Search

Chlorinated and fluorinated nitrophenols (HNCs) are widely used in agriculture and industry, with a global market valued at USD $25 billion, one which is expected to grow by 5% by 2030. However, these compounds pose significant environmental risks; they are classified as toxic by the International Agency for Research on Cancer (IARC). Existing treatment methods include advanced oxidation, adsorption, and bioremediation, though to date, there has been only limited research on fungal remediation of these halogenated pollutants. This study aims to explore a sustainable approach by using fungi's potential to degrade HNCs in minimal media. Ten fungi were selected through literature screening; Caldariomyces fumago and Curvularia sp. were highly effective, degrading over 50% of 2-chloro-4-nitrophenol (2C4NP) and 80% of 5-fluoro-2-nitrophenol (5F2NP) within 24 and 48 h, respectively. Additionally, five strains showed degradation potential for fluorinated compounds. Further studies revealed C. fumago could degrade up to 1 mM of chlorinated compounds and 12 mM of fluorinated compounds, far exceeding any known environmental concentrations of HNCs; importantly, ecotoxicology tests demonstrated reductions in toxicity of 77% and 85%, respectively. This work highlights fungi's underexplored ability to degrade toxic HNCs, offering a sustainable mycoremediation strategy and positioning mycology as a critical tool for future environmental remediation efforts. [ABSTRACT FROM AUTHOR]

Covalent organic frameworks (COFs) have garnered significant interest within the scientific community due to their distinctive ability to act as organic semiconductors responsive to visible light. This unique attribute makes them up-and-coming candidates for facilitating photocatalytic organic reactions. Herein, two donor–acceptor COFs, TPE-BSD-COF and TPE-BD-COF, have been designed and synthesized by incorporating electron-rich tetraphenylethylene and electron-deficient benzoselenadiazole and benzothiadiazole units into the framework through a Schiff-base polycondensation reaction. Both COFs exhibit exceptional crystallinity and enduring porosity. TPE-BSD-COF and TPE-BD-COF exhibit broad light absorption capabilities, a narrow optical band gap, and low electrochemical impedance spectrum (EIS) levels, indicating that the two COFs are effective heterogeneous photocatalysts for the reductive dehalogenation of phenacyl bromide derivatives under blue LED irradiation. A high photocatalytic yield of 98% and 95% was achieved by TPE-BSD-COF and TPE-BD-COF catalysts, respectively, within only one hour. [ABSTRACT FROM AUTHOR]

Mixed plastic packaging waste sorting residue (MPO323) was treated by thermal pyrolysis to utilize pyrolysis oil and char. The pyrolysis oil was found to contain aromatic and aliphatic hydrocarbons. The chlorine and bromine contents were as high as 40,000 mg/kg and 200 mg/kg, respectively. Additionally, other elements like sulfur, phosphorous, iron, aluminum, and lead were detected, which can be interpreted as impurities relating to the utilization of oils for chemical recycling. The pyrolysis char showed high contents of potentially active species like silicon, calcium, aluminum, iron, and others. To enhance the content of aromatic hydrocarbons and to reduce the level of contaminants, pyrolysis oil was reformed with the corresponding pyrolysis char to act as an active material in a fixed bed. The temperature of the reactor and the flow rate of the pyrolysis oil feed were varied to gain insights on the cracking and reforming reactions, as well as on performance with regard to decontamination. [ABSTRACT FROM AUTHOR]

Fluorescent lead halide perovskite quantum dots (LH PQDs) micropatterns hold great potential for photonic applications. However, current photolithography for LH PQDs micropatterning is hindered by their incompatibility with traditional photolithography methods, which involve development processes using numerous solvents and exhibit poor stability due to the ionic characteristics of LH PQDs. Herein, a direct in situ photolithography to fabricate CsPbBr3 PQDs micropatterns based on ultraviolet‐C light‐driven debromination is developed. Using this approach, fluorescent CsPbBr3 PQDs micropatterns with high theoretical information storage capacity (up to 10750205) can be achieved in a single step, without the need for tedious development processes. Furthermore, the fabricated CsPbBr3 PQDs micropatterns show high stability, remaining undamaged even after immersion in water for 6 months. The combination of excellent optical properties, development‐free process, high stability, and low cost makes the in situ photolithography strategy very promising for patterning LH PQDs toward photonic integrations. [ABSTRACT FROM AUTHOR]

Humic electron mediators can facilitate the reductive dehalogenation of organohalogenated compounds by accelerating electron transfer. To investigate the effect of humic electron mediators on the microbial anaerobic reductive dechlorination of Polychlorinated biphenyls (PCBs), three types of humic electron mediators, humin (HM), humic acid (HA), and anthraquinone-2,6-disulfonic acid (AQDS, HA analogs), were added to PCB dechlorination cultures enriched from different sources in terrestrial and marine environments (T and M cultures). The results showed that meta- and para-site dechlorination occurred in the M culture, while only meta-site dechlorination occurred in the T culture. The dechlorination process N and the dechlorination process H or H' are presented in both cultures. HM enhanced PCB dechlorination metabolic activity in both cultures mainly by promoting meta-site dechlorination. HA showed a weak promoting effect on the M culture by promoting para-chlorine removal but inhibited the dechlorination metabolism of the terrestrial-origin culture, inhibiting meta-chlorine removal. AQDS showed inhibitory effects on both cultures by inhibiting the microbial removal of meta-chlorine. High-throughput sequencing and qPCR results suggest that HM is not a carbon source for the potential dechlorinating metabolism of Dehalococcoides but may promote reductive dechlorination by changing the community structure, and AQDS may inhibit anaerobic reductive dechlorination of PCBs by inhibiting the growth of Dehalococcoides. This study provides insights into the mechanism of enhancing PCB microbial dechlorination mediated by humic substances and plays a significant role in extending the application prospects of PCBs bioremediation technology. [ABSTRACT FROM AUTHOR]

Halogenated organic compounds are persistent pollutants that pose a serious threat to human health and the safety of ecosystems. Cobamides are essential cofactors for reductive dehalogenases (RDase) in organohalide-respiring bacteria (OHRB), which catalyze the dehalogenation process. This review systematically summarizes the impact of cobamides on organohalide respiration. The catalytic processes of cobamide in dehalogenation processes are also discussed. Additionally, we examine OHRB, which cannot synthesize cobamide and must obtain it from the environment through a salvage pathway; the co-culture with cobamide producer is more beneficial and possible. This review aims to help readers better understand the importance and function of cobamides in reductive dehalogenation. The presented information can aid in the development of bioremediation strategies. [ABSTRACT FROM AUTHOR]

To assess the performance of hazardous waste sites remediation technologies like in situ chemical oxidation (ISCO) with persulfate (S2O82−) researchers must periodically measure concentrations of target contaminants. Due to the presence of relatively high concentrations of the residual oxidant expected in many samples, the standard analytical method requires the addition of a relatively high concentration of ascorbic acid to prevent the oxidation process from continuing after sample collection. We discovered that addition of ascorbic acid quencher results in a radical chain reaction that transforms two common halogenated solvents (i.e., tetrachloroethene and hexachloroethane). To avoid the artifact associated with the radical chain reaction, a small quantity of n-hexane can be added to aqueous samples to extract target compounds and protect them from the radical chain reaction initiated by addition of the quencher. We recommend the use of this alternative sample preservation method whenever high concentrations of residual S2O82− are expected to be present in water samples that are contaminated with halogenated solvents.

Despite the extensive application of advanced oxidation processes (AOPs) in water treatment, the efficiency of AOPs in eliminating various emerging contaminants such as halogenated antibiotics is constrained by a number of factors. Halogen moieties exhibit strong resistance to oxidative radicals, affecting the dehalogenation and detoxification efficiencies. To address these limitations of AOPs, advanced reduction processes (ARPs) have been proposed. Herein, a novel nucleophilic reductant—namely, the carbon dioxide radical anion (CO2·−)—is introduced for the simultaneous degradation, dehalogenation, and detoxification of florfenicol (FF), a typical halogenated antibiotic. The results demonstrate that FF is completely eliminated by CO2·−, with approximately 100% of Cl− and 46% of F− released after 120 min of treatment. Simultaneous detoxification is observed, which exhibits a linear response to the release of free inorganic halogen ions (R2 = 0.97, p 75%) in degrading a series of halogenated antibiotics, including chloramphenicol (CAP), thiamphenicol (THA), diclofenac (DLF), triclosan (TCS), and ciprofloxacin (CIP). The system shows high tolerance to the pH of the solution and the presence of natural water constituents, and demonstrates an excellent degradation performance in actual groundwater, indicating the strong application potential of CO2·−-based ARPs in real life. Overall, this study elucidates the feasibility of CO2·− for the simultaneous degradation, dehalogenation, and detoxification of halogenated antibiotics and provides a promising method for their regulation during water or wastewater treatment.

Catalytic defunctionalization of complex molecules has attracted significant attention in organic synthesis. This reaction enables common functional groups to serve as "traceless handles" for the new bond construction. In this mini-review, we have summarized the latest advances, methodologies and mechanistic insights into the selective cleavage of C-C and C-X bonds catalysed by cobalt complexes, shedding light on their increasing importance in modern chemical synthesis. The content of this review is categorized according to the type of functional group being removed from molecules. [ABSTRACT FROM AUTHOR]

Biological regulation often depends on reversible reactions such as phosphorylation, acylation, methylation, and glycosylation, but rarely halogenation. A notable exception is the iodination and deiodination of thyroid hormones. Here, we report detection of bromotyrosine and its subsequent debromination during Drosophila spermatogenesis. Bromotyrosine is not evident when Drosophila express a native flavin-dependent dehalogenase that is homologous to the enzyme responsible for iodide salvage from iodotyrosine in mammals. Deletion or suppression of the dehalogenase-encoding condet (cdt) gene in Drosophila allows bromotyrosine to accumulate with no detectable chloro-or iodotyrosine. The presence of bromotyrosine in the cdt mutant males disrupts sperm individualization and results in decreased fertility. Transgenic expression of the cdt gene in late-staged germ cells rescues this defect and enhances tolerance of male flies to bromotyrosine. These results are consistent with reversible halogenation affecting Drosophila spermatogenesis in a process that had previously eluded metabolomic, proteomic, and genomic analyses. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Electrochemistry is the property of Journal of Electrochemistry Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Cadmium sulfide (CdS)-based photocatalysts are prepared following a hydrothermal procedure (with CdCl2 and thiourea as precursors). The HydroThermal material annealed (CdS-HTa) is crystalline with a band gap of 2.31 eV. Photoelectrochemical investigation indicates a very reducing photo-potential of −0.9 V, which is very similar to that of commercial CdS. CdS-HTa, albeit having similar reducing properties, is more active than commercial CdS in the reductive dehalogenation of 2,2-dichloropropionic acid (dalapon) to propionic acid. Spectroscopic, electro-, and photoelectrochemical investigation show that photocatalytic properties of CdS are correlated to its electronic structure. The reductive dehalogenation of dalapon has a double significance: on one hand, it represents a demanding reductive process for a photocatalyst, and on the other hand, it has a peculiar interest in water treatment because dalapon can be considered a representative molecule of persistent organic pollutants and is one of the most important disinfection by products, whose removal from the water is the final obstacle to its complete reuse. HPLC-MS investigation points out that complete disappearance of dalapon passes through 2-monochloropropionic acid and leads to propionic acid as the final product. CdS-HTa requires very mild working conditions (room temperature, atmospheric pressure, natural pH), and it is stable and recyclable without significant loss of activity. [ABSTRACT FROM AUTHOR]

Background: Macroalgae, especially reds (Rhodophyta Division) and browns (Phaeophyta Division), are known for producing various halogenated compounds. Yet, the reasons underlying their production and the fate of these metabolites remain largely unknown. Some theories suggest their potential antimicrobial activity and involvement in interactions between macroalgae and prokaryotes. However, detailed investigations are currently missing on how the genetic information of prokaryotic communities associated with macroalgae may influence the fate of organohalogenated molecules. Results: To address this challenge, we created a specialized dataset containing 161 enzymes, each with a complete enzyme commission number, known to be involved in halogen metabolism. This dataset served as a reference to annotate the corresponding genes encoded in both the metagenomic contigs and 98 metagenome-assembled genomes (MAGs) obtained from the microbiome of 2 red (Sphaerococcus coronopifolius and Asparagopsis taxiformis) and 1 brown (Halopteris scoparia) macroalgae. We detected many dehalogenation-related genes, particularly those with hydrolytic functions, suggesting their potential involvement in the degradation of a wide spectrum of halocarbons and haloaromatic molecules, including anthropogenic compounds. We uncovered an array of degradative gene functions within MAGs, spanning various bacterial orders such as Rhodobacterales, Rhizobiales, Caulobacterales, Geminicoccales, Sphingomonadales, Granulosicoccales, Microtrichales, and Pseudomonadales. Less abundant than degradative functions, we also uncovered genes associated with the biosynthesis of halogenated antimicrobial compounds and metabolites. Conclusion: The functional data provided here contribute to understanding the still largely unexplored role of unknown prokaryotes. These findings support the hypothesis that macroalgae function as holobionts, where the metabolism of halogenated compounds might play a role in symbiogenesis and act as a possible defense mechanism against environmental chemical stressors. Furthermore, bacterial groups, previously never connected with organohalogen metabolism, e.g., Caulobacterales, Geminicoccales, Granulosicoccales, and Microtrichales, functionally characterized through MAGs reconstruction, revealed a biotechnologically relevant gene content, useful in synthetic biology, and bioprospecting applications. 7KFSwtia72NY8FA2HCcej3 Video Abstract [ABSTRACT FROM AUTHOR]

2,2’-Bis(4-dimethylaminophenyl)- and 2,2'-dicyclohexyl-1,1',3,3'-tetramethyl-2,2',3,3'-tetrahydro-2,2'-bibenzo[d]imidazole ((N-DMBI)2 and (Cyc-DMBI)2) are quite strong reductants with effective potentials of ca. −2 V vs ferrocenium/ferrocene, yet are relatively stable to air due to the coupling of redox and bond-breaking processes. Here, we examine their use in accomplishing electron transfer-induced bond-cleavage reactions, specifically dehalogenations. The dimers reduce halides that have reduction potentials less cathodic than ca. −2 V vs ferrocenium/ferrocene, especially under UV photoexcitation (using a 365 nm LED). In the case of benzyl halides, the products are bibenzyl derivatives, whereas aryl halides are reduced to the corresponding arenes. The potentials of the halides that can be reduced in this way, quantum-chemical calculations, and steady-state and transient absorption spectroscopy suggest that UV irradiation accelerates the reactions via cleavage of the dimers to the corresponding radical monomers.

Flavin-dependent monooxygenases (FDMOs) are known for their remarkable versatility and for their crucial roles in various biological processes and applications. Extensive research has been conducted to explore the structural and functional relationships of FDMOs. The majority of reported FDMOs utilize C4a-(hydro)peroxyflavin as a reactive intermediate to incorporate an oxygen atom into a wide range of compounds. This review discusses and analyzes recent advancements in our understanding of the structural and mechanistic features governing the enzyme functions. State-of-the-art discoveries related to common and distinct structural properties governing the catalytic versatility of the C4a-(hydro)peroxyflavin intermediate in selected FDMOs are discussed. Specifically, mechanisms of hydroxylation, dehalogenation, halogenation, and light-emitting reactions by FDMOs are highlighted. We also provide new analysis based on the structural and mechanistic features of these enzymes to gain insights into how the same intermediate can be harnessed to perform a wide variety of reactions. Challenging questions to obtain further breakthroughs in the understanding of FDMOs are also proposed. [ABSTRACT FROM AUTHOR]

In this study, we present a straightforward and highly effective photo-triggered hydrogenation method for aryl halides, devoid of transition-metal catalysts. Through the synergistic utilization of light, PhNHNH2, and a base, we have successfully initiated the desired radical-mediated hydrogenation process. Remarkably, utilizing mild reaction conditions, a wide range of aryl halides, including fluorides, chlorides, bromides, and iodides, can be selectively transformed into their corresponding (hetero)arene counterparts, with exceptional yields. Additionally, this approach demonstrates a remarkable compatibility with diverse functional groups and heterocyclic compounds, highlighting its versatility and potential for use in various chemical transformations. [ABSTRACT FROM AUTHOR]

Reductive dehalogenases are corrinoid and iron–sulfur cluster–containing enzymes that catalyze the reductive removal of a halogen atom. The oxygen-sensitive and membrane-associated nature of the respiratory reductive dehalogenases has hindered their detailed kinetic study. In contrast, the evolutionarily related catabolic reductive dehalogenases are oxygen tolerant, with those that are naturally fused to a reductase domain with similarity to phthalate dioxygenase presenting attractive targets for further study. We present efficient heterologous expression of a self-sufficient catabolic reductive dehalogenase from Jhaorihella thermophila in Escherichia coli. Combining the use of maltose-binding protein as a solubility-enhancing tag with the btuCEDFB cobalamin uptake system affords up to 40% cobalamin occupancy and a full complement of iron–sulfur clusters. The enzyme is able to efficiently perform NADPH-dependent dehalogenation of brominated and iodinated phenolic compounds, including the flame retardant tetrabromobisphenol, under both anaerobic and aerobic conditions. NADPH consumption is tightly coupled to product formation. Surprisingly, corresponding chlorinated compounds only act as competitive inhibitors. Electron paramagnetic resonance spectroscopy reveals loss of the Co(II) signal observed in the resting state of the enzyme under steady-state conditions, suggesting accumulation of Co(I)/(III) species prior to the rate-limiting step. In vivo reductive debromination activity is readily observed, and when the enzyme is expressed in E. coli strain W, supports growth on 3-bromo-4-hydroxyphenylacetic as a sole carbon source. This demonstrates the potential for catabolic reductive dehalogenases for future application in bioremediation. [ABSTRACT FROM AUTHOR]

Due to its favorable excited-state physicochemical properties, indium oxide (In2O3) has widely captured attention as a potentially great photocatalyst. However, an inferior charge separation efficiency limits its application. Recently, an increasing amount of evidence has demonstrated that the construction of surface defects is an effective strategy to boost photocatalytic performances. In this work, a ruthenium (Ru) species was successfully introduced into the lattice of In2O3 nanoparticles through co-precipitation and thermal treatment. It was found that the content of surface oxygen vacancies was directly related to the amount of Ru3+ doping, which further determines the separation efficiency of photogenerated carriers. As a result, the 0.5% Ru-In2O3 samples enriched with oxygen vacancies exhibit dramatically enhanced photocatalytic dehalogenation performances of decabromodiphenyl ether and hexabromobenzene, about four times higher than that of the pure In2O3 nanoparticles. This study emphasized the significance of the surface defects of the photocatalyst and may provide a valuable strategy to prepare highly active photocatalysts for photocatalytic dehalogenation reactions. [ABSTRACT FROM AUTHOR]

The effect of ionic liquids on the separation of chlorinated anionic dyes such as Mordant Blue 9 (MB9) or Acid Yellow 17 (AY17) via ion exchange has been investigated in model aqueous solutions that simulate wastewater from the textile dyeing industry. The effect of ionic liquids chemical nature on the separation efficiency of mentioned dyes has been compared. It was found that especially ionic liquid based on quaternary ammonium salts comprising two or three long alkyl chains bound to the quaternary ammonium nitrogen (typically benzalkonium chloride or Aliquat 336) are very effective for the separation of both studied MB9 and AY17 from aqueous solution. In addition, the innovative technique has been developed for the reactivation of spent ionic liquids which is based on the chemical reduction of the formed ion pairs using NaBH4/NiSO4, NaBH4/Na2S2O5 or Raney Al-Ni alloy/NaOH. Thus, only NaBH4/NiSO4 in co-action with Al-Ni alloy enables both effective reduction of the azo bond and subsequent hydrodechlorination of emerging chlorinated aromatic amines. The efficiency of tested dyes separation or regeneration of ion pairs was evaluated by determination of the absorbance at wavelength of the maximum absorbance, of the Chemical Oxidation Demand (COD), and of the Adsorbables Organically bound Halogens (AOX). The formation of ion pairs or products of reduction and hydrodechlorination of these ion pairs has been studied using the 1H NMR and LC-MS techniques. [ABSTRACT FROM AUTHOR]

Halogenated organic compounds (HOCs) pose a serious problem for the environment. Many are highly toxic and accumulate both in soil and in organisms. Their biological transformation takes place by dehalogenation, in which the halogen substituents are detached from the carbon in the organic compound by enzymes produced by microorganisms. This increases the compounds' water solubility and bioavailability, reduces toxicity, and allows the resulting compound to become more susceptible to biodegradation. The microbial halogen cycle in soil is an important part of global dehalogenation processes. The aim of the study was to examine the potential of microbial communities inhabiting natural and anthropogenically modified environments to carry out the dehalogenation process. The potential of microorganisms was assessed by analyzing the metagenomes from a natural environment (forest soils) and from environments subjected to anthropopression (agricultural soil and sludge from wastewater treatment plants). Thirteen genes encoding enzymes with dehalogenase activity were identified in the metagenomes of both environments, among which, 2-haloacid dehalogenase and catechol 2,3-dioxygenase were the most abundant genes. Comparative analysis, based on comparing taxonomy, identified genes, total halogens content and content of DDT derivatives, demonstrated the ability of microorganisms to transform HOCs in both environments, indicating the presence of these compounds in the environment for a long period of time and the adaptive need to develop mechanisms for their detoxification. Metagenome analyses and comparative analyses indicate the genetic potential of microorganisms of both environments to carry out dehalogenation processes, including dehalogenation of anthropogenic HOCs. [ABSTRACT FROM AUTHOR]

A series of 3,6-diamino-9-naphthylcarbazole derivatives were synthesized and characterized experimentally and computationally. As the lowest unoccupied molecular orbital of the naphthyl group has lower energy than that of the phenyl group, a charge transfer from carbazole to naphthyl in the excited states occurred causing solvatofluorochromism and solvent-dependency in fluorescence quantum yields. A molecule having two carbazole substituents sandwiching the central naphthyl ring had absorption reaching 470 nm and a high reducing capability in the excited state. This molecule could successfully photosensitize the hydrodehalogenation of haloarenes under visible light irradiation.

Extracellular electron transfer materials (EETMs) in the environment, such as humic substances and biochar, are formed from the humification/heating of natural organic materials. However, the distribution of extracellular electron transfer (EET) functionality in fresh natural organic materials has not yet been explored. In the present study, we reveal the wide distribution of EET functionality in proteinaceous materials for the first time using an anaerobic pentachlorophenol dechlorinating consortium, whose activity depends on EETM. Out of 11 natural organic materials and 13 reference compounds, seven proteinaceous organic materials (albumin, beef, milk, pork, soybean, yolk, and bovine serum albumin) functioned as EETMs. Carbohydrates and lipids did not function as EETMs. Comparative spectroscopic analyses suggested that a β-sheet secondary structure was essential for proteins to function as EETMs, regardless of water solubility. A high content of reduced sulfur was potentially involved in EET functionality. Although proteinaceous materials have thus far been considered simply as nutrients, the wide distribution of EET functionality in these materials provides new insights into their impact on biogeochemical cycles. In addition, structural information on EET functionality can provide a scientific basis for the development of eco-friendly EETMs. [Display omitted] • Natural proteinaceous materials had extracellular electron transfer (EET) function. • The β-sheet secondary structure of proteins was crucial for the EET function. • A high content of reduced sulfur was potentially involved in the EET function. • Wide distribution of natural EET materials impacts biogeochemical cycling. • Structural information paves the synthetic study of eco-friendly EET materials. [ABSTRACT FROM AUTHOR]

Pitch-based carbon fiber, as one of the important engineering materials, has been widely used in aerospace, defense, sports, and other fields. In the long production process of pitch-based carbon fiber, the property of pitch precursor is significant for the mechanical performance of obtained carbon fiber. Thus, it is crucial to improve the property of pitch precursor by efficient means. Halogenation--dehalogenation is a newly developed method for the controllable synthesis of a pitch precursor from the molecular dimension, including fluorination--defluorination, chlorination--dechlorination, and bromination--debromination. This work reviewed the mechanism and application, as well as the advantages and disadvantages of each halogenation--dehalogenation method. [ABSTRACT FROM AUTHOR]

A complete genome sequence of Caballeronia sp. strain S22 capable of growing with fluoroacetate as the sole source of carbon and energy was obtained by PacBio technology. It consists of seven circular replicons totaling 9,367 kb, with a gene cluster involved in fluoroacetate utilization on its smallest 172 kb plasmid.

To assess the performance of hazardous waste sites remediation technologies, like in situ chemical oxidation (ISCO) with persulfate ( S 2 O 8   2 - ) researchers must periodically measure concentrations of target contaminants. Due to the presence of relatively high concentrations of the residual oxidant expected in many samples, the standard analytical method requires the addition of a relatively high concentration of ascorbic acid to prevent the oxidation process from continuing after sample collection. We discovered that addition of ascorbic acid quencher results in a radical chain reaction that transforms two common halogenated solvents (i.e., tetrachloroethene and hexachloroethane). To avoid the artifact associated with the radical chain reaction, a small quantity of n-hexane can be added to aqueous samples to extract target compounds and protect them from the radical chain reaction initiated by addition of the quencher. We recommend the use of this alternative sample preservation method whenever high concentrations of residual S 2 O 8   2 - are expected to be present in water samples that are contaminated with halogenated solvents.

Since Indonesia have signed and ratified Stockholm Convention on Persistent Organic Pollutants (POPs) in 2009, the country must make efforts to manage POPs appropriately. A number of pollution evident of POPs has occurred in Indonesia, either air, soil or water. Agricultural soils are not excluded from POPs pollution as the result of halogenated pesticide uses or other unidentified sources. Contamination of POPs to humans have been detected, as well as indicated potential exposure of POPs to humans. Based-catalyzed decomposition is a method that can be used to decompose or decontaminate POPs. Limestone can be processed to produce calcium-based catalyst that can apply for POPs decomposition. Indonesia is a country rich in limestone natural resources to produce calcium. However, calcium is inferior to sodium or potassium in reactivity for the dehalogenation of POPs. Thus, more evaluation is needed in order for synthesizing proper and economical calcium-based catalyst to alleviate POPs pollution in Indonesia.

By fully considering its hydrophobic/electron-rich cavity, planar chirality, as well as rigid chemical structures, pillar[n]arene has the capacity of contributing its molecular recognition, self-assembly, as well as thus obtained advanced hierarchical materials in photocatalysis. In this review, we discussed and summarized the recent progress in pillar[n]arene-based photocatalysis. Interestingly, it was found that pillar[n]arene played diverse roles in photocatalysis, for example, providing host–guest interactions as phase transfer catalyst in photoreduction/dehalogenation/oxidation for improving the water-solubility of substrates and functional molecules, contributing hydrophobic/electron-rich cavity, inducing planar chirality as homogenous catalyst in photocyclodimerization/redox/dehalogenation for catalyzing selective substrates, and serving as building blocks or reactive sites in the fabrication of hierarchical (hybrid) heterogenous catalyst in selective reactions. The recent progress about pillar[n]arene-based phase transfer catalysts, homogeneous catalysts and heterogeneous catalysts in photocatalysis was summarized in this review. [ABSTRACT FROM AUTHOR]

Temperature is a key factor affecting microbial activity and ecology. An increase in temperature generally increases rates of microbial processes up to a certain threshold, above which rates decline rapidly. In the subsurface, temperature of groundwater is usually stable and related to the annual average temperature at the surface. However, anthropogenic activities related to the use of the subsurface, e.g. for thermal heat management, foremost heat storage, will affect the temperature of groundwater locally. This minireview intends to summarize the current knowledge on reductive dehalogenation activities of the chlorinated ethenes, common urban groundwater contaminants, at different temperatures. This includes an overview of activity and dehalogenation extent at different temperatures in laboratory isolates and enrichment cultures, the effect of shifts in temperature in micro- and mesocosm studies as well as observed biotransformation at different natural and induced temperatures at contaminated field sites. Furthermore, we address indirect effects on biotransformation, e.g. changes in fermentation, methanogenesis, and sulfate reduction as competing or synergetic microbial processes. Finally, we address the current gaps in knowledge regarding bioremediation of chlorinated ethenes, microbial community shifts, and bottlenecks for active combination with thermal energy storage, and necessities for bioaugmentation and/or natural repopulations after exposure to high temperature. [ABSTRACT FROM AUTHOR]

This review summarizes recent applications of copper or copper-based compounds as a nonprecious metal catalyst in N-nucleophiles-based dehalogenation (DH) reactions of halogenated aromatic compounds (Ar-Xs). Cu-catalyzed DH enables the production of corresponding nonhalogenated aromatic products (Ar-Nu), which are much more biodegradable and can be mineralized during aerobic wastewater treatment or which are principally further applicable. Based on available knowledge, the developed Cu-based DH methods enable the utilization of amines for effective cleavage of aryl-halogen bonds in organic solvents or even in an aqueous solution. [ABSTRACT FROM AUTHOR]

Single-atom catalysts (SACs) have emerged as promising materials in environmental catalysis, attributed to their outstanding performance, robust structural properties, and optimal use of active metal sites. However, there is a critical need for a comprehensive review to summarize the successful integration of SACs in electrochemical water treatment. In this paper, we provide an in-depth review of the in-situ preparation methods for SACs electrode. The design principles for SACs employed in electrochemical water treatment are outlined. We particularly focus on the application of SACs in wastewater treatment using electrochemical catalytic technology. The development and application potential of SACs in electrochemical water treatment are critically introduced from the aspects of electrochemical advanced oxidation processes (EAOPs), electrochemical nitrate reduction reaction (NO 3 RR), electrochemical advanced reduction processes (EARPs) dehalogenation and electrochemical micropollutant value-added. In conclusion, we discuss anticipated developments, further scientific research, and practical applications of SACs in electrochemical water treatment. [Display omitted] • The in-situ synthesis of SACs electrodes is summarized. • Design principles of SACs for electrochemical water treatment are presented. • The application and intrinsic mechanism of SACs for electrochemical water treatment are analyzed. • Challenges and directions for developing SACs for electrochemical water treatment are presented. [ABSTRACT FROM AUTHOR]

Reactions between phosphoric acid [H3PO4] or ammonium hydrogen phosphates [i.e., NH4H2PO4, (NH4)2HPO4] and halide salts can be used to dehalogenate (remove halides from) salt-based waste streams, where the process of removing halides yields products that have more efficient disposal pathways for repository storage. In this context, the term efficiency is defined as higher waste loadings and simplified immobilization processes with potential for recycle of certain salt components (e.g., 37Cl as H37Cl or NH437Cl). The main streams identified for these processes are nuclear wastes generated during electrochemical reprocessing of used nuclear fuel as well as used halide salts from molten salt reactor operation. The potential byproducts of these reactions are fairly consistent across the range of halide species (i.e., F, Cl, Br, I) where the most common are hydrogen halides [e.g., HCl(g)] or ammonium halides (e.g., NH4Cl). However, trihalide compounds (e.g., NCl3), nitrogen triiodide ammine adducts [NI3·(NH3)x], and ammonium triiodide (NH4I3) are also possible. Several of these byproducts (i.e., NCl3, NBr3, NI3, and NH4I3) are shock-sensitive contact explosives so their production in these processes must be tracked and carefully controlled, which includes methods of immediate neutralization upon production such as direct transport to a caustic scrubber for dissolution. Several benefits arise from utilizing H3PO4 as the phosphate additive during dehalogenation reactions for making iron phosphate waste forms including more oxidized iron (higher Fe3+:Fe2+ ratios), higher chemical durabilities, and the avoidance of trihalides, but the byproducts are hydrogen halides, which are corrosive and require special handling.

Halogenated organic compounds (HOCs) pose a serious problem for the environment. Many are highly toxic and accumulate both in soil and in organisms. Their biological transformation takes place by dehalogenation, in which the halogen substituents are detached from the carbon in the organic compound by enzymes produced by microorganisms. This increases the compounds’ water solubility and bioavailability, reduces toxicity, and allows the resulting compound to become more susceptible to biodegradation. The microbial halogen cycle in soil is an important part of global dehalogenation processes. The aim of the study was to examine the potential of microbial communities inhabiting natural and anthropogenically modified environments to carry out the dehalogenation process. The potential of microorganisms was assessed by analyzing the metagenomes from a natural environment (forest soils) and from environments subjected to anthropopression (agricultural soil and sludge from wastewater treatment plants). Thirteen genes encoding enzymes with dehalogenase activity were identified in the metagenomes of both environments, among which, 2-haloacid dehalogenase and catechol 2,3-dioxygenase were the most abundant genes. Comparative analysis, based on comparing taxonomy, identified genes, total halogens content and content of DDT derivatives, demonstrated the ability of microorganisms to transform HOCs in both environments, indicating the presence of these compounds in the environment for a long period of time and the adaptive need to develop mechanisms for their detoxification. Metagenome analyses and comparative analyses indicate the genetic potential of microorganisms of both environments to carry out dehalogenation processes, including dehalogenation of anthropogenic HOCs.

Host-specific microbial communities thrive within sponge tissues and this association between sponge and associated microbiota may be driven by the organohalogen chemistry of the sponge animal. Several sponge species produce diverse organobromine secondary metabolites (e.g. brominated phenolics, indoles, and pyrroles) that may function as a chemical defense against microbial fouling, infection or predation. In this study, anaerobic cultures prepared from marine sponges were amended with 2,6-dibromophenol as the electron acceptor and short chain organic acids as electron donors. We observed reductive dehalogenation from diverse sponge species collected at disparate temperate and tropical waters suggesting that biogenic organohalides appear to enrich for populations of dehalogenating microorganisms in the sponge animal. Further enrichment by successive transfers with 2,6-dibromophenol as the sole electron acceptor demonstrated the presence of dehalogenating bacteria in over 20 sponge species collected from temperate and tropical ecoregions in the Atlantic and Pacific Oceans and the Mediterranean Sea. The enriched dehalogenating strains were closely related to Desulfoluna spongiiphila and Desulfoluna butyratoxydans , suggesting a cosmopolitan association between Desulfoluna spp. and various marine sponges. In vivo reductive dehalogenation in intact sponges was also demonstrated. Organobromide-rich sponges may thus provide a specialized habitat for organohalide-respiring microbes and D. spongiiphila and/or its close relatives are responsible for reductive dehalogenation in geographically widely distributed sponge species. [ABSTRACT FROM AUTHOR]

[Display omitted] In this work, three artificial light-harvesting systems are constructed by a supramolecular approach in aqueous environment. The water-soluble bipyridinium derivatives (DPY1, DPY2, and DPY3) were self-assembled with cucurbit[7]uril (CB[7]) to form the host–guest DPY-CB[7] complexes, which can highly disperse in water as small nanoparticles. The excited DPY-CB[7] assemblies can transfer energy to the sulfo-rhodamine 101 (SR101) molecules at a high donor/acceptor ratio. With the help of hydrophobic cavity of CB[7], the DPY-CB[7] + SR101 systems can works as a nanoreactor for effective dehalogenation of α -bromoacetophenone and its derivatives in aqueous medium under white light irradiation. Such light-harvesting systems has greatly potential applications to realize some organic photocatalytic synthesis in aqueous environment. [ABSTRACT FROM AUTHOR]

Dichloromethane (DCM, methylene chloride) is a toxic halogenated volatile organic compound massively used for industrial applications, and consequently often detected in the environment as a major pollutant. DCM biotransformation suggests a sustainable decontamination strategy of polluted sites. Among methylotrophic bacteria able to use DCM as a sole source of carbon and energy for growth, Methylorubrum extorquens DM4 is a longstanding reference strain. Here, the primary 5′-ends of transcripts were obtained using a differential RNA-seq (dRNA-seq) approach to provide the first transcription start site (TSS) genome-wide landscape of a methylotroph using DCM or methanol. In total, 7231 putative TSSs were annotated and classified with respect to their localization to coding sequences (CDSs). TSSs on the opposite strand of CDS (antisense TSS) account for 31% of all identified TSSs. One-third of the detected TSSs were located at a distance to the start codon inferior to 250 nt (average of 84 nt) with 7% of leaderless mRNA. Taken together, the global TSS map for bacterial growth using DCM or methanol will facilitate future studies in which transcriptional regulation is crucial, and efficient DCM removal at polluted sites is limited by regulatory processes. [ABSTRACT FROM AUTHOR]

Dehalococcoides mccartyi strains harboring vinyl chloride (VC) reductive dehalogenase (RDase) genes are keystone bacteria for VC detoxification in groundwater aquifers, and bioremediation monitoring regimens focus on D. mccartyi biomarkers. We isolated a novel anaerobic bacterium, "Candidatus Dehalogenimonas etheniformans" strain GP, capable of respiratory dechlorination of VC to ethene. This bacterium couples formate and hydrogen (H2) oxidation to the reduction of trichloroethene (TCE), all dichloroethene (DCE) isomers, and VC with acetate as the carbon source. Cultures that received formate and H2 consumed the two electron donors concomitantly at similar rates. A 16S rRNA gene-targeted quantitative PCR (qPCR) assay measured growth yields of (1.2 + 0.2) × 108 and (1.9 + 0.2) × 108 cells per mmol of VC dechlorinated in cultures with H2 or formate as electron donor, respectively. About 1.5-fold higher cell numbers were measured with qPCR targeting cerA, a single-copy gene encoding a putative VC RDase. A VC dechlorination rate of 215 6 40 mmol L21 day21 was measured at 30°C, with about 25% of this activity occurring at 15°C. Increasing NaCl concentrations progressively impacted VC dechlorination rates, and dechlorination ceased at 15 g NaCl L21. During growth with TCE, all DCE isomers were intermediates. Tetrachloroethene was not dechlorinated and inhibited dechlorination of other chlorinated ethenes. Carbon monoxide formed and accumulated as a metabolic by-product in dechlorinating cultures and impacted reductive dechlorination activity. The isolation of a new Dehalogenimonas species able to effectively dechlorinate toxic chlorinated ethenes to benign ethene expands our understanding of the reductive dechlorination process, with implications for bioremediation and environmental monitoring. [ABSTRACT FROM AUTHOR]

Background: The deep sea harbors the majority of the microbial biomass in the ocean and is a key site for organic matter (OM) remineralization and storage in the biosphere. Microbial metabolism in the deep ocean is greatly controlled by the generally depleted but periodically fluctuating supply of OM. Currently, little is known about metabolic potentials of dominant deep-sea microbes to cope with the variable OM inputs, especially for those living in the hadal trenches—the deepest part of the ocean. Results: In this study, we report the first extensive examination of the metabolic potentials of hadal sediment Chloroflexi, a dominant phylum in hadal trenches and the global deep ocean. In total, 62 metagenome-assembled-genomes (MAGs) were reconstructed from nine metagenomic datasets derived from sediments of the Mariana Trench. These MAGs represent six novel species, four novel genera, one novel family, and one novel order within the classes Anaerolineae and Dehalococcoidia. Fragment recruitment showed that these MAGs are globally distributed in deep-sea waters and surface sediments, and transcriptomic analysis indicated their in situ activities. Metabolic reconstruction showed that hadal Chloroflexi mainly had a heterotrophic lifestyle, with the potential to degrade a wide range of organic carbon, sulfur, and halogenated compounds. Our results revealed for the first time that hadal Chloroflexi harbor pathways for the complete hydrolytic or oxidative degradation of various recalcitrant OM, including aromatic compounds (e.g., benzoate), polyaromatic hydrocarbons (e.g., fluorene), polychlorobiphenyl (e.g., 4-chlorobiphenyl), and organochlorine compounds (e.g., chloroalkanes, chlorocyclohexane). Moreover, these organisms showed the potential to synthesize energy storage compounds (e.g., trehalose) and had regulatory modules to respond to changes in nutrient conditions. These metabolic traits suggest that Chloroflexi may follow a "feast-or-famine" metabolic strategy, i.e., preferentially consume labile OM and store the energy intracellularly under OM-rich conditions, and utilize the stored energy or degrade recalcitrant OM for survival under OM-limited condition. Conclusion: This study expands the current knowledge on metabolic strategies in deep-ocean Chlorolfexi and highlights their significance in deep-sea carbon, sulfur, and halogen cycles. The metabolic plasticity likely provides Chloroflexi with advantages for survival under variable and heterogenic OM inputs in the deep ocean. CxfeXiBUAN16RTa_sQ4c7H Video Abstract [ABSTRACT FROM AUTHOR]

Dehalogenases are microbial enzyme catalysed the cleavage of carbon-halogen bond of halogenated organic compounds. It has potential use in the area of bio-technology such as bioremediation and chemical industry. Halogenated organic compounds can be found in the environment due to utili-zation in agriculture and industry, such as pesticides and herbicides. The presence of halogenated compound in the environment have been implicated on the health and natural ecosystem. Microbial dehalogenation is a significant method to tackle this problem. This review intends to briefly describe the microbial dehalogenases in relation to the environment where they are isolated. The basic information about dehalogenases in relation to dehalogenation mechanisms, classification, sources and the transportation of these pollutants into bacterial cytoplasm will be de-scribed. We also summarised readily available synthetic halogenated organic compounds in the environment.

Perchloroethene (PCE) is a widely used chlorinated solvent. PCE is toxic to humans and has been identified as an environmental contaminant at thousands of sites worldwide. Several Dehalococcoides mccartyi strains can transform PCE to ethene, and thus contribute to bioremediation of contaminated sites. Humic acids (HA) are ubiquitous redox-active compounds of natural aquatic and soil systems and have been intensively studied because of their effect in electron transfer. In this study, we observed the dechlorination of PCE was accelerated by HA in mixed cultures containing Dehalococcoides strains. Anthraquinone-2,6-disulfonic acid (AQDS), a humic acid analogue, inhibited PCE dechlorination in our cultures and thus induced an opposite effect on PCE dehalogenation than HA. We observed the same effect on PCE dechlorination with the pure culture of Dehalococcoides mccartyi strain CBDB1. Not only in mixed cultures but also in pure cultures, growth of Dehalococcoides was not influenced by HA but inhibited by AQDS. Enzymatic activity tests confirmed the dehalogenating activity of strain CBDB1 was increased by HA, especially when using hydrogen as electron donor. We conclude that HA enhanced PCE dechlorination by increasing the reaction speed between hydrogen and the dehalogenase enzyme rather than acting as electron shuttle through its quinone moieties. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new hybrid material with highly dispersed Pd NPs supported onto the Fh was prepared. • A synergistic effect between Pd nanocatalyst and Fh support was demonstrated. • Fh facilitated the adsorption of chlorophenol on the material via hydrogen bonding. • Fh as electron mediator promoted electron transfer in the dehalogenation process. • Catalyst activity was due to the dispersed Pd NPs and its electron-rich nature. Organic chlorides are a group of ubiquitous environmental pollutants that have attracted wide attention because of their carcinogenetic effect on human. Catalytic hydrodechlorination represents one of the most promising methods for the removal of these contaminants, but it suffers from drawbacks such as catalytic inefficiency and/or instability, and the danger of using H 2 as hydrogen source. The relationship between the catalyst structure and its dehalogenation activity has not been completely understood. By combining the advantages of Pd nanocatalyst and mesoporous ferrihydrite (Fh) with its distinctive structure, here we present a new composite material with Pd nanoparticles (NPs) supported onto the Fh (Pd/Fh), which has excellent catalytic dehalogenation performance with a rapid, complete dechlorination of chlorophenol (turnover frequency 25.2 min−1) and the ability to perform well over a wide range of pH and temperature. The superior catalytic property of Pd/Fh can be attributed to the three unique functions of Fh, including: 1) having abundant hydroxyl groups that provide interaction sites with metals for incorporating highly dispersed small Pd NPs; 2) facilitating the fast adsorption of chlorophenol onto the catalyst surface via hydrogen bonding and importantly, 3) working as an electron mediator to greatly enhance the electron transfer from iron or chemicals (e.g., NaBH 4) to the catalyst, thereby achieving a synergistic effect between Pd catalyst and support, and an enhanced dechlorination activity. In essence, this work presents a promising catalyst for the efficient dehalogenation of chlorinated environmental pollutants and provides an insight into the relationship between catalyst structure and dehalogenation activity. [ABSTRACT FROM AUTHOR]

On-surface synthesis has become a powerful approach to produce low-dimensional carbon-based nanostructures with atomistic precision. A large variety of analytical tools and methods are available to provide efficient monitoring of on-surface reactions, among which, scanning probe microscopy (SPM) has proven to be particularly efficient to characterize reaction intermediates and products down to the atomic scale. Nevertheless, due to limited temporal resolution, difficulties to explore the full temperature range, and lack of identifying the chemical environment of all elements involved in on-surface processes, SPM is ideally complemented with temperature programmed X-ray photoelectron spectroscopy (TP-XPS). In this short review, we aim to unveil some of the capabilities of synchrotron based TP-XPS reporting on our own research on Ullmann-type on-surface coupling reactions.

HadA is a flavin-dependent monooxygenase catalyzing hydroxylation plus dehalogenation/denitration, which is useful for biodetoxification and biodetection. In this study, the X-ray structure of wild-type HadA (HadAWT) co-complexed with reduced FAD (FADH-) and 4-nitrophenol (4NP) (HadAWT-FADH--4NP) was solved at 2.3-Å resolution, providing the first full package (with flavin and substrate bound) structure of a monooxygenase of this type. Residues Arg101, Gln158, Arg161, Thr193, Asp254, Arg233, and Arg439 constitute a flavin-binding pocket, whereas the 4NP-binding pocket contains the aromatic side chain of Phe206, which provides π-π stacking and also is a part of the hydrophobic pocket formed by Phe155, Phe286, Thr449, and Leu457. Based on site-directed mutagenesis and stopped-flow experiments, Thr193, Asp254, and His290 are important for C4a-hydroperoxyflavin formation with His290, also serving as a catalytic base for hydroxylation. We also identified a novel structural motif of quadruple π-stacking (π-π-π-π) provided by two 4NP and two Phe441 from two subunits. This motif promotes 4NP binding in a nonproductive dead-end complex, which prevents C4a-hydroperoxy-FAD formation when HadA is premixed with aromatic substrates. We also solved the structure of the HadAPhe441Val-FADH--4NP complex at 2.3-Å resolution. Although 4NP can still bind to this variant, the quadruple π-stacking motif was disrupted. All HadAPhe441 variants lack substrate inhibition behavior, confirming that quadruple π-stacking is a main cause of dead-end complex formation. Moreover, the activities of these HadAPhe441 variants were improved by 20%, suggesting that insights gained from the flavin-dependent monooxygenases illustrated here should be useful for future improvement of HadA's biocatalytic applications. [ABSTRACT FROM AUTHOR]

The sequencing electroreduction-electrooxidation process has emerged as a promising approach for the degradation of the chloronitrobenzenes (CNBs) due to its elimination of electro-withdrawing groups in the reduction process, facilitating further removal in the subsequent oxidation process. Herein, we developed a cathode consisting of atom Pd on a Ti plate, which enabled the electro-generation of atomic hydrogen (H*) and the efficient electrocatalytic activation of H 2 O 2 to hydroxyl radical (•OH). Cyclic voltammetry (CV) curves and electron spin resonance (ESR) spectra verified the existence of H* and •OH. The electroreduction-electrooxidation system achieved 94.7% of 20 mg L−1 2,4-DCNB removal with a relatively low H 2 O 2 addition (5 mM). Moreover, the inhibition rate of Photobacterium phosphoreum in the effluent decreased from 95% to 52% after the sequencing electroreduction-electrooxidation processes. It was further revealed that the H* dominated the electroreduction process and triggered the electrooxidation process. Our work sheds light on the effective removal of electron-withdrawing groups substituted aromatic contaminants from water and wastewater. [Display omitted] • A sequencing electroreduction-electrooxidation system was driven by H*. • Efficient 2,4-DCNB removal (94.7%) was achieved in the obtained system. • The toxicity of the intermediates was significantly reduced after the operation. • The system acquires relatively low dosage of H 2 O 2 and low energy consumption. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fe(II)-bearing minerals alone are non-reactive to trichloroethylene reduction. • Fe(II)-bone char could effectively reduce trichloroethylene to acetylene. • The Fe(II)-bone char were prepared by simple mixing in water. • Fast kinetics did not guarantee high electron efficiency. • Suitable crystallinity of Fe(II) enable steady and long lasting TCE reduction. Fe(II)-bearing minerals might be able to drive the attenuation of chlorinated ethene in soil and groundwater, however, with relatively slow kinetics. In this study, bone char(BC) was selected as an efficient and benign catalyst to prepare composites with three different Fe(II)-bearing minerals (Green rust (GR), Fe(OH) 2 and FeS), respectively, for enhanced trichloroethylene (TCE) dehalogenation. The kinetics experiment demonstrated that the presence of BC could effectively switch on the TCE dehalogenation by these solids, while these Fe(II)-bearing minerals alone can barely reduce any TCE. Surprisingly, the Fe(OH) 2 -BC showed fastest TCE reduction rate, followed by GR-BC and FeS-BC in sequence. Acetylene was confirmed as the major dehalogenation products while other chlorinated byproducts were hardly detected. The electron efficiency (η e) for TCE reduction was further calculated and compared among these BC amended systems, the results show that the highest η e value was recorded in GR-BC system as 33.14% with high loading of TCE. Solid phase characterization confirmed that the high loading of amorphous Fe(II) on the BC surface might effectively improve the TCE dehalogenation kinetics, while the well crystallized Fe(II)-bearing minerals would increase the electron efficiency. According to this mechanism, it might be possible to achieve balance between kinetics and electron efficiency. Stress resistance test in real groundwater matrix and life cycle analysis (LCA) was conducted to further verify the application potential of these composites. [ABSTRACT FROM AUTHOR]

[Display omitted] • An efficient magnetite-activated PDS degradation system was established. • Fe(III)/Fe(II) conversion was crucial for the induced activation of PDS. • The activation mechanism of graphite-carbon enhanced PDS was identified. • Excellent detoxification and dechlorination capabilities was achieved. The current Sulfate Radical Advanced Oxidation Process (SR-AOP) system faces several limitations, such as expensive catalysts, susceptibility to secondary pollutants, limited cycle stability, and suboptimal electron consumption efficiency. Therefore, developing a cost-effective, recyclable, and eco-friendly catalyst holds great promise for improving catalyst performance and electron utilisation efficiency. In this investigation, the effectiveness of natural magnetite treated through ball milling (NMP B) in activating peroxydisulfate (PDS) to generate sulfate radicals (SO 4 −) were explored and the combination of NMP B and PDS demonstrated outstanding catalytic efficiency in degrading 2,4,6-trichlorophenol (TCP), achieving a degradation efficiency exceeding 90 % within 6 h. The naturally occurring Fe(II) and graphitised carbon structure within NMP B were crucial in facilitating PDS activation and promoting efficient electron transfer. Subsequently, potential degradation mechanisms for TCP in the NMP B /PDS system was proposed, and the activation mechanism of graphite-carbon enhanced PDS was identified by DFT calculation. Additionally, excellent stability and reusability of NMP B was demonstrated through iron leaching experiment and circulation experiment. Furthermore, TCP degradation intermediates were identified through liquid chromatography combined with mass spectroscopy (LC-MS) and potential TCP degradation pathways were proposed. Importantly, toxicity assessment revealed that the intermediates generated during the TCP degradation process exhibited lower toxicity than TCP. In summary, the NMP B /PDS system demonstrated its effectiveness as an environmentally friendly technology for degrading organic pollutants in contaminated groundwater and surface water environments. [ABSTRACT FROM AUTHOR]

Glutathione s-transferases (GSTs) are ubiquitous family of enzymes well known for their detoxification function. Several different classes of the enzyme exist with beta class being the one specific to bacteria. Recently, the enzymes were found to exhibit other functions, in particular dehalogenation of some organic compounds. This property could be extremely useful especially in the bioremediation of some organochlorine pollutants. A beta class GST from Acidovorax sp. KKS102 designated as KKS-BphK was previously cloned and characterized. In this research, molecular docking study was first employed to investigate the possibility of binding of the protein to dichlorobenzoates; byproducts of polychlorobiphenyl degradation. The wild type enzyme together with other mutants were expressed using E. coli BL21 (DE3) cells and purified. The dehalogenation function of the enzymes against dichlorobenzoate derivatives was also investigated through chloride ion detection assay. The results of the molecular docking study indicated the possibility of binding of KKS-BphK to these substrates. Both the wild type and the mutants showed dehalogenation function against the model substrate 1-chloro-2,4- dinitrobenzene (CDNB). Furthermore, the enzymes also showed dehalogenation function against 2,4-dichlorobenzoate derivatives. However, in testing the activity of the enzymes toward 2,5- dichlorobenoate and 2,6-dichlorobenzoate, only K107T and A180P mutants showed some activity while the wild type and C10F mutant showed zero activity. The research indicates the usefulness of beta class GST in the dehalogenation of dichlorobenzoates in addition to their known function of dehalogenating monochlorobenzoates.

In this work, hierarchically porous carbon spheres co-doped by iron and nitrogen were synthesized via in situ dehalogenation. The rich porous structure and relatively high specific surface area (210 m2/g) facilitate the formation of an ultra-fine Fe2N active phase and FeN4 active centers within the carbon matrix. Transmission electron microscopy and X-ray photoelectron spectroscopy analysis further reveal the presence of a dominant Fe2N phase and minor FeN4 bonds in the as-prepared Fe-N-C-pd-800 samples. Because of this, the oxygen reduction reaction (ORR) process can more readily take place on Fe2N than on FeN4, and the Fe2N phase enriched Fe-N-C-pd-800 carbon spheres exhibit a promising onset potential (Eonset=1.02 V) and half-wave potential (E1/2=0.86 V) in alkaline media. In addition, Fe-N-C-pd-800 also shows excellent methanol resistance and long-cycling stability. [ABSTRACT FROM AUTHOR]

Cytochrome P450 enzymes, or P450s, are haem monooxygenases renowned for their ability to insert one atom from molecular oxygen into an exceptionally broad range of substrates while reducing the other atom to water. However, some substrates including many organohalide and nitro compounds present little or no opportunity for oxidation. Under hypoxic conditions P450s can perform reductive reactions, contributing electrons to drive reductive elimination reactions. P450s can catalyse dehalogenation and denitration of a range of environmentally persistent pollutants including halogenated hydrocarbons and nitroamine explosives. P450-mediated reductive dehalogenations were first discovered in the context of human pharmacology but have since been observed in a variety of organisms. Additionally, P450-mediated reductive denitration of synthetic explosives has been discovered in bacteria that inhabit contaminated soils. This review will examine the distribution of P450-mediated reductive dehalogenations and denitrations in nature and discuss synthetic biology approaches to developing P450-based reagents for bioremediation.