Fe doped δ-phase MnO2 (δ-MnO2) as the nanocatalyst, the phenol (PhOH) could be removed with high selectivity as well as effective conversion into non-toxic phenolic polymers via a non-radical electron transfer route, instead of complete mineralization by common radical attacking route. Oxygen vacancies in δ-MnO2 were enriched by Fe doping, which greatly improved the activation of peroxymonosulfate (PMS) by extending the length of the O-O bond in PMS. A 6.68-fold enhancement of the removal rate of PhOH was achieved by Fe doping δ-MnO2, compared to the pristine δ-MnO2. Moreover, the consumption of PMS could be reduced by up to 95.08 %, and the carbon emissions were also reduced by up 99.13 % during the polymerization process. The present study manifests that rationally designing a non-radical route offers significant potential for the cost-effective use of oxidation agents as well as reducing carbon emissions, presenting a superior approach for the target of achieving carbon neutrality in environmental remediation.