Nonradical activation of peroxymonosulfate by hematite for oxidation of organic compounds: A novel mechanism involving high-valent iron species

Peroxymonosulfate Activation by Palladium(II) for Pollutants Degradation: A Study on Reaction Mechanism and Molecular Structural Characteristics

“…As shown in Figure 3 , phenol degradation was largely suppressed by the presence of p-BQ, FFA, N 3 - , and L-histidine. Whereas such inhibition was ascribed to the direct PMS depletion by these oxidant scavengers in their excess amounts ( Figure S5 ), therein PMS was consumed around 98% for FFA, L-histidine, and N 3 - , and over 93% for p-BQ at the reaction time of 0.5 min, which was also in agreement with recent works [ 43 , 44 ]. To further determine the occurrence of 1 O 2 during the Pd(II)/PMS system, a control experiment was conducted in D 2 O solution according to D 2 O which could extend the lifetime of 1 O 2 by tenfold [ 45 ], thus the solvent exchange would promote the singlet oxygenation of pollutant [ 43 ].…”

Enhanced anaerobic digestion of waste activated sludge with periodate-based pretreatment

“…To further assess the potential contributions of these reactive species for WAS disintegration, the batch scavenging experiments were performed in the presence of different oxidant scavengers (i.e., phenol, tert -butyl alcohol (TBA), p-benzoquinone (p-BQ), and furfuryl alcohol (FFA)). It was reported that TBA, p-BQ, and FFA were used as •OH (k •OH = 3.8–7.6 × 10 8 M s −1 ), •O 2 − ( = 9.8 × 10 8 M s −1 ), and 1 O 2 (k 1 O 2 = 1.2 × 10 8 M s −1 ) scavenger [ 25 ], respectively. Besides, phenol has been documented as a scavenger for both iodine radicals (e.g., •IO 3 and •IO 4 ) and •OH [ 26 ].…”

Outlook on Single Atom Catalysts for Persulfate-Based Advanced Oxidation

“…High-valent metal-oxo species (M (n+2)+ O), including Mn 5+ , Ru 5+ , Co 4+ , and Fe 4+ , − have been reported as the main contributors in some dissolved metal ion or metal oxide/nanoparticle systems. Recently, the same species have also been proposed as the main contributors for Fe SACs using both experiments and DFT calculations (Figure b). ,,− To identify the role of M (n+2)+ O, sulfoxides such as methyl phenyl sulfoxide (PMSO) can be used.…”

“…Despite some literature discussion, two key questions remain: (1) what the actual oxidation state of the metal in metal-oxo species is and (2) how SAC differs from nanoparticle and dissolved ion in forming high-valent metal-oxo species. To answer the first question, some studies have employed ex situ XANES to examine the oxidation states of the metal after the reaction. , This is based on the unverified hypothesis that the high-valent metal-oxo species can stably remain on the catalyst surface after the reaction instead of being reduced back to low-valent species to complete the redox cycle. However, high-valent species can (i) react with low-valent species to median-valent species ( e.g.…”

“…To answer the first question, some studies have employed ex situ XANES to examine the oxidation states of the metal after the reaction. 59,240 This is based on the unverified hypothesis that the high-valent metal-oxo species can stably remain on the catalyst surface after the reaction instead of being reduced back to lowvalent species to complete the redox cycle. However, high-valent species can (i) react with low-valent species to median-valent species (e.g., Fe IV O 2+ + Fe 2+ + 2H + → 2Fe 3+ + H 2 O, k = 1.4 × 10 5 M −1 s −1 , pH = 1); 247,248 (ii) self-decay in H 2 O (e.g., 4Fe IV O 2+ + 4H + → 4Fe 3+ + O 2 + 2H 2 O, k = 0.1 s −1 ); 249 or (iii) react with persulfate (e.g., 2Fe IV O 2+ + S 2 O 8 2− → 2Fe 3+ + 2SO 4 2− + O 2 , k = 1 × 10 4 M −1 s −1 ).…”