Selective Transformation of Micropollutants in Saline Wastewater by Peracetic Acid: The Overlooked Brominating Agents

Abstract

Peracetic acid (PAA) is an emerging alternative disinfectant for saline waters; HOBr or HOCl is known as the sole species contributing to halogenation reactions during PAA oxidation and disinfection. However, new results herein strongly indicated that the brominating agents (e.g., BrCl, Br 2 , BrOCl, and Br 2 O) are generated at concentrations typically lower than HOCl and HOBr but played significant roles in micropollutants transformation. The presence of Cl − and Br − at environmentally relevant levels could greatly accelerate the micropollutants (e.g., 17α-ethinylestraiol (EE2)) transformation by PAA. The kinetic model and quantum chemical calculations collectively indicated that the reactivities of bromine species toward EE2 follow the order of BrCl > Br 2 > BrOCl > Br 2 O > HOBr. In saline waters with elevated Cl − and Br − levels, these overlooked brominating agents influence bromination rates of more nucleophilic constituents of natural organic matter and increase the total organic bromine. Overall, this work refines our knowledge regarding the species-specific reactivity of brominating agents and highlights the critical roles of these agents in micropollutant abatement and disinfection byproduct formation during PAA oxidation and disinfection.

Effects of Halides on Organic Compound Degradation during Plasma Treatment of Brines

“…Consequently, our measured [HOX] tot , if present primarily as HOBr, overpredicts the observed degradation rate of para -hydroxybenzoate, possibly due to an overestimation of the bimolecular rate constant between para -hydroxybenzoate and HOBr (Table S4). Recently, reactions with organic compounds involving previously overlooked species (e.g., Br 2 O, Br 2 ) have been found to contribute to rate constants for reactions attributed to HOBr being overestimated by similar orders of magnitude. , While re-evaluation of this bimolecular rate constant is beyond the scope of this work, our analysis with currently available values suggests that hypohalous acids are present at sufficient concentrations, if not in excess, to account for the observed rate of para -hydroxybenzoate degradation.…”

Trace Br– Inhibits Halogenated Byproduct Formation in Saline Wastewater Electrochemical Treatment

“…10,21 However, our research indicated that these species should play an insignificant role in the electrochemical oxidation process. HOBr, predicted to be the most abundant bromine species 19,55 and highly reactive with phenolic compounds, 56 was identified as the main contributor if free bromines were involved in phenol oxidation. Other bromine species like BrCl and BrOCl were not considered due to their rapid transformation into HOBr.…”

“…Other bromine species like BrCl and BrOCl were not considered due to their rapid transformation into HOBr. 19 It is evident from Figure 2b that k' BPA (0.031 min −1 ) was only slightly higher than k' IBU (0.021 min −1 ), but k HOBr,BPA (9.4 × 10 4 M −1 s −1 ) exceeded k HOBr,IBU (0.39 M −1 s −1 ) by 5 orders of magnitude, 22 reflecting that HOBr was not the predominant reactive species in the Br − -involved electrochemical system. In addition, the small difference in k' BPA values obtained in the absence or presence of Br − suggests that free halogens may not be crucial contributors to the reaction.…”

“…The conventional view suggests that free bromines (e.g., HOBr, OBr − , BrCl, and BrOCl) play a predominant role in electrophilic addition or substitution reactions with pollutants, resulting in the formation of halogenated products. 14,19,25 On the other hand, some researchers propose the involvement of brominating radical species (e.g., Br • and Br 2…”

Overlooked Role of Coexistent Hydrogen Peroxide in Activated Peracetic Acid by Cu(II) for Enhanced Oxidation of Organic Contaminants

“…Nevertheless, PAA alone could only directly degrade certain organic contaminants with electron-rich structures (e.g., sulfur moiety, aromatic ring, and CC bond) . Up to now, a number of activation strategies have been proposed to enhance the oxidative performance of PAA, such as energy input (e.g., ultraviolet, , heat, electrochemistry, microwave, and ultrasound), metal catalysts (e.g., homogeneous − and heterogeneous − transition metals), carbon materials, , and anionic catalysts (e.g., phosphate, bromide, , iodine, , chloride, and nitrite), etc.…”