Journal
ENVIRONMENTAL SCIENCE & TECHNOLOGY
Volume 55, Issue 22, Pages 15400-15411Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.est.1c04600
Keywords
Vo-dominated; peroxymonosulfate activation; single-electron transfer; nonradical pathway; selective degradation; O-2 circulation
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Funding
- National Natural Science Foundation of China [52000050, 42007115]
- Postdoctoral Science Foundation of China [2019M663245, 2020M670913]
- Heilongjiang Postdoctoral Fund [LBH-Z20063]
- State Key Laboratory of Urban Water Resource and Environment (Harbin Institute of Technology) [2021TS22]
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Ubiquitous oxygen vacancies in metallic compounds can activate peroxymonosulfate for water treatment, with O-2 identified as a critical trigger. Mechanistic studies show that Vo captures electrons to form O-2 and withdraws electrons from organics for degradation. The collaboration of kinetics and thermodynamics allows PMS to donate electrons to Vo, forming intermediate species that accelerate the electron-recycling process and improve organic degradation.
Ubiquitous oxygen vacancies (Vo) existing in metallic compounds can activate peroxymonosulfate (PMS) for water treatment. However, under environmental conditions, especially oxygenated surroundings, the interactions between Vo and PMS as well as the organics degradation mechanism are still ambiguous. In this study, we provide a novel insight into the PMS activation mechanism over Vo-containing Fe-Co layered double hydroxide (LDH). Experimental results show that Vo/PMS is capable of selective degradation of organics via a single-electron-transfer nonradical pathway. Moreover, O-2 is firstly demonstrated as the most critical trigger in this system. Mechanistic studies reveal that, with abundant electrons confined in the vacant electron orbitals of Vo, O-2 is thermodynamically enabled to capture electrons from Vo to form O-2(center dot-) under the imprinting effect and start the activation process. Simultaneously, Vo becomes electron-deficient and withdraws the electrons from organics to sustain the electrostatic balance and achieve organics degradation (32% for Bisphenol A without PMS). Different from conventional PMS activation, under the collaboration of kinetics and thermodynamics, PMS is endowed with the ability to donate electrons to Vo as a reductant other than an oxidant to form O-1(2). In this case, O-1(2) and O-2(center dot-) act as the indispensable intermediate species to accelerate the circulation of O-2 (as high as 14.3 mg/L) in the micro area around Vo, and promote this nano-confinement electron-recycling process with 67% improvement of Bisphenol A degradation. This study provides a brand-new perspective for the nonradical mechanism of PMS activation over Vo-containing metallic compounds in natural environments.
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