Simultaneous Activation of Peroxydisulfate and Hydrogen Peroxide by Sulfidated Nanoscale Zero-Valent Iron for Efficient MTBE Degradation: Significant Role of Oxygen Vacancy
Jiaolong Qin, Yan Wei, Wei Geng, Xiaojuan Yu, Baoxue Zhou, Mingce Long
Abstract
Nanoscale zero-valent iron (nZVI)-based advanced oxidation processes (AOPs) are limited by the rapidly formed surface layer of iron (oxyhydr) oxides. This restriction can be broken by the simultaneous activation of H 2 O 2 and peroxydisulfate (PDS, S 2 O 8 2– ) over sulfidated nanoscale ZVI (S-nZVI), which displayed a synergistic effect to alleviate the drawbacks of the oxidants used alone. In this work, a biochar-supported S-nZVI (noted as S-nZVI@BC) was employed to simultaneously activate PDS and H 2 O 2 for methyl tert-butyl ether (MTBE) degradation, and the rate constant for S-nZVI@BC/Bi-ox (Bi-ox, bi-oxidant at 1:1 molar ratio of PDS and H 2 O 2 ) was 3.7-, 4.5-, and 12.8-fold higher than that of nZVI@BC/Bi-ox, S-nZVI@BC/PDS, and S-nZVI@BC/H 2 O 2 . According to electron paramagnetic resonance (EPR), X-ray photoelectric spectroscopy (XPS), and in-situ oxygen detection analyses, oxygen vacancies were generated over the shell of S-nZVI@BC during PDS activation, and the oxygen vacancy-contained surface layers promoted H 2 O 2 adsorption and dissociation to produce surface-bound · OH ( · OH ads ), thus significantly improving H 2 O 2 utilization efficiency and accelerating MTBE degradation. These findings provide promising S-nZVI-based AOPs by combining H 2 O 2 and peroxydisulfate activation for environmental remediation and bring insights for the creation of oxygen vacancy-containing materials for peroxide activation.