Effect of UV/chlorine treatment on photophysical and photochemical properties of dissolved organic matter

Abstract

Dissolved organic matter (DOM) is a ubiquitous component in effluents, DOM discharged with an effluent can affect the composition and properties of natural DOM in the receiving waters. As the photophysical and photochemical properties of effluent DOM can be changed by wastewater treatment processes, the effect of UV/chlorine treatment on the photophysical and photochemical properties of DOM was investigated using Suwannee River fulvic acid (SRFA) and Suwannee River natural organic matter (SRNOM) as representatives. Results showed that the absorbance of the two DOM was significantly decreased. The evolution trends of three representative photophysical parameters upon increase of chlorine dosages were observed. Also, a decrease in DOM aromaticity, molecular weight and electron-donating capacity was observed upon increasing chlorine dosage. Quantum yields of excited triplet state of DOM ( 3 DOM * ), singlet oxygen ( 1 O 2 ) and hydroxyl radicals ( •OH) first decreases and then increased in the UV/chlorine systems upon increasing chlorine dosages due to the different reaction pathways of the two DOM. Moreover, 3 DOM * can not only be regarded as a "controller" of other reactive intermediates, but also effectively promote the photodegradation of bezafibrate, which is classified as a persistent organic contaminant. This study gives deep insights into effects of UV/chlorine on the photophysical and photochemical properties of DOM, and is helpful for understanding the dynamic roles of DOM in the photodegradation of micropollutants.

Singlet Oxygen Quantum Yields in Environmental Waters

“…Palma et al, 256 Chen et al, 257 Wasswa et al, 258 Wan et al, 259 Guo et al, 260 Leresche et al, 261 Wang et al, 262 and Zhou et al 263 ) have been published after March 2020 and are not included in this review.…”

“…Nine additional papers reporting 1 O 2 quantum yield values (Wang et al, Palma et al, Chen et al, Wasswa et al, Wan et al, Guo et al, Leresche et al, Wang et al, and Zhou et al) have been published after March 2020 and are not included in this review.…”

Redox-Active Moieties in Dissolved Organic Matter Accelerate the Degradation of Nitroimidazoles in SO4•–-Based Oxidation

“…DOM is ubiquitous in natural waters and wastewater. 2,64 Besides scavenging oxidants and causing inner filter effects, the redox-active moieties, such as quinones moieties (∼1 to 10 μM per ∼5 mg C L −1 DOM), present in DOM are believed to be the predominant moieties that are involved in reversible electron-transfer pathways. 65−68 Their enrollment in the redox reactions of TrOCs in the AOPs may be non-negligible.…”

“…DOM is ubiquitous in natural waters and wastewater. , Besides scavenging oxidants and causing inner filter effects, the redox-active moieties, such as quinones moieties (∼1 to 10 μM per ∼5 mg C L –1 DOM), present in DOM are believed to be the predominant moieties that are involved in reversible electron-transfer pathways. − Their enrollment in the redox reactions of TrOCs in the AOPs may be non-negligible. In this work, reactive species (SQ •– and O 2 •– ) generated from the reactions of SO 4 •– with quinones and polyphenol moieties in DOM were found to account for the enhanced transformation of NZs in the UV/PS AOP, with SQ •– playing a dominant role.…”

“…SO 4 •– is a strong oxidant with a reduction potential of 2.60–3.10 V versus normal hydrogen electrode (NHE), higher than that of HO • (1.90–2.70 V vs NHE) . SO 4 •– mainly reacts with TrOCs via electron transfer, while HO • mainly reacts with them via hydrogen abstraction and/or radical addition. , SO 4 •– exhibits high reactivity toward a variety of TrOCs, with second-order reaction rate constants in the range of 10 4 to 10 10 M –1 ·s –1 . ,− …”