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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.

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.

This work investigated byproduct formation and in vitro genotoxicity and cytotoxicity at four facilities using UV/chlorine advanced oxidation for potable reuse or drinking water treatment. In arguably the most common application of UV/chlorine, treating reverse osmosis permeate for potable reuse, organic byproduct formation was always either not detected or well-below typical drinking water levels. At a groundwater-source drinking water treatment plant, the trihalomethanes and haloacetic acids each increased by up to 12 μg/L through the UV reactor and 40 μg/L during secondary disinfection, but the final concentrations remained low relative to regulatory limits. Overall, and aside from the known pathways of chlorate formation, the UV/chlorine byproduct and in vitro toxicity formation observed in this study was lower than what is generally found in many chlor(am)inated drinking waters, although there was some observed shift to more brominated species, which might be deserving of future research, given their higher in vitro toxicity compared to typical chlorinated species.

Regulations typically use four trihalomethanes (THM4) and five haloacetic acids (HAA5) as metrics of consumer exposure to disinfection byproducts (DBPs) and their chronic health risks. Their use as exposure metrics assumes that their concentrations correlate with DBP-associated toxicity. For a chlorine-disinfected surface water, this study demonstrates that increasing chlorine contact time from 1 to 7 days was associated with a 62-76% increase in THM4 and HAA5 but a 40-47% decrease in total cytotoxicity. Thus, the use of THM4 and HAA5 may divert regulatory attention away from the low water age sections of distribution systems near treatment facilities that may feature the highest cytotoxicity but lowest THM4/HAA5 concentrations. Among common options to reduce THM4/HAA5, this study also shows that chlorine disinfection followed by chloramines for maintaining a distribution system residual did not substantially reduce cytotoxicity. Granular activated carbon followed by chlorine reduced cytotoxicity by 28-80%, even at the lowest water ages where cytotoxicity was maximized. These findings highlight the need to identify DBPs that better correlate with toxicity than THM4/HAA5 to serve as metrics of exposure. These metrics could help identify distribution system locations exhibiting higher consumer risk and develop modifications to disinfection systems that effectively reduce consumer risk.

Pterins, including biopterin prevalent during cyanobacterial blooms, are nitrogen-containing heterocyclic compounds ubiquitous in both natural and engineered environments. However, their roles and associated human risks in water treatment remain poorly understood. This study systematically investigated the kinetics, disinfection byproducts (DBPs), and toxicity of biopterin in chlorination. For deciphering the reaction kinetics, 1,3,5-trimethoxybenzene proved to be a more effective chlorine quencher than the commonly used reducing agents, as it preserved N-chlorinated intermediates without reversing them back to biopterin. The pH-dependent kinetics demonstrated that both chlorine and biopterin species had a significant influence on the reaction rates, with deprotonated biopterin exhibiting a markedly higher reactivity toward HClO/ClO - . Based on time-of-flight mass spectrometry, ten transformation products (TPs) including seven halogenated N-Cl ones, have been identified for the first time. These cyclic TPs were transformed into various aliphatic carbonaceous and nitrogenous DBPs during the subsequent chlorination process. Notably, theoretical predictions and the luminescent bacteria assay confirmed potential higher toxicities of these products than biopterin. These findings highlight the potential risks of pterins during water disinfection and provide a reference framework for accurately revealing the chlorination behavior of emerging nitrogenous chemicals.

Halogenated polycyclic aromatic hydrocarbons (XPAHs) present potential risk owing to their greater toxicity than PAHs. This study aimed to explore their profiles in commercial salt-tolerant rice, effects of saline cultivation (0‰ and 3‰ saline conditions), and formation during home cooking. A validated SPE-GC-MS/MS method was used to analyze PAHs and XPAHs in 16 commercial salt-tolerant rice samples. The PAH24 and XPAH18 concentrations were 6.95-32.73 μg kg -1 and 0.013-0.593 μg kg -1 , respectively. Chlorinated PAHs (ClPAHs) were significantly greater in salt-tolerant rice (0.14 μg kg -1 ) than in normal rice (0.048 μg kg -1 ). During cooking, a notable increase (210-1120%) in ClPAHs and a significant correlation ( r = 0.70-0.81, p < 0.05) between newly formed ClPAHs and their parent PAHs were observed, suggesting cooking-induced chlorination of PAHs. Moreover, chlorine radical-induced chlorination of PAHs may be the primary mechanism involved. These findings highlight increased exposure to ClPAHs due to saline cultivation and cooking and provide new insight into ClPAH formation from household cooking.

Limonene, a key volatile chemical product (VCP) commonly found in personal care and cleaning agents, is emerging as a major indoor air pollutant. Recently, elevated levels of reactive chlorine species during bleach cleaning and disinfection have been reported to increase indoor oxidative capacity. However, incomplete knowledge of the indoor transformation of limonene, especially the missing chlorine chemistry, poses a barrier to evaluating the environmental implications associated with the concurrent use of cleaning agents and disinfectants. Here, we investigated the reaction mechanisms of chlorinated limonene peroxy radicals (Cl-lim-RO 2 •), key intermediates in determining the chlorine chemistry of limonene, and toxicity of transformation products (TPs) using quantum chemical calculations and toxicology modeling. The results indicate that Cl-lim-RO 2 • undergoes a concerted autoxidation process modulated by RO 2 • and alkoxy radicals (RO•), particularly emphasizing the importance of RO• isomerization. Following this generalized autoxidation mechanism, Cl-lim-RO 2 • can produce low-volatility precursors of secondary organic aerosols. Toxicological findings further indicate that the majority of TPs exhibit increased respiratory toxicity, mutagenicity, and eye/skin irritation compared to limonene, presenting an occupational hazard for indoor occupants. The proposed near-explicit reaction mechanism of chlorine-initiated limonene significantly enhances our current understanding of both RO 2 • and RO• chemistry while also highlighting the health risks associated with the concurrent use of cleaning agents and disinfectants.

Chlorine, serving as the mainstream disinfectant, can react with dissolved organic matter (DOM) to form undeserved disinfection by-products (DBPs). Free available chlorine (FAC) concentration is crucial to ensure effective disinfection while minimizing the formation of toxic DBPs. In this study, we propose a convenient method using sodium sulfite (Na 2 SO 3 ) to reduce oxidized chlorine in FAC. The molar concentration of reduced chloride ion (Cl - ) was quantified directly by ion chromatography to reflect FAC concentration. Compared with common FAC detection techniques including DPD colorimetry, iodometry, and UV methods, this novel reduction method exhibits a lower detection limit and is more resistant to interference. Common water matrices, such as DOM and anions did not affect the method accuracy (< 3.6%). Furthermore, carbonaceous DBPs (C-DBPs) like regulated trihalomethanes and halogenacetic acids, unregulated aromatic chlorophenols, did not interfere with the determination of FAC by using this reduction method. This lack of interference can be attributed to the low redox potential of Na 2 SO 3 , which does not readily react with these C-DBPs. However, nitrogenated DBPs (N-DBPs) like dichloroacetonitrile displayed slight interference (the effect of common dichloroacetonitrile concentration in water on FAC was less than 0.0007 μM). This suggests that this method is well-suited for determining FAC in chlorination processes where the C-DBPs predominated. Overall, the reduction method enables precise determination of FAC and proves valuable in assessing residual chlorine levels in both laboratory and real disinfected water samples dominated by C-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 Elsevier Ltd. All rights reserved.)

The electrochemical treatment of saline wastewater is prone to the formation of inorganic chlorinated byproducts, being a significant challenge for this technology. In this study, we introduce an electrooxidation system utilizing a self-supporting nitrogen-doped carbon-based cathode embedded in carbon cloth (N@C-CC), designed to generate H₂O₂. This system aims to rapidly neutralize free chlorine produced at the anode, a precursor to inorganic chlorinated byproducts, thereby reducing their formation. Our results demonstrate that using the N@C-CC cathode in saline wastewater treatment yielded considerably lower concentrations of ClO₃⁻ and ClO₄⁻ (0.08 mM and 0.024 mM, respectively), which were only 20.5% and 22.7% of the levels produced using a Pt cathode without H₂O₂ generation. Moreover, the presence of cathodically generated H₂O₂ that quenches free chlorine did not significantly impact the degradation performance of phenol. Electron paramagnetic resonance tests and quenching experiments indicated that 1 O₂ was primarily responsible for phenol removal. Validation with real wastewater demonstrated reductions of 68.6% and 56.3% in ClO 3 - and ClO 4 - concentrations, respectively, while effectively removing other pollutants. This study thus offers a compelling method for mitigating the formation of inorganic chlorinated byproducts during the electrooxidation of saline wastewater., 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.)

Safe drinking water requires sound monitoring and maintenance of residual chlorine within drinking water distribution networks (DWDNs) to suppress possible microbial regrowth. However, in the developing world, DWDNs face unique challenges, including aging infrastructure, water pipes laid near or even aboveground thus exposing water to high temperature fluctuations, and relatively high organic loads. Therefore, safely maintaining sustainable residual chlorine levels and restricting the problems of hazardous disinfection by-products (DBPs) formation and of antimicrobial resistance (AMR), both tracing back to extensive chlorination, is a difficult exercise in those settings. Here, the temperature dependent bulk chlorine decay, i.e., the rate at which chlorine residual is consumed, was estimated for a typical DWDN system in South Africa. To this end, experimental assays were performed and a mathematical model was developed to predict chlorine levels within the DWDN under study. A direct relationship (R 2 = 0.99) between bulk chlorine decay and initial chlorine dosage was identified, with bulk chlorine decay following the first-order decay model. The bulk chlorine decay rate coefficient (Kb) and the reaction constant with the pipe walls (Kw) were experimentally estimated, with the first being the main chlorine consumer and the latter only slightly contributing to chlorine decay. EPANET was used to simulate the chlorine concentrations within the examined DWDN, while residual chlorine concentrations were modelled using COMSOL. The software programs were calibrated and validated using experimental results. The optimum liquid chlorine dosage was 5 mg L -1 , and this could maintain residual levels at 0.5 mg L -1 for 3500 min in the water distribution tanks. Yet, the residual chlorine levels at the distal end of the DWDN were below the recommended safety limits, suggesting the need for chlorine booster stations to supplement residual chlorine rather than further increasing chlorine initial dosages which will lead to unsafe chlorine levels at the proximal points and inevitably will increase DBPs in drinking water. This relatively high chlorine dosage reflects the overall poor quality of the raw water that feeds the drinking water treatment plant under study, which is consistent with the poor water quality of surface water in South Africa. Overall, this methodology can be replicated in DWDNs in South Africa and across the developing world, where similar challenges persist and ensure safe drinking water but not at the expense of DBPs formation and possibly AMR spreading., 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 Inc. All rights reserved.)

The UV/chlorine (UV/Cl 2 ) process is a developing advanced oxidation process and can efficiently remove antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs). However, the transportation and storage of chlorine solutions limit the application of the UV/Cl 2 process, especially for decentralized water treatment. To overcome the limitation, an electrochemically driven UV/Cl 2 process (E-UV/Cl 2 ) where Cl 2 can be electrochemically produced in situ from anodic oxidation of chloride (Cl - ) ubiquitously present in various water matrices was evaluated in this study. >5-log inactivation of the ARB (E. coli) was achieved within 5 s of the E-UV/Cl 2 process, and no photoreactivation of the ARB was observed after the treatment. In addition to the ARB, intracellular and extracellular ARGs (tetA, sul1, sul2, and ermB) could be effectively degraded (e.g., log(C 0 /C) > 4 for i-ARGs) within 5 min of the E-UV/Cl 2 process. Atomic force microscopy showed that the most of the i-ARGs were interrupted into short fragments (< 30 nm) during the E-UV/Cl 2 process, which can thus effectively prevent the self-repair of i-ARGs and the horizontal gene transfer. Modelling results showed that the abatement efficiencies of i-ARG correlated positively with the exposures of •OH, Cl 2 - •, and ClO• during the E-UV/Cl 2 process. Due to the short treatment time (5 min) required for ARB and ARG removal, insignificant concentrations of trihalomethanes (THMs) were generated during of the E-UV/Cl 2 process, and the energy consumption (E EO ) of ARG removal was ∼0.20‒0.27 kWh/m 3 -log, which is generally comparable to that of the UV/Cl 2 process (0.18-0.23 kWh/m 3 -log). These results demonstrate that the E-UV/Cl 2 process can provide a feasible and attractive alternative to the UV/Cl 2 process for ARB and ARG removal in decentralized water treatment system., 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.)

Removal of Mn(II) is an essential step for addressing water discoloration in water treatment utilities worldwide. However, conventional chlorination suffers from poor oxidation of Mn(II) due to its low homogeneous oxidation kinetics. This study explored the oxidation capability of a new chemical dosing strategy employing peroxymonosulfate (PMS) to assist the chlorination process (PMS@Cl 2 ) for effective Mn(II) oxidation. The study comprehensively explored both oxidation kinetics and underlying mechanisms associated with homogeneous and heterogeneous oxidation within the PMS@Cl 2 system. At an [Mn(II)] 0 of 1 mg/L, chlorination demonstrated inability in oxidizing Mn(II), with <10 % oxidation even at an elevated [Cl 2 ] of 150 μM (∼10 mg/L). By contrast, PMS completely oxidized 100 % Mn(II) within a 30-minute reaction at a much lower [PMS] of 60 μM (k obs = 0.07 min -1 and t 1/2 = 9 min), demonstrating its superior Mn(II) oxidation kinetics (over one order of magnitude faster than conventional chlorine). PMS@Cl 2 exhibited an interesting synergistic benefit when combining a lower dose PMS with a higher routine dose Cl 2 (loPMS@hiCl 2 ), e.g. [PMS]:[Cl 2 ] at 15:30 or 30:30 μM. Both conditions achieved 100 % Mn(II) oxidation, with even better values of k obs and t 1/2 (0.16-0.17 min -1 and ∼4 min) relative to PMS alone at 60 µM. The synergic benefit of PMS@Cl 2 was attributed to distinct functions played by PMS and Cl 2 in both homogeneous and heterogeneous oxidation processes. Reactive species identification excluded the possible involvement of SO 4 •- , OH • , or chlorine radicals in the homogeneous oxidation of the PMS@Cl 2 system. Instead, the dominant species was O 2 •- radical generated during the reaction of Mn(II) and PMS. Furthermore, the heterogeneous oxidation emphasized the important role of combining Cl 2 dosing, which demonstrated an increased reactivity and electron transfer with the Mn-O-Mn complex, surpassing PMS. Overall, heterogeneous oxidation accelerated the oxidation kinetics of the PMS@Cl 2 system by 1.1-2 orders of magnitude relative to the homogeneous oxidation of Cl 2 alone. We here demonstrated that PMS@Cl 2 could offer a more efficient mean of soluble Mn(II) mitigation, achieved with a relatively low routine dose of oxidant in a short reaction period. The outcomes of this study would address the existing limitations of traditional chlorine oxidation, minimizing the trade-offs associated with high residual chlorine levels after treatments for soluble manganese-containing 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 © 2024. Published by Elsevier Ltd.)

The practical application of Cu(II)-catalyzed Fenton-like reaction (Cu(II)/H 2 O 2 ) exhibits a low efficiency in the degradation of refractory compounds of wastewater. The impact of chloride ions (Cl - ) on Fenton-like reactions have been investigated, but the influence mechanism is still unclear. Herein, the presence of Cl - (5 mM) significantly accelerated the degradation of benzoic acid (BA) under neutral conditions. The degradation of BA follows pseudo-first-order kinetics, with a degradation rate 7.3 times higher than the Cu(II)/H 2 O 2 system. Multiple evidences strongly demonstrated that this reaction enables the production of reactive chlorine species (RCS) rather than HO • and high-valent copper (Cu(III)). The kinetic model revealed that Cl - could shift reactive species from the key intermediate (Cu(III)-chloro complexes) to RCS. Dichlorine radicals (Cl 2 •- ) was discovered to play a crucial role in BA degradation, which was largely overlooked in previous reports. Although the reaction rate of Cl 2 •- with BA (k = 2.0 × 10 6  M -1  s -1 ) is lower than that of other species, its concentration is 10 orders of magnitude higher than that of Cu(III) and HO • . Furthermore, the exceptional efficacy of the Cu(II)/H 2 O 2 system in BA degradation was observed in saline aquatic environments. This work sheds light on the previously unrecognized role of the metal-chloro complexes in production the RCS and water purification., 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.)

Galvanic corrosion of lead-tin solder in copper plumbing can be a major contributor to water lead contamination. Here, we report the electrochemical reversal of the copper-solder galvanic couple, in which the normally anodic solder becomes cathodic to copper via a reaction with free chlorine. This reversal occurred after a few months of exposure to continuously circulating water with relatively low pH and low alkalinity, causing dramatically decreased lead release and the formation of a Pb(IV) scale. Chloramine did not similarly inhibit solder corrosion over the 4-9 month test duration, resulting in up to 100 times more lead contamination of the water relative to free chlorine. These findings have major implications for corrosion control and public health and can help explain anomalously low levels of lead contamination in some waters with free chlorine that are normally considered corrosive to solder.

The selective photoreduction of nitrate to nontoxic nitrogen gas has emerged as an energy-efficient and environmentally friendly route for nitrate removal. However, the coexisting high-concentration chloride ions in wastewater can exert a significant influence on nitrate reduction due to the competitive adsorption and corrosion of Cl - on photocatalysts. Herein, we prepared ethylene glycol-Cu/TiO 2- x (EG-Cu/TiO 2- x ) through a solvothermal reaction of Cu-doped TiO 2 in an EG solution. The photodegradation of nitrate using EG-Cu/TiO 2- x without adding sacrificial agents can efficiently occur in near-neutral pH solutions containing 50 mM Cl - with 95.26% of NO 3 - removal and 76.52% of N 2 selectivity. Moreover, the photocatalyst performance remained at a high level after 8 cycles. In this work, NO 3 - was first converted to NH 4 + by Cu 0 and Ti 3+ , followed by the NH 4 + -to-N 2 conversion by photogenerated chlorine free radicals. Compared to HO • , Cl • , and Cl 2 •- , ClO • is proved to play the predominant role in transforming NH 4 + to N 2 . The EG radicals produced by UV light impede Cl - adsorption on Cu, protecting Cu 0 from being corroded. What's more, photoelectrons can reduce Ti 4+ to Ti 3+ and protect Cu 0 from being oxidized, enabling the stability of reactive sites. This work provides novel insights and understanding on designing photocatalysts for NO 3 - removal in solutions containing chloride ions, highlighting the significance of eliminating Cl - by EG radicals and adjusting the conversion process of NO 3 - for the efficient removal of NO 3 - .

Chlorite (ClO 2 - ) is a regulated byproduct of chlorine dioxide water treatment processes. The transformation of chlorite under UV irradiation into chloride (Cl - ) and chlorate (ClO 3 - ) involves reactive species chain reactions that could enhance chlorine dioxide water treatment efficiency while reducing residual chlorite levels. This study conducted a mechanistic investigation of chlorite phototransformation by analyzing reaction intermediates and stable end products, including chlorine dioxide (ClO 2 ), free chlorine (HOCl/OCl - ), hydroxyl‑radical ( • OH), Cl - , and ClO 3 - through combined experimental and modeling approaches. Experiments were performed at UV 254 irradiation in pure buffered water within the pH range of 6 to 8. Results indicated that the apparent quantum yields for chlorite phototransformation increased from 0.86 to 1.45, and steady-state • OH concentrations at 1 mM initial chlorite concentration rose from 8.16 × 10 -14 M - 16.1 × 10 -14 M with decreasing pH values. It was observed that under UV irradiation, chlorite acts as both a significant producer and consumer of reactive species through three distinct reaction pathways. The developed kinetic model, which incorporates optimized intrinsic chlorite quantum yields Φ chlorite in ranging from 0.33 to 0.39, effectively simulated the loss of oxidants and the formation of major products. It also accurately predicted steady-state concentrations of various species, including • OH, • ClO, Cl • and O 3 . For the first time, this study provides a comprehensive transformation pathway scheme for chlorite phototransformation. The findings offer important insights into the mechanistic aspects of product and oxidizing species formation during chlorite phototransformation., 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 Ltd.. All rights reserved.)

Hydroxyl radical (HO • ) and chlorine atom (Cl • ) are common reactive species in aqueous environments. However, the intrinsic difference in their reactions with organic compounds has not been revealed. This study compared the reaction mechanisms of HO • and Cl • with 13 aromatic and 11 aliphatic compounds by quantum chemical calculation and laser flash photolysis. Both HO • and Cl • can spontaneously react with aromatic compounds via radical adduct formation (RAF), hydrogen atom transfer (HAT), and single electron transfer (SET) pathways. The SET reactions of Cl • were more thermodynamically favorable than HO • , but contrary results were obtained for HAT reactions. According to the free energy of activation (Δ G aq ‡ ), the dominant oxidation mechanisms of aromatic compounds were RAF and SET by HO • and SET by Cl • . The important role of SET in the HO • reactions with aromatic compounds was further verified by accurately calculating the solvation free energy of HO • /HO - and experimentally tracking the radical cations, which were generally neglected in previous studies. Meanwhile, the Δ G aq ‡ value of each reaction pathway of Cl • was lower than that of HO • , resulting in higher rate constants of Cl • with aromatic compounds than HO • . For saturated aliphatic compounds, HAT was found to be the only mechanism accounting for their transformation by HO • and Cl • . This study proposed general rules for the reaction mechanisms of HO • and Cl • and unraveled their differences in the aspects of thermodynamics and kinetics, providing fundamental information for understanding contaminant transformation in processes involving HO • and Cl • .

Isoquinoline (IQL), as a typical nitrogen-containing heterocyclic contaminant in coking wastewater, poses a serious threat to the aquatic environment and human health. Due to its chemical stability, traditional sewage treatment technology is not highly efficient in IQL removal. Advanced oxidation processes (AOPs) driven by ultraviolet radiation could be an effective treatment method, but it could generate toxic byproducts. In this work, the removal of IQL initiated by HO•, ClO•, Cl•, and SO 4 •- in UV/chlorine and UV/persulfate (PDS) process was comprehensively investigated, clarifying the degradation mechanism, reaction kinetics, and ecological toxicity. The findings indicate that the dominant oxidation mechanism of IQL by HO•, ClO•, and Cl• is radical adduct formation (RAF), while single electron transfer (SET) is the main reaction pathway of SO 4 •- with IQL. At 298 K and 1 atm, the order of rate constants for the reactions of IQL with active radicals is Cl• (6.23 × 10 10  M -1  s -1 ) > SO 4 •- (8.81 × 10 9  M -1  s -1 ) > HO• (1.66 × 10 9  M -1  s -1 ) > ClO• (1.62 × 10 8  M -1  s -1 ). The acute and chronic toxicity of IQL and its degradation byproducts at three different trophic levels were evaluated using ECOSAR program. The byproducts produced by the oxidative degradation of IQL by HO• and SO 4 •- are mostly "not harmful", and their toxicity shows a decreasing trend compared to that of IQL. The byproducts derived from the reaction of IQL with Cl• are all "toxic" or "harmful", and the ranking of harm to three types of aquatic organisms is green algae > fish > daphnia. Hence, UV/PDS process could be more secure in pollutant disposal in wastewater. In actual water treatment process, merit attention should be paid to the potential hazards of the byproducts generated by various 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.)

Degradation of antibiotic resistance genes (ARGs) in water chlorination can be influenced by bromide (Br - ), a common component in water matrices; however, detailed kinetic information on this process is limited. This study investigated the degradation kinetics tetA and bla TEM-1 genes, contained within the plasmid pWH1266, when exposed to bromine, chlorine, and chlorine with varying concentrations of Br - across a pH range of 7.0-8.5. The degradation of four ARG amplicons, measured using quantitative polymerase chain reaction, was observed to pursue second-order kinetics with bromine, exhibiting k of 4.0 × 10 2 - 1.6 × 10 3  M -1  s -1 at pH 7.0 and 2.6 × 10 2 - 9.6 × 10 2  M -1  s -1 at pH 8.5. These k values increased linearly with the length of the ARG sequences (209-1136 bps), yielding sequence-independent k of 1.2 and 7.4 × 10 -1 (M AT + GC) -1  s -1  at pH 7.0 and 8.5, respectively. The degradation rate of ARGs during chlorination increased with rising Br - concentration due to the bromine formation through the reaction between chlorine with Br - , which subsequently degrades ARGs more rapidly than chlorine. This behavior was successfully simulated using a kinetic model derived from the reaction kinetics of bromine and chlorine reactions with ARGs. The existence of dissolved organic matter extracts only marginally decreased the enhanced degradation of ARGs with Br - , while ammonia significantly inhibited this process during chlorination, both with and without Br - , due to the low reactivity of NH 2 Cl and NH 2 Br toward ARGs. These findings highlight the importance of Br - in ARG degradation during water chlorination and the need for further studies in diverse water matrices., 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.)

In this study, we fabricated phosphorus-modified carbon felt electrode anodes for chloride oxidation in saline solutions to produce HClO via electrocatalysis, forming a compound fungicide saline applicable for debridement and disinfection. A low-cost phosphorus-modified carbon felt electrode (P@CF) with high chlorine evolution reaction activity was synthesized to address the reduced efficiency of CER and the solution's pH increase. Heteroatoms P and O were introduced into the carbon felt by phosphoric acid activation followed by heat treatment. The maximum active chlorine concentration on the P@CF electrode could reach 616.8 mg/L in 60 min under the optimal synthesis conditions of a phosphoric acid mass fraction of 30%, a phosphoric acid impregnation time of 3 h, and a heat treatment temperature of 300 °C. The active chlorine concentration was 1.8 times higher on the P@CF electrode compared to the original carbon felt electrode. The optimal reaction conditions for the generation of active chlorine were as follows: salt concentration of 9 g/L, voltage of 7 V, and electrode spacing of 2 cm as verified by response surfaces. This electrolysis reaction follows one-stage reaction kinetics. Subsequently, the disinfection efficacy of the produced disinfectants was examined. The prepared disinfectant was also compared to a commercially available hypochlorite disinfectant, showing similar disinfection effects on E. coli for both., 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.)

As a strong oxidizing agent, ozone is used in some water treatment facilities for disinfection, taste and odor control, and removal of organic micropollutants. Phenylalanine (Phe) was used as the target amino acid to comprehensively investigate variability of disinfection byproducts (DBPs) formation during chlorine disinfection and residual chlorine conditions subsequent to ozonation. The results showed that subsequent to ozonation, the typical regulated and unregulated DBPs formation potential (DBPsFP), including trichloromethane (TCM), dichloroacetonitrile (DCAN), chloral hydrate (CH), dichloroacetic acid (DCAA), trichloroacetic acid (TCAA), and trichloroacetamide (TCAcAm) increased substantially, by 2.4, 3.3, 5.6, 1.2, 2.5, and 6.0 times, respectively, compared with only chlorination. Ozonation also significantly increased the DBPs yield under a 2 day simulated residual chlorine condition that mimicked the water distribution system. DBPs formations followed pseudo first order kinetics. The formation rates of DBPs in the first 6 hr were higher for TCM (0.214 hr -1 ), DCAN (0.244 hr -1 ), CH (0.105 hr -1 ), TCAcAm (0.234 hr -1 ), DCAA (0.375 hr -1 ) and TCAA (0.190 hr -1 ) than thereafter. The peak DBPsFP of TCM, DCAN, CH, TCAcAm, DCAA, and TCAA were obtained when that ozonation time was set at 5-15 min. Ozonation times > 30 min increased the mineralization of Phe and decreased the formation of DBPs upon chlorination. Increasing bromine ion (Br - ) concentration increased production of bromine- DBPs and decreased chlorine-DBPs formation by 59.3%-92.2% . Higher ozone dosages and slight alkaline favored to reduce DBP formation and cytotoxicity. The ozonation conditions should be optimized for all application purposes including DBPs reduction., 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 © 2023. Published by Elsevier B.V.)

This study discussed the effect of ferric salt addition on UV/electro-chlorine advanced oxidation process using a train of electrolytic and UV flow cells with an ozone-free low-pressure mercury vapour lamp (total irradiance:0.60 W at 254 nm). Ferric salt addition enhanced 1,4-dioxane degradation at an electrolytic current of 0.100 A. By contrast, an inhibitory effect of ferric salt addition was observed at a current of 0.500 A. The enhanced accumulation of free chlorine at a current of 0.500 A directly decreased the 1,4-dioxane degradation rate by scavenging reactive radicals like HO˙ and Cl˙. However, at an electrolytic current of 0.100 A, UV irradiance was relatively excessive for electrochemical chlorine production. The excess UV energy enhanced the photoreduction of FeOH 2+ , followed by the Fenton-type reaction of Fe 2+ and HOCl, which produced HO˙ and consumed free chlorine. As a result, the free chlorine concentration decreased, and the reaction efficiency between the reactive radicals and 1,4-dioxane improved. Thus, the addition of ferric salt to a UV/electro-chlorine system is recommended when the UV irradiance in the system is excessive compared to the electrochemical chlorine supply.

Conventional wastewater treatment methods cannot completely remove the ultraviolet (UV) filters or dissolved organic matter. The transformation characteristics of these substances during chlorination disinfection and the varying species-specific toxicities of their combinations remain unclear. Here, Daphnia magna and zebrafish were exposed to benzophenone-3 (BP-3) and humic acid (HA) before and after chlorination disinfection. The results from chemical indicators showed that chlorination treatment decreased UV254 values and changed the intensity of parallel factors in three-dimensional fluorescence. Based on chemical analysis, the chlorine concentration and chlorination time for the toxicity experiments were set at 5 mg/L and 6 h, respectively. Exposure to HA and BP-3 before and after chlorination decreased the heart rate (by 1.37-28.12 %) in both species. However, species-specific responses, including survival rate, swimming distance, and expression of genes related to neurodevelopment, growth, and oxidative stress, were induced by chlorination. Chlorination reduced the impact of HA exposure but worsened the effects of HA and BP-3 co-exposure on D. magna. However, in zebrafish, the toxic effects intensified in most of the exposure groups after chlorination. Correlation analysis showed that the parallel factors of three-dimensional fluorescence were correlated with toxic effects on zebrafish, whereas UV254 was more significantly correlated with toxic effects on D. magna. This study provides insights into the combined toxicity of UV filters and dissolved organic matter in different aquatic organisms during chlorination, which is useful for risk control and optimization of the chlorination process., 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.)

The fast development of the waste incineration industry requires deeper insights into heating surface corrosion behavior at higher operating parameters with complex corrosion sources. This research investigates the corrosion behaviors of three types of plates, namely SA210-C, TP310, and 12CrMoV, when subjected to simulated flue gas and fly ash deposition simultaneously at temperatures ranging from 500℃ to 620℃. The results indicate that the weight loss due to coupling corrosion was 2.5 to 84.5 times higher than that of gas-phase corrosion under the same operating conditions. Among the three stainless-steels, TP310 demonstrates superior corrosion resistance. It is worth noting that, under the gas-solid coupling corrosion conditions, we observed a distinct two-layer structure of corrosion products. Despite the fly ash simulants detaching over time, the two-layer structure remained unchanged. Based on the theory of eutectic molten salt formation, we propose that alkali metal chlorides only initiate the formation of the molten layer in the initial stage of corrosion. Furthermore, we offer additional suggestions for the mechanism of sustaining the molten layer in the absence of alkali metal chlorides., 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.)

Chalcones, secondary plant metabolites, exhibit various biological properties. The introduction of a chlorine and a glucosyl substituent to the chalcone could enhance its bioactivity and bioavailability. Such compounds can be obtained through a combination of chemical and biotechnological methods. Therefore, 4-chloro-2'-hydroxychalcone and 5'-chloro-2'-hydroxychalcone were obtained by synthesis and then glycosylated in two filamentous fungi strains cultures, i.e., Isaria fumosorosea KCH J2 and Beauveria bassiana KCH J1.5. The main site of the glycosylation of both compounds by I. fumosorosea KCH J2 was C-2' and C-3 when the second strain was utilized. The pharmacokinetics of these compounds were predicted using chemoinformatics tools. Furthermore, antimicrobial activity tests were performed. Compounds significantly inhibited the growth of the bacteria strains Escherichia coli 10536, Staphylococcus aureus DSM 799, and yeast Candida albicans DSM 1386. Nevertheless, the bacterial strain Pseudomonas aeruginosa DSM 939 exhibited significant resistance to their effects. The growth of lactic acid bacteria strain Lactococcus acidophilus KBiMZ 01 bacteria was moderately inhibited, but strains Lactococcus rhamnosus GG and Streptococcus thermophilus KBM-1 were completely inhibited. In summary, chalcones substituted with a chlorine demonstrated greater efficacy in inhibiting the microbial strains under examination compared to 2'-hydroxychalcone, while aglycones and their glycosides exhibited similar effectiveness.

Ultrafiltration (UF) is widely used in drinking water plants; however, membrane fouling is unavoidable. Natural organic matter (NOM) is commonly considered as an important pollutant that causes membrane fouling. Herein, we proposed VUV/H 2 O 2 as a UF pretreatment and used UV/H 2 O 2 for comparison. Compared to UV/H 2 O 2 , the VUV/H 2 O 2 system presented superior NOM removal. In the VUV/H 2 O 2 system, the steady-state concentration of HO• was approximately twice that in the UV/H 2 O 2 system, which was ascribed to the promoting effect of the 185 nm photons. Specifically, 185 nm photons promoted HO• generation by decomposing mainly H 2 O at a low H 2 O 2 dose or by decomposing mainly H 2 O 2 at a high H 2 O 2 dose. The VUV/H 2 O 2 pretreatment also demonstrated better membrane fouling mitigation performance than did UV/H 2 O 2 . An increase in the H 2 O 2 dose promoted HO• generation, thereby enhancing the performance of NOM degradation and membrane fouling alleviation and shifting the major membrane fouling mechanism from cake filtration to standard blocking. The VUV/H 2 O 2 (0.60 mM) pretreatment effectively reduced disinfection byproducts (DBPs) formation during chlorine disinfection. Additionally, the oxidant H 2 O 2 affected the membrane surface morphology and performance but had no evident effect on the mechanical properties. In actual water treatment, the VUV/H 2 O 2 pretreatment exhibited better performance than the UV/H 2 O 2 pretreatment in easing membrane fouling, ameliorating water quality, and reducing DBPs formation and acute toxicity., 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.)

Food-waste biochar holds significant potential as a bio-solid fuel for achieving carbon neutrality; however, its high content of sodium (Na), potassium (K), calcium (Ca), chlorine (Cl), and nitrogen, inhibits its potential use. This study explored the effects of post-treatment with ascorbic, acetic, citric, and iminodiacetic acids on the properties of food-waste biochar and volatile ionic substances to establish a foundation for assessing both the environmental impact and practical use of food waste. Post-treatment with organic acids achieved 92% Cl-removal efficiency and induced deformation of the functional groups of food-waste biochar surfaces, leading to the re-adsorption of alkali and alkaline earth metals. This re-adsorption of alkali metal ions showed a distinct correlation with NO x mitigation. The amount of re-adsorbed Na and K varied based on the types of organic acids, resulting in different NO x emission reduction effects. Iminodiacetic acid was particularly effective in alleviating Ca and PO 4 volatilization, whereas citric acid exhibited the highest Ca elution performance, and the Ca-contained leachate is a potential source of CO 2 storage through indirect mineral carbonation. Acetic acid is the most feasible alternative, considering both economic and environmental aspects. The findings suggest that the post-treatment of food-waste biochar effectively mitigates air pollutants during combustion and is beneficial for sustainable biosolid fuel production and bio-waste management., 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.)

In this research, we employed a synergistic three-dimensional (3D)-electrode technology in combination with a photocatalytic method to effectively treat wastewater containing chlorine derived from sulfonated phenolic resin (SMP). To modulate the band gap of single ZnO through semiconductor compounding, we successfully synthesized a ZnO/pyrolusite composite particle electrode on the surface of a pyrolusite particle electrode via a hydrothermal method. By incorporating MnO 2 into pyrolusite, the ZnO band gap was modified, leading to a reduction in bandwidth of approximately 1.21 eV compared to pristine ZnO. Consequently, the light absorption range of the material was significantly broadened. Through the synergistic effect of photocatalysis, we achieved an impressive 96.45% removal rate of chemical oxygen demand (COD) in SMP wastewater, which effectively enhanced the photocatalytic performance of the material. Furthermore, our quenching experimental study confirmed the involvement of active chlorine species (ACl: Cl 2 , HClO, and ClO - ), OH, h + , and O 2- in the degradation process of SMP within the photocatalytic system constructed by the ZnO/pyrolusite composite particle electrode. The relative contributions were ranked as follows: ACl > h +  > ·OH > ·O 2- .

Dechlorination of waste PVC (WPVC) by hydrothermal treatment (HTT) is a potential technology for upcycling WPVC in order to create non-toxic products. Literature suggests that acids can improve the HTT process, however, acid is expensive and also results in wastewater. Instead, the acidic process fluid (PF) of hydrothermal carbonization (HTC) of orange peel was utilized in this study to enhance the dechlorination of WPVC during HTT. Acidic HTT (AHTT) experiments were carried out utilizing a batch reactor at 300-350 °C, and 0.25-4 h. The finding demonstrated that the dechlorination efficiency (DE) is high, which indicates AHTT can considerably eliminate chlorine from WPVC and relocate to the aqueous phase. The maximum DE of 97.57 wt% was obtained at 350 °C and 1 h. The AHTT temperature had a considerable impact on the WPVC conversion since the solid yield decreases from 56.88 % at 300 °C to 49.85 % at 350 °C. Moreover, AHTT char and crude oil contain low chloride and considerably more C and H, leading to a considerably higher heating value (HHV). The HHV increased from 23.48 to 33.07 MJ/kg when the AHTT time was raised from 0.25 to 4 h at 350 °C, indicating that the AHTT time has a beneficial effect on the HHV. The majority fraction of crude oil evaporated in the boiling range of lighter fuels include gasoline, kerosene, and diesel (57.58-83.09 wt%). Furthermore, when the AHTT temperature was raised from 300 to 350 °C at 1 h, the HHV of crude oils increased from 26.11 to 33.84 MJ/kg. Crude oils derived from AHTT primarily consisted of phenolic (50.47-75.39 wt%), ketone (20.1-36.34 wt%), and hydrocarbon (1.08-7.93 wt%) constituents. In summary, the results indicated that AHTT is a method for upcycling WPVC to clean fuel., 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 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]

In comparison to pure water, seawater is widely accepted as an unlimited resource. The direct seawater splitting is economical and eco-friendly, but the key challenges in seawater, especially the chlorine-related competing reactions at the anode, seriously hamper its practical application. The development of earth-abundant electrocatalysts toward direct seawater splitting has emerged as a promising strategy. Highly efficient electrocatalysts with improved selectivity and stability are of significance in preventing the interference of side reactions and resisting various impurities. This review first discusses the macroscopic understanding of direct seawater electrolysis and then focuses on the strategies for rational design of electrocatalysts toward direct seawater splitting. The perspectives of improved electrocatalysts to solve emerging challenges and further development of direct seawater splitting are also provided. [ABSTRACT FROM AUTHOR]

The coupling of thermal remediation with microbial reductive dechlorination (MRD) has shown promising potential for the cleanup of chlorinated solvent contaminated sites. In this study, thermal treatment and bioaugmentation were applied in series, where prior higher thermal remediation temperature led to improved TCE dechlorination performance with both better organohalide-respiring bacteria (OHRB) colonization and electron donor availability. The 60 °C was found to be a key temperature point where the promotion effect became obvious. Amplicon sequencing and co-occurrence network analysis demonstrated that temperature was a more dominating factor than bioaugmentation that impacted microbial community structure. Higher temperature of prior thermal treatment resulted in the decrease of richness, diversity of indigenous microbial communities, and simplified the network structure, which benefited the build-up of newcoming microorganisms during bioaugmentation. Thus, the abundance of Desulfitobacterium increased from 0.11 % (25 °C) to 3.10 % (90 °C). Meanwhile, released volatile fatty acids (VFAs) during thermal remediation functioned as electron donors and boosted MRD. Our results provided temperature-specific information on synergistic effect of sequential thermal remediation and bioaugmentation, which contributed to better implementation of the coupled technologies in chloroethene-impacted sites., 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.)

Disinfection efficiency and disinfection byproduct (DBP) formation are two important aspects deserving careful consideration when evaluating different disinfection protocols. However, most of the previous studies on the selection of disinfection methods by comparing DBP formation were carried out under the same initial/residual dose and contact time of different disinfectants, and such a practice may cause overdose or underdose of a certain disinfectant, leading to the inaccurate evaluation of disinfection. In this study, a comprehensive and quantitative comparison of chlorine (Cl 2 ) and chlorine dioxide (ClO 2 ) disinfection was conducted with regard to their DBP formation under equal disinfection efficiency. The microbial inactivation models as well as the Cl 2 and ClO 2 demand models were developed. On such basis, the integral CT (ICT) values were determined and used as a bridge to connect disinfection efficiency and DBP formation. For 3-log 10 and 4-log 10 reductions of Pseudomonas aeruginosa, ClO 2 had 1.5 and 5.8 times higher inactivation ability than Cl 2 , respectively. In the premise of equal disinfection efficiency (i.e., the ICT ratios of Cl 2 to ClO 2 = 1.5 and 5.8), the levels of total organic chlorine, total organic bromine, and total organic halogen formed in the Cl 2 disinfection were significantly higher than those formed in the ClO 2 disinfection. Among the 35 target aliphatic DBPs, trihalomethanes (THMs) and haloacetic acids (HAAs) were the dominant species formed in both Cl 2 and ClO 2 disinfection. The total THM levels formed in Cl 2 disinfection were 14.6 and 30.3 times higher than those in ClO 2 disinfection, respectively. The total HAA levels formed in Cl 2 disinfection were 3.5 and 5.4 times higher than those in ClO 2 disinfection, respectively. Formation of the target 48 aromatic DBPs was much favored in Cl 2 disinfection than that in ClO 2 disinfection, and the formation levels was dominated by contact time. This study demonstrated that ClO 2 had significant advantages over Cl 2 , especially at higher microorganism inactivation and lower DBP formation requirements., 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.)

Algal blooms have become a significant challenge in water treatment all over the world. In chlorination of drinking water, algal organic matter (AOM) leads to the formation of organic chloramines. The objectives of this review are to comprehensively summarize and discuss the up-to-date researches on AOM-derived organic chloramines and their chemical activities and toxicity, thereby drawing attention to the potentially chemical and hygienic risks of organic chloramines. The predominant algal species in water sources varied with location and season. AOM from cyanobacteria, green algae, and diatoms are composed of diverse composition. AOM-derived amino acids take a low portion of the precursors of organic chloramines. Both experimental kinetic data and quantum chemical calculation demonstrate the preferential formation of organic chloramines in the chlorination of model compounds (amino acids and peptides). Organic chloramines are persistent in water and can transform into dichloro- and trichloro-organic chloramines, unknown low-molecular-weight organic chloramines, and nitrogenous disinfection byproducts with the excess of free chlorine. The active chlorine (Cl + ) in organic chloramines can lead to the formation of chlorinated phenolic compounds. Organic chloramines influence the generation and species of radicals and subsequent products in UV disinfection. Theoretical predictions and toxicological tests suggest that organic chloramines may cause oxidative or toxic pressure to bacteria or cells. Overall, organic chloramines, as one group of high-molecular-weight disinfection byproducts, have relatively long lifetimes, moderate chemical activities, and high hygienic risks to the public. Future perspectives of organic chloramines are suggested in terms of quantitative detection methods, the precursors from various predominant algal species, chemical activities of organic chloramines, and toxicity/impact., 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.)

Metal ions are liable to form metal-dissolved organic matter [dissolved organic matter (DOM)] complexes, changing the chemistry and chlorine reactivity of DOM. Herein, the impacts of iron and zinc ions (Fe 3+ and Zn 2+ ) on the formation of unknown chlorinated disinfection byproducts (Cl-DBPs) were investigated in a chlorination system. Fe 3+ preferentially complexed with hydroxyl and carboxyl functional groups, while Zn 2+ favored the amine functional groups in DOM. As a consequence, electron-rich reaction centers were created by the C-O-metal bonding bridge, which facilitated the electrophilic attack of α-C in metal-DOM complexes. Size-reactivity continuum networks were constructed in the chlorination system, revealing that highly aromatic small molecules were generated during the oxidation and decarbonization of metal-DOM complexes. Molecular transformation related to C-R (R represents complex sites) loss was promoted via metal complexation, including decarboxylation and deamination. Consequently, complexation with Fe 3+ and Zn 2+ promoted hydroxylation by the C-O-metal bonding bridge, thereby increasing the abundances of unknown polychlorinated Cl-DBPs by 9.6 and 14.2%, respectively. The study provides new insights into the regulation of DOM chemistry and chlorine reactivity by metal ions in chlorination systems, emphasizing that metals increase the potential health risks of drinking water and more scientific control standards for metals are needed.

Chlorination on microplastic (MP) biofilms was comprehensively investigated with respect to disinfection efficiency, morphology, and core microbiome. The experiments were performed under various conditions: i) MP particles; polypropylene (PP) and polystyrene (PS), ii) MP biofilms; Escherichia coli for single-species and river water microorganisms for multiple-species, iii) different chlorine concentrations, and iv) different chlorine exposure periods. As a result, chlorination effectively inactivated the MP biofilm microorganisms. The disinfection efficiency increased with increasing the free chlorination concentration and exposure periods for both single- and multiple-species MP biofilms. The multiple-species MP biofilms were inactivated 1.3-6.0 times less than single-species MP biofilms. In addition, the PP-MP biofilms were more vulnerable to chlorination than the PS-MP biofilms. Morphology analysis verified that chlorination detached most MP biofilms, while a small part still remained. Interestingly, chlorination strongly changed the biofilm microbiome on MPs; the relative abundance of some microbes increased after the chlorination, suggesting they could be regarded as chlorine-resistant bacteria. Some potential pathogens were also remained on the MP particles after the chlorination. Notably, chlorination was effective in inactivating the MP biofilms. Further research should be performed to evaluate the impacts of residual MP biofilms on the environment., Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Kyungjin Cho reports financial support was provided by National Research Foundation of Korea (NRF). 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 B.V. All rights reserved.)

The kinetic study of the gas-phase reactions of hydroxyl (OH) radicals and chlorine (Cl) atoms with CF 3 CHFCF 2 OCH 3 (HFE-356mec3) and CHF 2 CHFOCF 3 (HFE-236ea1) was performed by the pulsed laser photolysis/laser-induced fluorescence technique and a relative method by using Fourier Transform infrared (FTIR) spectroscopy as detection technique. The temperature dependences of the OH-rate coefficients (k OH (T) in cm 3 s -1 ) between 263 and 353 K are well described by the following expressions: 9.93 × 10 -13 exp{-(988 ± 35)/T}for HFE-356mec3 and 4.75 × 10 -13 exp{-(1285 ± 22)/T} for HFE-236ea1. Under NO x -free conditions, the rate coefficients k Cl at 298 K and 1013 mbar (760 Torr) of air were determined to be (2.30 ± 1.08) × 10 -13 cm 3 s -1 and (1.19 ± 0.10) × 10 -15 cm 3 s -1 , for HFE-356mec3 and HFE-236ea1, respectively. Additionally, the relative kinetic study of the Cl + CH 2 ClCHCl 2 reaction was investigated at 298 K, as it was used as a reference reaction in the kinetic study of the Cl-reaction with HFE-356mec3 and discrepant rate coefficients were found in the literature. The global atmospheric lifetimes were estimated relative to CH 3 CCl 3 at the tropospheric mean temperature (272 K) as 1.4 and 8.6 years for HFE-356mec3 and HFE-236ea1, respectively. These values combined with the radiative efficiencies for HFE-356mec3 and HFE-236ea1 derived from the measured IR absorption cross sections (0.27 and 0.41 W m -2 ppv -1 ) yield global warming potentials at a 100-yrs time horizon of 143 and 1473, respectively. The contribution of HFE-356mec3 and HFE-236ea1 to global warming of the atmosphere would be large if they become widespread increasing their atmospheric concentration., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Trace iron ions (Fe(III)) are commonly found in water and wastewater, where free chlorine is very likely to coexist with Fe(III) affecting the disinfectant's stability and N-DBPs' fate during UV/chlorine disinfection, and yet current understanding of these mechanisms is limited. This study investigates the effects of Fe(III) on the formation and toxicity alteration of halonitromethanes (HNMs), dichloroacetonitrile (DCAN), and dichloroacetamide (DCAcAm) from polyethyleneimine (PEI) during UV/chlorine disinfection. Results reveal that the maxima concentrations of HNMs, DCAN, and DCAcAm during UV/chlorine disinfection with additional Fe(III) were 1.39, 1.38, and 1.29 times higher than those without additional Fe(III), instead of being similar to those of Fe(III) inhibited the formation of HNMs, DCAN and DCAcAm during chlorination disinfection. Meanwhile, higher Fe(III) concentration, acidic pH, and higher chlorine dose were more favorable for forming HNMs, DCAN, and DCAcAm during UV/chlorine disinfection, which were highly dependent on the involvement of HO· and Cl·. Fe(III) in the aquatic environment partially hydrolyzed to the photoactive Fe(III)‑hydroxyl complexes Fe(OH) 2+ and [Fe(H 2 O) 6 ] 3+ , which undergone UV photoactivation and coupling reactions with HOCl to achieve effective Fe(III)/Fe(II) interconversion, a process that facilitated the sustainable production of HO·. Extensive product analysis and comparison verified that the HO· production enhanced by the Fe(III)/Fe(II) internal cycle played a primary role in increasing HNMs, DCAN, and DCAcAm productions during UV/chlorine disinfection. Note that the incorporation of Fe(III) increased the cytotoxicity and genotoxicity of HNMs, DCAN, and DCAcAm formed during UV/chlorine disinfection, and yet Fe(III) did not have a significant effect on the acute toxicity of water samples before, during, and after UV/chlorine disinfection. The new findings broaden the knowledge of Fe(III) affecting HNMs, DCAN, and DCAcAm formation and toxicity alteration during UV/chlorine disinfection., 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.)

The study investigates the effect of the presence of a chlorine atom in the 2'-hydroxychalcone molecule on its interaction with model lipid membranes, in order to discern its potential pharmacological activity. Five chlorine derivatives of 2'-hydroxychalcone were synthesized and evaluated against liposomes composed of POPC and enriched with cationic (DOTAP) or anionic (POPG) lipids. The physicochemical properties of the compounds were initially simulated using SwissAdame software, revealing high lipophilicity (ilogP values: 2.79-2.90). The dynamic light scattering analysis of liposomes showed that chloro chalcones induce minor changes in the diameter of liposomes of different surface charges. Fluorescence quenching assays with a TMA-DPH probe demonstrated the strong ability of the compounds to interact with the lipid bilayer, with varying quenching capacities based on chlorine atom position. FTIR studies indicated alterations in carbonyl, phosphate, and choline groups, suggesting a transition area localization rather than deep penetration into the hydrocarbon chains. Additionally, dipole potential reduction was observed in POPC and POPC-POPG membranes, particularly pronounced by derivatives with a chlorine atom in the B ring. Antibacterial and antibiofilm assays revealed enhanced activity of derivatives with a chlorine atom compared to 2'-hydroxychalcone, especially against Gram-positive bacteria. The MIC and MBIC 50 values showed increased efficacy in the presence of chlorine with 3'-5'-dichloro-2'-hydroxychalcone demonstrating optimal antimicrobial and antibiofilm activity. Furthermore, antiproliferative assays against breast cancer cell lines indicated higher activity of B-ring chlorine derivatives, particularly against MDA-MB-231 cells. In general, the presence of a chlorine atom in 2'-hydroxychalcone improves its pharmacological potential, with derivatives showing improved antimicrobial, antibiofilm, and antiproliferative activities, especially against aggressive breast cancer cell lines. These findings underscore the importance of molecular structure in modulating biological activity and highlight chalcones with a chlorine as promising candidates for further drug development 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 Elsevier B.V. All rights reserved.)

Temperature-dependent kinetics of OH radical and Cl atom-initiated reaction of an important halogenated alkene, 2,3-Dichloropropene (23DCP), were investigated using absolute and relative methods over 278-363 K. Pulsed laser photolysis - laser induced fluorescence technique and relative rate method using gas chromatography with flame ionization detector were employed for studying the kinetics of 23DCP with OH radical and Cl atom, respectively. The obtained Arrhenius expressions were k OH (expt)=(4.08 ± 1.63) × 10 -13 exp{(1043 ± 124)/T} cm 3 molecule -1 s -1 and k Cl (expt)=(1.54 ± 0.24) × 10 -11 exp{(705 ± 48)/T} cm 3 molecule -1 s -1 . Computational calculations were conducted to validate our experimental kinetic results and provide new insights into the importance of a particular pathway among all based on thermodynamic parameters. The addition of OH/Cl to the terminal carbon of the double bond present in 23DCP proved to be the predominant pathway across the selected temperature range for the present study (200-400 K). The degradation mechanism of these reactions was proposed by analyzing the products with the aid of gas chromatography with mass spectrometry. Calculating various atmospheric implication parameters can help to understand how the release of 23DCP may affect the troposphere., Competing Interests: Declaration of competing interest The authors declare that there are no significant competing financial or personal interests that might have influenced the work described in this manuscript., (Copyright © 2024. Published by Elsevier Ltd.)

As global effects of water scarcity raise concerns and environmental regulations evolve, contemporary wastewater treatment plants (WWTPs) face the challenge of effectively removing a diverse range of contaminants of emerging concern (CECs) from municipal effluents. This study focuses on the assessment of advanced oxidation processes (AOPs), specifically UV-C/H 2 O 2 and UV-C/Chlorine, for the removal of 14 target CECs in municipal secondary effluent (MSE, spiked with 10 μg L -1 of each CEC) or in the subsequent MSE nanofiltration retentate (NF R , no spiking). Phototreatments were carried out in continuous mode operation, with a hydraulic retention time of 3.4 min, using a tube-in-tube membrane photoreactor. For both wastewater matrices, UV-C photolysis (3.3 kJ L -1 ) exhibited high efficacy in removing CECs susceptible to photolysis, although lower treatment performance was observed for NF R . In MSE, adding 10 mg L -1 of H 2 O 2 or Cl 2 enhanced treatment efficiency, with UV-C/H 2 O 2 outperforming UV-C/Chlorine. Both UV-C/AOPs eliminated the chronic toxicity of MSE toward Chlorella vulgaris. In the NF R , not only was the degradation of target CECs diminished, but chronic toxicity to C. vulgaris persisted after both UV-C/AOPs, with UV-C/Chlorine increasing toxicity due to potential toxic by-products. Nanofiltration permeate (NF P ) exhibited low CECs and microbial content. A single chlorine addition effectively controlled Escherichia coli regrowth for 3 days, proving NF P potential for safe reuse in crop irrigation (<1 CFU/100 mL for E. coli; <1 mg L -1 for free chlorine). These findings provide valuable insights into the applications and limitations of UV-C/H 2 O 2 and UV-C/Chlorine for distinct wastewater treatment scenarios., 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 Ltd.. All rights reserved.)

Elevated levels of atmospheric molecular chlorine (Cl 2 ) have been observed during the daytime in recent field studies in China but could not be explained by the current chlorine chemistry mechanisms in models. Here, we propose a Cl 2 formation mechanism initiated by aerosol iron photochemistry to explain daytime Cl 2 formation. We implement this mechanism into the GEOS-Chem chemical transport model and investigate its impacts on the atmospheric composition in wintertime North China where high levels of Cl 2 as well as aerosol chloride and iron were observed. The new mechanism accounts for more than 90% of surface air Cl 2 production in North China and consequently increases the surface air Cl 2 abundances by an order of magnitude, improving the model's agreement with observed Cl 2 . The presence of high Cl 2 significantly alters the oxidative capacity of the atmosphere, with a factor of 20-40 increase in the chlorine radical concentration and a 20-40% increase in the hydroxyl radical concentration in regions with high aerosol chloride and iron loadings. This results in an increase in surface air ozone by about 10%. This new Cl 2 formation mechanism will improve the model simulation capability for reactive chlorine abundances in the regions with high emissions of chlorine and iron.

Shaerhu (SEH) coal is abundant in Xinjiang, China. The utilization of SEH suffers from severe ash deposition, slagging, and fouling problems due to its high-chlorine-alkaline characteristics. The co-combustion of high-alkaline coal and other type coals containing high Si/Al oxides has been proven to be a simple and effective method that will alleviate ash-related problems, but the risk of heavy metals (HMs) contamination in this process is nonnegligible. Hence, the volatilization rates and chemical speciation of Pb, Cu, and Zn in co-combusting SEH and a high Si/Al oxides coal, i.e., Yuanbaoshan (YBS) coal were investigated in this study. The results showed that the addition of SEH increased the volatilization rates of Pb, Cu, and Zn during the co-combustion at 800°C from 23.70%, 23.97%, and 34.98% to 82.31%, 30.01%, and 44.03%, respectively, and promoted the extractable state of Cu and Zn. In addition, the interaction between SEH and YBS inhibited the formation of the Pb residue state. SEM-EDS mapping results showed that compared to Zn and Cu, the signal intensity of Pb was extremely weak in regions where some of the Si and Al signal distributions overlap. The DFT results indicated that the O atoms of the metakaolin (Al 2 O 3 ⋅2SiO 2 ) (001) surface were better bound to the Zn and Cu than Pb atoms after adsorption of the chlorinated HMs. These results contribute to a better understanding of the effects of high-alkaline coal blending combustion on Pb, Cu, and Zn migration and transformation., Competing Interests: Declaration of Competing Interests 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 © 2023. Published by Elsevier B.V.)