The persistence of chlorinated alkanes in aquatic environments poses significant health risks due to its biotoxicity and high volatility,which contributes to both water and air pollution.This study investigates the ef...The persistence of chlorinated alkanes in aquatic environments poses significant health risks due to its biotoxicity and high volatility,which contributes to both water and air pollution.This study investigates the efficacy of carbon dioxide radical anion(CO_(2)·^(-))mediated advanced reduction processes(ARPs)for the reductive dechlorination of chlorinated alkanes using small molecular monocarboxylic acids(SMAs)under UV irradiation.The study focused on formic acid(HCOOH),acetic acid(CH_3COOH),and propionic acid(CH_3CH_(2)COOH)to generate CO_(2)·^(-),revealing that UV/HCOOH system exhibits a notably high chloroform(CF)degradation efficiency of 97.8%in 90 min.Kinetic studies indicated a linear relationship between the HCOOH concentrations and the observed reaction rate constants(k_(obs)),demonstrating that CO_(2)·^(-)production is crucial for CF degradation.Electron paramagnetic resonance spectroscopy identified CO_(2)·^(-)and hydroxyl radicals(HO·)as the active species,with the former playing a predominant role in CF degradation.The study also explored the influence of carbon chain length in SMAs on CF degradation,finding that longer chains decrease the degradation efficiency,potentially due to reduced UV activation.A higher reaction rate constant(k_(obs))under acidic conditions,with a marked decrease in efficiency as the pH exceeds 3.7,where HCOO^(-)becomes predominant.This study enhances our understanding of CO_(2)·^(-)mediated ARPs and explores potential applications in environmental remediation,providing insights into the pathways and mechanisms of CF degradation.The UV/SMAs systems offer advantages for practical applications,such as milder reaction conditions and higher efficiency compared to traditional methods.展开更多
A laboratory sequential anaerobic aerobic bioreactor system, which consisted of an anaerobic fixed film reactor and two aerobic chemostats, was set up to degrade tetrachloroethylene (PCE) without accumulating highly ...A laboratory sequential anaerobic aerobic bioreactor system, which consisted of an anaerobic fixed film reactor and two aerobic chemostats, was set up to degrade tetrachloroethylene (PCE) without accumulating highly toxic degradation intermediates. A soil enrichment culture, which could reductively dechlorinate 900 μM (ca. 150 mg/L) of PCE stoichiometrically into cis 1,2 dichloroethylene ( cis DCE), was attached to ceramic media in the anaerobic fixed film reactor. A phenol degrading strain, Alcaligenes sp. R5, which can efficiently degrade cis DCE by co metabolic oxidation, was used as inoculum for the aerobic chemostats consisted of a transformation reactor and a growth reactor. The anaerobic fixed film bioreactor showed more than 99 % of PCE transformation into cis DCE in the range of influent PCE concentration from 5 μM to 35 μM at hydraulic retention time of 48h. On the other hand, efficient degradation of the resultant cis DCE by strain R5 in the following aerobic system could not be achieved due to oxygen limitation. However, 54% of the maximum cis DCE degradation was obtained when 10 μmol of hydrogen peroxide (H 2O 2) was supplemented to the transformation reactor as an additional oxygen source. Further studies are needed to achieve more efficient co metabolic degradation of cis DCE in the aerobic reactor.展开更多
Chlorinated organic pollutants(COPs),both emerging and traditional,are typical persistent pollutants that harm soil health worldwide.Dechlorinators mediated reductive dechlorination is the optimal way to completely re...Chlorinated organic pollutants(COPs),both emerging and traditional,are typical persistent pollutants that harm soil health worldwide.Dechlorinators mediated reductive dechlorination is the optimal way to completely remove COPs from anaerobic soil through a redox reaction driven by electron transfer during microbial anaerobic respiration.Generally,the dechlorinated depletion of COPs in situ often interacts with multiple element biogeochemical activities,e.g.,methanogenesis,sulfate reduction,iron reduction,and denitrification.Elucidating the relevance of biogeochemical cycles between COPs and multiple elements and the coupled mechanisms involved,thus,helps to develop effective pollution control strategies with the balance between pollution degradation and element cycles in heterogeneous soil,ultimately contributing to“one health”goal.In this review,we summarized the microbial-chemical coupling redox processes and the driving factors,elucidated the interspecies metabolites exchange and electron transfer mechanisms within COP-dechlorinating communities,and further proposed a detailed design,construction,and analysis framework of engineering COP-dechlorinating microbiomes via“top-down”selfassembly and“bottom-up”synthesis to pave the way from laboratory to practical field application.Especially,we delve into the major challenges and perspectives surrounding the design of state-of-the-art synthetic microbial communities.Our goal is to improve the understanding of the microbial-mediated coupling between reductive dechlorination and element biogeochemical cycling,with a particular focus on the implications for health-integrated soil bioremediation under the“one health”concept.展开更多
It is common that 2,4,6-trichlorophenol （TCP） coexists with nitrate or nitrite in industrial wastewaters. In this work, simultaneous reductive dechlorination of TCP and denitrification of nitrate or nitrite competed...It is common that 2,4,6-trichlorophenol （TCP） coexists with nitrate or nitrite in industrial wastewaters. In this work, simultaneous reductive dechlorination of TCP and denitrification of nitrate or nitrite competed for electron donor, which led to their mutual inhibition. All inhibitions could be relieved to a certain degree by augmenting an organic electron donor, but the impact of the added electron donor was strongest for TCP. For simultaneous reduction ofTCP together with nitrate, TCP＇s removal rate value increased 75% and 150%, respectively, when added glucose was increased from 0.4 mmol· L^-1 to 0.5 mmol· L^-1 and to 0.76 mmol· L^-1 For comparison, the removal rate for nitrate increased by only 25% and 114% for the same added glucose. The relationship between their initial biodegradation rates versus their initial concentrations could be represented well with the Monod model, which quantified their half-maximum-rate concentration （Ks value）, and Ks values for TCP, nitrate, and nitrite were larger with simultaneous reduction than independent reduction. The increases in Ks are further evidence that competition for the electron donor led to mutual inhibition. For bioremediation of wastewater containing TCP and oxidized nitrogen, both reduction reactions should proceed more rapidly if the oxidized nitrogen is nitrite instead of nitrate and if readily biodegradable electron acceptor is augmented.展开更多
Chlorinated persistent organic pollutants, including polychlorinated biphenyls （PCBs）, represent a particularly serious environmental problem and human health risk worldwide. Leguminous plants and their symbiotic ba...Chlorinated persistent organic pollutants, including polychlorinated biphenyls （PCBs）, represent a particularly serious environmental problem and human health risk worldwide. Leguminous plants and their symbiotic bacteria （rhizobia） are important components of the biogeochemical cycling of nitrogen in both agricultural and natural ecosystems. However, there have been relatively few detailed studies of the remediation of PCB-contaminated soils by legume-rhizobia symbionts. Here we report for the first time evidence of the reductive dechlorination of 2,4,4＇-trichlorobiphenyl （PCB 28） by an alfalfa-rhizobium nitrogen fixing symbiont. Alfalfa （Medicago sativa L.） inoculated with wild-type Sinorhizobiurn meliloti had significantly larger biomass and PCB 28 accumulation than alfalfa inoculated with the nitrogenase negative mutant rhizobium SmY. Dechlorination products of PCB 28, 2,4＇-dichlorobiphenyl （PCB 8）, and the emission of chloride ion （C1-） were also found to decrease significantly in the ineffective nodules infected by the mutant strain SmY. We therefore hypothesize that N2-fixation by the legume-rhizobium symbiont is coupled with the reductive dechlorination of PCBs within the nodules. The combination of these two processes is of great importance to the biogeochemical cycling and bioremediation of organochlorine pollutants in terrestrial ecosystems.展开更多
The dehalogenation of organohalides has been a research hotspot in bioremediation field;however,the influence of tourmaline,a natural ore that can generate spontaneous electric field,on organohalide-respiring bacteria...The dehalogenation of organohalides has been a research hotspot in bioremediation field;however,the influence of tourmaline,a natural ore that can generate spontaneous electric field,on organohalide-respiring bacteria(OHRB)and their dechlorination process is not well known.In this study,the effect and mechanism of tourmaline on the reductive dechlorination of 2,3-dichlorophenol(2,3-DCP)by Desulfitobacterium hafniense DCB-2Twere explored.The characterization results confirmed that tourmaline had good stability and the optimal dosage of tourmaline was 2.5 g/L,which shortened the total time required for dechlorination reaction to 72 hr.Besides,tourmaline amendment also increased the proportion of 2-chlorophenol(2-CP)from 18%to 30%of end products,while that of 3-CP decreased correspondingly.The theoretical calculations showed that the bond charge of the orthosubstituted chlorine declined from-0.179 to-0.067,and that of meta-substituted chlorine increased from-0.111 to-0.129,which indicated that the spontaneous electric field of tourmaline affected the charge distribution of 2,3-DCP and was more conducive to the generation of 2-CP.Overall,tourmaline with the spontaneous electric field affected the reductive dechlorination pathway of Desulfitobacterium,and the tourmaline-OHRB combining system might serve as a novel strategy for the bioremediation of environments polluted with chlorinated phenols.展开更多
The toxic and recalcitrant polychlorinated biphenyls （PCBs） adversely affect human and biota by bioaccumulation and biomagnification through food chain. In this study, an anaerobic microcosm was developed to extensi...The toxic and recalcitrant polychlorinated biphenyls （PCBs） adversely affect human and biota by bioaccumulation and biomagnification through food chain. In this study, an anaerobic microcosm was developed to extensively dechlorinate hexa- and hepta-CBs in Aroclor 1260. After 4 months of incubation in defined mineral salts medium amended PCBs （70μmol· L^-1） and lactate （10 mmol· L^-1）, the culture dechlorinated hexa-CBs from 40.2% to 8.7% and hepta-CBs 33.6% to 11.6%, with dechlorination efficiencies of 78.3% and 65.5%, respectively （all in moL ratio）. This dechlorination process led to tetra-CBs （46.4%） as the predominant dechlorination products, followed by penta- （22.1%） and tri-CBs （5.4%）. The number of meta chlorines per biphenyl decreased from 2.50 to 1.41. Results of quantitative real-time PCR show that Dehalococcoides cells increased from 2.39 × 10^5±0.5× 10^5 to 4.99 ×10^7±0.32 ×10^7 copies mL^-1 after 120 days of incubation, suggesting that Dehalococcoides play a major role in reductive dechlorination of PCBs. This study could prove the feasibility of anaerobic reductive culture enrichment for the dehalogenation of highly chlorinated PCBs, which is priorto be applied for in situ biorernediation of notorious halogenated compounds.展开更多
Herein,the degradation of florfenicol(FLO)over zero-valent iron(ZVI)enhanced by SiC was systematically investigated.It was found that 5 g/L of ZVI/SiC(1:3)at pH 3.0 could completely degrade 20 mg/L of FLO within 1 h,w...Herein,the degradation of florfenicol(FLO)over zero-valent iron(ZVI)enhanced by SiC was systematically investigated.It was found that 5 g/L of ZVI/SiC(1:3)at pH 3.0 could completely degrade 20 mg/L of FLO within 1 h,with a Kobsvalue of 0.0873 min^(-1),12.5 times greater than that of pure ZVI(0.0069 min^(-1)).Vibrating sample magnetometer(VSM)characterizations revealed that the use of SiC supporter reduces the magnetic intensity of ZVI,which mitigates iron particle agglomeration,increases Brunauer-Emmett-Teller(BET)surface area,and enhances FLO degradation efficiency.Furthermore,ZVI/SiC exhibits a much lower hydrogen evolution potential(HEP)and significantly higher corrosion currents compared to pure ZVI.FLO was proposed to undergo degradation via reductive dechlorination,involving a hydrogenolysis mechanism that entails the cleavage of theσbond.This study provides new insights into the reduction hydrogenation mechanism of ZVI.展开更多
The application of electron donor and electron shuttle substances has a vital influence on electron transfer,thus may affect the reductive dechlorination of 1,1,1-trichoro-2,2-bis（p-chlorophenyl）ethane（DDT） in ana...The application of electron donor and electron shuttle substances has a vital influence on electron transfer,thus may affect the reductive dechlorination of 1,1,1-trichoro-2,2-bis（p-chlorophenyl）ethane（DDT） in anaerobic reaction systems.To evaluate the roles of citric acid and anthraquinone-2,6-disulfonate（AQDS） in accelerating the reductive dechlorination of DDT in Hydragric Acrisols that contain abundant iron oxide,a batch anaerobic incubation experiment was conducted in a slurry system with four treatments of（1） control,（2） citric acid,（3） AQDS,and（4） citric acid ＋ AQDS.Results showed that DDT residues decreased by 78.93%-92.11% of the initial quantities after 20 days of incubation,and 1,1-dichloro-2,2-bis（4-chlorophenyl）-ethane（DDD） was the dominant metabolite.The application of citric acid accelerated DDT dechlorination slightly in the first 8 days,while the methanogenesis rate increased quickly,and then the acceleration effect improved after the 8th day while the methanogenesis rate decreased.The amendment by AQDS decreased the Eh value of the reaction system and accelerated microbial reduction of Fe（III） oxides to generate Fe（II）,which was an efficient electron donor,thus enhancing the reductive dechlorination rate of DDT.The addition of citric acid ＋ AQDS was most efficient in stimulating DDT dechlorination,but no significant interaction between citric acid and AQDS on DDT dechlorination was observed.The results will be of great significance for developing an efficient in situ remediation strategy for DDT-contaminated sites.展开更多
Chlorobenzene was dechlorinated by Pd/Fe bimetallic system in water through catalytic reduction. The dechlorination rate increases with increase of bulk loading of Pd due to the increase of both the surface loading o...Chlorobenzene was dechlorinated by Pd/Fe bimetallic system in water through catalytic reduction. The dechlorination rate increases with increase of bulk loading of Pd due to the increase of both the surface loading of the Pd and the total surface area. For conditions with 0.005% Pd/Fe, 45% dechlorination efficiency was achieved within 5 h. The dechlorinated reaction is believed to take place on the bimetal surface in a pseudo-first-order reaction, with the rate constant being 0.0043 min-1.展开更多
Catalytic reductive dechlorination of monochlorobenzene(MCB) was carried out in the palladium/iron system. With low Pd loading(0 005%), 45% dechlorination efficiency was achieved within 5 h. Pd as catalyst accelerated...Catalytic reductive dechlorination of monochlorobenzene(MCB) was carried out in the palladium/iron system. With low Pd loading(0 005%), 45% dechlorination efficiency was achieved within 5 h. Pd as catalyst accelerated the reductive dechlorination reaction. Dechlorination mechanism and kinetics were discussed. The reaction took place on the bimetal surface in a pseudo first order reaction, with the rate constant being 0 0071 min -1 ( K SA =8 0×10 -3 L/(m 2·h). The reduction product for MCB was benzene.展开更多
o-Dichlorobenzene (o-DCB) was dechlorinated by Pd/Fe powder in water throughcatalytic reduction. The dechlorination reaction is believed to take place on the surface site ofthe catalyst via a pseuclo-first-order react...o-Dichlorobenzene (o-DCB) was dechlorinated by Pd/Fe powder in water throughcatalytic reduction. The dechlorination reaction is believed to take place on the surface site ofthe catalyst via a pseuclo-first-order reaction. The final reduction product of o-DCB is benzene.The dechlorination rate increases with the increase of bulk loading of palladium due to the increaseof both the surface loading of palladium and the total surface area. Dechlorination efficiencyaccounts for 90% at Pd/Fe mass ratio 0.02% and metal to solution ratio about 53.3g · L^(-1) in 120minutes. Dechlorination is affected by the reaction temperature, pH, Pd/Fe ratio and the addition ofPd/Fe. E_a is found to be 102.5 kJ · mol^(-1) in the temperature range of 287—313 K.展开更多
Activation of(bi)sulfite(S(IV))by metal oxides is strongly limited by low electrons utilization.In this study,two carbon-supported cobalt ferrites spinels(CoFe^(2)O_(4) QDs-GO and CoFe^(2)O_(4) MOFs-CNTs)have been suc...Activation of(bi)sulfite(S(IV))by metal oxides is strongly limited by low electrons utilization.In this study,two carbon-supported cobalt ferrites spinels(CoFe^(2)O_(4) QDs-GO and CoFe^(2)O_(4) MOFs-CNTs)have been successfully synthesized by one-step solvothermal method.It was found that both catalysts could efficiently activate S(IV),with rapid reductive dechlorination and then oxidative degradation of a recalcitrant antibiotic chloramphenicol(CAP).Characterizations revealed that CoFe^(2)O_(4) spinels were tightly coated on the carbon bases(GO and CNTs),with effectiveness of the internal transfer of electrons.O_(2)˙−was identified for the reductive dechlorination of CAP,with simultaneously detection of both•OH and SO_(4)^(˙−)responsible for further oxidative degradation.The sulfur oxygen radical conversion reactions and molecular oxygen activation would occur together upon the carbon-based spinels.Spatial-separated interfacial reductive-oxidation of CAP would occur with dechlorination of CAP by O_(2)^(˙−)on the carbon bases,and oxidative degradation of intermediates by SO_(4)^(˙−/•)OH upon the CoFe^(2)O_(4) catalysts.展开更多
Dicofol type DDTs-contamination is of great concern as environmental organochlorine pollutant. In the present study, dechlorination time-course ofp,p＇-DDT and p,p＇-DDE in dithionite treated waterlogged DDTs-contamin...Dicofol type DDTs-contamination is of great concern as environmental organochlorine pollutant. In the present study, dechlorination time-course ofp,p＇-DDT and p,p＇-DDE in dithionite treated waterlogged DDTs-contaminated soil, non-contaminated soil solution and citrate-bicarbonate buffer （0, 50, 100 mmol L^-1, dithionite） for 72 hrs was investigated based on residual amount of p,p＇-DDTs （p,p＇-DDT and p,p＇-DDE） analyzed by GC-ECD. The metabolites ofp,p＇-DDTs in dithionite treated non-contaminated soil solution, and citrate-bicarbonate buffer were detected by GC-MSD. The dechlorination time-course of p,p＇-DDT and p,p＇-DDE exhibited rapid dechlorination at the first 3.0 hrs, slow dechlorination after 3.0 hrs. For 50 mmol L^-1 dithionite treatments, the dechlorination ratios ofp,p＇-DDT and p,p＇-DDE were 36.42% and 35.08% respectively at 3.0 hrs. For 100 mmol L^-1 dithionite treatments, the dechlorination ratios of p,p＇-DDT and p,p＇-DDE were 58.62% and 57.39% respectively at 3.0 hrs in DDTs-contaminated soils. Significant differences of dechlorination ratio were also confirmed in dependence on dithionite concentrations, reaction systems and the chemical structure of DDTs. The dechlorination ratio ofp,p＇-DDT/DDE increased with the increasing of dithionite concentrations irrespective of reaction systems. Dithionite-induced dechlorination ratio of p,p＇-DDT was higher than that of p,p＇-DDE. The p,p＇-DDD （1,1-dichloro-2,2-bis（4-chlorophenyl）-ethane）, p,p＇-DDE and p,p＇-DDMU （1-chloro-2,2-bis（4-chloropheny）-ethylene） were identified to be metabolites ofp,p＇-DDT in buffer and non-contaminated soil solution, however, no metabolites ofp,p＇-DDE treated by dithionite were detected. The possible pathways explaining the dechlorination of p,p＇-DDT and p,p＇-DDE by dithionite were also proposed. Dithionite could be used to develop an effective and fast remediation option for DDTs-contaminated soils and sediments.展开更多
Detoxification of chlorinated organic compounds via reaction with nickel/iron powder was implemented in aqueous solution. Compared to iron, nickel/iron bimetallic powder had higher hydrodechlorination activities for b...Detoxification of chlorinated organic compounds via reaction with nickel/iron powder was implemented in aqueous solution. Compared to iron, nickel/iron bimetallic powder had higher hydrodechlorination activities for both atrazine (ATR) and p-chlorophenol (pCP); nickel/iron (2.96%, w/w) was shown to have the largest specific surface area and the optimum proportion for the dechlorination of both ATR and pCP. Electrochemical measurements showed that the adsorbed hydrogen atom on the nickel must have been the dominant reductive agent for the dechlorination of both ATR andpCP in this system.展开更多
Research works in the recent past have revealed three major biodegradation processes leading to the degradation of trichloroethylene. Reductive dechlorination is an anaerobic process in which chlorinated ethenes are u...Research works in the recent past have revealed three major biodegradation processes leading to the degradation of trichloroethylene. Reductive dechlorination is an anaerobic process in which chlorinated ethenes are used as electron acceptors. On the other hand, cometabolism requires oxygen for enzymatic degradation of chlorinated ethenes, which however yields no benefit for the bacteria involved. The third process is direct oxidation under aerobic conditions whereby chlorinated ethenes are directly used as electron donors by microorganisms. This review presented the current research trend in understanding biodegradation mechanisms with regard to their field applications. All the techniques used are evaluated, with the focus being on various factors that influence the process and the outcome.展开更多
Degradation of 2, 4, 6 trichlorophenol(TCP) with co immobilizing anaerobic granular sludge and isolated aerobic bacterial species was studied in coupled anaerobic/aerobic integrated reactors. The synergism of aerobe...Degradation of 2, 4, 6 trichlorophenol(TCP) with co immobilizing anaerobic granular sludge and isolated aerobic bacterial species was studied in coupled anaerobic/aerobic integrated reactors. The synergism of aerobes and anaerobes within co immobilized granule might facilitate degrading the TCP and exchange of anaerobic metabolites 4 CP, which promoted system organic removal efficiency and recovered from organic shock loads more quickly. The biomass specific activities experiment further confirmed that strict anaerobes be not affected over the course of this experiment by the presence of an oxic environment, aerobic activity predominated in the outer co immobilized granule layers, while the interior was characterized by anaerobic activity. The co immobilized granule could thus enable both aerobic and anaerobic microbes function in the same reactor and thereby integrate the oxidative and reductive catabolism.展开更多
Humic substances acting as an electron shuttle and nitrogen transformation process influence remarkably the electron transfer in anaerobic reaction systems and thus may affect the reductive dechlorination of hexachlor...Humic substances acting as an electron shuttle and nitrogen transformation process influence remarkably the electron transfer in anaerobic reaction systems and thus may affect the reductive dechlorination of hexachlorobenzene(HCB). In order to develop an efficient agricultural strategy for the remediation of organochlorine-contaminated soils, a batch incubation experiment was conducted to study the effects of humic acid, urea, and their interaction on the reductive dechlorination of HCB in a Hydragric Acrisol with high iron oxide content. After 44 d of anaerobic incubation, the five treatments, sterile control,control, humic acid, urea, and humic acid + urea decreased HCB residues by 28.8%, 47.8%, 64.7%, 57.8%, and 71.3%, respectively. The amendment of humic acid or urea significantly decreased soil Eh values and accelerated Fe(Ⅲ) reduction to Fe(Ⅱ), thus promoting markedly reductive dechlorination of HCB. Humic acid had a larger dechlorination effect than urea. Since there was a synergistic interaction between humic acid and urea that accelerated HCB dechlorination, the treatment having both amendments together was the most efficient for HCB dechlorination. The results showed that the combination of NH4^(+)_(-)N supplied by a fertilizer and humic substance is a feasible strategy for the remediation of organochlorine-contaminated soils with abundant iron oxide.展开更多
Tetrachloroethene （PCE） is biodegraded by reductive dechlorination with co-metabolism substrates under anaerobic conditions. By inoculating sludge from an anaerobic pool, a biodegradation test of PCE is conducted in...Tetrachloroethene （PCE） is biodegraded by reductive dechlorination with co-metabolism substrates under anaerobic conditions. By inoculating sludge from an anaerobic pool, a biodegradation test of PCE is conducted in the anaerobic condition. In the test, several substrates including methanol, ethanol, formate, acetate, lactate and glucose, are conducive to the conversion from PCE to TCE and 1,1-DCE. The results show the microbe can be cultivated well under the anaerobic circumstances of mixture of sewage （sludge） and soil with the index of COD after eleven days. Degradation of PCE accords with one order reaction kinetics equation. The sequence of the reaction rate constant is Kacetate 〉Kglucose 〉 Klactate 〉 Kethanol 〉 Kformate 〉 Kmethanol, and acetate is an outstanding co-metabolism substratum whose reaction rate constant is 0.6632d^-1.展开更多
Electro-bioremediation offers a promising approach for eliminating persistent pollutants from groundwater since allows the stimulation of biological dechlorinating activity,utilizing renewable electricity for process ...Electro-bioremediation offers a promising approach for eliminating persistent pollutants from groundwater since allows the stimulation of biological dechlorinating activity,utilizing renewable electricity for process operation and avoiding the injection of chemicals into aquifers.In this study,a two-chamber microbial electrolysis cell has been utilized to achieve both reductive and oxidative degradation of tetrachloroethane(TeCA).By polarizing the graphite granules cathodic chamber at650 mV vs the standard hydrogen electrode and employing a mixed metal oxide(MMO)counter electrode for oxygen production,the reductive and oxidative environment necessary for TeCA removal has been established.Continuous experiments were conducted using two feeding solutions:an optimized mineral medium for dechlorinating microorganisms,and synthetic groundwater containing sulphate and nitrate anions to investigate potential side reactions.The bioelectrochemical process efficiently reduced TeCA to a mixture of trans-dichloroethylene,vinyl chloride,and ethylene,which were subsequently oxidized in the anodic chamber with removal efficiencies of 37±2%,100±4%,and 100±5%,respectively.The introduction of synthetic groundwater with nitrate and sulphate stimulated reductions in these ions in the cathodic chamber,leading to a 17%decrease in the reductive dechlorination rate and the appearance of other chlorinated by-products,including cis-dichloroethylene and 1,2-dichloroethane(1,2-DCA),in the cathode effluent.Notably,despite the lower reductive dechlorination rate during synthetic groundwater operation,aerobic dechlorinating microorganisms within the anodic chamber completely removed VC and 1,2-DCA.This study represents the first demonstration of a sequential reductive and oxidative bioelectrochemical process for TeCA mineralization in a synthetic solution simulating contaminated groundwater.展开更多
基金supported by the National Natural Science Foundation of China(Nos.52270165 and 51978537)the Key Laboratory of Safety for Geotechnical and Structural Engineering of Hubei Province。
文摘The persistence of chlorinated alkanes in aquatic environments poses significant health risks due to its biotoxicity and high volatility,which contributes to both water and air pollution.This study investigates the efficacy of carbon dioxide radical anion(CO_(2)·^(-))mediated advanced reduction processes(ARPs)for the reductive dechlorination of chlorinated alkanes using small molecular monocarboxylic acids(SMAs)under UV irradiation.The study focused on formic acid(HCOOH),acetic acid(CH_3COOH),and propionic acid(CH_3CH_(2)COOH)to generate CO_(2)·^(-),revealing that UV/HCOOH system exhibits a notably high chloroform(CF)degradation efficiency of 97.8%in 90 min.Kinetic studies indicated a linear relationship between the HCOOH concentrations and the observed reaction rate constants(k_(obs)),demonstrating that CO_(2)·^(-)production is crucial for CF degradation.Electron paramagnetic resonance spectroscopy identified CO_(2)·^(-)and hydroxyl radicals(HO·)as the active species,with the former playing a predominant role in CF degradation.The study also explored the influence of carbon chain length in SMAs on CF degradation,finding that longer chains decrease the degradation efficiency,potentially due to reduced UV activation.A higher reaction rate constant(k_(obs))under acidic conditions,with a marked decrease in efficiency as the pH exceeds 3.7,where HCOO^(-)becomes predominant.This study enhances our understanding of CO_(2)·^(-)mediated ARPs and explores potential applications in environmental remediation,providing insights into the pathways and mechanisms of CF degradation.The UV/SMAs systems offer advantages for practical applications,such as milder reaction conditions and higher efficiency compared to traditional methods.
文摘A laboratory sequential anaerobic aerobic bioreactor system, which consisted of an anaerobic fixed film reactor and two aerobic chemostats, was set up to degrade tetrachloroethylene (PCE) without accumulating highly toxic degradation intermediates. A soil enrichment culture, which could reductively dechlorinate 900 μM (ca. 150 mg/L) of PCE stoichiometrically into cis 1,2 dichloroethylene ( cis DCE), was attached to ceramic media in the anaerobic fixed film reactor. A phenol degrading strain, Alcaligenes sp. R5, which can efficiently degrade cis DCE by co metabolic oxidation, was used as inoculum for the aerobic chemostats consisted of a transformation reactor and a growth reactor. The anaerobic fixed film bioreactor showed more than 99 % of PCE transformation into cis DCE in the range of influent PCE concentration from 5 μM to 35 μM at hydraulic retention time of 48h. On the other hand, efficient degradation of the resultant cis DCE by strain R5 in the following aerobic system could not be achieved due to oxygen limitation. However, 54% of the maximum cis DCE degradation was obtained when 10 μmol of hydrogen peroxide (H 2O 2) was supplemented to the transformation reactor as an additional oxygen source. Further studies are needed to achieve more efficient co metabolic degradation of cis DCE in the aerobic reactor.
基金supported by the National Natural Science Foundation of China(Grant Nos.42225705,42177006)Zhejiang Provincial Key Research and Development Program of China(Grant No.2023C02004)+1 种基金the National Key Research and Development Program of China(Grant No.2022YFC3702401)China Agriculture Research System of MOF and MARA(Grant No.CARS-04).
文摘Chlorinated organic pollutants(COPs),both emerging and traditional,are typical persistent pollutants that harm soil health worldwide.Dechlorinators mediated reductive dechlorination is the optimal way to completely remove COPs from anaerobic soil through a redox reaction driven by electron transfer during microbial anaerobic respiration.Generally,the dechlorinated depletion of COPs in situ often interacts with multiple element biogeochemical activities,e.g.,methanogenesis,sulfate reduction,iron reduction,and denitrification.Elucidating the relevance of biogeochemical cycles between COPs and multiple elements and the coupled mechanisms involved,thus,helps to develop effective pollution control strategies with the balance between pollution degradation and element cycles in heterogeneous soil,ultimately contributing to“one health”goal.In this review,we summarized the microbial-chemical coupling redox processes and the driving factors,elucidated the interspecies metabolites exchange and electron transfer mechanisms within COP-dechlorinating communities,and further proposed a detailed design,construction,and analysis framework of engineering COP-dechlorinating microbiomes via“top-down”selfassembly and“bottom-up”synthesis to pave the way from laboratory to practical field application.Especially,we delve into the major challenges and perspectives surrounding the design of state-of-the-art synthetic microbial communities.Our goal is to improve the understanding of the microbial-mediated coupling between reductive dechlorination and element biogeochemical cycling,with a particular focus on the implications for health-integrated soil bioremediation under the“one health”concept.
基金Acknowledgements The authors acknowledge the financial support of the ability construction project of local Colleges and Universities in Shanghai （No. 16070503000）, Special Fund of State Key Joint Laboratory of Environment Simulation and Pollution Control （No. 16K10ESPCT）, Shanghai Gaofeng ＆ Gaoyuan Project for University Academic Program Development, and the United States National Science Foundation （No. O651794）.
文摘It is common that 2,4,6-trichlorophenol （TCP） coexists with nitrate or nitrite in industrial wastewaters. In this work, simultaneous reductive dechlorination of TCP and denitrification of nitrate or nitrite competed for electron donor, which led to their mutual inhibition. All inhibitions could be relieved to a certain degree by augmenting an organic electron donor, but the impact of the added electron donor was strongest for TCP. For simultaneous reduction ofTCP together with nitrate, TCP＇s removal rate value increased 75% and 150%, respectively, when added glucose was increased from 0.4 mmol· L^-1 to 0.5 mmol· L^-1 and to 0.76 mmol· L^-1 For comparison, the removal rate for nitrate increased by only 25% and 114% for the same added glucose. The relationship between their initial biodegradation rates versus their initial concentrations could be represented well with the Monod model, which quantified their half-maximum-rate concentration （Ks value）, and Ks values for TCP, nitrate, and nitrite were larger with simultaneous reduction than independent reduction. The increases in Ks are further evidence that competition for the electron donor led to mutual inhibition. For bioremediation of wastewater containing TCP and oxidized nitrogen, both reduction reactions should proceed more rapidly if the oxidized nitrogen is nitrite instead of nitrate and if readily biodegradable electron acceptor is augmented.
基金supported by the National Natural Science Foundation of China(Grant Nos.41201313&41230858)
文摘Chlorinated persistent organic pollutants, including polychlorinated biphenyls （PCBs）, represent a particularly serious environmental problem and human health risk worldwide. Leguminous plants and their symbiotic bacteria （rhizobia） are important components of the biogeochemical cycling of nitrogen in both agricultural and natural ecosystems. However, there have been relatively few detailed studies of the remediation of PCB-contaminated soils by legume-rhizobia symbionts. Here we report for the first time evidence of the reductive dechlorination of 2,4,4＇-trichlorobiphenyl （PCB 28） by an alfalfa-rhizobium nitrogen fixing symbiont. Alfalfa （Medicago sativa L.） inoculated with wild-type Sinorhizobiurn meliloti had significantly larger biomass and PCB 28 accumulation than alfalfa inoculated with the nitrogenase negative mutant rhizobium SmY. Dechlorination products of PCB 28, 2,4＇-dichlorobiphenyl （PCB 8）, and the emission of chloride ion （C1-） were also found to decrease significantly in the ineffective nodules infected by the mutant strain SmY. We therefore hypothesize that N2-fixation by the legume-rhizobium symbiont is coupled with the reductive dechlorination of PCBs within the nodules. The combination of these two processes is of great importance to the biogeochemical cycling and bioremediation of organochlorine pollutants in terrestrial ecosystems.
基金supported by the Natural Science Foundation of Hunan Province of China (No.2020JJ4194)the Shenzhen Science and Technology Program (No.JCYJ20220530160412027)+4 种基金the Changsha Science and Technology Program (No.kq2004022)the Science and Technology Innovation Program of Hunan Province (No.2022RC1026)the Project of the National Key Research and Development Program of China (No.2021YFC1910400)the Technical Innovation Leading Plan Project for Hunan High-tech Industry (Nos.2020SK2042 and2022GK4062)the Key R&D Project of Hunan Province of China (No.2022SK2067)。
文摘The dehalogenation of organohalides has been a research hotspot in bioremediation field;however,the influence of tourmaline,a natural ore that can generate spontaneous electric field,on organohalide-respiring bacteria(OHRB)and their dechlorination process is not well known.In this study,the effect and mechanism of tourmaline on the reductive dechlorination of 2,3-dichlorophenol(2,3-DCP)by Desulfitobacterium hafniense DCB-2Twere explored.The characterization results confirmed that tourmaline had good stability and the optimal dosage of tourmaline was 2.5 g/L,which shortened the total time required for dechlorination reaction to 72 hr.Besides,tourmaline amendment also increased the proportion of 2-chlorophenol(2-CP)from 18%to 30%of end products,while that of 3-CP decreased correspondingly.The theoretical calculations showed that the bond charge of the orthosubstituted chlorine declined from-0.179 to-0.067,and that of meta-substituted chlorine increased from-0.111 to-0.129,which indicated that the spontaneous electric field of tourmaline affected the charge distribution of 2,3-DCP and was more conducive to the generation of 2-CP.Overall,tourmaline with the spontaneous electric field affected the reductive dechlorination pathway of Desulfitobacterium,and the tourmaline-OHRB combining system might serve as a novel strategy for the bioremediation of environments polluted with chlorinated phenols.
基金Acknowledgements This work was financial supported by grants from the National Natural Science Foundation of China （Grant Nos. 51108014 and 41671310）.
文摘The toxic and recalcitrant polychlorinated biphenyls （PCBs） adversely affect human and biota by bioaccumulation and biomagnification through food chain. In this study, an anaerobic microcosm was developed to extensively dechlorinate hexa- and hepta-CBs in Aroclor 1260. After 4 months of incubation in defined mineral salts medium amended PCBs （70μmol· L^-1） and lactate （10 mmol· L^-1）, the culture dechlorinated hexa-CBs from 40.2% to 8.7% and hepta-CBs 33.6% to 11.6%, with dechlorination efficiencies of 78.3% and 65.5%, respectively （all in moL ratio）. This dechlorination process led to tetra-CBs （46.4%） as the predominant dechlorination products, followed by penta- （22.1%） and tri-CBs （5.4%）. The number of meta chlorines per biphenyl decreased from 2.50 to 1.41. Results of quantitative real-time PCR show that Dehalococcoides cells increased from 2.39 × 10^5±0.5× 10^5 to 4.99 ×10^7±0.32 ×10^7 copies mL^-1 after 120 days of incubation, suggesting that Dehalococcoides play a major role in reductive dechlorination of PCBs. This study could prove the feasibility of anaerobic reductive culture enrichment for the dehalogenation of highly chlorinated PCBs, which is priorto be applied for in situ biorernediation of notorious halogenated compounds.
基金financially supported by the Guangdong Basic and Applied Basic Research Foundation(No.2021A1515110954)National Key Research and Development Projects of China(No.2022YEC3203302)+1 种基金Guangdong Province Enterprise Science and Technology Commissioner Project(No.GDKTP2021048000)National Natural Science Foundation of China(No.41907292)。
文摘Herein,the degradation of florfenicol(FLO)over zero-valent iron(ZVI)enhanced by SiC was systematically investigated.It was found that 5 g/L of ZVI/SiC(1:3)at pH 3.0 could completely degrade 20 mg/L of FLO within 1 h,with a Kobsvalue of 0.0873 min^(-1),12.5 times greater than that of pure ZVI(0.0069 min^(-1)).Vibrating sample magnetometer(VSM)characterizations revealed that the use of SiC supporter reduces the magnetic intensity of ZVI,which mitigates iron particle agglomeration,increases Brunauer-Emmett-Teller(BET)surface area,and enhances FLO degradation efficiency.Furthermore,ZVI/SiC exhibits a much lower hydrogen evolution potential(HEP)and significantly higher corrosion currents compared to pure ZVI.FLO was proposed to undergo degradation via reductive dechlorination,involving a hydrogenolysis mechanism that entails the cleavage of theσbond.This study provides new insights into the reduction hydrogenation mechanism of ZVI.
基金supported by the National Natural Science Foundation of China (No.41201314)the Open Fund Project of State Key Laboratory of Soil and Sustainable Agriculture (No.0812201227)
文摘The application of electron donor and electron shuttle substances has a vital influence on electron transfer,thus may affect the reductive dechlorination of 1,1,1-trichoro-2,2-bis（p-chlorophenyl）ethane（DDT） in anaerobic reaction systems.To evaluate the roles of citric acid and anthraquinone-2,6-disulfonate（AQDS） in accelerating the reductive dechlorination of DDT in Hydragric Acrisols that contain abundant iron oxide,a batch anaerobic incubation experiment was conducted in a slurry system with four treatments of（1） control,（2） citric acid,（3） AQDS,and（4） citric acid ＋ AQDS.Results showed that DDT residues decreased by 78.93%-92.11% of the initial quantities after 20 days of incubation,and 1,1-dichloro-2,2-bis（4-chlorophenyl）-ethane（DDD） was the dominant metabolite.The application of citric acid accelerated DDT dechlorination slightly in the first 8 days,while the methanogenesis rate increased quickly,and then the acceleration effect improved after the 8th day while the methanogenesis rate decreased.The amendment by AQDS decreased the Eh value of the reaction system and accelerated microbial reduction of Fe（III） oxides to generate Fe（II）,which was an efficient electron donor,thus enhancing the reductive dechlorination rate of DDT.The addition of citric acid ＋ AQDS was most efficient in stimulating DDT dechlorination,but no significant interaction between citric acid and AQDS on DDT dechlorination was observed.The results will be of great significance for developing an efficient in situ remediation strategy for DDT-contaminated sites.
文摘Chlorobenzene was dechlorinated by Pd/Fe bimetallic system in water through catalytic reduction. The dechlorination rate increases with increase of bulk loading of Pd due to the increase of both the surface loading of the Pd and the total surface area. For conditions with 0.005% Pd/Fe, 45% dechlorination efficiency was achieved within 5 h. The dechlorinated reaction is believed to take place on the bimetal surface in a pseudo-first-order reaction, with the rate constant being 0.0043 min-1.
文摘Catalytic reductive dechlorination of monochlorobenzene(MCB) was carried out in the palladium/iron system. With low Pd loading(0 005%), 45% dechlorination efficiency was achieved within 5 h. Pd as catalyst accelerated the reductive dechlorination reaction. Dechlorination mechanism and kinetics were discussed. The reaction took place on the bimetal surface in a pseudo first order reaction, with the rate constant being 0 0071 min -1 ( K SA =8 0×10 -3 L/(m 2·h). The reduction product for MCB was benzene.
基金the Returnee Foundation of Ministry of Education of China (No. 2002-247)Science and Technology Project of Zhejiang Province (No. 2004C34006).
文摘o-Dichlorobenzene (o-DCB) was dechlorinated by Pd/Fe powder in water throughcatalytic reduction. The dechlorination reaction is believed to take place on the surface site ofthe catalyst via a pseuclo-first-order reaction. The final reduction product of o-DCB is benzene.The dechlorination rate increases with the increase of bulk loading of palladium due to the increaseof both the surface loading of palladium and the total surface area. Dechlorination efficiencyaccounts for 90% at Pd/Fe mass ratio 0.02% and metal to solution ratio about 53.3g · L^(-1) in 120minutes. Dechlorination is affected by the reaction temperature, pH, Pd/Fe ratio and the addition ofPd/Fe. E_a is found to be 102.5 kJ · mol^(-1) in the temperature range of 287—313 K.
基金financially-supported by the National Natural Science Foundation of China(Nos.21677055,22006045 and 21407052)the National Key Technical Research and Development Program of China(No.2019YFC1805204)+1 种基金Leading Plan for Scientific and Technological Innovation of High-tech Industries of Hunan Province(No.2021GK4060)the Fundamental Research Funds for the Central Universities,HUST(No.2017KFXKJC004).
文摘Activation of(bi)sulfite(S(IV))by metal oxides is strongly limited by low electrons utilization.In this study,two carbon-supported cobalt ferrites spinels(CoFe^(2)O_(4) QDs-GO and CoFe^(2)O_(4) MOFs-CNTs)have been successfully synthesized by one-step solvothermal method.It was found that both catalysts could efficiently activate S(IV),with rapid reductive dechlorination and then oxidative degradation of a recalcitrant antibiotic chloramphenicol(CAP).Characterizations revealed that CoFe^(2)O_(4) spinels were tightly coated on the carbon bases(GO and CNTs),with effectiveness of the internal transfer of electrons.O_(2)˙−was identified for the reductive dechlorination of CAP,with simultaneously detection of both•OH and SO_(4)^(˙−)responsible for further oxidative degradation.The sulfur oxygen radical conversion reactions and molecular oxygen activation would occur together upon the carbon-based spinels.Spatial-separated interfacial reductive-oxidation of CAP would occur with dechlorination of CAP by O_(2)^(˙−)on the carbon bases,and oxidative degradation of intermediates by SO_(4)^(˙−/•)OH upon the CoFe^(2)O_(4) catalysts.
基金Acknowledgments This research was jointly supported by National Science Foundation of China （No. 20777092）, the ministry of Science and Technology of China （2007CB407304） and Natural science foundation of Zhejiang province of China （Y307025）.
文摘Dicofol type DDTs-contamination is of great concern as environmental organochlorine pollutant. In the present study, dechlorination time-course ofp,p＇-DDT and p,p＇-DDE in dithionite treated waterlogged DDTs-contaminated soil, non-contaminated soil solution and citrate-bicarbonate buffer （0, 50, 100 mmol L^-1, dithionite） for 72 hrs was investigated based on residual amount of p,p＇-DDTs （p,p＇-DDT and p,p＇-DDE） analyzed by GC-ECD. The metabolites ofp,p＇-DDTs in dithionite treated non-contaminated soil solution, and citrate-bicarbonate buffer were detected by GC-MSD. The dechlorination time-course of p,p＇-DDT and p,p＇-DDE exhibited rapid dechlorination at the first 3.0 hrs, slow dechlorination after 3.0 hrs. For 50 mmol L^-1 dithionite treatments, the dechlorination ratios ofp,p＇-DDT and p,p＇-DDE were 36.42% and 35.08% respectively at 3.0 hrs. For 100 mmol L^-1 dithionite treatments, the dechlorination ratios of p,p＇-DDT and p,p＇-DDE were 58.62% and 57.39% respectively at 3.0 hrs in DDTs-contaminated soils. Significant differences of dechlorination ratio were also confirmed in dependence on dithionite concentrations, reaction systems and the chemical structure of DDTs. The dechlorination ratio ofp,p＇-DDT/DDE increased with the increasing of dithionite concentrations irrespective of reaction systems. Dithionite-induced dechlorination ratio of p,p＇-DDT was higher than that of p,p＇-DDE. The p,p＇-DDD （1,1-dichloro-2,2-bis（4-chlorophenyl）-ethane）, p,p＇-DDE and p,p＇-DDMU （1-chloro-2,2-bis（4-chloropheny）-ethylene） were identified to be metabolites ofp,p＇-DDT in buffer and non-contaminated soil solution, however, no metabolites ofp,p＇-DDE treated by dithionite were detected. The possible pathways explaining the dechlorination of p,p＇-DDT and p,p＇-DDE by dithionite were also proposed. Dithionite could be used to develop an effective and fast remediation option for DDTs-contaminated soils and sediments.
基金Project (No. 30270767) supported by the National Natural Science Foundation of China
文摘Detoxification of chlorinated organic compounds via reaction with nickel/iron powder was implemented in aqueous solution. Compared to iron, nickel/iron bimetallic powder had higher hydrodechlorination activities for both atrazine (ATR) and p-chlorophenol (pCP); nickel/iron (2.96%, w/w) was shown to have the largest specific surface area and the optimum proportion for the dechlorination of both ATR and pCP. Electrochemical measurements showed that the adsorbed hydrogen atom on the nickel must have been the dominant reductive agent for the dechlorination of both ATR andpCP in this system.
基金support of the experimental tasks for the Savannah River Operations Office under grant No.DE-RP0902SR22229
文摘Research works in the recent past have revealed three major biodegradation processes leading to the degradation of trichloroethylene. Reductive dechlorination is an anaerobic process in which chlorinated ethenes are used as electron acceptors. On the other hand, cometabolism requires oxygen for enzymatic degradation of chlorinated ethenes, which however yields no benefit for the bacteria involved. The third process is direct oxidation under aerobic conditions whereby chlorinated ethenes are directly used as electron donors by microorganisms. This review presented the current research trend in understanding biodegradation mechanisms with regard to their field applications. All the techniques used are evaluated, with the focus being on various factors that influence the process and the outcome.
文摘Degradation of 2, 4, 6 trichlorophenol(TCP) with co immobilizing anaerobic granular sludge and isolated aerobic bacterial species was studied in coupled anaerobic/aerobic integrated reactors. The synergism of aerobes and anaerobes within co immobilized granule might facilitate degrading the TCP and exchange of anaerobic metabolites 4 CP, which promoted system organic removal efficiency and recovered from organic shock loads more quickly. The biomass specific activities experiment further confirmed that strict anaerobes be not affected over the course of this experiment by the presence of an oxic environment, aerobic activity predominated in the outer co immobilized granule layers, while the interior was characterized by anaerobic activity. The co immobilized granule could thus enable both aerobic and anaerobic microbes function in the same reactor and thereby integrate the oxidative and reductive catabolism.
基金supported by the Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences (No. SEPR20174)the National Natural Science Foundation of China (No. 41671318)。
文摘Humic substances acting as an electron shuttle and nitrogen transformation process influence remarkably the electron transfer in anaerobic reaction systems and thus may affect the reductive dechlorination of hexachlorobenzene(HCB). In order to develop an efficient agricultural strategy for the remediation of organochlorine-contaminated soils, a batch incubation experiment was conducted to study the effects of humic acid, urea, and their interaction on the reductive dechlorination of HCB in a Hydragric Acrisol with high iron oxide content. After 44 d of anaerobic incubation, the five treatments, sterile control,control, humic acid, urea, and humic acid + urea decreased HCB residues by 28.8%, 47.8%, 64.7%, 57.8%, and 71.3%, respectively. The amendment of humic acid or urea significantly decreased soil Eh values and accelerated Fe(Ⅲ) reduction to Fe(Ⅱ), thus promoting markedly reductive dechlorination of HCB. Humic acid had a larger dechlorination effect than urea. Since there was a synergistic interaction between humic acid and urea that accelerated HCB dechlorination, the treatment having both amendments together was the most efficient for HCB dechlorination. The results showed that the combination of NH4^(+)_(-)N supplied by a fertilizer and humic substance is a feasible strategy for the remediation of organochlorine-contaminated soils with abundant iron oxide.
文摘Tetrachloroethene （PCE） is biodegraded by reductive dechlorination with co-metabolism substrates under anaerobic conditions. By inoculating sludge from an anaerobic pool, a biodegradation test of PCE is conducted in the anaerobic condition. In the test, several substrates including methanol, ethanol, formate, acetate, lactate and glucose, are conducive to the conversion from PCE to TCE and 1,1-DCE. The results show the microbe can be cultivated well under the anaerobic circumstances of mixture of sewage （sludge） and soil with the index of COD after eleven days. Degradation of PCE accords with one order reaction kinetics equation. The sequence of the reaction rate constant is Kacetate 〉Kglucose 〉 Klactate 〉 Kethanol 〉 Kformate 〉 Kmethanol, and acetate is an outstanding co-metabolism substratum whose reaction rate constant is 0.6632d^-1.
基金This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 826244-ELECTRA”.Prof.Mauro Majone is acknowledged for his fruitful support during the experimental activity.
文摘Electro-bioremediation offers a promising approach for eliminating persistent pollutants from groundwater since allows the stimulation of biological dechlorinating activity,utilizing renewable electricity for process operation and avoiding the injection of chemicals into aquifers.In this study,a two-chamber microbial electrolysis cell has been utilized to achieve both reductive and oxidative degradation of tetrachloroethane(TeCA).By polarizing the graphite granules cathodic chamber at650 mV vs the standard hydrogen electrode and employing a mixed metal oxide(MMO)counter electrode for oxygen production,the reductive and oxidative environment necessary for TeCA removal has been established.Continuous experiments were conducted using two feeding solutions:an optimized mineral medium for dechlorinating microorganisms,and synthetic groundwater containing sulphate and nitrate anions to investigate potential side reactions.The bioelectrochemical process efficiently reduced TeCA to a mixture of trans-dichloroethylene,vinyl chloride,and ethylene,which were subsequently oxidized in the anodic chamber with removal efficiencies of 37±2%,100±4%,and 100±5%,respectively.The introduction of synthetic groundwater with nitrate and sulphate stimulated reductions in these ions in the cathodic chamber,leading to a 17%decrease in the reductive dechlorination rate and the appearance of other chlorinated by-products,including cis-dichloroethylene and 1,2-dichloroethane(1,2-DCA),in the cathode effluent.Notably,despite the lower reductive dechlorination rate during synthetic groundwater operation,aerobic dechlorinating microorganisms within the anodic chamber completely removed VC and 1,2-DCA.This study represents the first demonstration of a sequential reductive and oxidative bioelectrochemical process for TeCA mineralization in a synthetic solution simulating contaminated groundwater.
