Simultaneous Degradation, Dehalogenation, and Detoxification of Halogenated Antibiotics by Carbon Dioxide Radical Anions

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(CO_(2)^(·-))—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 CO_(2)^(·-),with approximately 100%of Cland 46%of Freleased after 120 min of treatment.Simultaneous detoxification is observed,which exhibits a linear response to the release of free inorganic halogen ions(R^(2)=0.97,p<0.01).The formation of halogen-free products is the primary reason for the superior detoxification performance of this method,in comparison with conventional hydroxyl-radical-based AOPs.Products identification and density functional theory(DFT)calculations reveal the underlying dehalogenation mechanism,in which the chlorine moiety of FF is more susceptible than other moieties to nucleophilic attack by CO_(2)^(·-).Moreover,CO_(2)^(·-)-based ARPs exhibit superior dehalogenation efficiencies(>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 CO_(2)^(·-)-based ARPs in real life.Overall,this study elucidates the feasibility of CO_(2)^(·-)for the simultaneous degradation,dehalogenation,and detoxification of halogenated antibiotics and provides a promising method for their regulation during water or wastewater treatment.

Potassium iodide catalyzed reductive dehalogenation ofα-halo-ketones using Hantzsch ester diethyl 1,4-dihydro-2,6-dimethylpyridine-3,5-dicarboxylate as reductant

In the presence of diethyl 1,4-dihydro-2,6-dimethylpyridine-3,5-dicarboxylate（DHP） and a catalytic amount of potassium iodide,severalα-halo ketones were easily reduced to the corresponding ketones in acetone media.The procedure presented here showed several merits such as short reaction time,practical experimental and isolated procedure,and excellent yields of products.

Light-driven activation of carbon-halogen bonds by readily available amines for photocatalytic hydrodehalogenation

A straightforward protocol using readily available aromatic amines,N,N,N',N'-tetramethyl-p-phenylenediamine or N,N,N',N'-tetramethylbenzidine,as photocatalysts was developed for theefficient hydrodehalogenation of organic halides,such as 4'-bromoacetophenone,polyfluoroarenes,cholorobenzene,and 2,2',4,4'-tetrabromodiphenyl ether(a resistant and persistent organic pollu-tant).The strongly reducing singlet excited states of the amines enabled diffusion-controlled disso-ciative electron transfer to effectively cleave carbon-halogen bonds,followed by radical hydrogena-tion.Diisopropylethylamine served as the terminal electron/proton donor and regenerated theamine sensitizers.

Dehalogenation of Aryl Halides Catalyzed by MontK10 Immobilized PVP-Pd-Sn Catalyst in Aqueous System

A series of PVP-Pd-Sn/MontK10 catalysts were prepared by immobilization of PVP[poly(N-vinyl-2-pyrrolidone)] supported bimetallic catalyst using MontK10 as carrier. This catalyst has good catalytic activity for hydrogen transfer dehalogenation of aryl halides. The catalytic reaction was carried out in aqueous system in the presence of phase transfer catalyst and sodium formate as hydrogen source. The catalyst with loading Pd 0.19wt% and molar ratio of Pd/Dn 8:1 gives the highest activity and good stability. This catalyst is more reducible with NaBH4. It is also found that the catalyst is easily separated from the reaction system.

Advances in study of dehalogenation of plastic waste by pyrolysis

Several methods ofdehalogenation by pyrolysis were summarized in this paper. Some crucial academic problems have been brought forward after analyzing and comparing the technical character as well as dehalogenation efficiency of these methods, which should be emphasized in the future research.

Dehalogenation of Aryl Halides Catalyzed by Montmorillonite Immobilized Bimetal Catalyst in Aqueous System

A novel bisupported bimetal catalyst PVP-PdCl2-FeSO4/Al-Mont-PEG600 was prepared by immobilization of PVP （poly （N-vinyl-2-pyrrolidone）） supported bimetallic catalyst using alumina pillared inartificial montmorillonite as the carrier. This catalyst has good dehalogenation activity and selectivity to aryl halides o-chlorotoluene in aqueous system in the presence of phase transfer catalyst （PEG） and sodium formate as hydrogen source. The catalyst also shows good reusability.

Quantitative structure－activity study on the reductive dehalogenation potency of the halogenated aromatics

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Novel insights into the dehalogenation mechanism and ecotoxicity assessment of 6:2 Cl-PFESA from density functional theory calculations

The electroplating industry is the main source of 6:2 chlorinated polyfluorinated ether sulfonate(6:2 Cl-PFESA)pollution,which presents risks to human health and the environment.It is therefore crucial to develop effective 6:2 Cl-PFESA degradation techniques.Persulfate oxidation is a potential treatment method for 6:2 Cl-PFESA due to its outstanding oxidative degradability following the generation of the sulfate radical(SO_(4)^(•−))and hydroxyl radical(•OH).It has proven difficult to acquire a full understanding of the reaction mechanism and formation of intermediate(IM)products through conventional experimental studies because they are costly and time-consuming.Therefore,a theoretical analysis method based on density functional theory(DFT)calculations was applied.The DFT results showed that electron transfer for the degradation of 6:2 Cl-PFESA could be initiated by the protonated sulfate radical(HSO_(4)•,ΔG≠SET=9.16 kcal/mol),rather than SO4•−(ΔG≠SET=41.60 kcal/mol).After desulfonation,the reaction underwent stepwise decarboxylation cycles under the action of•OH,leading to the elimination of the CF_(2) units until there was complete mineralization into HCl,HF,and CO_(2).Furthermore,the IMs and the end products of 6:2 Cl-PFESA were evaluated using ECOSAR and TEST software.The low bioaccumulation of the short-chain IMs meant that they could be considered safe in terms of ecotoxicity and health effects.This research determined the theoretical and mechanistic basis of the effects of persulfate in the treatment of water containing 6:2 Cl-PFESA,and its structural analogues.

Simultaneous Dehalogenation and Hydrogenation in Sonogashira Coupling

We herein report a simultaneous dehalogenation and hydrogenation(DHH)reaction in Sonogashira coupling involving hexahalogenobenzene C6X6(X=I,Br),in which a halogen on the aryl polyhalide substrate was substituted by a hydrogen atom.First,a steric bulky terminal alkyne 5 was designed and synthesized to study the influence of the reaction conditions(e.g.,catalyst,solvent,temperature)and the halogens on the substrates C6X6 on the DHH reaction.Moreover,based on the optimized conditions,a terminal alkyne 6 with less steric hindrance was further synthesized to investigate the influence of alkyne on the DHH reaction.As a result,two aromatic polyynes 7 and 8 were were further studied and compared.The influence produced by the alkynes and aryl polyhalides substrate provide insights into Sonogashira coupling involving terminal alkyne with huge steric hindrance and polyhalogenated aromatic hydrocarbons.

Integration of microbial reductive dehalogenation with persulfate activation and oxidation(Bio-RD-PAO)for complete attenuation of organohalides

Due to the toxicity of bioaccumulative organohalides to human beings and ecosystems,a variety of biotic and abiotic remediation methods have been developed to remove organohalides from contaminated environments.Bioremediation employing organohalide-respiring bacteria(OHRB)-mediated microbial reductive dehalogenation(Bio-RD)represents a cost-effective and environmentally friendly approach to attenuate highly-halogenated organohalides,specifically organohalides in soil,sediment and other anoxic environments.Nonetheless,many factors severely restrict the implications of OHRB-based bioremediation,including incomplete dehalogenation,low abundance of OHRB and consequent low dechlorination activity.Recently,the development of in situ chemical oxidation(ISCO)based on sulfate radicals(SO_(4)^(·−))via the persulfate activation and oxidation(PAO)process has attracted tremendous research interest for the remediation of lowly-halogenated organohalides due to its following advantages,e.g.,complete attenuation,high reactivity and no selectivity to organohalides.Therefore,integration of OHRB-mediated Bio-RD and subsequent PAO(Bio-RD-PAO)may provide a promising solution to the remediation of organohalides.In this review,we first provide an overview of current progress in Bio-RD and PAO and compare their limitations and advantages.We then critically discuss the integration of Bio-RD and PAO(Bio-RD-PAO)for complete attenuation of organohalides and its prospects for future remediation applications.Overall,Bio-RD-PAO opens up opportunities for complete attenuation and consequent effective in situ remediation of persistent organohalide pollution.

Dechlorination of Aromatic Chlorides in Aqueous System Catalyzed by Functionalized MontK10 Supported Palladium-tin

A novel bisupporter bimetal catalyst PVP-PdCl2-SnCl4/MontK10-PEG400, using for dehalogenation of insoluable aromatic halides in aqueous system, has shown high dechlorination activity and selectivity, without any organic solvent or phase transfer catalyst. The conversion of aromatic chlorides can reach 100%. The catalyst is easy to prepare and has good reusability.

Photobiodegradation of halogenated aromatic pollutants

Release of wide range of compounds as a consequence of industrial development is now a serious environmental problem. Numerous hazardous waste sites have been generated worldwide resulting from the accumulation of xenobiotics in soil and water. Aromatic compounds constitute a large and diverse group of chemicals that are responsible for causing widespread environmental pollution. Among them halogenated aromatic hydrocarbons are very stable to undergo degradation due to resonance energy and inertness of carbon-halogen, carbon-hydrogen and carbon-carbon covalent bonds. The physico-chemical remedial strategies to clean up sites contaminated by these compounds are inadequate and economically inefficient. Therefore, research is increasingly being focused on development of biological approaches for their remediation. The hunt for the microorganisms degrading halogenated aromatic pollutants has been successful in discovering a diverse range of aerobic, anaerobic and phototrophic bacteria. The bacteria mineralize the toxic halogenated pollutants into harmless products thereby contributing towards conservation of the environment quality.

Facile Synthetic Method and Crystal Structure of 2,3,3',4'-Biphenyltetracarboxylic Dianhydride

A facile method for the synthesis of 2,3,3＇,4＇-biphenyltetracarboxylic dianhydride（a-BPDA） was reported,which comprises the steps of the dehalogenative coupling of dimethyl 4-chlorophthalate（4-DMCP） and dimethyl 3-chlorophthalate（3-DMCP） catalyzed by low-cost（Ph 3 P） 2 NiCl 2,the hydrolysis of tetra-ester and the dehydration of tetra-acid.In contrast to the conventional methods,this method has the advantage of low cost,convenient manipulation,available condition,high purity and good overall yield.Moreover,the single crystal structure of a-BPDA was analyzed by X-ray diffraction method.The X-ray data suggest that a-BPDA is a rigid,non-coplanar and non-linear structure.It contains three crystallographically independent molecules,in which the dihedral angles of the two linked phenyl rings are 44.75（4）°,46.37（3）° and 42.32（3）°,respectively.The title molecule is governed by a stronger intermolecular interaction in contrast to van der Waals interaction because of the special positions of anhydride groups.

Recent Advances in Deuteration Reactions

The deuteration of organic compounds has attracted more attentions in recent years for the potential applications in new drug discovery and synthetic chemistry.For this purpose,many efficient deuterium labeling methodologies have been developed,including hydrogen isotope exchange(HIE),reductive deuteration,and dehalogenative deuteration that allow for the synthesis of selectively deuterated compounds.In the last few years,great breakthroughs in selective isotope labeling have been achieved and the interest in new methodologies for the deuteration of organic molecules is rising.In this review,we summarized the recent developments in the selective deuteration of organic molecules since 2021.Several types of key processes in deuterium incorporation reactions,including H/D exchange,reductive deuteration and dehalogenative deuteration,are introduced and discussed.

Assessment of aerobic biodegradation of lower-chlorinated benzenes in contaminated groundwater using field-derived microcosms and compound-specific carbon isotope fractionation

Biodegradation of lower chlorinated benzenes(tri-, di-and monochlorobenzene) was assessed at a coastal aquifer contaminated with multiple chlorinated aromatic hydrocarbons. Field-derived microcosms, established with groundwater from the source zone and amended with a mixture of lower chlorinated benzenes, evidenced biodegradation of monochlorobenzene(MCB) and 1,4-dichlorobenzene(1,4-DCB) in aerobic microcosms,whereas the addition of lactate in anaerobic microcosms did not enhance anaerobic reductive dechlorination. Aerobic microcosms established with groundwater from the plume consumed several doses of MCB and concomitantly degraded the three isomers of dichlorobenzene with no observable inhibitory effect. In the light of these results, we assessed the applicability of compound stable isotope analysis to monitor a potential aerobic remediation treatment of MCB and 1,4-DCB in this site. The carbon isotopic fractionation factors(ε) obtained from field-derived microcosms were-0.7‰ ± 0.1 ‰ and-1.0‰ ± 0.2 ‰ for MCB and1,4-DCB, respectively. For 1,4-DCB, the carbon isotope fractionation during aerobic biodegradation was reported for the first time. The weak carbon isotope fractionation values for the aerobic pathway would only allow tracing of in situ degradation in aquifer parts with high extent of biodegradation. However, based on the carbon isotope effects measured in this and previous studies, relatively high carbon isotope shifts(i.e., Δδ13C > 4.0 ‰) of MCB or 1,4-DCB in contaminated groundwater would suggest that their biodegradation is controlled by anaerobic reductive dechlorination.

Facile and Economical Electrochemical Dehalogenative Deuteration of(Hetero)Aryl Halides

Deuterated compounds are valuable in synthetic,pharmaceutical,and analytical chemistry.The deuteration of halides is a widespread method for highly site-selective deuterium installation.However,the facile,efficient,and economical deuterium incorporation remains challenging.In this work,we introduced a practical deuteration of(hetero)aryl halides through an electrochemical reduction method.This transformation proceeded smoothly at room temperature without metal catalysts,external reductants,or toxic or dangerous reagents.Remarkably,low-cost and chemically equivalent D2O was the sole deuterium source in this reaction.Professional electrosynthesis equipment was not essential because we demonstrated common batteries and electrodes were enough for this reaction.

N-doped crumpled graphene: bottom-up synthesis and its superior oxygen reduction performance

The crumpled graphene(CrG) was fabricated by applying defluorination of polyvinylidenefluoride(PVDF)on highly curved surface of CaC_2 particle through bottom-up synthetic strategy. The limited reaction depth between PVDF and CaC_2 leads to the formation of CrG with thin layer(3.6 layer graphene) and reasonable high specific surface area(~324.8 m^2 g^(-1)). CrG with N incorporation(N-CrG)was applied as electrode material for reducing oxygen(i.e.,oxygen reduction reaction, ORR) in alkaline, showing close onset potential to that of Pt/C and better mass-diffusion behavior. Surprisingly, with increased mass loading of catalysts,N-CrG exhibits steady current increase while Pt/C shows clear current plateau. Meanwhile, the N-CrG sample reveals high cycling stability and tolerance to contaminant,demonstrating its high potential for practical applications.Additionally, the bottom-up synthetic pathway to CrG via polymer dehalogenation on solid alkaline may find more applications which require controlled morphology and thickness of deposited thin graphitic carbon layers.