New Insights into the Activation of Peracetic Acid by Co(II): Role of Co(II)-Peracetic Acid Complex as the Dominant Intermediate Oxidant

Abstract

The combination of Co(II) and peracetic acid (PAA) is an important alternative advanced oxidation process (AOPs), in which R-O • radicals including acetyloxyl radicals (CH 3 C(O)O • ) and acetylperoxyl radicals (CH 3 C(O)OO • ) have been considered to be the primary reactive species for the oxidative degradation of contaminants. However, it is still unclear how the active Co species participates in this process. In this study, we conduct a series of experiments including chemical probing, radical quenching, electron paramagnetic resonance (EPR), and Co(III) oxidation to investigate the degradation mechanism of contaminants in the Co(II)/PAA process, using bisphenol A (BPA) as target pollutant. On the basis of these results, we propose a Co(II)-PAA complex (Co(II)-OO(O)CCH 3 ) to be the primary reactive species, while R-O • radicals and Co(III) (available as dimeric Coperoxide species) derived from the decomposition of Co(II)-PAA complex are the minor contributors for the oxidation of BPA. Factors, including PAA concentration, Co(II) concentration, solution pH, inorganic anions, and natural organic matters (NOM), that might affect the oxidation performance of the Co(II)/PAA process were also investigated systematically. This study sheds new light on the mechanistic understanding of the Co(II)/PAA process for the oxidation of contaminants in water.

Peracetic Acid Enhances Micropollutant Degradation by Ferrate(VI) through Promotion of Electron Transfer Efficiency

“…CBZ has been used as a probe in Co­(II)-PAA AOPs to verify the role of Co­(IV). , In those studies, CBZ was assumed to be unreactive with the organic radicals (R-O • ) because it could not be degraded in UV/PAA/TBA or heat-activated PAA systems. , However, these conclusions are debatable. It is noteworthy that there are several kinds of organic radicals in PAA-based AOPs, including CH 3 C­(O)­O • and its degradation products (e.g., • CH 3 , and • OOCH 3 ) and CH 3 C­(O)­OO • (eqs –) .…”

“…Ferrate­(VI) [Fe­(VI), HFeO 4 – /FeO 4 2– ] − and peracetic acid [PAA, CH 3 C­(O)­OOH] , are two promising alternative oxidants that are attracting growing interest from environmental engineers and scientists due to their great capacity for pathogen inactivation − and micropollutant abatement. ,− Nonetheless, ferrate­(VI) and PAA both undergo self-decay under environmentally relevant conditions, and their reactivity toward certain contaminants is limited. ,− Thus, various methods for enhancing the oxidation ability of PAA and ferrate­(VI) have been developed in recent years. For example, UV, , Fe­(II), Fe­(III)-picolinic acid-, Co­(II), − Ru­(III), MoS 2 , and Co-based catalysts − have been developed to activate PAA. These PAA-based advanced oxidation processes (AOPs) efficiently degrade various PPCPs, in which organic radicals [e.g., CH 3 C­(O)­O • /CH 3 C­(O)­OO • ] and high-valent metals [e.g., Fe­(IV), Co­(IV)] are proposed as the major reactive species.…”

Reduced Graphene Oxide Triggers Peracetic Acid Activation for Robust Removal of Micropollutants: The Role of Electron Transfer

“…The O–O bond energy of PAA (159 kJ mol –1 ) is comparable to persulfate (140 kJ mol –1 ) and smaller than H 2 O 2 (213 kJ mol –1 ), , indicating great potential of PAA activation. Reported PAA activation processes include an external energy input (e.g., thermal activation, UV irradiation, and photocatalysis), homogeneous catalysis [e.g., Co­(II), ,− Cu­(II), , Mn­(II), and Fe­(II) − ], and heterogeneous catalysis [e.g., MnO 2 , CoFe 2 O 4 , and activated carbon fibers­(ACFs)]. Till date, activated PAA oxidation processes are mainly attributed to the radical-mediated oxidation, where hydroxyl radicals ( • OH) and organic radicals (R–O • ) are the main radicals in situ generated by the activated PAA.…”

“…Reaction conditions: [SMX] = 10 μM, [PAA] = 100 μM, [rGO] = 0.1 g L −1 , pH = 5 (the SMX degradation efficiency under pH 5 is the highest according to Figure S16), and T = 25 ± 2 °C. The inset depicts the linear fitting of kinetic data to obtain the pseudo-first-order rate constant (k obs ) (R 2 = 0.978).Specifically, the initial rate of the fitting curve was used to determine the reaction rate constant (solid line); the following data points (dashed line) slightly deviated from the first-order kinetics, which was likely due to the loss of PAA as the reaction progressed.36,68 (b) Comparison of k obs of the SMX degradation in different catalytic PAA oxidation systems, including CoFe 2 O 4 /PAA, MoS 2 /PAA, and Co 2+ / PAA systems 21,42,43.…”

“…36,68 (b) Comparison of k obs of the SMX degradation in different catalytic PAA oxidation systems, including CoFe 2 O 4 /PAA, MoS 2 /PAA, and Co 2+ / PAA systems 21,42,43. …”