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Powered by clean energy, the hydrogen fuel production from seawater electrolysis is a sustainable green hydrogen technology, however, chlorine corrosion and correlative oxidation reactions severely erode the catalysts. Our previous work demonstrates that direct seawater electrolysis without a desalination process and strong alkali addition can be realized by introducing a hard Lewis acid oxide on the catalyst surface to capture OH−. However, the criteria for selecting Lewis acid oxides and the origin of OH− enrichment in chlorine chemistry inhibition on the catalyst surface remain unexplored. Here, we compare the ability of a series of Lewis acid oxides with different acidity constants (pKa), including MnO2, Fe2O3, and Cr2O3, to enrich OH− on the Co3O4 anode catalyst surface. Comprehensive analyses suggest that the lower pKa value of the Lewis acid oxide, the higher concentration of OH− enriched on Co3O4 surface, and the lower Cl− concentration. As established correlation among pKa of Lewis acid oxide, OH− enrichment and Cl− repulsion provide direct guidance for future design of highly active, selective and durable catalysts for natural seawater electrolysis. [ABSTRACT FROM AUTHOR]

Two fundamental halocarbon ions, CH2Cl+ and CH3ClH+, were studied in the gas phase using the FELion 22-pole ion trap apparatus and the Free Electron Laser for Infrared eXperiments (FELIX) at Radboud University, Nijmegen (the Netherlands). The vibrational bands of a total of four isotopologs, CH235,37Cl+ and CH335,37ClH+, were observed in selected wavenumber regions between 500 and 2900 cm−1 and then spectroscopically assigned based on the results of anharmonic force field calculations performed at the CCSD(T) level of theory. As the infrared photodissociation spectroscopy scheme employed probes singly Ne-tagged weakly bound complexes, complementary quantum-chemical calculations of selected species were also performed. The impact of tagging on the vibrational spectra of CH2Cl+ and CH3ClH+ is found to be virtually negligible for most bands; for CH3ClH+–Ne, the observations suggest a proton-bound structural arrangement. The experimental band positions as well as the best estimate rotational molecular parameters given in this work provide a solid basis for future spectroscopic studies at high spectral resolutions. [ABSTRACT FROM AUTHOR]

Seawater electrolysis is an attractive way of making H2 in coastal areas, and NiFe‐based materials are among the top options for alkaline seawater oxidation (ASO). However, ample Cl− in seawater can severely corrode catalytic sites and lead to limited lifespans. Herein, we report that in situ carbon oxyanion self‐transformation (COST) from oxalate to carbonate on a monolithic NiFe oxalate micropillar electrode allows safeguard of high‐valence metal reaction sites in ASO. In situ/ex situ studies show that spontaneous, timely, and appropriate COST safeguards active sites against Cl− attack during ASO even at an ampere‐level current density (j). Our NiFe catalyst shows efficient and stable ASO performance, which requires an overpotential as low as 349 mV to attain a j of 1 A cm−2. Moreover, the NiFe catalyst with protective surface CO32− exhibits a slight activity degradation after 600 h of electrolysis under 1 A cm−2 in alkaline seawater. This work reports effective catalyst surface design concepts at the level of oxyanion self‐transformation, acting as a momentous step toward defending active sites in seawater‐to‐H2 conversion systems. [ABSTRACT FROM AUTHOR]

The chlorine radical (Cl) plays a crucial role in the formation of secondary air pollutants by determining the total atmospheric oxidative capacity (AOC). However, there are still large discrepancies among studies on chlorine chemistry, mainly due to uncertainties from three aspects: (a) Anthropogenic emissions of reactive chlorine species from disinfectant usage are typically overlooked. (b) The heterogeneous reaction uptake coefficients used in air quality models resulted in certain differences. (c) The co‐effect of anthropogenic and natural emissions is rarely investigated. In this study, the Weather Research and Forecasting (WRF)‐Community Multiscale Air Quality (CMAQ) modeling system (updated with 21 new reactions and a comprehensive emissions inventory) was used to simulate the combined impact of chlorine emissions on the air quality of a coastal city cluster in the Yangtze River Delta (YRD) region. The results indicate that the new emissions of reactive chlorine and the updated gas‐phase and heterogeneous chlorine chemistry can significantly enhance the AOC by 21.3%, 8.7%, 43.3%, and 58.7% in spring, summer, autumn, and winter, respectively. This is more evident in inland areas with high Cl concentrations. Our updates to the chlorine chemistry also increases the monthly mean maximum daily 8‐hr average (MDA 8) O3 mixing ratio by 4.1–7.0 ppbv in different seasons. Additionally, chlorine chemistry promotes the formation of fine particulate matter (PM2.5), with maximum monthly average enhancements of 4.7–13.3 μg/m3 in different seasons. This study underlines the significance of adding full chlorine emissions and updating chlorine chemistry in air quality models, and demonstrates that chlorine chemistry may significantly impact air quality over coastal regions. Plain Language Summary: The chlorine radical (Cl) plays an important role in the formation of air pollutants such as fine particulate matter and ozone. To better understand its influence, we made significant updates to chlorine chemistry in the widely used chemical transport model Weather Research and Forecasting‐Community Multiscale Air Quality (WRF‐CMAQ). These updates included the addition of 21 new reactions: 13 gas phase and eight heterogeneous reactions. Additionally, we introduced new emissions sources of Cl2 and HOCl resulting from the use of chlorine disinfectants. The impact of reactive chlorine emissions from both anthropogenic sources and sea salt on air quality over a coastal city cluster in the Yangtze River Delta was investigated. These results suggest that chlorine affects the atmospheric oxidation capacity, consequently affecting the formation of ozone and fine particulate matter, especially during autumn and winter. Its impact in inland areas is more significant than that in coastal areas owing to intense anthropogenic emissions. Key Points: The impact of new chlorine emissions from disinfectant usage in the Weather Research and Forecasting‐Community Multiscale Air Quality (WRF‐CMAQ) model was evaluated against observations in the Yangtze River DeltaThe Cl chemistry of WRF‐CMAQ was updated by adding 21 new reactions, including 13 gas‐phase and eight heterogeneous reactionsChlorine chemistry has different impacts on O3 and PM2.5 in different seasons, with higher impacts found in autumn and winter [ABSTRACT FROM AUTHOR]

Keeping global surface temperatures below international climate targets will require substantial measures to control atmospheric CO _2 and CH _4 concentrations. Recent studies have focused on interventions to decrease CH _4 through enhanced atmospheric oxidation. Here for the first time using a set of models, we evaluate the effect of adding iron aerosols to the atmosphere to enhance molecular chlorine production, and thus enhance the atmospheric oxidation of methane and reduce its concentration. Using different iron emission sensitivity scenarios, we examine the potential role and impact of enhanced iron emissions on direct interactions with solar radiation, and on the chemical and radiative response of methane. Our results show that the impact of iron emissions on CH _4 depends sensitively on the location of the iron emissions. In all emission regions there is a threshold in the amount of iron that must be added to remove methane. Below this threshold CH _4 increases. Even once that threshold is reached, the iron-aerosol driven chlorine-enhanced impacts on climate are complex. The radiative forcing of both methane and ozone are decreased in the most efficient regions but the direct effect due to the addition of absorbing iron aerosols tends to warm the planet. Adding any anthropogenic aerosol may also cool the planet due to aerosol cloud interactions, although these are very uncertain, and here we focus on the unique properties of adding iron aerosols. If the added emissions have a similar distribution as current shipping emissions, our study shows that the amount of iron aerosols that must be added before methane decreases is 2.5 times the current shipping emissions of iron aerosols, or 6 Tg Fe yr ^−1 in the most ideal case examined here. Our study suggests that the photoactive fraction of iron aerosols is a key variable controlling the impact of iron additions and poorly understood. More studies of the sensitivity of when, where and how iron aerosols are added should be conducted. Before seriously considering this method, additional impacts on the atmospheric chemistry, climate, environmental impacts and air pollution should be carefully assessed in future studies since they are likely to be important.

The knowledge of chloropropanediols (MCPD) fatty acid esters formation pathways is an important condition for these processing contaminants mitigation. This study aimed to assess the potential of a group of lipophilic environmental contaminants, polychlorinated alkanes, commonly known as chlorinated paraffins (CPs), to contribute to the formation of MCPD esters. Laboratory-scale model systems representing vegetable oils contaminated with both a technical mixture of short-chained CPs and individual short-chained CPs were designed and subjected to heat treatment (230 °C, 2 h) to simulate the deacidification and deodorisation processes. A substantial increase in MCPD content (up to 3.4 times the control levels) was observed in systems spiked with a technical mixture. MCPD formation seems to correlate very well with the concentration of CPs in these systems. Based on the generated data, we can conclude that the processing of vegetable oils contaminated with CPs might contribute to elevated concentrations of MCPD., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Species-specific second-order rate constants for the reactions of eight model sulfoxides with hypochlorous acid (k HOCl ) were determined to be in the range of 2.7 M -1 s -1 to 5.8 × 10 3 M -1 s -1 . A quantitative structure-activity relationships (QSAR) with Taft σ* constants was developed based on eight measured k HOCl -values, showing a good linear correlation (R 2 = 0.89) with a negative slope ρ = -1.5 typical for electrophilic reactions. The reaction is mainly controlled by HOCl, with a minor contribution of OCl - . The contributions of other reactive chlorine species (e.g., Cl 2 and Cl 2 O) to the overall kinetics are only 7 % for Cl 2 O and 5 % for Cl 2 under typical drinking water treatment conditions. A combination of several analytical methods (HPLC-MS/MS, HPLC-ICP-MS/MS, and NMR) was applied for the identification of transformation products. Major transformation products from the reactions of chlorine with sulfoxides are sulfones, Cl-substituted sulfoxides, aldehydes, and sulfonic acids potentially formed via a transient chlorosulfonium cation. In general, sulfoxides react more readily with chlorine compared to bromine. This might be caused by a partial positive charge on the sulfur which leads to a stronger interaction with Cl in HOCl having a smaller partial positive charge than Br in HOBr. The ratios of the species-specific second-order rate constants for the reactions of the selected sulfoxides with chlorine or bromine (k HOCl /k HOBr ) range from 6 to 480. For sulfoxide compounds with strong electron-withdrawing substituents the reaction occurs most likely via a carbanion intermediate for which the reaction with HOBr is preferred, resulting in a k HOCl /k HOBr = 0.8., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)

Pyrolysis is an effective process for disposing of municipal sewage sludge (SS). Plastics can affect the SS pyrolysis behaviour and pyrolysis products due to their low ash and high hydrocarbon ratio. The secondary pollutants from the pyrolysis process may also be affected. Therefore, polyethylene terephthalate (PET), a typical plastic, was chosen to investigate the release characteristics of pollutants containing nitrogen, sulphur, and chlorine via SS pyrolysis, and the changes of biochar to adsorb two typical heavy metals, Pb and Cu. The pyrolysis of PET plastics facilitates the migration of N toward solid and liquid-phase products, S and Cl to the gas-phase products via pyrolysis. Oxygenated compounds of pyrolytic volatiles decreased from 38.18% to 28.43%, concurrently promoting the formation of phenolic compounds. The co-pyrolysis improved the quality of biochar and the ability to adsorb Pb and Cu. This systematic study can provide some support for the further improvement of SS pyrolysis technology, and will also be beneficial for subsequent applications.

The high chlorine content in municipal solid waste incineration (MSWI) fly ash is a key factor restricting its treatment and disposal. In this study, a new treatment method was proposed to enhance the deep dechlorination of fly ash by coupling supercritical CO 2 (SC) treatment with water washing. Simultaneously the alkaline compounds in fly ash can fix CO 2 and achieve CO 2 credits. The results showed that supercritical CO 2 significantly improved the removal of chlorine. The treatment of "double water washing + SC + washing again" reduced the chlorine content in fly ash to 0.83 %, while "SC + double water washing + SC + washing again" reduced the chlorine content to 0.88 %, and the removal rate of chlorine was as high as 96.8 % and 96.5 %, respectively. In addition, supercritical CO 2 promoted the decomposition of insoluble chloride (Friedel's salt) and the removal rate of insoluble chloride salts can reach 89.1 %. On the other hand, after supercritical CO 2 treatment, fly ash can quickly and efficiently absorb CO 2 , and the amount of CO 2 absorbed after two supercritical CO 2 treatments was 64 g/kg. Lastly, supercritical CO 2 could significantly stabilize heavy metals in fly ash and reduce the concentrations of Pb and Cr in the washing solution., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

The impact of chlorination on quorum sensing molecules (QSMs) is not often addressed in disinfection research. Yet pathogenicity and biofilm formation are controlled by quorum sensing (QS) in many bacteria. Chemical transformation of the compounds could have an impact on all of these processes. For this reason, our study elucidated the reaction kinetics and transformation pathways of several N-acyl homoserine lactones (AHLs) and 2-heptyl-4-quinolone (HHQ) in contact with free available chlorine (FAC), a potent QS inhibitor. Both AHLs and HHQ, are known as QSMs for Gram-negative bacteria. Using FAC, a complete degradation of the target compound was observed for p-coumaroyl AHL (pC-AHL), C 14:1 -AHL, HHQ and 3-Oxo-C 14 -AHL. The reaction order for FAC varied between 1.19 (±0.07) (pC-AHL) to 1.62 (±0.13) (HHQ). This means that different reactive species (e.g. hypochlorous acid and dichlorine monoxide) are likely to be involved in the reaction mechanism. The first-order rate constants were strongly pH-dependent. For C 14:1 -AHL and HHQ, the first-order rate constants decreased from pH 6.0 to pH 8.5. A maximum was observed for pC-AHL at pH 8.5 ranging from pH 6.0 to 10. In addition to the distribution of the reactive species, the phenol/phenolate ratio strongly influenced the first-order rate constants for pC-AHL. In total, at pH 7 (phosphate buffered) 29 transformation products were identified and the related transformation pathways were proposed via non-target and suspect screening using high-resolution mass spectrometry. The observed reaction mechanisms can be transferred to structurally similar QSMs to further understand QS-controlled processes during chlorination. We assumed that the transformation of the QSMs affects QS of the bacteria, thereby blocking QS-controlled processes such as biofilm formation., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)

Many processes can contribute to the attenuation of the frequently detected and toxic herbicides atrazine and metolachlor in surface water, including photodegradation. Multi-element compound-specific isotope analysis has the potential to decipher between these different degradation pathways as Cl is a promising tool for both pathway identification and a sensitive indicator of degradation for both atrazine and metolachlor. In this study, photodegradation experiments of atrazine and metolachlor were conducted under simulated sunlight in buffered solutions (direct photodegradation) and with nitrate (indirect photodegradation by OH radicals) to determine kinetics, transformation products and isotope fractionation for C, N and for the first time Cl. For metolachlor, the C-Cl dual isotope slope (Λ C/Cl  = 0.46 ± 0.19) is identical to previously reported values for hydrolysis and biodegradation in soils, suggesting the same reaction mechanism (C-Cl bond breakage by SN 2 nucleophilic substitution). For atrazine, both direct and indirect photodegradation resulted in a pronounced inverse isotope effect for chlorine (ε Cl  = 6.9 ± 3.3 ‰, and ε Cl  = 2.3 ± 1.2 ‰, respectively), leading to characteristic dual isotope slopes (Λ C/Cl  = -0.49 ± 0.17 and Λ C/Cl  = -0.31 ± 0.10, respectively). These values are distinct from those previously reported for abiotic hydrolysis, biotic hydrolysis and oxidative dealkylation which are all relevant processes in surface water, opening the path for pathway identification in future field studies., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Recent regulations on perfluorinated compounds in drinking water underscore the need for a deeper understanding of the formation of perfluorinated compounds from polyfluoroalkyl substances during chlorine disinfection. Among the compounds investigated in this study, N-(3-(dimethylaminopropan-1-yl)perfluoro-1-hexanesulfonamide (N-AP-FHxSA) underwent rapid transformation during chlorination. Within an hour, it produced quantitative yields of various poly- and per-fluorinated products, including perfluorohexanoic acid (PFHxA). Sixteen reactions involving chlorine with N-AP-FHxSA and its quaternary ammonium analog were investigated; seven were confirmed, while the remainder were either disproved or found to be insignificant. The quaternary ammonium moiety did not determine a polyfluoroalkyl substance's reactivity toward chlorine. For example, while 6:2 fluorotelomer sulfonamide betaine transformed rapidly to PFHxA, other quaternary-ammonium-containing polyfluoroalkyl substances, such as 5:1:2 and 5:3 fluorotelomer betaines, showed significant resistance to chlorination. Further investigation identified potential sites for electrophilic attacks near the amine region by examining the highest occupied molecular orbitals of the polyfluoroalkyl substances. Visualization techniques helped pinpoint electron-deficient and electron-rich sites as potential targets for nucleophilic and electrophilic attacks, respectively. Increasing the solution pH from 6 to 10 did not diminish the apparent degradation of the studied polyfluoroalkyl substances, likely due to the greater reactivity of the deprotonated forms compared to the conjugate acids. Finally, we also examined the hydrolysis of polyfluoroalkyl substances at pH 6 to 11 in the absence of chlorine.

The main bottleneck in the catalytic combustion of chlorinated volatile organic compounds (CVOCs) is deactivation and the production of chlorine-containing byproducts originating from the chlorine species deposited on the catalyst. Herein, Ru supported on SnO 2 (Ru/SnO 2 ) was prepared with the lattice matching principle. As RuO 2 and SnO 2 are both rutile phases, Ru species were present as highly dispersed RuO 2 particles on the Ru/SnO 2 catalyst. These particles adsorbed chlorine species with greater efficiency during the CVOCs combustion, thereby protecting the oxygen vacancies. Therefore, the double sites, oxygen vacancy to oxidize and RuO 2 to adsorb chlorine species, on the Ru/SnO 2 catalyst led to a notable enhancement in activity, stability, and byproduct selectivity. In contrast, the high dispersion of Ru species on the CeO 2 support, as the typical catalyst for chlorinated hydrocarbon combustion, gave rise to a predominantly Ru-O-Ce structure. This structure did not prevent the adsorption of chlorine species on the oxygen vacancies, resulting in deactivation at low temperatures and an increased polychlorinated byproduct concentration. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) further corroborated the variation in the adsorption sites of chlorine species on the two catalysts. This work provides a new strategy for designing efficient Ru-based catalysts for catalytic CVOCs combustion.

Lead(IV) oxide (PbO 2 ) is an important component of the scale in many lead pipes used for water supply. Promoting conditions that maintain its stability could be an effective method for limiting lead release. In this study, we applied a method that combined electrochemical and free chlorine conditioning to form PbO 2 scales on coupons. Lead coupons were then used to investigate the impacts of water stagnation time and residual free chlorine on PbO 2 stability. Free chlorine depletion and associated lead release were investigated from 30 min to 5 days for different initial free chlorine concentrations (0.5-3.0 mg/L as Cl 2 ). There was a lag time of up to 24 h between free chlorine depletion and observed lead increases. With daily readjustment of free chlorine to 0.2 mg/L or higher, the stability of the PbO 2 scale on the lead coupon was maintained and dissolved lead remained consistently below 10 μg/L. This study provides information on key factors affecting reductive dissolution of PbO 2 present in lead scales. It bridges the theoretical threshold free chlorine to maintain PbO 2 stability with experimental results and provides implications for actual water quality monitoring and household drinking water use.

In this study, a novel process of dielectric barrier discharge (DBD)/chlorine for levofloxacin (LEV) degradation was investigated. The combined system boosted the degradation efficiency of LEV from 77.8% to 97.5%, improved the reaction rate constant by 2.3 times, and reduced energy consumption by 64.5%. DBD/chlorine process was highly efficient for LEV degradation across a pH range of 3.3-10.8, with removal rates varying from 90.3% to 97.5%. The electron paramagnetic resonance and scavenging experiments demonstrated the generation of reactive oxygen species (ROS, including HO•, 1 O 2 , and O 2 •- ) and reactive chlorine species (RCS) in the DBD/chlorine system, with 1 O 2 in the nonradical pathway being crucial for LEV removal. Crucially, effective activation of chlorine not only encouraged the production of reactive species but also prevented the formation of disinfection by-products (DBPs), successfully controlling the ecotoxicity of the reaction system. DBD could activate chlorine to form chlorate and HO•, which in turn triggered the production of RCS. The comparison of the LEV degradation pathway was proposed with or without chlorine in the DBD process. Finally, the effects of different water quality and water bodies demonstrated the application prospects of the DBD/chlorine process. This work provided an efficient technique for the elimination of antibiotics by non-thermal plasma/chlorine., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

ABSTRACT The production and widespread transmission of antibiotic-resistant bacteria (ARB) pose an emerging threat to global public health. Electrochemical disinfection (ED) is an environmentally friendly disinfection technology widely utilized to inactivate ARB. This study explored the effect of modified activated carbon material (MACM) assisted ED on multi-ARB inactivation and the regeneration ability. The established ED technique was proven to be effective in inactivating multi-resistant ARB. Specifically, a 5-log ARB removal was achieved within 30 min treatment of MACM-assisted ED at 2.5 V. Additionally, no ARB regrowth was observed, indicating a permanent inactivation of ARB. The high level of reactive chlorine induced by MACM electrolysis was stressful to the ARB. Reactive chlorine led to overproduction of reactive oxygen species and damage of cell membranes in cells, accelerating the inactivation of ARB. Conclusively, the MACM-assisted ED method demonstrated efficient performance for ARB inactivation, implying this method is a promising alternative to traditional disinfection methods in countering ARB transmission.

The dechlorination of epoxidized Cardol (E-Cardol), which is a high-performance and sustainable adhesive and packaging material for electronics, remains challenging. The previous work proposed a new alcohol-sodium refining method to efficiently remove the chlorine of E-Cardol. However, this method is strongly limited by the trade-off between the dechlorination efficiency and its polymerization side effect, which leads to the viscosity as well as the epoxy equivalent increase of E-Cardol. Based on the detailed analysis of the refining process using fourier transform infrared spectroscopy (FTIR), simultaneous thermal analysis (STA), and nuclear magnetic resonance spectrometer (NMR) epoxidized Cardol (E-Cardol), this trade-off is studied. It is found that the dechlorination efficiency increases with the increase of the usage of the alcohol sodium. Meanwhile, when the residual alcohol-sodium content after refining exceeds 3000 ppm, the viscosity of the E-Cardol increases significantly due to the increased polymerization of E-Cardol by epoxy ring-opening reaction. It is demonstrated that the alcohol-sodium refining method can efficiently reduce the chlorine content of E-Cardol with the initial hydrolyzable chlorine content not higher than 3000 ppm to below 300 ppm without influencing their epoxy equivalent and viscosity. This paper thoroughly explores the mechanism and application range of the proposed alcohol-sodium refining method, which is crucial for the facile preparation of electronic-grade E-Cardol materials., (© 2024 Wiley‐VCH GmbH.)

Fe(II) and Mn(II) are abundant in groundwater and require operationally simple and efficient method to remove in drinking water treatment. The rapid oxidation of Mn(II) is essential in water treatment. This study investigates the efficiency of Mn(II) oxidation by free chlorine in the presence of Fe(II). The results demonstrate that the presence of Fe(II) significantly accelerates the oxidation rate of Mn(II) by free chlorine under neutral and alkaline conditions. The rapid oxidation of Fe(II) by free chlorine and the presence of Mn(II) promote the formation of in situ Mn(II)-doped ferrihydrite. Kinetic modeling and characterization of Fe(III) oxides confirm that the heterogeneous catalytic effect of the Mn(II)-doped ferrihydrite, rather than manganese oxides or their coupled catalytic effect, is responsible for the enhanced oxidation rates. The doped Mn(II) substitutes the tetrahedral Fe(III) ions in the ferrihydrite, introducing additional negative charges at the doped sites. The increased charge enhances Mn(II) adsorption and lowers its redox potential, thereby accelerating Mn(II) oxidation rate through direct electron transfer with adjacent free chlorine. Additionally, the lepidocrocite formed by the reaction between Fe(II) and dissolved oxygen significantly impedes the catalytic performance. These findings provide new insights into the catalytic co-oxidation mechanism of Fe(II) and Mn(II), and help the optimization of water treatment engineering practices., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)

Nitrogenous disinfection byproducts (N-DBPs) are notorious for their serious health risks, yet nitrate (NO 3 - ) mediates N-DBPs generation during UV/chlorine treatment remains unexplored. This study investigated the interaction of chlorine and NO 3 - on N-DBPs formation and developed a specific fragment-based screening method using UPLC-QTOF-MS to explore the underlying mechanism. Results showed that the chlorine-to-nitrogen (Cl/NO 3 - -N) molar ratio significantly affects dichloroacetonitrile (DCAN) and dichloroacetamide (DCAM) generation, with peak concentrations at a Cl/NO 3 - -N molar ratio of around 15. NO 3 - promotes the production of HO • , which positively correlates with DCAN and DCAM concentrations, also peaking at this ratio. Utilizing our developed method, three key hydroxyl-substituted intermediates that circumvent the previously reported "limiting-steps" in DCAN formation were identified. This reaction proceeds via a stepwise mechanism involving hydroxylation and chlorine substitution to produce hydroxyl-phenylacetonitrile and hydroxyl-chlorine-phenylacetonitrile. The conversion rate of hydroxyl-chlorine-phenylacetonitrile to DCAN was 8.6 times higher at Cl/NO 3 - -N molar ratio of 15 compared to conditions without NO 3 - , attributed to the weakened bond strength of the side chain, as supported by density functional theory calculations. This study provides novel insights into the mechanistic pathways of DCAN and DCAM formation, critical for developing more effective drinking water disinfection technologies to control N-DBPs., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)

Background: Aquaculture water plays an important role in the dissemination of antibiotic-resistant bacteria during harvest of shrimps. Mitigation of bacteria through discharge is essential to prevent dissemination downstream. Chemical disinfection of culture water is feasible compared to other methods of bacterial inactivation., Objective: To study the effect of different disinfectant agent's viz., chlorine, Fenton's reagent, and hydrogen peroxide (H2O2) on inactivation of bacteria from shrimp pond water., Methods: The water samples were subjected to treatment with various concentrations of chlorine (0.0, 1.0, 2.5, 5.0, and 10.0 mg/L), Fenton's reagent (1:10 mM ratio of Fe2+:H2O2; 2:20, 3:30, 4:40, 5:50) and H2O2 (20, 30, 40, and 50 mM) for different time durations (5, 15, 30, and 60 min)., Results: The results indicated that all the disinfecting agents inactivated both the total heterotrophic bacteria and tetracycline-resistant bacteria with increased concentrations and time. At the end of 60 min treatment with chlorination (2.5 mg Cl2/L), Fenton's reagent (2 mM Fe2+ + 20 mM H2O2), and H2O2 (50 mM H2O2), the total heterotrophic bacterial count in the water samples gradually decreased by 2.35, 2.65, and 1.38 Log10 CFU/mL, and tetracycline-resistant bacterial count reduced by 1.57, 1.66, and 1.43 Log10 CFU/mL respectively, from initial bacterial load., Conclusion: The study revealed that disinfection agents can be successfully employed in the inactivation of antibiotic-resistant bacteria discharged through aquaculture water. Among three disinfection agents, Fenton's reagent has been found effective in inhibiting both heterotrophic bacteria and tetracycline-resistant bacteria from water samples., Highlights: Bacterial inactivation studies were carried with chlorination, Fenton's reagent, and hydrogen peroxide. The highest reduction in Heterotrophic Plate Count (HPC) (2.65 Log) and tetracycline-resistant count (1.66 Log) was noticed in the water samples treated with Fenton's reagent. The use of disinfection agents effectively mitigates antibiotic-resistant bacteria from aquaculture wastewater., (© The Author(s) 2024. Published by Oxford University Press on behalf of AOAC INTERNATIONAL. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

Seawater desalination is widely used to overcome the freshwater shortage worldwide. However, even after three-stage reverse osmosis treatment, the desalinated water still contained 14.6 μg/L of aliphatic disinfection byproducts (DBPs), 384.2 ng/L of bromophenolic DBPs, 3.5 ng/L of iodophenolic DBPs, 1024.7 μg/L of Br - , 2.8 μg/L of I - , and 2.4 mg C/L of dissolved organic carbon (DOC). After the desalinated water was disinfected with chlor(am)ine, the concentrations of halogenated aliphatic and phenolic DBPs further increased, and bromophenolic DBPs were the toxicity forcing agents. When surface water was mixed with desalinated water and then chlorinated, the yield of aliphatic and phenolic DBPs significantly elevated. Separately chlorinating desalinated water and surface water before mixing could mitigate this adverse situation. Chloramine disinfection was more conducive to reducing the total calculated toxicity of disinfected desalinated waters and mixed waters compared to chlorine disinfection. The treatment of desalinated water with granular activated carbon could effectively remove DOC and UV 254 , leading to a reduction in the content of total organic halogen after chlor(am)ination. Although anion exchange resin could adsorb Br - , it also released the organic precursors of DBPs, ultimately increasing the yield of DBPs. The results of this study can provide a reference for the seawater desalination industry to improve seawater pre-treatment and desalination processes and thus minimize the DBPs., Competing Interests: Declaration of competing interest The authors declare no competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Chlorine (Cl) radicals strongly affect atmospheric oxidation and the fate of pollutants. Despite several observations, the potential impacts of nitrogen chemistry associated with NO 2 on Cl chemistry are poorly understood. Here, we provided direct field evidence that the nitrogen chemistry enhancements triggered by the increased NO 2 drove daytime nitrate (NO 3 - ) photolysis and nighttime NO 3 -N 2 O 5 reactions, significantly promoting the increases in the concentrations of ClNO 2 and Cl 2 after the Chinese Spring Festival. The enhancement in the Cl chemistry facilitated the elevations of both O 3 and atmospheric oxidation capacity during the winter daytime. Our findings highlighted the importance of nitrogen chemistry induced by the increased NO 2 in enhanced Cl chemistry.

Electro-oxidation (EO) is an efficient approach to removing refractory organics in wastewater. However, the interference from chlorine ions (Cl - ) can generate reactive chlorine species (RCS), potentially leading to the production of undesirable chlorinated byproducts. A novel approach involving the cathodic oxygen reduction reaction (ORR) for in situ H 2 O 2 production has emerged as a promising strategy to counteract this issue. This study systematically investigated the dynamics and transformation of RCS and reactive oxygen species (ROS) in an ORR/chloride-containing EO (EO-Cl) system, elucidating their respective roles in organic removal and chlorinated byproduct minimization. Distinct generation rates and patterns were observed for free chlorine and H 2 O 2 in the ORR/EO-Cl system. The rapid generation of free chlorine at the anode quickly reached a dynamic equilibrium, which contrasted with the moderate, continuous cathodic production of H 2 O 2 , resulting in considerable H 2 O 2 accumulation over time. This difference established kinetics-driven ROS and RCS formation and distribution, influencing the subsequent organic degradation process. Three distinct stages were identified in the degradation process. In stage I, free chlorine was the primary species, along with reactive species including Cl 2 •- , 1 O 2 , ClO • , HO • , and Cl • . In stage II, the gradual accumulation of H 2 O 2 consumed free chlorine, favoring the formation of 1 O 2 and HO • . In stage III, excessive H 2 O 2 quenched the free radicals. Insights into these multistage mechanisms reveal that the rapid degradation of chlorinated byproducts by 1 O 2 and HO • occurs in stage II of the ORR/EO-Cl system.

The development of fluorescence-based methods for bioassays and medical diagnostics requires the design and synthesis of specific markers to target biological microobjects. However, biomolecular recognition in real cellular systems is not always as selective as desired. A new concept for creating fluorescent biomolecular probes, utilizing a fluorogenic dye and biodegradable, biocompatible nanomaterials, is demonstrated. The synthesis of a new dicationic asymmetric monomethine cyanine dye with benzo[d]thiazolium-N-propionamide and chloroquinoline end groups is presented. The photophysical properties of the newly synthesized dye were examined through the combined application of spectroscopic and theoretical methods. The applicability of the dye as a fluorogenic nucleic acid probe was proven by UV-VIS spectroscopy and fluorescence titration. The dye-nucleic acid interaction mode was investigated by UV-Vis and CD spectroscopy. The newly synthesized dicationic dye, like other similar fluorogenic structures, limited permeability, which restricts its use as a probe for RNA and DNA. To enhance cellular delivery, we utilized a patented technology that employs solid, insoluble lipid nanoparticles. This method ensures the complete introduction of the dye into cells while minimizing activity outside the cells. In our study involving two human cell lines, we observed improved penetration through the cell membrane and distinctive selectivity in visualizing nucleic acids within the cytoplasm and nucleus.

Simulation of secondary organic aerosol (SOA) in models has been an uncertain component in determining the impacts of atmospheric aerosols on air quality and climate. Recent studies have shown that reactive chlorine can rapidly oxidize volatile organic compounds (VOCs), trigger SOA formation, and alter other oxidants, thus having a potentially significant effect on SOA, which has not been thoroughly investigated at the global scale. Here, we developed a chlorine-SOA simulation within a global chemical transport model along with updated anthropogenic continental chlorine emissions. Our simulations demonstrate that chlorine chemistry increases the annual mean boundary layer SOA by 5-12% over most continents while decreasing SOA by 5-11% over northern Atlantic and Pacific oceans, which are in the right direction to narrow existing discrepancies between models and observations. Notably, sensitivity simulations in China with observed high chlorine levels capture the temporal variations of both observed fine Cl - and organic aerosol, showing an increase in SOA by more than 100%. Our study also reveals that polluted regions, which have ample emissions of both chlorine species and VOCs, exhibit potential chlorinated SOA, which are commonly toxic, contributing up to 15% to total SOA.

Heat treatment, known for its detoxification and volume reduction characteristics, is a promising technology for the management of municipal solid waste incineration fly ash (MFA) and municipal sludge (MS). This paper uses the solid residue from MFA and MS after co-washing as the raw material to study the melting properties, phase transformations, changes in Cl content, heavy metal removal efficiency, and leaching toxicity. The results indicated that co-processing of MFA and MS can effectively reduce the melting temperature. The migration of Cl elements was influenced by the CaO/(SiO 2  + Al 2 O 3 ) ratio and the formation of Cl-containing phases. During the heat treatment process, Cr and Ni remained relatively stable, while Zn, Pb, Cu, and Cd were affected by Cl migration. Chlorine can promote the volatilization and escape of these heavy metals, but as Cl became fixed within Ca 10 (SiO 4 ) 3 (SO 4 ) 3 Cl 2 and Ca 5 (PO 4 ) 3 Cl, the removal efficiency decreased. To achieve the highest removal rates for these elements, the addition of MFA should be limited to no more than 20%, and the CaO/(SiO 2  + Al 2 O 3 ) ratio should be below 2.9. After heat treatment, the leaching concentrations of Zn, Pb, Cu, Cr, Cd, and Ni met applicable standards. The findings of this study could provide a method for the treatment of MFA and MS after co-washing and can serve as guidance for heat treatment processes., Competing Interests: Declarations: Ethical Responsibilities of Authors. All authors have read, understood, and have complied as applicable with the statement on “Ethical responsibilities of Authors” as found in the Instructions for Authors. Conflict of interest: The authors declare no competing interests., (© 2024. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

Residual chlorine from widespread disinfection processes forms byproducts in water that are harmful to humans and ecosystems. Portable sensors are essential tools for the on-site monitoring of residual chlorine in environmental samples. Here, an inexpensive colorimetric sensor was developed by grafting via amidation the chromogen orthotolidine (OTO) to the surface of a TEMPO-oxidized cellulose filter paper (O-TOFP). A thorough characterization of the sensor strip demonstrated that it was highly stable and that it could be stored for a long period before usage. O-TOFP had a fast response time of 30 s, was highly selective for residual chlorine ions (ClO - ) with an accuracy of at least 95 %, and exhibited an excellent limit of detection of only 0.045 mg/L when combined with smartphone image acquisition. With its many positive features, the easy-to-use and robust O-TOFP sensor described here could become a useful tool for the determination of residual chlorine in different water samples., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

In recent years, there has been a growing demand for high-quality sunscreens that combine high efficacy with ecological characteristics. This trend has led to an increased use of triazine compounds, which represent an emerging class of UV filters. While it is well-established that sunscreens can have significant environmental impacts, there is limited data on the degradation of triazine UV filters, despite available information on their environmental persistence, particularly in relation to disinfection processes. This study investigates the chemical fate of ethylhexyl triazone (EHT) under chlorination conditions, typical of swimming pools. Twelve disinfection byproducts (DBPs) were isolated and fully identified using nuclear magnetic resonance and mass spectrometry, with three of these byproducts being identified for the first time. DBP1-DBP12 were isolated at relative percentages of 1.26, 9.68, 1.05, 0.42, 0.84, 3.37, 3.58, 1.89, 0.84, 1.47, 0.42, and 0.63. Additionally, a mechanism for their formation was proposed. The ecotoxicological assessment of EHT and of byproducts (DBP1-DBP4) was conducted using acute, sub-chronic or chronic toxicity tests in producers and primary consumers of the freshwater trophic chain. The organisms included the alga Raphidocelis subcapitata, the rotifer Brachionus calyciflorus, the crustacean anostracan Thamnocephalus platyurus and the benthic ostracod Heterocypris incongruens. EHT caused a lethal median concentration in rotifers, with values in the range of tens of mg/L. EHT, DBP1, and DBP4 exhibited sub-chronic effects in ostracods at concentrations in the μg/L range, with EC50s of 210, 9, 20 μg/L, respectively. Rotifers were slightly affected by DBP3 with a chronic EC50 of 200 μg/L. Algae were not affected by either EHT or byproducts., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Author(s). Published by Elsevier B.V. All rights reserved.)

The ultraviolet (UV)/chlorine process has been widely applied for water treatment. However, the transformation of microplastic-leached dissolved organic matter (MP-DOM) in advanced treatment of real wastewater remains unclear. Here, we investigated alterations in the photoproperties of MP-DOM leached from biodegradable and conventional microplastics (MPs) and their subsequent effects on the degradation of sulfamethazine (SMT) by the UV/chlorine process. Spectroscopy was used to assess photophysical properties, focusing on changes in light absorption capacity, functional groups, and fluorescence components, while photochemical properties were determined by calculating the apparent quantum yields of reactive intermediates (Φ RIs ). For photophysical properties, our findings revealed that the degree of molecular structure modification, functional group changes, and fluorescence characteristics during UV/chlorine treatment are closely linked to the type of MPs. For photochemical properties, the Φ RIs increased with higher chlorine dosages due to the formation of new functionalities. Both singlet oxygen ( 1 O 2 ) and hydroxyl radicals (•OH) formation were strongly correlated with excited triplet state of DOM ( 3 DOM*) in the UV/chlorine treatment. Additionally, we found that the four types of MP-DOM inhibit the degradation of SMT and elucidated the mechanisms behind this inhibition. We also proposed degradation pathways for SMT and assessed the ecotoxicity of the resulting intermediates. This study provides important insights into how the characteristics and transformation of MP-DOM affect contaminant degradation, which is critical for evaluating the practical application of UV-based advanced oxidation processes (UV-AOPs)., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Biofilms in drinking water (DW) systems persistently challenge traditional disinfection methods due to intricate microbial interactions, with coaggregation playing a crucial role in forming multispecies biofilms. This study examined the implications of coaggregation on tolerance towards sodium hypochlorite (NaOCl) disinfection. Dual-species biofilms were formed for seven days on polyvinyl chloride coupons, comprising a strain of the emerging pathogen Stenotrophomonas maltophilia and the coaggregating strain Delftia acidovorans 005 P. For comparison, dual-species biofilms were also formed with a non-coaggregation strain (D. acidovorans 009 P). The minimum bactericidal concentration (MBC) for each planktonic strain varied (D. acidovorans: 1 mg/L, S. maltophilia: 1.5 mg/L) below the safe DW treatment limits. However, high NaOCl doses (10 ×MBC and 100 ×MBC,) showed low efficacy against dual-species biofilms, indicating significant biofilm tolerance to disinfection. Membrane damage occurred at sub-MBC without culturability loss, underscoring biofilm resilience. The biofilm analysis revealed a complex interplay between the composition of extracellular polymeric substances and the architecture, which was influenced by the presence of the coaggregating strain. Overall, coaggregation significantly influenced biofilm formation and resilience, impacting NaOCl disinfection. These findings underscore the challenges of microbial interactions in biofilms, emphasizing the need for improved disinfection strategies to control biofilms in drinking water systems., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

There is increasing concern about discoloration problems and microbial risks in drinking water. Until recently, how to control iron release and pathogenic bacterial growth in distribution pipes has been a knowledge gap. In our study, nanofiltration removed 13.3 % of lignins, 33.1 % of tannins and 17.7 % of proteins from dissolved organic matter (DOM). These DOM components were closely related to enzymes involved in the tricarboxylic acid (TCA) cycle. Therefore, nanofiltration followed by chlorine or chloramine disinfection inhibited the TCA cycle and induced lower adenosine triphosphate (ATP) and extracellular polymeric substance (EPS) production, resulting in reduced pathogenic bacterial growth. The number of Pseudomonas aeruginosa decreased to 7.43 × 10 5 and 2.43 × 10 5 gene copies/mL, respectively. Moreover, lower DOM concentrations increased the abundance of iron-reducing bacteria (IRBs) in the biofilm. IRBs can convert Fe(III) into Fe(II) through cellular c-type cytochromes, including CymA, MtrA, Cytc3, MacA, PpcA, and OcmB. The higher abundance of IRB and their cytochromes led to more Fe 3 O 4 formation on the surface of the distribution pipes, resulting in lower iron release. The total iron concentration was 16.9 μg/L in the effluent of pipes treated with nanofiltration and chloramine disinfection. Therefore, nanofiltration followed by different disinfection methods, especially chloramine disinfection, effectively controlled iron release and pathogenic bacterial growth in distribution pipes. This study strongly contributes to maintaining the drinking water quality in distribution pipes., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

This study investigates the use of multi-element compound-specific isotope analysis (ME-CSIA) to monitor degradation processes of methoxychlor, a persistent organochlorine insecticide. Laboratory experiments examined the kinetics, release of transformation products, and carbon and chlorine isotope effects during methoxychlor degradation through alkaline hydrolysis, oxidation with alkaline-activated persulfate, and biotic reductive dechlorination. Results showed that hydrolysis and oxidation did not cause significant carbon and chlorine isotope fractionation, indicating that C-H rather than C-Cl bond cleavage was the rate-determining step. Conversely, biotic reductive dechlorination by a field-derived microcosm under strictly anoxic conditions displayed significant carbon (ε C = -0.9 ± 0.3 ‰) and chlorine (ε Cl = -1.9 ± 1.0 ‰) isotope fractionation. Its corresponding calculated dual isotope slope (Λ C/Cl = 0.4 ± 0.1) and apparent kinetic isotope effects (AKIE C = 1.014 ± 0.005 and AKIE Cl = 1.006 ± 0.003) indicate a C-Cl bond cleavage as the rate-determining step, highlighting the difference with respect to the other studied degradation mechanisms. Changes in the microbial community diversity revealed that families such as Dojkabacteria, Anaerolineaceae, Dysgonomonadaceae, Bacteroidetes vadinHA17, Pseudomonadaceae, and Spirochaetaceae, may be potential agents of methoxychlor reductive dechlorination under anoxic conditions. This study advances the understanding of degradation mechanisms of methoxychlor and improves the ability to track its transformation in contaminated environments, including for the first time an isotopic perspective., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

The slow rate of anaerobic microbial dechlorination in natural environments limits the application of polychlorinated biphenyl (PCB) bioremediation. Anaerobic digested sludge (ADS), abundant in nutrients and microorganisms, could be an effective additive to improve microbial dechlorination. This research investigates the influence of ADS on Aroclor 1260 dechlorination performance, microbial community composition, and the abundance of functional genes. Moreover, further enrichment of organohalide-respiring bacteria (OHRB) was examined using tetrachloroethene (PCE) as the electron acceptor, followed by the serial dilution-to-extinction method in conjunction with resuscitation promoting factor (Rpf) supplementation. The results demonstrated that the addition of 5 g/L ADS achieved more extensive and efficient dechlorination of PCBs. ADS enhanced the removal of meta- and para-chlorine without significantly changing the dechlorination pathways. The abundances of dechlorinators, including Dehalobium and Dehalobacter within the Chloroflexi and Firmicutes phyla, as well as non-dechlorinators from the Desulfobacterota, Euryarchaeota, and Bacteroidetes phyla, were significantly increased with ADS amendment. Similarly, an increased abundance of bacteria, OHRB, reductive dehalogenase (RDase) genes, and archaeal 16S rRNA genes was observed. Additionally, obligate OHRB, such as Dehalobacter and Dehalobium, were further enriched. These findings indicate that ADS effectively enhances microbial reductive dechlorination and highlight the potential for enriching and isolating OHRB with Rpf., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Analyzing the reactivity of organic matter to oxidants such as chlorination and ozonation is crucial for evaluating the effectiveness of water treatment systems and their potential impacts on environmental safety and human health. This study explored the changes in organic substances, specifically bovine serum albumin (BSA), humic acid sodium salt (HA), and effluent organic matter (EfOM) from a wastewater treatment facility during chlorination and ozonation. Four spectrometric techniques were employed: ultraviolet absorbance at 254 nm (UVA 254 ), fluorescent excitation-emission matrix (EEM), synchronous fluorescence two-dimensional correlation spectroscopy (SF-2DCOS), and EEM-parallel factor integrated 2DCOS (EEM-PARAFAC-2DCOS). The findings revealed that ozone possesses superior oxidizing properties compared to chlorine, as evidenced by UVA 254 and EEM analyses, resulting in more diverse structural modifications in EfOM. SF-2DCOS and EEM-PARAFAC-2DCOS provided comprehensive details on the direction and sequence of these changes, with EEM-PARAFAC-2DCOS delivering clear and intuitive insights. Protein-like and fulvic-like substances were susceptible to chlorination and ozonation, exhibiting different reaction sequences with each oxidant. Furthermore, variations in protein-like and humic-like components in actual EfOM samples may not align precisely with those in model substances, emphasizing the importance of considering specific organic matter variations in real EfOM samples compared to model substances. This research offered a deeper understanding of the reactivity and transformation of organic matter in wastewater treatment processes through simple and rapid spectroscopic methods, potentially improving the management and mitigation of undesired byproducts., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

The use of electrochemical oxidation with boron-doped diamond (BDD) as an anode has been demonstrated to be an effective means of removing dissolved organic matter (DOM) from biologically treated waste leachate. However, in the presence of chloride ions, undesired chlorine evolution occurs on the anode; this forms chlorinated DOM, mostly of unknown molecular composition. We investigate the molecular composition and formation mechanism of chlorinated DOM during electrochemical oxidation process of biologically treated leachate DOM. At a current density of 8 mA/cm 2 , after 120 min of electrolysis, 479 unknown chlorinated DOMs were detected in the treated effluent, comprising 21.55% of the total. The unknown species are dominated by oxygen-rich, highly unsaturated structures, and exhibit higher oxidation degrees, lower unsaturation, and lower aromaticity compared to the removed nonchlorinated DOM. An additional 43.63 mg/L of known chlorinated DOM species, predominantly dichloroacetic and trichloroacetic acids, also accumulate in the treated effluent. Introducing hydroxyl radicals (HO • ) to the anode surface forms reactive chlorine species including chlorine radical (Cl • ), dichlorine radical (Cl 2 •- ), and hypochlorous acid/hypochlorite (HOCl/OCl - ); the concentration of HOCl/OCl - reaches 529.2 mg/L. These species react with reduced and aromatic dissolved organic matter via reaction pathways such as chlorine substitution for hydrogen (Cl + H - ) and the HOCl addition reaction (HO + Cl + ) to generate unknown chlorinated DOM species; the known chlorinated DOM are formed afterward via ring opening and dealkylation pathways. Our results provide a theory for the prevention and control of chlorinated DOM during treatment of chlorine-laden organic wastewater by an electrochemical oxidation system with a boron-doped diamond anode., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)

One new chlorinated sesquiterpenoid (compound 1, ablepharolide) and twenty-one known compounds were obtained from the aerial parts of Artemisia blepharolepis. Their structures were established by spectroscopic methods and the absolute configuration was further determined by single-crystal X-ray diffraction analysis for ablepharolide. Ablepharolide is a rare sesquiterpenoid with a 4-methyl-7-isopropyl-9-ethyl-perhydroindene skeleton that incorporates a chlorine atom. It significantly inhibited the growth of MCF-7 cells with IC 50 value of 8.34±0.77 μM. Further investigations demonstrated that ablepharolide induced morphological changes in MCF-7 cells, inhibited proliferation in a time- and dose-dependent manner. Furthermore, western blot analysis revealed that ablepharolide induced a significant increase in cleaved caspase-8, cleaved caspase-3 and cleaved poly(ADP-ribose) polymerase (PARP) in MCF-7 cells. All of these results supported that ablepharolide induced exogenous apoptosis in MCF-7 cells., (© 2024 Wiley-VHCA AG, Zurich, Switzerland.)

In this work, the rate coefficients for OH radical, k 1 (T), and Cl atom, k 2 (T), reaction with allyl 1,1,2,2-tetrafluoroethyl ether, CH 2 =CHCH 2 OCF 2 CHF 2 , were studied as a function of temperature and pressure in a collaborative effort made between UCLM, Spain, and LAPKIN, Greece. OH rate coefficients were determined in UCLM, between 263 and 353 K and 50-600 Torr, using the absolute rate method of pulsed laser photolysis-laser-induced fluorescence technique, while Cl kinetics were studied in temperature (260-363 K) and pressure (34-721 Torr) ranges, using the relative rate method of the thermostated photochemical reactor equipped with Fourier transform infrared spectroscopy as the detection technique. In both OH and Cl reactions, a negative temperature dependence of the measured rate coefficients was observed, which is consistent with complex association reactions. The temperature dependence of OH rate coefficients was found to be well represented by the following expression: k 1 (T) = (2.30 ± 0.35) × 10 -12 exp[(544 ± 46) K/T] cm 3 molecule -1  s -1 . In the case of the Cl-initiated reaction, a slight curvature was observed in the Arrhenius plot for k 2 (T), and the kinetic data were fitted to a modified Arrhenius expression: k 2 (T) = (4.42 ± 0.32) × 10 -16 T 2 exp[(610 ± 22) K/T] cm 3 molecule -1  s -1 . No pressure dependence was observed in either case. These results are consistent with a complex reaction mechanism that is not uncommon in radical association reactions to the unsaturated bond. As part of this work, UV (200-400 nm) and infrared absorption spectra (500-3200 cm -1 ) were also measured to further evaluate CH 2 =CHCH 2 OCF 2 CHF 2 atmospheric impact. Atmospheric lifetimes with respect to OH radical and Cl atom reactions were estimated to be 19.8 h and 38 days, respectively, showing that OH radicals dominate atmospheric oxidation. CH 2 =CHCH 2 OCF 2 CHF 2 is a very weak absorber in the solar actinic region, while its relatively low radiative efficiency in the atmospheric IR window, 0.0034 W m -2 ppbv -1 , and the short lifetime led to a very low GWP value relative to CO 2 , 1.2 × 10 -2 and 3.3 × 10 -3 , at time horizons of 20 and 100 years, respectively., Competing Interests: Declarations. Ethical approval: Not applicable. Consent for publication: Not applicable. Competing interests: The authors declare no competing interests., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Ironmaking can have an important role in the circular economy by utilising alternative carbon bearing materials, which are otherwise of low value in use or landfilled. Biomass and plastic wastes have been proposed as alternatives for coke and coal in sintering, blast furnace ironmaking and direct iron ore reduction processes. However, introduction of the alternative carbon sources with higher chlorine contents may influence the formation of some pollutants, most notably, dioxins. This study investigated the effects of carbon bearing materials, i.e., coke, biomass and polyvinyl chloride (PVC), on formation of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and polychlorinated biphenyls (PCBs) during high temperature processing of iron ore. The effect of copper (Cu) as a known dioxin synthesis catalyst, on formation of the dioxins was also investigated. The study found an exponential increasing relationship between the chlorine content in the fuel source and the dioxin emissions. The addition of both biomass and PVC materials contributed to significantly increased dioxin formation, especially for the case of plastics. PCBs had higher concentrations than PCDD/Fs in all cases except when CuCl 2 was added due to its catalytic properties to synthesise PCDD/Fs. PCDF concentrations far outweighed the PCDDs, suggesting that de novo reaction mechanism, where carbon particles are oxidised by a transition metal in presence of chlorine, dominated the formation of the dioxins in the process., Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Vladimir Strezov reports financial support was provided by Australian Research Council. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

The inorganic chlorine (Cly) and odd nitrogen (NOy) chemical families influence stratospheric O3. In January 2020 Australian wildfires injected record‐breaking amounts of smoke into the southern stratosphere. Within 1–2 months ground‐based and satellite observations showed Cly and NOy were repartitioned. By May, lower stratospheric HCl columns declined by ∼30% and ClONO2 columns increased by 40%–50%. The Cly perturbations began and ended near the equinoxes, increased poleward, and peaked at the winter solstice. NO2 decreased from February to April, consistent with sulfate aerosol reactions, but returned to typical values by June ‐ months before the Cly recovery. Transport tracers show that dynamics not chemistry explains most of the observed O3 decrease after April, with no significant transport earlier. Simulations assuming wildfire smoke behaves identically to sulfate aerosols couldn't reproduce observed Cly changes, suggesting they have different composition and chemistry. This undermines our ability to predict ozone in a changing climate. Plain Language Summary: Smoke injected into the stratosphere by the massive 2020 Australian wildfires affected stratospheric chemical composition in a way never before seen. These changes occurred gradually over a 4–5 month period after the fires, then gradually reversed over another 4 months. The greatest changes involved chemicals containing chlorine, which can affect stratospheric ozone amounts. Satellite data showed that lower stratospheric aerosol levels in the southern hemisphere middle latitudes were more than doubled for about 5 months. Model simulations using stratospheric sulfate aerosol reactions were unable to reproduce the observed changes in the chlorine species. This means that the Australian wildfire smoke did not behave chemically like sulfate aerosols. It's important to figure out what chemical reactions occur on wildfire aerosols so we can predict how stratospheric ozone will be impacted if massive wildfires occur more often in a warming climate. Key Points: Wildfire aerosols appear to repartition stratospheric chlorine over a 7‐month period, with the greatest effect where nights are longestSimulations show that observed chlorine repartitioning is inconsistent with chemistry on sulfuric acid/water aerosolsLong‐lived trace gases show that most of the observed midlatitude O3 decrease after April is explained by transport [ABSTRACT FROM AUTHOR]

In the current study, the temperature dependence of the Cl atom rate coefficient with 2‐methyl‐3‐butene‐2‐ol (MBO) is re‐assessed. Relative rate kinetic measurements were performed inside THALAMOS (thermally regulated atmospheric simulation chamber) facility under atmospheric pressure (760 Torr) of zero air in the temperature range of 256–353 K. The rate coefficient of the title reaction was found to be independent of temperature with a value of kMBO = (3.20 ± 0.10) × 10−10 cm3 molecule–1 s–1, where the quoted error corresponds to 2σ standard error of the mean value and includes the overall uncertainty of the measurements. Besides the kinetic study we have also determined the yields of the major products formed, in the temperature range of 273–353 K. Acetone and chloroacetaldehyde were identified as primary oxidation products with almost identical yields, ranging between 60% and 80%. Formaldehyde and methyl vinyl ketone were also observed with yields below 10% and 0.5%, respectively. Our experimental results indicate that the dominant reaction pathway is the addition of Cl atoms to the terminal carbon atom of MBO. [ABSTRACT FROM AUTHOR]

Rate coefficients of the gas-phase reactions of Cl atoms with a series of fluorinated diketones (FDKs): CF 3 C(O)CH 2 C(O)CH 3 (TFP), CF 3 C(O)CH 2 C(O)CH 2 CH 3 (TFH) and CF 3 C(O)CH 2 C(O)CH(CH 3 ) 2 (TFMH), have been measured at (298 ± 2) K and under atmospheric pressure. The experiments were performed using the relative-rate method with a GC-FID detection system. From different determinations and references used, the following rate coefficients were obtained (in cm 3 /(molecule·sec)): k 4 (TFP + Cl) = (1.75 ± 0.21) × 10 -10 , k 5 (TFH + Cl) = (2.05 ± 0.23) × 10 -10 , k 6 (TFMH + Cl) = (2.71 ± 0.34) × 10 -10 . Reactivity trends of FDKs were discussed and Free Energy Relationships analysis was developed. The expression lgk OH = 1.68 lgk Cl + 5.71 was obtained for the reactivity of the studied FDKs together with similar unsaturated VOCs with Cl and OH radicals Additionally, acetic acid (CH 3 C(O)OH) and trifluoroacetic acid (CF 3 C(O)OH) were positively identified and quantified as degradation products using in situ FTIR spectroscopy. According to the identified products, atmospheric chemical mechanisms were proposed. The atmospheric implications of the studied reactions were assessed by the estimation of the tropospheric lifetimes of TFP, TFH, and TFMH concerning their reaction with Cl atoms to be 48, 41, and 31 hours, respectively. The relatively short residence in the atmosphere of the fluorocarbons studied will have a local/regional impact with restricted transport. Global warming potential (GWP (20 yr) ) calculated for the studied fluoro diketones were 0.014, 0.003 and 0.001 for TFP, TFH and TFMH, respectively with a negligible contribution to the greenhouse effect., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier B.V.)

This study investigates carbon, hydrogen, nitrogen and chlorine isotope fractionation during the transformation of 3-chloroaniline (3-CA) via direct photolysis, TiO 2 photocatalytic degradation at neutral condition and hydrolysis at pH 3, pH 7 and pH 11. Direct photolysis and ∙OH reaction (UV/H 2 O 2 ) showed similar inverse isotope fractionation (ε) for carbon (1.9 ± 0.4 ‰ and 1.9 ± 0.6 ‰), for hydrogen (6.9 ± 1.6 ‰ and 5.0 ± 2.6 ‰), and inverse chlorine (13.9 ± 3.8 ‰ and 11.9 ± 2.9 ‰) and no nitrogen isotope fractionation, respectively. In contrast, significantly different normal carbon (-0.5 ± 0.1 ‰), inverse hydrogen (6.6 ± 1.5 ‰), and normal nitrogen (-0.8 ± 0.2 ‰) and inverse chlorine (5.2 ± 3.7 ‰) isotope fractionations were observed for the photocatalysis of 3-CA by TiO 2 indicating a different degradation pathway as expected from ∙OH. For hydrolysis, inverse carbon (0.7 ± 0.3 ‰) and hydrogen (12.5 ± 3.3 ‰) isotope fractionation have been found at pH 3 while a normal carbon isotope fractionation was observed at pH 7 (-0.9 ± 0.3 ‰) and pH 11 (-1.3 ± 0.4 ‰), respectively. The correlation of 2 H and 13 C, 15 N and 13 C, and 37 Cl and 13 C isotope fractionation (Λ) allowed to distinguish direct photodegradation (Λ H C = -4.6 ± 1.7 (Λ H C-YORK =-5.2 ± 1.0) and Λ Cl- C = 8.7 ± 0.9 (Λ Cl-C-YORK =8.0 ± 0.3)), UV/H 2 O 2 oxidation (Λ H C = -4.7 ± 1.0 (Λ H C-YORK =-4.5 ± 0.6) and Λ Cl- C = 6.7 ± 0.8 (Λ Cl-C-YORK =7.0 ± 1.0)), UV/TiO 2 photocatalysis (Λ H C = -9.2 ± 3.1 (Λ H C-YORK =-9.3 ± 1.4), Λ Cl-C = -10.2 ± 1.5 (Λ Cl-C-YORK =-12.4 ± 1.7) and Λ N C -2.2 ± 0.3 (Λ N C-YORK =-2.3 ± 0.4)) and the modes of hydrolysis (Λ H C = 15.2 ± 5.3 (Λ H C-YORK =17.9 ± 2.9) and Λ Cl- C = 0.9 ± 0.2 (Λ Cl-C-YORK =1.1 ± 0.1) at pH 3) of 3-CA. The results were mechanistically interpreted highlighting the potential of CSIA to elucidate chemical oxidation and hydrolysis mechanisms of 3-CA., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)

Dissolved oxygen (DO) is essential for the health of aquatic ecosystems, supporting biogeochemical cycles and the decomposition of organic matter. However, continuous untreated external inputs from illicit discharges or sewer overflows, coupled with inadequate ecological base flow, have led to widespread river deoxygenation and serious ecological crises. This study demonstrates that chlorinated wastewater treatment plant (WWTP) effluent can significantly enhance DO levels in downstream rivers, particularly in areas with high pollution loads or poor ecological base flow. Notably, DO increases in receiving waters were positively correlated with initial chorine doses. Residual chlorine in WWTP effluent reduced inorganic nitrogen and dissolved organic matter (DOM). Analysis of DOM and molecular properties showed that residual chlorine preferentially reacts with low-molecular-weight organics like amino acids, increasing their hydrophobicity and electrophilicity. These molecular changes inhibit enzyme interactions, reducing the bioavailability of these compounds for oxygen-consuming processes. Field studies demonstrated that through on-site optimization of the full-scale WWTP disinfection process, specifically by controlling residual chlorine levels in effluents, DO levels downstream increased by an average of 15 %, with a maximum of 48 % compared to upstream levels, while typical disinfection byproducts (i.e., trihalomethanes, haloacetic acids and haloacetonitriles) remained below regulatory thresholds. This work provides new insights into the positive effects of chlorinated WWTP effluent on DO levels in receiving waters., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)

It has been demonstrated that chlorine predominately reacts with phenolic compounds through an electrophilic aromatic substitution, yielding chlorinated phenols. Previous studies showed that copper oxide (CuO), a water pipe corrosion product, can catalytically enhance the reactivity of chlorine and its disproportionation. In this study, kinetics and mechanisms for the reactions of chlorine with phenolic compounds in the presence of CuO were investigated. CuO at 100 mg/L increases the apparent second-order rate constants (k app ) for reactions of chlorine with phenol, chlorophenols, bromophenols, iodophenols, 2,6-dimethylphenol, acetaminophen, and 4-hydroxybenzoic acid at pH 7.6 and 21 °C by up to 50 times. For the same reaction conditions, increasing CuO concentrations from 0 to 200 mg/L increase the k app of phenol chlorination from ∼42 to 608 M -1 s -1 . In general, a stronger enhancement of the chlorine reactions with phenols was observed in the pH range of 6.6-7.6 than 7.6-9.0, indicating that CuO more readily activates hypochlorous acid. Moreover, CuO significantly changes the pathway for phenol chlorination. Yields of chlorophenols decreased from 98 % to < 5 % as the CuO concentration increased from 0 to 100 mg/L. Non-chlorinated compounds (e.g., catechol, 2,3-dihydroxymuconic acid, maleic acid, and oxalic acid) are major transformation products. Model simulations suggest a pre-equilibrium step with the formation of a CuO-HOCl complex as the rate-limiting step for the overall reactions. Heterogeneous chlorination processes with limited formation of chlorinated phenols tend to be predominant for CuO concentrations > ∼ 5 - 36 mg/L for various phenols. These findings have implications for the transformation of phenolic compounds during chlorination in copper-containing water distribution systems., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

The kinetics of polyamide membrane degradation by free chlorine and halide ions (Br - and Cl - ) were innovatively evaluated based on physicochemical properties and filtration performance, using water/solute permeability coefficient in addition to bromide incorporation as important indicators. The reaction rate constants for the reduced water and H 3 BO 3 permeability coefficient were 1-2 orders of magnitude higher at 0-1 h than 1-10 h. N-bromination and bromination-promoted hydrolysis are dominant degradation mechanisms at 0-1 h (reflected by the breakage of hydrogen bond, the increased Ca binding content, and the increased charge density), and ring-bromination further occurs at 1-10 h (reflected by the disappearance or weakening of aromatic amide band and the nearly constant hydrogen bond). The more reactive but less abundant brominating agents (Br 2 O, BrOCl, BrCl, and Br 2 ) played significant roles in membrane degradation, contradicting the conventional belief that HOBr is the only reactive species. BrCl at pH 4.0 and BrOCl and Br 2 O at pH 7.0 made significantly higher contributions to membrane degradation than HOBr (>76 % vs. <13 %). The increased contribution of BrCl and Br 2 with the increased [Cl - ] and [Br - ] ex (the excess bromide, defined as [Br - ] o - [HOCl] o when [Br - ] o > [HOCl] o ), respectively, was responsible for the greater reduction of water permeability coefficient. The innovative and simple approach developed in this study provides important insights to evaluate and predict membrane degradation., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)

Halogenated bisphenol compounds are prevalent in urban water systems and may pose greater environmental risks than their bisphenol precursors. This study explored the formation of halogenated bisphenol F (BPF) in water chlorination and their subsequent transformation behaviors in receiving waters. The kinetics and pathways of BPF halogenation with chlorine, bromine, and iodine were firstly investigated. BPF chlorination followed second-order kinetics, with pH-dependent second-order rate constants (k app ) ranging from 1.0 M -1 s -1 at pH 5.0 to 50.4 M -1 s -1 at pH 9.0. The k app of BPF with bromine and iodine were 4 - 5 orders of magnitude higher than those of chlorine. The degradation potential of halogenated BPF products in sunlit surface waters was also evaluated, focusing on both direct and indirect photolysis. Indirect photolysis, involving reactions with excited triplet state of CDOM ( 3 CDOM*), • OH and 1 O 2 , emerged as the primary degradation pathway for BPF, while both direct photolysis and indirect photolysis with 3 CDOM* predominated for mono- and dihalogenated BPF products. Compared with BPF, the photodegradation of halogenated products was significantly enhanced. Photolysis experiments in wastewater-receiving wetland water demonstrated effective degradation of halogenated BPF products, highlighting the pivotal role of sunlight in their environmental fate. Overall, this study advances understanding of the formation and fate of halogenated BPF products and provides valuable insights for managing the environmental impacts of these emerging contaminants., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Global concern regarding transformation products (TPs) derived from contaminants, including pesticides, in the environment and during water treatment has been growing markedly. In the present study, we investigated the anti-acetylcholinesterase (AChE) activity of an aqueous solution of the organophosphorus insecticide disulfoton, a toxicological endpoint for determining the acceptable daily intake of disulfoton, both in the presence and the absence of metabolism during chlorination. Disulfoton rapidly reacted with free chlorine and completely disappeared within 0.25 h. Although the aqueous disulfoton solution did not induce anti-AChE activity before chlorination, the chlorinated samples did induce anti-AChE activity, both with (indirect toxicity) and without (direct toxicity) metabolism. These observations clearly indicated that disulfoton was converted into toxic TPs through reactions with free chlorine. Liquid chromatographic fractionation followed by an anti-AChE activity assay revealed that three TPs were responsible for the observed direct toxicity. Further mass spectrometric analyses showed that these TPs were disulfoton-oxon-sulfone, and mono- and dichloro-substituted derivatives of disulfoton-oxon-sulfoxide (O-(1-chloroethyl) S-[2-(ethanesulfinyl)ethyl] O-ethyl phosphorothioate and O-(1,2-dichloroethyl) S-[2-(ethanesulfinyl)ethyl] O-ethyl phosphorothioate, respectively), none of which were simply oxon. Results of the anti-AChE activity assay on the chemical standard of disulfoton-oxon-sulfone after metabolism and quantification of the disulfoton-oxon-sulfone in the chlorinated samples revealed that the observed indirect toxicity was solely induced by this TP. It is recommend that drinking water treatment plants that use free chlorine as a disinfectant monitor the concentrations of at least disulfoton-oxon-sulfone, which is commercially available, in finished water in addition to disulfoton itself, to ensure the safety of tap water., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2025 Elsevier Ltd. All rights reserved.)

The degradation of rubber seal (RS), particularly ethylene-propylene-diene (EPDM), in the drinking water networks has been confirmed, yet the role of RS as a disinfection by-product (DBP) precursor remains unknown. This study provides explicit proof of the formation of halogenated disinfection by-products (X-DBPs) from RS in chlorinated drinking water within water supply systems. Over time, exposure to chlorinated water ages RS, releasing high levels of organic compounds, which act as DBP precursors. Trihalomethanes (THMs) and haloacetic acids (HAAs) emanating from RS recorded 12.1 μg L -1 and 2.3 μg L -1 , respectively, after contact with chlorinated water. RS additionally revealed modest amounts (∼1.5 and 0.25-0.3 μg L -1 ) of haloacetaldehydes (HALs) and haloacetonitriles (HANs), respectively, posing potential cytotoxic risks. Scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FT-IR) analyses showed remarkable morphological alterations in RS due to exposure to chlorinated water, whether in ultrapure water or real water. Moreover, the correlation analysis of 2D-COS-FT-IR exhibited the hydroxyl group (O-H) as the most sensitive functional group among other groups toward chlorine. The biofilm in the plastic pipes exposed a negligible role in the formation of X-DBPs, emphasizing the main contributions of RS and the water matrix to the formation of X-DBPs in drinking water. Our results highlight the need to consider them alongside other DBP precursors to safeguard water quality and to explore safer alternatives for sealing water pipes within the distribution system., Competing Interests: Declaration of competing interest We declare that this manuscript is original, has not been published before and is not currently being considered for publication elsewhere. We know of no conflicts of interest associated with this publication, and no financial support for this work that could have influenced its outcome., (Copyright © 2025. Published by Elsevier Ltd.)

Reducing the cost of RuO 2 /TiO 2 catalysts is still one of the urgent challenges in catalytic HCl oxidation. In the present work, a Ce-doped TiO 2 supported RuO 2 catalyst with a low Ru loading was developed, showing a high activity in the catalytic oxidation of HCl to Cl 2 . The results on some extensive characterizations of both Ce-doped TiO 2 carriers and their supported RuO 2 catalysts show that the doping of Ce into TiO 2 can effectively change the lattice parameters of TiO 2 to improve the dispersion of the active RuO 2 species on the carrier, which facilitates the production of surface Ru species to expose more active sites for boosting the catalytic performance even under some harsh reaction conditions. This work provides some scientific basis and technical support for chlorine recycling., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier B.V.)