Laser Flash Photolysis Techniques Research Articles

Chloride-mediated transformation of sulfate radicals to hydroxyl radicals for enhanced contaminant degradation in high-temperature wastewater

Using the excess heat in high-temperature industrial wastewater to activate oxidant precursors for organic contaminant degradation would make advanced oxidation processes more sustainable in the context of carbon neutrality, while the salt-mediated radical transformation chemistry in such wastewater is poorly understood. We herein demonstrate that chloride (Cl–) in the range of 0.28–56.34 mM accelerates the degradation of organic contaminants in the heat activated persulfate process in both synthetic and authentic wastewater. We use laser flash photolysis technique together with kinetic modeling to directly determine the bimolecular rate constants of radical–radical (e.g., kSO4·--SO4·- = 2.50 × 109 M−1 s−1), Cl–-radical (e.g., kSO4·--Cl- = 3.75 × 108 M−1 s−1), and radical-contaminant (e.g., kHO·-BA = 1.02 × 1010 M−1 s−1) reactions at 55 °C, which are substantially higher than those at ambient water temperature (25 °C). We also combine experimental and modelling results to calculate the contribution of different radicals to contaminant removal at 55 °C. The results clearly demonstrate that Cl– in the range of 0.28–56.34 mM promotes the transformation of SO4– to HO at 55 °C, with reactive chlorine species involved as the intermediates. The findings improve fundamental understanding of Cl–-mediated radical chemistry in high-temperature water and provide an engineering strategy to recycle the heat in wastewater to enhance contaminant remediation.

Reactivity of the phosphaethynolate anion with stabilized carbocations: mechanistic studies and synthetic applications.

The reactivity of sodium phosphaethynolate Na(OCP) towards various Mayr's reference electrophiles was investigated using conventional UV-visible and laser-flash photolysis techniques. The kinetic data, along with density functional theory (DFT) calculations, enabled the first experimental quantification of the phosphorus nucleophilicity of [OCP]-. Product studies of these reactions demonstrate the formation of secondary as well as tertiary phosphines. The mechanism of this unprecedented phosphorus-atom transfer reaction is thoroughly discussed, with key intermediates successfully isolated and characterized. Importantly, some bulky secondary phosphine oxides synthesized using this approach, have demonstrated high efficiency as ligands in the Suzuki coupling reaction.

An Alternative Method to Determine the Quantum Yield of the Excited Triplet State Using Laser Flash Photolysis

The excited triplet state of a molecule (T1) is one of the principal intermediate products in various photochemical processes due to its high reactivity and relatively long lifetime. The T1 quantum yield (φT) is one of the most important characteristics in the study of photochemical reactions. It is of special interest to determine the φT of various photoactive compounds (photosensitizer, PS) used in photodynamic therapy (PDT). PDT is an effective medical technique for the treatment of serious diseases, such as cancer and bacterial, fungal and viral infections. This technique is based on the introduction of a PS to a patient’s organism and its further excitation by visible light, producing reactive oxygen species (ROS) via electron or energy transfer from the PS T1 state to the biological substrate or molecular oxygen. Therefore, information on the φT value is fundamental in the search for new and effective PSs. There are various experimental methods to determine φT values; however, these methods demonstrate a high discrepancy between φT values. This stimulates the analysis of various factors that can affect the determined φT. In this study, we analyze the effect of the intensity profile of the exciting laser pulse on the calculation of the φT value obtained by the Laser Flash Photolysis technique. The φT values were determined by analyzing the variation of a sample transient absorption in the function of the exciting laser pulse intensity, in combination with the spectral and kinetic PS characteristics obtained in nonlinear optical experiments by solving the rate equations of a five-level-energy diagram. Well-studied PSs: meso-tetra(4-sulfonatophenyl) (TPPS4) porphyrins, its zinc complex (ZnTPPS4) and the zinc complex of meso-tetrakis(N-methylpyridinium-4-yl) (ZnTMPyP) were chosen as test compounds to evaluate the proposed model. The φT values were determined through a comparison with the φT,TMPyP = 0.82 of meso-tetrakis(N-methylpyridinium-4-yl) (TMPyP), used as a standard. The obtained results (φT,TPPS4=0.75±0.02, φT,ZnTMPyP=0.90±0.03), and φT,ZnTPPS4=0.89±0.03) are highly compatible with the medium φT values obtained using the known methods.

Laser flash photolysis of titanium dioxide suspensions for the evaluation of solvent-mediated radical reactions.

The chemistry originating from the scavenging of the highly electrophilic hole in TiO2 can be readily monitored using laser flash photolysis techniques. Dilute suspensions are sufficiently transparent in the UV region that long lived signals from reactions of solvent radicals with 1,1-diphenylethylene can be readily monitored. Transient signals originating from hole, electron and trapped radicals are extremely long lived showing stretched exponentials (nanoseconds to milliseconds), adequately described by fractal models.

Detection of excited triplet species from photolysis of carbonyls: Direct evidence for single oxygen formation in atmospheric environment.

Excited triplet species play an important role in the photolytic formation of 1O2 from carbonyls, but the related mechanism is still uncertain, due to lack of direct evidence. In this study, steady-state and transient photolysis of eleven carbonyls to produce 1O2 was investigated. Dicarbonyl displayed greater 1O2 production ability than monocarbonyl, while dicarbonyl containing both ketone and carboxyl groups connected by CC bond (i.e., pyruvic acid (PA)) showed the highest 1O2 steady-state concentration ([1O2]SS). For the first time, the production of 3PA* from PA with narrow energy gap was confirmed by laser flash photolysis technique and the second-order decay rate constant of 3PA* was 2.78 × 107 M-1 s-1. Quenching results verified the dominant contribution of 3PA* to 1O2 production from PA. Addition of inorganic salt or increase in solution pH showed negligible effect on 3PA*, but significantly decreased the [1O2]SS of PA by up to two orders of magnitude, due to reduction of hydrate content. Photolysis of methylglyoxal and dimethylamine mixture led to higher content of excited triplet species at pH ≈ 11 and remarkably enhanced [1O2]SS, which was 2.3 times of that from PA and dimethylamine mixture. These findings provide direct evidence for the contribution of transient species from carbonyls or their product to 1O2 formation in atmospheric environment.

Sulfate radical anion: Laser flash photolysis study and application in water disinfection and decontamination

Sulfate radicals (SO4•-) reactivity against gram-negative (E. coli) and gram-positive (E. faecalis) bacteria and Contaminants of Emerging Concern (CECs) (Diclofenac-DCF, Sulfamethoxazole-SMX and Trimethoprim-TMP) was investigated through laser flash photolysis (LFP) technique. Analysis of the lifetime of SO4•- in presence of cell-wall compounds of bacteria and CECs allowed determining reactivity of SO4•- towards these compounds. Results showed that SO4•- reacts with common cell-wall components through H-abstraction mechanism (kSO4•− < 108 M-1s-1). By contrast, kSO4•− > 109 M-1s-1 were found using aromatic amino acids (AAA) only present in Porins of the gram-negative outer-membrane. The intermediates detected from the reaction of SO4•- with the AAA confirmed the involvement of electron transfer processes. Moreover, kSO4•− values determined for DCF, TMP and SMX also agreed with an electron transfer mechanism. Interestingly, bacteria and CECs removal at pilot plant scale by UV-C/SO4•- is in accordance with the kSO4•− obtained using the LFP: E. coli > E. faecalis and DCF > TMP ≅ SMX.

Photochemical transformations of 2, 6-dichlorophenol and 2-chlorophenol with superoxide ions in the atmospheric aqueous phase

The possible photochemical transformation pathways of chlorophenols (2, 6-dichlorophenol and 2-chlorophenol) with superoxide anion radical (O2·−) were studied by steady-state irradiation and 355 nm laser flash photolysis technique. O2·− was generated by irradiating riboflavin O2-saturated solution with an UVA light (maximum at 365 nm). The steady-state experimental results suggested that the transformation efficiency of chlorophenols improved with the increase of the initial riboflavin concentration and solution initial pH value, while the increase of chlorophenols concentration would inhibit the photochemical reaction. The second-order rate constant of the reaction of O2·− with 2, 6-DCP phenoxyl radical (2, 6-DCP·) and 2-CP phenoxyl radical (2-CP·) were determined as (8.39 ± 0.99) × 109 L mol−1 s−1 and (5.17 ± 0.68) × 109 L mol−1 s−1 by laser flash photolysis techniques, respectively. The transformation of chlorophenols was accompanied by the formation of Cl− induced by superoxide radicals after the mixed riboflavin and chlorophenols solution with UVA irradiation. The main conversion products of the reaction between 2, 6-DCP and O2·− were identified by GC-MS, as 2-chlorophenol, 2, 6-dichloro-1, 4-benzoquinone, 2, 6-dichloro-hydroquinone and 3-chlorocatechol, while 2-CP with O2·− was 2-chloro-1, 4-benzoquinone, 2-chlorohydroquinone and phenol, respectively. The transformation pathways of 2, 6-DCP and 2-CP with O2·− were also proposed.

Laser flash photolytic generation of radical ions of carotenoids in organic solvents. Studies of their subsequent fates, including formation of stable carotenoid sigma dimer radical anion (CAR)2[rad

In this study, time-resolved laser flash photolysis technique (LFP) was used to generate and study extraordinary stable transients formed following the decay of radical anions of canthaxanthin (CAN) and astaxanthin (ASTA). The radical anions were obtained via one-electron reduction of CAN and ASTA by acetone ketyl radical (AC−) in various solvents. At room temperature, the decay of CAN− (λmax = 870 nm) and ASTA− (λmax = 1000 nm), in acetonitrile (ACN), led to the formation of indefinitely stable colored transients (blue-green for CAN and navy blue for ASTA) absorbing at shorter wavelengths (λmax = 690 nm and 720 nm, respectively) relative to their corresponding radical anions. Rapid quenching by oxygen was observed indicating the radical nature of these transients, which was further confirmed by EPR spectroscopy. By employing EPR spectroscopy, LFP technique, and UV–visible absorption measurements, these extraordinary stable transients were identified as sigma-dimer radical anions ((CAR)2−) formed via the dimerization of the parent carotenoid (CAR) with its radical anion (CAR−). The suggested structures of these dimers were postulated using DFT calculations, which indicated that the unpaired electron is delocalized over the entire molecule. This result is extremely important because of the paucity of reports on dimer radical anions in solution.

Iron (III) hydroxocomplex-methyl viologen dication system as a prospective tool for determination of hydroxyl radical reaction rate constants with environmental pollutants.

Reactivity of oxidative species with target pollutants is one of the crucial parameters for application of any system based on advanced oxidation processes (AOPs). This work presents new useful approach how to determine the hydroxyl radical reaction rate constants (kOH) using UVA laser flash photolysis technique. Fe (III) hydroxocomplex at pH 3 was applied as a standard source of hydroxyl radicals and methyl viologen dication (MV2+) was used as selective probe for •OH radical. Application of MV2+ allows to determine kOH values even for compounds which do not generate themselves optically detectable transient species in reaction with hydroxyl radicals. Validity of this approach was tested on a wide range of different persistent pesticides and its main advantages and drawbacks in comparison with existing steady-state and time-resolved techniques were discussed.

Photophysical properties of a β-Carboline Rhenium (I) complex. Solvent effects on excited states and their redox reactivity

The photochemical and photophysical properties of a Re(I) tricarbonyl complex, ClRe(CO)3(nHo)2, where nHo = 9H-pyrido[3,4-b] indole (norharmane), were investigated in solution phase by a combination of steady state emission spectroscopy, laser flash photolysis (LFP) and pulse radiolysis (PR) techniques. These results allowed us to identify and study the reactivity of the β-carboline (nHo) Rhenium(I) complex main excited states. The absorption spectrum as well as the steady-state and time-resolved luminescence of the complex exhibits a marked dependence with the solvent properties. These experimentally observed results were corroborated by quantum chemical calculations, TD-DFT. The most important electronic transitions present in the spectrum in all solvents are MLLCTRe(CO)3→nHo1, nHo2 along with a mixture of ILnHo and LLCTCl→nHo transitions. The relationship between the dipole moment and the polarity of the solvent was rationalized in terms of the electron density inside and outside the complex. While the luminescence of the complex is mainly attributed to the emitting 1ILnHo state, in LFP experiments a MLCT excited state was also detected. The species generated in either reductive or oxidative conditions in LFP experiments were compared with those obtained in PR. Also, the quenching rate constant (kq) of the excited state with MV+2 was calculated. The excited state of the complex can efficiently generate singlet oxygen in acetonitrile yielding a ΦΔ = 0.25 ± 0.02. Optoacoustic measurements showed that, after photonic excitation, almost all the absorbed energy by the complex is released to the medium as prompt heat. The investigated photophysical and photochemical properties of ClRe(CO)3(nHo)2 are of significant importance in relation to the use of this β-carboline Rhenium(I) complex in several biomedical fields, such as photodynamic therapy and photoactivated chemotherapy as well as new alternative therapies such as regional hyperthermia.

Synthesis and characterization of multiarm (Benzoin‐PS)m‐polyDVB star polymer as a polymeric photoinitiator for polymerization of acrylates and methacrylates

AbstractIn this study, a new benzoin‐based multi‐arm star polymer was synthesized by using ATRP, and characterization was achieved by spectrophotometric and chromatographic methods. Obtained multiarm (Benzoin‐PS)m‐polyDVB star polymer was employed as a polymeric photoinitiator for polymerization of methacrylates and acrylates. Photophysical properties of this initiator were determined by fluorescence and phosphorescence measurements, the phosphorescence lifetime was calculated as 29 ms hence the lowest triplet state nature was n‐π* character, and laser flash photolysis technique was additionally used to get more information about triplet state and triplet lifetime which was calculated as 1.34 ms. Photokinetics of difunctional acrylate such as HDDA was studied with a multi‐arm (Benzoin‐PS)m‐polyDVB star polymeric initiator using Photo‐DSC.

Photochemical reactions between superoxide ions and 2,4,6-trichlorophenol in atmospheric aqueous environments

The superoxide anion radical (O2•−) is an important reactive oxygen species (ROS), and participates in several chemical reactions and biological processes. In this report, O2•− was produced by irradiating riboflavin in an O2-saturated solution by ultraviolet light with a maximum emission at 365 nm. And the contribution of O2•− to 2, 4, 6-trichlorophenol (2, 4, 6-TCP) was investigated by a combination of laser flash photolysis (LFP) and UV light steady irradiation technique. The results of steady-state experiments showed that the photochemical decomposition efficiency of 2, 4, 6-TCP decreased with the increase of the initial concentration of TCP, while the increase of pH and riboflavin concentration promoted the photochemical reaction. The second-order rate constant of the reaction of the superoxide anion radical with 2, 4, 6-TCP phenoxyl radical (TCP•) was (9.9 ± 0.9) × 109 L mol−1 s−1 determined by laser flash photolysis techniques. The dechlorination efficiency was 61.5% after illuminating the mixed solution with UV light for 2 h. The conversion of 2, 4, 6-trichlorophenol was accompanied by the reductive dechlorination process induced by superoxide ions. The main steady products of the photochemical reaction of 2, 4, 6-TCP with O2•− were 2, 6-dichlorophenol (DCP), 2, 6-dichloro-1, 4-benzoquinone (DCQ) and 2, 6-dichlorohydroquinone (DCHQ). The addition process was the preferred process in the total reaction of superoxide ions with 2, 4, 6-TCP phenoxyl radical. These results indicated that the reaction of 2, 4, 6-TCP with O2•− was a potential conversion pathway and contribute to atmospheric aqueous phase chemistry.

Thioetherification Inducing Efficient Excited Triplet State and Singlet Oxygen Generation: Heavy Atom-Free BODIPY Photosensitizer Based on the S1(n,π*) State

We have examined the ability of the newly synthesized thioalkyl and thiophenyl (SR) BODIPYs to generate the excited triplet state (T1) using the laser flash photolysis technique. Compared to the un...

Photochemical reaction kinetics and mechanism of bisphenol A with K2S2O8 in aqueous solution: a laser flash photolysis study

The photochemical reaction kinetics and mechanism of bisphenol A (BPA) with potassium persulfate (K2S2O8) were investigated by using 266 nm laser flash photolysis and gas chromatography mass spectrum (GC-MS) technique. Sulfate radical (SO4•−), generated upon K2S2O8 photolysis, reacted with BPA with the overall rate constant of (1.61 ± 0.15) × 109 L mol−1 s−1, and two main reaction mechanisms were involved. One was addition channel to generate BPA–SO4•− adduct with a specific second-order rate constant of (1.09 ± 0.15) × 109 L mol−1 s−1. Molecular oxygen was involved in the decay of the BPA–SO4•− adduct with a rate constant of (1.28 ± 0.14) × 108 L mol−1 s−1. Another channel was the formation of BPA’s phenoxyl radical, likely derived from a deprotonation of the cation radical (BPA•+) generated from single electron transfer reactions. The specific rate constant of BPA’s phenoxyl radical formation was determined to be (6.16 ± 0.08) × 108 L mol−1 s−1. The overall rate constant was in line with the sum of aforementioned two specific rate constants for two main reaction channels. By comparing these rate constants, it was indicated that SO4•− addition channel accounted for ∼65% (1.09/1.61) to the overall reaction, and phenoxyl radical formation accounted for only ∼35% (0.62/1.61). The transformation products of BPA were identified by using GC-MS including 4-isopropylphenol, 4-isopropenylphenol, and 2,4-di-tert-butylphenol, and the reaction mechanism was proposed. These results may provide microscopic kinetics and mechanism information on BPA degradation using SO4•−-based advanced oxidation processes.

Multiple fluorescence of tetraarylimidazole and azomethinocoumarin dyad with dual excited-state intramolecular proton transfer

Synthesis and structure of novel dyad which molecule includes two fluorophores - 1,2,4,5-tetraarylimidazole and 8-arylazomethino-7-hydroxycoumarin, are described with the aim to obtain compounds with tunable luminescence. The fluorescent excited states of both fluorofores are formed as a result of excited-state intramolecular proton transfer (ESIPT) in each of them. The fluorophores in the dyad were connected by the diphenyl oxide bridge that provided limited interaction between them and the ability to implement both ESIPTs and corresponding dual fluorescence in polymers as well as in solutions. Steady state and transient UV–Vis absorption and fluorescence of the dyad and model compounds were studied using conventional as well as nanosecond and femtosecond laser flash photolysis techniques. Novel dyad demonstrates combinations of different fluorescences processes controlled by the excitation wavelength and the medium.

Early Events of Photosensitized Oxidation of Sulfur-Containing Amino Acids Studied by Laser Flash Photolysis and Mass Spectrometry.

The mechanism of photooxidation of methionine (N-Ac-Met-NH-CH3, 1) and methyl-cysteine (N-Ac-MeCys-NH-CH3, 2) analogues by 3-carboxybenzophenone triplet (3CB*) in neutral aqueous solution was studied using techniques of nanosecond laser flash photolysis and steady-state photolysis. The short-lived transients derived from 3CB and sulfur-containing amino acids were identified, and their quantum yields and kinetics of formation and decay were determined. The stable photoproducts were analyzed using liquid chromatography coupled with high-resolution mass spectrometry. Substantial differences in the mechanisms were found for methionine and S-methyl-cysteine analogues for both primary and secondary photoreactions. A new secondary reaction channel (back hydrogen atom transfer from the ketyl radical to the carbon-centered α-thioalkyl radical yielding reactants in the ground states) was suggested. The detailed mechanisms of 3CB* sensitized photooxidation of 1 and 2 are proposed and discussed.

Novel Two-Dimensional AgInS2/SnS2/RGO Dual Heterojunctions: High Spatial Charge and Toxicity Evaluation

A single semiconductor employed into photo(electro)catalysis is not sufficient for charge carrier separation. Designing a multiple heterojunction system is a practical method for photo(electro)catalysis. Herein, novel two-dimensional AgInS2/SnS2/RGO (AISR) photocatalysts with multiple junctions were prepared by a simple hydrothermal method. The synthesized AISR heterojunctions showed superior photoelectrochemical performance and photocatalytic degradation of norfloxacin, with a high degradation rate reaching 95%. More importantly, the toxicity of photocatalytic products decreased within the reaction process. High spatial separation efficiency of photogenerated electron-hole pairs was evidenced by optical and photoelectrochemical characterizations. Furthermore, a laser flash photolysis technique was carried on investigating the lifetime of the charge carrier of the fabricated dual heterostructures. In addition, sulfur and oxygen vacancies existed in AISR heterojunctions could largely constrain the recombination of electron-hole pairs. Density functional theory calculations were carried out to analyze the mechanism of photoinduced interfacial redox reactions, showing that reduced graphene oxide and AgInS2 act as electron and hole trappers in the photocatalytic reaction, respectively. Due to the interfacial electric field formed from AISR dual heterojunctions, the effective spatial charge separation and transfer contributed to the boosting photo(electro)catalytic performance.

Lanthanide (III) ions as multichannel acceptors for bimolecular photoinduced electron transfer reactions with coumarin dyes

Understanding the kinetics and energetics of photoinduced electron transfer (PET) reactions is of considerable research interest in photochemical sciences. In this study, interactions between trivalent lanthanide ions (Ln(III)) as electron acceptors and coumarin dyes as electron donors have been investigated in aqueous media using ground state absorption, steady-state (SS) emission, time-resolved (TR) fluorescence and laser flash photolysis (LFP) techniques. Among different Ln(III) ions, only Eu(III), Yb(III) and Sm(III) are found to display substantial interaction with the excited singlet (S1) state of the coumarin dyes, which correspond well with the favorable free energy changes (negative ΔG0) associated with the PET reactions in these coumarin-Ln(III) systems. For other Ln(III) ions, as ΔG0 is not favorable, they do not show any interaction with the excited coumarin dyes. Among the interacting coumarin-Ln(III) systems, bimolecular quenching rate constant (kq) increases consistently with the increasing exergonicity (−ΔG0), when each of the Ln(III) ions are considered independently, except for Eu(III), for which the kq values have already reached the diffusion controlled limit. However, considering all the Ln(III) ions together, the kq values do not show any common correlation with the changing ΔG0 values. The kq values are in general much lower for Yb(III) quencher as compared to Sm(III), even though the exergonicity values for coumarin-Yb(III) systems are more favorable than the coumarin-Sm(III) systems. Correlating the observed results based on the diffusion mediated bimolecular reaction model, we infer that depending on the ΔG0 values, some Ln(III) quenchers possibly also engage their upper electronic energy states as well to assist multichannel ET with the excited coumarin donors, and thereby modulating the kq values very substantially for different coumarin-Ln(III) systems. Apparently, the involvement of multichannel ET causes the total reorganization energy (λ) for ET reactions to differ largely for different Ln(III) ions, which would otherwise be very similar for all the coumarin-Ln(III) pairs. Observed results suggest that the intramolecular reorganization energy (λi) associated with lower electronic states of the hydrated Ln(III) ions is much larger than that associated with higher electronic states of these ions. While the involvement of multichannel ET is itself an intriguing inference, modulation in the ET kinetics and total λ values for different Ln(III) quenchers through the differential participation of the multichannel PET is also expected to find potential uses in the controlled utilization of such PET reactions in many practical areas.

Kinetics of Photoinduced Reactions at the Single-Molecule Level: The KACB Method.

The kinetics of photoinduced reactions can be approached by laser flash photolysis techniques. Although such techniques allow for a detailed understanding of the important photophysics of molecules, they normally require a substantial amount of sample for measurements (>1 nmol), and thus, they are difficult to apply to analytical and diagnostic applications. The photophysics of a fluorescent molecule can be accessed by monitoring the kinetics of the fluctuation of fluorescence, which is called blinking. Blinking is a phenomenon that can be monitored only if molecules are observed at the single-molecule level. In bulk solution, blinking kinetics can be measured by using fluorescence correlation spectroscopy (FCS), which normally requires more than 105 times less sample than that required for laser flash photolysis. Blinking is controlled to extract fruitful microenvironmental information around a fluorescent molecule, by using a method named kinetic analysis based on the control of fluorescence blinking (KACB). This Concept highlights the adaption of the KACB method to investigate the local conformation of DNA with less than 1 pmol of DNA sample.

Sulfate radical mediated degradation of 5-halogenosalicylic acids: Phenoxyl radical transformation pathways

In the present study, we investigated the degradation kinetics and transformation pathways of two 5-halogenosalicylic acids (5XSAs), namely, 5-chlorosalicylic acid (5ClSA) and 5-bromosalicylic acid (5BrSA) by sulfate radical (SO4•−) in a thermo-activated persulfate system. The reaction pathways and mechanisms were proposed based on laser flash photolysis (LFP) techniques, HPLC-HRMS and molecular orbital calculations. Our results revealed that efficient removal of 5XSAs could be achieved by thermo-activated persulfate, and phenoxyl radicals were found to play key roles in the primary oxidation pathways. The subsequent transformation of phenoxyl radicals included hydroxylation and coupling processes. The resulting coupling products could undergo secondary reactions with sulfate radical, including dehalogenation, decarboxylation and hydroxylation. Hydroxylated products were in turn oxidized by SO4•−, leading to the ring opening and the formation of a series of small molecular carbonyl byproducts. These processes could be responsible for the mineralization and the release of Br− or Cl−. In addition, the degradation rate constants of 5XSAs increased appreciably with increasing temperature, and higher efficiency of oxidation was observed around neutral initial pH. Moreover, degradation kinetics were found to be hardly affected by dissolved oxygen (DO), showing the possibility of applying SR-AOPs under environmental realistic conditions, not only for surface waters, but also for oxygen-deficient underground waters. The present work could increase our understanding on the reactivity and pathways of halogen phenols widely present in natural waters.