Effects of Low-Molecular-Weight Organics on the Photoreduction of Bromate in Water

Guan

et al. 2022

Environ. Sci. Technol.

Radicals in advanced oxidation processes (AOPs) degrade micropollutants during water and wastewater treatment, but the transformation of dissolved organic matter (DOM) may be equally important. Ketone moieties in DOM are known disinfection byproduct precursors, but ketones themselves are intermediates produced during AOPs. We found that aromatic alcohols in DOM underwent transformation to ketones by one-electron oxidants (using SO 4•− as a representative), and the formed ketones significantly increased trichloromethane (CHCl 3 ) formation potential (FP) upon subsequent chlorination. CHCl 3 -FPs from aromatic ketones (Ar−CO−CH 3 , average of 22 mol/mol) were 6−24 times of CHCl 3 -FPs from aromatic alcohols (Ar−CH(OH)−CH 3 , average of 0.85 mol/mol). At a typical SO 4•− exposure of 7.0 × 10 −12 M•s, CHCl 3 -FPs from aromatic alcohol transformation increased by 24.8%−112% with an average increase of 53.4%. Notably, SO 4•− oxidation of aliphatic alcohols resulted in minute changes in CHCl 3 -FPs due to their low reactivities with SO 4•− (∼10 7 M −1 s −1 ). Other one-electron oxidants (Cl 2 •−, Br 2•− ,and CO 3 •− ) are present in AOPs and also lead to aromatic alcohol−ketone transformations similar to SO 4•− . This study highlights that subtle changes in DOM physicochemical properties due to one-electron oxidants can greatly affect the reactivity with free chlorine and the formation of chlorinated byproducts.

Section: ■ Materials and Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

One-Electron Oxidant-Induced Transformations of Aromatic Alcohol to Ketone Moieties in Dissolved Organic Matter Increase Trichloromethane Formation

Guan

et al. 2022

Environ. Sci. Technol.

“…Second, the analysis of mono- and di-HALs typically requires a separate PFBHA derivatization before LLE owning to their high polarity and reactivity, while tri-HALs can be directly analyzed without derivatization. ,− Considering the polarity and reactivity of mono-/di-HALs were similar to tri-HALs, mono-/di-HALs also can be directly analyzed without derivatization theoretically along with THMs, iodo-THMs, HKs, HAMs, and HNMs like tri-HALs, which will greatly enhance the efficiency of sample analysis and pretreatment. Third, DB-5 or HP-5 as a common column has been used to analyze some DBPs successfully, − , however, no paper reported the performance of them on 9 classes of regulated and priority DBPs synchronously.…”

Section: Introductionmentioning

confidence: 99%

Simple and Sensitive Method for Synchronous Quantification of Regulated and Unregulated Priority Disinfection Byproducts in Drinking Water

Zhang

Aziz

et al. 2023

Anal. Chem.

Due to their elevated concentrations in drinking water, compared to other emerging environmental contaminants, disinfection byproducts (DBPs) have become a global concern. To address this, we have created a simple and sensitive method for simultaneously measuring 9 classes of DBPs. Haloacetic acids (HAAs) and iodo-acetic acids (IAAs) are determined using silylation derivatization, replacing diazomethane or acidic methanol derivatization with a more environmentally friendly and simpler treatment process that also offers greater sensitivity. Mono-/di-haloacetaldehydes (mono-/di-HALs) are directly analyzed without derivatization, along with trihalomethanes (THMs), iodo-THMs, haloketones, haloacetonitriles, haloacetamides, and halonitromethanes. Of the 50 DBPs studied, recoveries for most were 70–130%, LOQs for most were 0.01–0.05 μg/L, and relative standard deviations were <30%. We subsequently applied this method to 13 home tap water samples. Total concentrations of 9 classes of DBPs were 39.6–79.2 μg/L, in which unregulated priority DBPs contributed 42% of total DBP concentrations and 97% of total calculated cytotoxicity, highlighting the importance of monitoring their presence in drinking water. Br-DBPs were the dominant contributors to total DBPs (54%) and total calculated cytotoxicity (92%). Nitrogenous DBPs contributed 25% of total DBPs while inducing 57% of total calculated cytotoxicity. HALs were the most important toxicity drivers (40%), particularly four mono-/di-HALs, which induced 28% of total calculated cytotoxicity. This simple and sensitive method allows the synchronous analysis of 9 classes of regulated and unregulated priority DBPs and overcomes the weaknesses of some other methods especially for HAAs/IAAs and mono-/di-HALs, providing a useful tool for research on regulated and unregulated priority DBPs.

“…•− ), and hydrated electrons (e aq − ), photochemical methods have been widely studied for the conversion of organic refractory pollutants and toxic oxysalts. 14−17 In recent years, with the increasing demand for the selectivity of reactions, lowmolecular weight organic compound-mediated photochemical processes, such as ultraviolet/peracetic acid (UV/PAA) 18 and UV/acetylacetone (UV/AA), 19 are becoming the cutting-edge topics in the field of advanced oxidation and reduction processes. Carbon-centered or oxygen-centered free radicals from the photolysis of PAA and AA, such as , are believed as the main active species in the UV/PAA and UV/AA processes.…”

Section: ■ Introductionmentioning

confidence: 99%

“…Owing to the facile generation of strongly active species, such as hydroxyl radicals ( • OH), sulfate radicals (SO 4 •– ), and hydrated electrons (e aq – ), photochemical methods have been widely studied for the conversion of organic refractory pollutants and toxic oxysalts. − In recent years, with the increasing demand for the selectivity of reactions, low-molecular weight organic compound-mediated photochemical processes, such as ultraviolet/peracetic acid (UV/PAA) and UV/acetylacetone (UV/AA), are becoming the cutting-edge topics in the field of advanced oxidation and reduction processes. Carbon-centered or oxygen-centered free radicals from the photolysis of PAA and AA, such as • CH 3 , CH 3 C • (O), • CO 2 – , CH 3 C(O)O • , and CH 3 C(O)OO • , are believed as the main active species in the UV/PAA and UV/AA processes. − The abovementioned carbon-centered or oxygen-centered radicals have modest standard reduction potentials ( E 0 ) in the range of −1.50 to 0.95 V, which endow them with the potential for the selective conversion of substrates …”

Section: Introductionmentioning

confidence: 99%

UV-Induced Redox Conversion of Tellurite by Biacetyl

Zheng

Zhang

et al. 2021

Environ. Sci. Technol.

Self Cite

Tellurium (Te) is a rare element of great value, but it exists mainly in the toxic form of tellurite (Te IV ) in water. Effective approaches that are able to reduce the toxicity and recover Te from contaminated water are highly needed. Here, we developed a simple but effective way to reduce toxic Te IV to widely applicable elemental Te 0 . With the combination of ultraviolet (UV) and biacetyl (BD), the oxidation state of Te could be feasibly changed from IV to 0 or VI. The consumption of dissolved oxygen (DO) was a key factor in the redox conversion of Te IV . Under UV irradiation, BD was first cleaved to acetyl radicals, which could then combine with water molecules to form more reductive diol radicals or combine with DO to form strongly oxidative peroxide radicals. Even without deoxygenation, the UV/BD system could rapidly change from being oxidative to being reductive because of the fast depletion of DO. Owing to the high quantum yield of the acetyl radical, the reduction efficiency of the UV/BD system was about 1 order of magnitude higher than that of UV/sulfite and was more efficient than the commonly used biological methods. This work provides a proof of concept for the reduction of tellurite, which could have relevant implications for water treatment and resource recovery applications.