Efficient biodegradation of chlorobenzene via monooxygenation pathways by Pandoraea sp. XJJ-1 with high potential for groundwater bioremediation.

Chlorobenzene (CB), extensively used in industrial processes, has emerged as a significant contaminant in soil and groundwater. The eco-friendly and cost-effective microbial remediation has been increasingly favored to address this environmental challenge. In this study, a degrading bacterium was isolated from CB-contaminated soil at a pesticide plant, identified as Pandoraea sp. XJJ-1 (CCTCC M 2021057). This strain completely degraded 100 mg·L-1 CB and showed extensive degradability across a range of pH (5.0-9.0), temperature (10-37 °C), and CB concentrations (100-600 mg·L-1). Notably, the degradation efficiency was 85.2% at 15 °C, and the strain could also degrade six other aromatic hydrocarbons, including benzene, toluene, ethylbenzene, and xylene (o-, m-, p-). The metabolic pathway of CB was inferred using ultraperformance liquid chromatography, gas chromatography-mass spectrometry, and genomic analysis. In strain XJJ-1, CB was metabolized to o-chlorophenol and 3-chloroxychol by CB monooxygenase, followed by ortho-cleavage by the action of 3-chlorocatechol 1,2-dioxygenase. Moreover, the presence of the chlorobenzene monooxygenation pathway metabolism in strain XJJ-1 is reported for the first time in Pandoraea. As a bacterium with low-temperature resistance and composite pollutant degradation capacity, strain XJJ-1 has the potential application prospects in the in-situ bioremediation of CB-contaminated sites.

AIEE-active dichlorobenzene and chlorobenzene ratiometric fluorescent probe based on [2.2]paracyclophane.

Two AIEE-active [2.2]paracyclophanyl-based diester and monoester (1a and 1b) were facilely synthesized by one-pot method and applied as ratiometric fluorescent probe to detect dichlorobenzene (DCB) and chlorobenzene (CB). Compared with compound 1b, 1a exhibits high sensitivity and low detection limits for DCB and CB in dichloromethane (DCM), particularly, the detection sensitivities for ortho-dichlorobenzene (o-DCB), meta-dichlorobenzene (m-DCB) and chlorobenzene can be modulated by AIEE behavior with lower detection limits of 23.64, 56.27, and 5.92 ppm, respectively in THF/H2O mixed solutions with water fraction (fw) of 70 % due to the formation of aggregation-state. The X-ray structure analysis, theoretical calculations and photophysical properties in different solvents were investigated to reveal the distinctive photophysical behaviors of 1a and 1b. The facile synthesis, X-ray structure, AIEE modulated sensing properties for o-DCB, m-DCB, and CB in DCM and THF/H2O mixed solutions make 1a potential application as fluorescent probe for trace DCB and CB detection in drinking water.

Catalytic Oxidation of Chlorobenzene over Amorphous Manganese-Chromium Catalysts Supported by UiO-66-Derived ZrOx.

The development of efficient catalysts with longevity to remove chlorobenzene is challenging due to Cl poisoning. Herein, a series of Mn-Cr/ZrOx catalysts supported by Zr-based metal-organic framework (UiO-66)-derived ZrOx was prepared and investigated for chlorobenzene (CB) catalytic oxidation. MnCr/ZrOx-M prepared via a wet impregnation method presented an amorphous structure, indicating the homogeneous dispersion of Cr and Mn, which improved acid and redox properties. 40Mn7Cr3/ZrOx-M exhibited the best catalytic activity for chlorobenzene oxidation with T90 of 293 °C, which is mainly due to the strong interaction between manganese and chromium promoted by the large specific surface area of the ZrOx support. Furthermore, 40Mn7Cr3/ZrOx-M presented excellent stability for chlorobenzene oxidation.

Effect of support structure of Pt/silicaite-1 catalyst on non-thermal plasma (NTP) assisted chlorobenzene degradation and PCDD/Fs formation.

Development of efficient catalysts for non-thermal plasma (NTP) assisted catalysis to mitigate the formation of harmful by-products is a significant challenge in the degradation of chlorinated volatile organic compounds (Cl-VOCs). In this study, catalytically active Pt nanoparticles supported on non-porous SiO2 and silicalite-1 zeolites (S1) with different pore structure were comparatively investigated for catalytic chlorobenzene degradation under NTP condition. It was shown that the pore structure could significantly impact the metal size and metal dispersion rate. Pt supported on modified S1 hierarchical meso-micro-porous silicalite-1 (Pt/D-S1) exhibited the smallest particle size (∼6.19 nm) and the highest dispersion rate (∼1.87). Additionally, Pt/D-S1 demonstrated superior catalytic performance compared to the other catalysts, achieving the highest chlorobenzene conversion and COx selectivity at about 80% and 75%, respectively. Furthermore, the pore structure also affected the formation of by-products according to the findings from GC-MS analysis. Pt/SiO2 generated a total of 18 different species of organic compounds, whereas only 12 species of organic by-products were identified in the Pt/D-S1 system (e.g. polychlorinated compounds like 3,4 dichlorophenol were exclusively identified in Pt/SiO2). Moreover, dioxin-like polychlorinated biphenyl and other chlorinated organic compounds, which have potential to form highly toxic dioxins, were detected in the catalysts. HRGC-HRMS confirmed and quantified the 17 different dioxin/furans formed on Pt/SiO2 (25,100 ng TEQ kg-1), Pt/S1 (515 ng TEQ kg-1) and Pt/D-S1 (367 ng TEQ kg-1). The correlation between synthesis-structure-performance in this study provides insights into the design of catalysts for deep oxidation of Cl-VOCs in NTP system.

Reduction characteristic of chlorobenzene by a newly isolated Paenarthrobacter ureafaciens LY from a pharmaceutical wastewater treatment plant.

A highly efficient chlorobenzene-degrading strain was isolated from the sludge of a sewage treatment plant associated with a pharmaceutical company. The strain exhibited a similarity of over 99.9% with multiple strains of Paenarthrobacter ureafaciens. Therefore, the strain was suggested to be P. ureafaciens LY. This novel strain exhibited a broad spectrum of pollutant degradation capabilities, effectively degrading chlorobenzene and other organic pollutants, such as 1, 2, 4-trichlorobenzene, phenol, and xylene. Moreover, P. ureafaciens LY co-metabolized mixtures of chlorobenzene with 1, 2, 4-trichlorobenzene or phenol. Evaluation of its degradation efficiency showed that it achieved an impressive degradation rate of 94.78% for chlorobenzene within 8 h. The Haldane-Andrews model was used to describe the growth of P. ureafaciens LY under specific pollutants and its concentrations, revealing a maximum specific growth rate (µmax ) of 0.33 h-1 . The isolation and characterization of P. ureafaciens LY, along with its ability to degrade chlorobenzene, provides valuable insights for the development of efficient and eco-friendly approaches to mitigate chlorobenzene contamination. Additionally, investigation of the degradation performance of the strain in the presence of other pollutants offers important information for understanding the complexities of co-metabolism in mixed-pollutant environments.

Catalytic Oxidation of Chlorobenzene over HSiW/CeO2 as a Co-Benefit of NOx Reduction: Remarkable Inhibition of Chlorobenzene Oxidation by NH3.

There is an urgent need to develop novel and high-performance catalysts for chlorinated volatile organic compound oxidation as a co-benefit of NOx. In this work, HSiW/CeO2 was used for chlorobenzene (CB) oxidation as a co-benefit of NOx reduction and the inhibition mechanism of NH3 was explored. CB oxidation over HSiW/CeO2 primarily followed the Mars-van-Krevelen mechanism and the Eley-Rideal mechanism, and the CB oxidation rate was influenced by the concentrations of surface adsorbed CB, Ce4+ ions, lattice oxygen species, gaseous CB, and surface adsorbed oxygen species. NH3 not only strongly inhibited CB adsorption onto HSiW/CeO2, but also noticeably decreased the amount of lattice oxygen species; hence, NH3 had a detrimental effect on the Mars-van-Krevelen mechanism. Meanwhile, NH3 caused a decrease in the amount of oxygen species adsorbed on HSiW/CeO2, which hindered the Eley-Rideal mechanism of CB oxidation. Hence, NH3 significantly hindered CB oxidation over HSiW/CeO2. This suggests that the removal of NOx and CB over this catalyst operated more like a two-stage process rather than a synergistic one. Therefore, to achieve simultaneous NOx and CB removal, it would be more meaningful to focus on improving the performances of HSiW/CeO2 for NOx reduction and CB oxidation separately.

Efficient Catalytic Elimination of Chlorobenzene Based on the Water Vapor-Promoting Effect within Mn-Based Catalysts: Activity Enhancement and Polychlorinated Byproduct Inhibition.

Achieving no or low polychlorinated byproduct selectivity is essential for the chlorinated volatile organic compounds (CVOCs) degradation, and the positive roles of water vapor may contribute to this goal. Herein, the oxidation behaviors of chlorobenzene over typical Mn-based catalysts (MnO2 and acid-modified MnO2) under dry and humid conditions were fully explored. The results showed that the presence of water vapor significantly facilitates the deep mineralization of chlorobenzene and restrains the formation of Cl2 and dichlorobenzene. This remarkable water vapor-promoting effect was conferred by the MnO2 substrate, which could suitably synergize with the postconstructed acidic sites, leading to good activity, stability, and desirable product distribution of acid-modified MnO2 catalysts under humid conditions. A series of experiments including isotope-traced (D2O and H218O) CB-TPO provided complete insights into the direct involvement of water molecules in chlorobenzene oxidation reaction and attributed the root cause of the water vapor-promoting effect to the proton-rich environment and highly reactive water-source oxygen species rather than to the commonly assumed cleaning effect or hydrogen proton transfer processes (generation of active OOH). This work demonstrates the application potential of Mn-based catalysts in CVOCs elimination under practical application conditions (containing water vapor) and provides the guidance for the development of superior industrial catalysts.

Defects materials of Institut Lavoisier-125(Ti) materials enhanced photocatalytic activity for toluene and chlorobenzene mixtures degradation: Mechanism study.

In this paper, the effect of three monocarboxylic acids on MIL-125 synthesis was systematically investigated and the results were discussed in detail. X-ray diffractometry (XRD) and nitrogen adsorption-desorption curves indicated that small molecule acids (acetic acid, propionic acid and butyric acid) affected the morphology of MIL-125 and induced lamellar pores and structural defects in the crystals. Thermogravimetric measurements confirmed the presence of acid-regulated defective metal-organic frameworks (MOFs). Electrochemical tests and density function theory calculations indicated that acid modulation could change the forbidden bandwidth of the material. The acid modification strategy effectively promoted the transfer of photogenerated electrons and enhanced the adsorption and activation of O2 and H2O molecules, generating reactive radicals. The modified MOFs also showed excellent performance in the removal of mixed toluene and chlorobenzene. The degradation pathways of the mixture were analyzed by in situ infrared (IR) and gas chromatography-mass spectrometry (GC-MS). The mixture was converted to chlorophenolic intermediates in the presence of reactive oxygen species, further decomposed to form ethers and ethanol, and finally formed small molecules such as carbon dioxide and water. A feasible method was provided for the preparation of photocatalysts for the treatment of mixed VOCs.

Enhanced chlorobenzene removal by internal magnetic field through initial cell adhesion and biofilm formation.

Magnetic fields (MF) have been proven efficient in bioaugmentation, and the internal MFs have become competitive because they require no configuration, despite their application in waste gas treatment remaining largely unexplored. In this study, we firstly developed an intensity-regulable bioaugmentation with internal MF for gaseous chlorobenzene (CB) treatment with modified packing in batch bioreactors, and the elimination capacity increased by up to 26%, surpassing that of the external MF. Additionally, the microbial affinity to CB and the packing surface was enhanced, which was correlated with the ninefold increased secreted ratio of proteins/polysaccharides, 43% promoted cell surface hydrophobicity, and half reduced zeta potential. Furthermore, the dehydrogenase content was promoted over 3 times, and CB removal steadily increased with the rising intensity indicating enhanced biofilm activity and reduced CB bioimpedance; this was further supported by kinetic analysis, which resulted in improved cell adhesive ability and biological utilisation of CB. The results introduced a novel concept of adjustable magnetic bioaugmentation and provided technical support for industrial waste gas treatments. KEY POINTS: • Regulable magnetic bioaugmentation was developed to promote 26% chlorobenzene removal • Chlorobenzene mineralisation was enhanced under the magnetic field • Microbial adhesion was promoted through weakening repulsive forces.

Catalytic degradation of chlorinated volatile organic compounds (CVOCs) over Ce-Mn-Ti composite oxide catalysts.

Developing industrially moldable catalysts with harmonized redox performance and acidity is of great significance for the efficient disposal of chlorinated volatile organic compounds (CVOCs) in actual exhaust gasses. Here, commercial TiO2, typically used for molding catalysts, was chosen as the carrier to fabricate a series of Ce0.02Mn0-0.24TiOx materials with different Mn doping ratios and employed for chlorobenzene (CB) destruction. The introduction of Mn remarkedly facilitated the synergistic effect of each element via the electron transfer processes: Ce3++Mn4+/3+↔Ce4++Mn3+/2+ and Mn4+/3++Ti4+↔Mn3+/2++Ti3+. These synergistic interactions in Ce0.02Mn0.04-0.24TiOx, especially Ce0.02Mn0.16TiOx, significantly elevated the active oxygen species, oxygen vacancies and redox properties, endowing the superior catalytic oxidation of CB. When the Mn doping amount increased to 0.24, a separate Mn3O4 phase appeared, which in turn might weaken the synergistic effect. Furthermore, the acidity of Ce0.02Mn0.04-0.24TiOx was decreased with the Mn doping, regulating the balance of redox property and acidity. Notably, Ce0.02Mn0.16TiOx featured relatively abundant B-acid sites. Its coordinating redox ability and moderate acidity promoted the deep oxidation of CB and RCOOH- intermediates, as well as the rapid desorption of Cl species, thus obtaining sustainable reactivity. In comparison, CeTiOx owned the strongest acidity, however, its poor redox property was not sufficient for the timely oxidative decomposition of the easier adsorbed CB, resulting in its rapid deactivation. This finding provides a promising strategy for the construction of efficient commercial molding catalysts to decompose the industrial-scale CVOCs.

Metal-organic framework derived bio-anode enhances chlorobenzene removal and electricity generation: Special Ru4+/Ru3+-bridged intracellular electron transfer.

Efficient removal of chlorinated organic contaminants using the microbial fuel cell (MFC) provides a promising strategy to alleviate water pollution and energy crisis. However, bio-degradation is challenged by poor biofilm formation and sluggish intracellular electron transfer, causing unsatisfactory electricity generation. To address those problems, a metal-organic framework derivative, Ru-porous TiO2 (Ru-PT) bio-anode has been artfully designed herein for chlorobenzene removal. The Ru-PT bio-anode not only formed a compact anodic biofilm due to the large specific surface area of PT, but more importantly, it introduced special pseudocapacitance-enhanced intracellular electron transfer by slowly implanting Ru4+/Ru3+ redox pair into bacteria. Such a Ru4+/Ru3+ implantation was then found to directionally induce the enrichment of a dual-functional genus (degrader & exoelectrogen), Pseudomonas, thereby enhancing the conversion of bio-refractory chlorophenols towards biodegradable carboxylic acids. These features allowed our MFC to have a resilient chlorobenzene removal and accompanied satisfactory electricity generation, with power density, coulombic efficiency, and turnover frequency reaching 662 mW m-2, 8.7%, and 386,622 s-1, which outcompeted those of other MFCs reported. Further, benefiting from the reversible pseudocapacitance, the Ru-PT bio-anode intriguingly functioned as an internal capacitor for electricity storage. This work provided important insights into cost-effective bio-anode development and offered an avenue for engineering MFC.

Wearable Device for Cumulative Chlorobenzene Detection and Accessible Mitigation Strategies.

Chronic exposure to low concentrations of volatile organic compounds (VOCs), such as chlorobenzene, is not being monitored in industrializing countries, although VOC exposure is associated with carcinogenic, organ-toxic, and endocrine-disrupting effects. Current VOC-sensing technologies are inaccessible due to high cost, size, and maintenance or are ineffective due to poor sensitivity or reliability. In particular, marginalized individuals face barriers to traditional prescription VOC treatments due to cost, lack of transportation, and limited access to physicians; thus, alternative treatments are needed. Here, we created a novel cumulative wearable color-changing VOC sensor with a paper-based polydiacetylene sensor array for chlorobenzene. With a single smartphone picture, the sensor displays 14 days of logged chlorobenzene exposure data, interpreted by machine-learning (ML) techniques, including principal component analysis. Further, we explored the efficacy of affordable and accessible treatment options to mitigate a VOC's toxic effects. Vitamin D and sulforaphane are naturally found in cruciferous vegetables, like broccoli, and can be used to treat chlorobenzene-mediated bone degradation. Our platform combines these components into a smartphone app that photographs the sensor's colorimetric data, analyzes the data via ML techniques, and offers accessible treatments based on exposure data.

Homogeneous and heterogeneous atmospheric ozonolysis of chlorobenzene:Mechanism, kinetics and ecotoxicity assessment.

The reactions between chlorobenzene(CB) and ozone have been studied comprehensively in this paper. Chlorobenzene is a commonly found chlorinated aromatic volatile organic compound(VOC), and its emission into the atmosphere can cause harm to the ecosystem and human health. The frequent occurrence of mineral particles from sandstorms exerts a significant influence on the atmospheric chemistry of the troposphere. Mineral particles are abundant in SiO2 and Al2O3 content. Therefore, we investigated the homogeneous and heterogeneous reaction processes of CB and ozone in the atmosphere by using density functional theory (DFT) method at the M06-2X/6-311++g(3df,2p)//M06-2X/6-31+g(d,p) level. The atmospheric fate, reaction rate and toxicity evaluation of CB ozonation were studied in the gas-phase section. Toxicity evaluation results showed that ozonation of CB could effectively reduce its toxicity. For the heterogeneous process, we simulated three types of SiO2 clusters and nine types of (Al2O3)n clusters, and studied the configurations of CB adsorbed on the cluster surfaces. We found that adsorption of CB on the SiO2 clusters was achieved through hydrogen bonding, while adsorption of CB on the Al2O3 clusters was achieved through both hydrogen bonding and metal bonding. The energy for CB adsorption on the (Al2O3)n cluster surface was higher than that for the SixOy(OH)z cluster surface, and both types of clusters exhibited efficient adsorption of CB. As the SixOy(OH)z clusters grew larger, the rates for the reactions between O3 and CB increased. CB travelled long distances along the Al2O3 clusters, leading to an extended influence range.

Anti-Poisoning Mechanisms of Sb on Vanadia-Based Catalysts for NOx and Chlorobenzene Multi-Pollutant Control.

Modulating vanadia-based metal oxides is one of the effective methods for designing difunctional catalysts for simultaneous control of NOx and chlorobenzene (CB) from the emissions of industrial sources. Excessive NH3 adsorption and polychlorinated species accumulation on the surface are the primary issues poisoning catalysts and reducing their lifetime. Herein, Sb is selected as an NH3 adsorption alleviator and polychlorinated species preventor dopant on V2O5-WO3/TiO2. The catalyst exhibits an excellent performance for total NOx and 90% CB conversions at 300-400 °C under a gas hourly space velocity (GHSV) of 60,000 mL g-1 h-1. The HCl and N2 selectivities are maintained at 90 and 98%, respectively. The anti-poisoning ability could be attributed to the generated V-O-Sb chains on the surface: the band gap of vanadium is narrowed and the electron capability is strengthened. The above variation weakens the Lewis acid sites and blocks the electrophilic chlorination reactions of the catalyst surface (formation of polychlorinated species). In addition, oxygen vacancies on Sb-O-Ti also increase: the ring opening of benzoates is accelerated and NH3 adsorption energy is weakened. The above variation lowers the energy barriers of C-Cl cleavage even under NH3 pre-adsorption models and enhances NOx reduction thermodynamically and kinetically.

Nonthermal plasma coupled with liquid-phase UV/Fe-C for chlorobenzene removal.

Catalyst poisoning problems limit the application of gas-solid non-thermal plasma (NTP) catalyzed decomposition of chlorinated volatile organic compounds (Cl-VOCs). To mitigate the catalyst deactivation, catalyst iron-loaded activated carbon (Fe-C) was added to the UV-activated liquid phase downstream of the NTP reactor (NTP + UV/Fe-C(L)) for the degradation of chlorobenzene (CB) in this study. The CB removal efficiency and mineralization efficiency (MR) of NTP + UV/Fe-C(L) were up to 94% and 68%, respectively, which were increased by 39% and 30% compared with the single NTP system. Compared with the conventional gas-solid NTP + UV/Fe-C(S) system, the stability of the NTP + UV/Fe-C(L) system was significantly improved due to the dissolved organic intermediates and low residuals on the catalyst surface. Reactive oxygen species ·OH and ·O2- dominated the decomposition of CB in the liquid phase, and with the help of UV, much more ·OH and ·O2- were produced by Fe-C catalytic O3. In addition, Fe-C improved the removal of CB by increasing its absorption mass transfer coefficient from 0.0016 to 0.0157 s-1. The degradation pathway of CB in the NTP + UV/Fe-C(L) system was proposed based on the detected organic intermediates. Overall, this study provides a new tactic to solve the catalyst poisoning problem in the NTP catalytic oxidation of Cl-VOCs.

Three-dimensional porous CuO-modified CeO2-Al2O3 catalysts with chlorine resistance for simultaneous catalytic oxidation of chlorobenzene and mercury: Cu-Ce interaction and structure.

Chlorine poisoning effects are still challenging to develop efficient catalysts for applications in chlorobenzene (CB) and mercury (Hg0) oxidation. Herein, three-dimensional porous CuO-modified CeO2-Al2O3 catalysts with macroporous framework and mesoporous walls prepared via a dual template method were employed to study simultaneous oxidation of CB and Hg0. CuO-modified CeO2-Al2O3 catalysts with three-dimensional porous structure exhibited outstanding activity and stability for simultaneous catalytic oxidation of CB and Hg0. The results demonstrated that the addition of CuO into CeO2-Al2O3 can simultaneously enhance the acid sites and redox properties through the electronic inductive effect between CuO and CeO2 (Cu2++Ce3+↔Cu++Ce4+). Importantly, the synergistic effect between Cu and Ce species can induce abundant oxygen vacancies formation, produce more reactive oxygen species and facilitate oxygen migration, which is beneficial for the deep oxidation of chlorinated intermediates. Moreover, macroporous framework and mesoporous nanostructure dramatically improved the specific surface area for enhancing the contact efficiency between reactants and active sites, leading to a remarkable decrease of byproducts deposition. CB and Hg0 had function of mutual promotion in this reaction system. In tune with the experimental results, the possible mechanistic pathways for simultaneous catalytic oxidation of CB and Hg0 were proposed.

The XylR/NtrC-type regulator CbsR positively regulates upstream pathway of chlorobenzene degradation in Pandoraea pnomenusa.

AIMS: Pandoraea pnomenusa MCB032 completely degrades chlorobenzene, whose metabolic pathway is encoded by cbs and clc gene clusters. The putative regulatory factors ClcR and CbsR are predicted to regulate the cbs and clc gene clusters. This research aims to understand the function of ClcR and CbsR. METHODS AND RESULTS: RT-PCR analyses demonstrated that the cbsFAaAbAcAdB operon that encodes catabolic pathways for the degradation of chlorobenzene to chlorocatechol is located on an operon. Moreover, the clcABCDE operon is involved in the 3-chlorocatechol pathway. Gene knockout and transcriptional analysis showed that the transcription of the cbsFAaAbAcAdB operon is positively regulated by CbsR, whereas the clcABCDE operon is activated by ClcR. Primer extension analysis was used to locate the transcription start sites of the cbsFAaAbAcAdB and cbsR operons. Electrophoretic mobility shift assay analyses showed that CbsR is bound to the sites in the promoter regions of cbsFAaAbAcAdB and cbsR operons. CONCLUSION: The XylR/NtrC-type regulator CbsR positively regulates the transcription of the cbsFAaAbAcAdB operon encoding the upstream pathway of chlorobenzene catabolism, while the LysR-type regulator ClcR activates the clcABCDE operon encoding the downstream pathway.

Degradation behaviors and accumulative effects of coexisting chlorobenzene congeners on the dechlorination of hexachlorobenzene in soil by nanoscale zero-valent iron.

It is well known that many chlorinated organic pollutants can be dechlorinated by nanoscale zero-valent iron. However, in the real chlorinated organic compounds contaminated soil, the congeners of high- and low-chlorinated isomer often coexist and their dechlorination behaviors are poorly known, such as hexachlorobenzene (HCB). In this work, the degradation behaviors of three coexisting chlorobenzene congeners pentachlorobenzene (PeCB), 1,2,4,5-tetrachlorobenzene (1,2,4,5-TeCB) and 1,2,4-trichlorobenzene (1,2,4-TCB) and the influence of initial pH and reaction temperature on the dechlorination of HCB in HCB-contaminated soil by nanoscale zero-valent iron were studied. The amount and extent of accumulated coexisting chlorobenzenes was analyzed under different environmental conditions. The results indicate that nanoscale zero-valent iron can improve the degradation efficiency of highly toxic chlorinated benzenes and reduce the accumulative effects of highly toxic chlorinated benzenes on dechlorination of HCB. The accumulative effects of three coexisting chlorobenzene congeners on the dechlorination of HCB were ranked as follows: 1,2,4-TCB > 1,2,4,5-TeCB > PeCB.

Formation and Inventory of Polychlorinated Dibenzo-p-dioxins and Dibenzofurans and Other Byproducts along Manufacturing Processes of Chlorobenzene and Chloroethylene.

Chlorinated organic chemicals are produced and used extensively worldwide, and their risks to the biology and environment are of increasing concern. However, chlorinated byproducts [e.g., polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs)] formed during the commercial manufacturing processes and present in organochlorine products are rarely reported. The knowledge on the occurrences and fate of unintentional persistent organic chemicals in the manufacturing of organochlorine chemical is necessary for accurate assessment of the risks of commercial chemicals and their production. Here, PCDD/Fs were tracked throughout chlorobenzene and chloroethylene production processes (from raw materials to final products) by target analysis. Other byproducts that can further transform into PCDD/Fs were also identified by performing non-target screening. As a result, the PCDD/F concentrations were mostly the highest in bottom residues, and the octachlorinated congeners were dominant. Alkali/water washing stages may cause the formation of oxygen-containing byproducts including PCDD/Fs and acyl-containing compounds, so more attention should be paid to these stages. PCDD/Fs were of 0.17 and 0.21-1.2 ng/mL in monochlorobenzene and chloroethylene products, respectively. Annual PCDD/F emissions (17 g toxic equivalent in 2018) during chlorobenzene and chloroethylene production were estimated using PCDD/F emission factors. The results can contribute to the improvement of PCDD/F inventories for the analyzed commercial chemicals.

Synthesis of hierarchical porous carbon with high surface area by chemical activation of (NH4)2C2O4 modified hydrochar for chlorobenzene adsorption.

In this work, hydrothermal technique combined with KOH activation were employed to develop a series of porous carbons (NPCK-x) using tobacco stem as a low-cost carbon source and (NH4)2C2O4 as a novel nitrogen-doping agent. Physicochemical properties of NPCK-x were characterized by Brunauer-Emmett-Teller, field emission scanning electron microscopy, X-ray diffraction, Raman microscope, elemental analysis, and X-ray photoelectron spectroscopy. Results showed that the NPCK-x samples possessed large surface areas (maximum: 2875 m2/g), hierarchical porous structures, and high degree of disorder. N-containing functional groups decomposed during activation process, which could be the dominant reason for appearance of abundant mesopores and well-developed pore structure. Dynamic chlorobenzene adsorption experiments demonstrated that carbon materials with (NH4)2C2O4 modification exhibited higher adsorption capacity (maximum: 1053 mg/g) than those without modification (maximum: 723 mg/g). The reusability studies of chlorobenzene indicated that the desorption efficiency of (NH4)2C2O4 modified porous carbon reached 90.40% after thermal desorption at 100°C under N2 atmosphere. Thomas model fitting results exhibited that the existence of mesopores accelerated the diffusion rate of chlorobenzene in porous carbon. Moreover, Grand Canonical Monte Carlo simulation was conducted to verify that micropores with pore sizes of 1.2-2 nm of the optimized porous carbon were the best adsorption sites for chlorobenzene and mesopores with pore sizes of 2-5 nm were also highly active sites for chlorobenzene adsorption.