Dechlorination Performance Research Articles

Enhanced microbial dechlorination of PCBs by anaerobic digested sludge and enrichment of low-abundance PCB dechlorinators.

The slow rate of anaerobic microbial dechlorination in natural environments limits the application of polychlorinated biphenyl (PCB) bioremediation. Anaerobic digested sludge (ADS), abundant in nutrients and microorganisms, could be an effective additive to improve microbial dechlorination. This research investigates the influence of ADS on Aroclor 1260 dechlorination performance, microbial community composition, and the abundance of functional genes. Moreover, further enrichment of organohalide-respiring bacteria (OHRB) was examined using tetrachloroethene (PCE) as the electron acceptor, followed by the serial dilution-to-extinction method in conjunction with resuscitation promoting factor (Rpf) supplementation. The results demonstrated that the addition of 5g/L ADS achieved more extensive and efficient dechlorination of PCBs. ADS enhanced the removal of meta- and para-chlorine without significantly changing the dechlorination pathways. The abundances of dechlorinators, including Dehalobium and Dehalobacter within the Chloroflexi and Firmicutes phyla, as well as non-dechlorinators from the Desulfobacterota, Euryarchaeota, and Bacteroidetes phyla, were significantly increased with ADS amendment. Similarly, an increased abundance of bacteria, OHRB, reductive dehalogenase (RDase) genes, and archaeal 16S rRNA genes was observed. Additionally, obligate OHRB, such as Dehalobacter and Dehalobium, were further enriched. These findings indicate that ADS effectively enhances microbial reductive dechlorination and highlight the potential for enriching and isolating OHRB with Rpf.

Sulfate-driven microbial collaboration for synergistic remediation of chloroethene-heavy metal pollution

The treatment of heavy metal(loid) (HM) composite pollution has long posed a challenge for the bioremediation of organohalide-contaminated sites. Given the prevalent cohabitation of sulfate-reducing bacteria (SRB) with organohalide-respiring bacteria (OHRB), we proposed a sulfate-amendment strategy to achieve synergistic remediation of trichloroethene and diverse HMs [50μM of As(III), Ni(II), Cu(II), Pb(II)]. Correspondingly, 50–75 μM sulfate was introduced to HM inhibitory batches to investigate the enhancement effect of sulfate amendment on bio-dechlorination. Dechlorination kinetics and MATLAB modeling indicated that sulfate amendment comprehensively improved the reductive dechlorination performance in the presence of As(III), Ni(II), Pb(II) and mixed HMs, while no enhancement was observed under Cu(II) exposure. Additionally, sulfate introduction effectively accelerated the detoxification of Ni(II), Pb(II), Cu(II), and As(III), achieving removal efficiencies of 76.87 %, 64.01 %, 86.37 %, and 95.50 % within the first three days, respectively. Meanwhile, propionate dynamics and acetogenesis indicated enhanced carbon source and e-donor supply. 16S rRNA gene sequencing and metagenomic analysis results demonstrated that HM sequestration was accomplished jointly by SRB and HM-resistant bacteria via extracellular precipitation (metal sulfide) and intracellular sequestration, while their contribution depended on the specific coexisting HM species present. This study highlights the critical role of sulfate in the concurrent bioremediation of HM-organohalide composite contamination and provides insights for developing a cost-effective in-situ bioremediation strategy.

Innovative synthesis of ternary heterojunction CuInS2/BiOI/Bi2MoO6 for 2,4-DCP degradation and its dechlorination performance

This study focuses on a novel ternary heterojunction catalyst for the removal of 2,4-dichlorophenol (2,4-DCP), an organic pollutant that is difficult to degrade. An efficient CuInS2/BiOI/Bi2MoO6 ternary heterojunction photocatalyst was formed by constructing a CuInS2/BiOI composite layer on a Bi2MoO6 substrate using an in-situ growth technique. The microstructure and photoelectric conversion properties of the catalysts were comprehensively resolved by systematic material characterization, including scanning electron microscopy (SEM) observation, X-ray photoelectron spectroscopy (XPS) analysis and photoelectrochemical testing. The experimental results showed that the optimized catalyst at a loading of 2.0 g/L exhibited excellent photocatalytic degradation efficiency against 20 mg/L concentration of 2,4-DCP at neutral pH, reaching 80.3 % degradation rate in 120 min. This high performance was mainly attributed to the enhanced charge-carrier separation mechanism at the heterojunction interface, which effectively enhanced the utilization and transfer rate of photogenerated electron-hole pairs and enhanced the photocatalytic activity of the catalyst. In addition, the study also deeply explored the conversion pathway of elemental chlorine in the photocatalytic system, elucidated the mechanism of 2,4-DCP degradation and dechlorination, and provided a theoretical basis for further improving the environmental adaptability and dechlorination efficiency of the catalyst. Overall, the CuInS2/BiOI/Bi2MoO6 ternary heterojunction photocatalysts proposed in this study demonstrate a broad application prospect in the purification of 2,4-DCP and other organic pollutants, and open up a new way to solve the problems of industrial wastewater treatment, which is of great environmental significance and scientific value.

Low-temperature dechlorination methods for pyrolysis oil of municipal plastic waste

Pyrolysis oil produced from municipal plastic waste can be utilized as fuel and various valuable chemicals as an alternative to petroleum. However, pyrolysis oil usually contains a relatively high concentration of chlorinated compounds, obstructing its utilization in the chemical industry. The present research reveals that pyrolysis oil contains inorganic chlorine and organochlorine compounds, and differentiated approaches should be considered to remove Cl from covalent and ionic chlorine linkages. Transition metal-based ZSM-5 catalysts showed remarkable dechlorination performance via mild C-Cl cracking of 1-chlorooctane and 4-chlorotoluene at 180 °C or below. The neutralization method of mixing pyrolysis oil with an alkaline solution quickly eliminated ionic chlorine from inorganic chlorine compounds, reducing Cl concentrations by up to 70 % at temperature below 40 °C. Based on the different dechlorinating pathways, an ideal combination of these two methods was suggested to enhance chlorine removal efficiency from pyrolysis oil.

S-ZVI@biochar constructs a directed electron transfer channel between dechlorinating bacteria, Shewanella oneidensis MR-1 and trichloroethylene

The combination of micron zero-valent iron (mZVI) and microorganisms is an effective method for trichloroethylene (TCE) degradation, but electron transfer efficiency needs improvement. A new chem-bio hybrid process using a composite material (S-ZVI@biochar) was developed, consisting of sulfurized mZVI and biochar as a chemical remover, and Shewanella oneidensis MR-1 and dechlorinating bacteria (DB) as a biological agent for TCE degradation. S-ZVI@biochar showed improved stability, biocompatibility, and TCE removal compared to ZVI and S-ZVI. The hybrid system DB + MR-1 + S-ZVI@biochar exhibited the highest TCE removal efficiency at 96.5% after 30 days, which was 3.7 times higher than that of bare ZVI. The study revealed that the enhanced dechlorination performance was due to improved electron transfer efficiency, adjustment of microbial community structure, and iron recycling. S-ZVI@biochar constructed electron transport channels in the composite system, improving the overall dechlorination capacity. This system shows promise for long-term TCE removal in anaerobic environments.

Synergistic degradation of 2,4-dichlorophenoxyacetic acid in water by interfacial pre-reduction enhanced peroxymonosulfate activation derived from novel zero-valent iron/biochar

Iron-based biochar exhibits great potential in degrading emerging pollutants and remediation of water environments. In this study, a highly efficient catalytic Fe0/biochar (MZB-800) was synthesized by the co-pyrolysis of poplar sawdust and K2FeO4 at 800 °C. A novel water purification technology of pre-reduction followed by PMS activation for MZB-800 was proposed to degrade the refractory 2,4-dichlorophenoxyacetic acid (2,4-D) pesticide. The corrosive effect of the strong oxidizing potassium salt endowed the MZB-800 surface with more Fe0 and porous structure, achieving greater 2,4-D adsorption binding energy. The removal efficiency of MZB-800 on 2,4-D was greater than that of biochar (BC) and conventional Fe0/biochar (Fe-BC) prepared by FeCl3·6 H2O as the precursor. The proposed novel water purification technology showed the synergistic effect between the interfacial pre-reduction and the PMS activation derived by MZB-800. Regarding 2,4-D degradation and dechlorination performance, the synergistic coefficient between pre-reduction and subsequent PMS activation for MZB-800 were 2 and 1.4 respectively. Based on the normalized kinetic analysis and the Langmuir-Hinshelwood model, we proposed the underlying mechanism of MZB-800 interfacial pre-reduction and subsequent PMS activation for synergistic removal of 2,4-D. The large amount of Fe2+ and hydroxyl density accumulated by the Fe0 and hydroquinone structures on the MZB-800 surface during the pre-reduction stage provided abundant active sites for the subsequent activation of PMS. The improved activation reaction rate generated more reactive oxygen species, further strengthening the removal efficiency of 2,4-D. This work manifested that the novel water purification technology of pre-reduction/PMS activation of iron-based biochar is feasible for removing emerging pollutants in the water environment. Environmental ImplicationExtensive abuse of 2,4-dichlorophenoxyacetic acid (2,4-D) herbicide with high solubility and refractory degradation has caused environmental pollution and ecological deterioration. This manuscript described a novel water purification technology, centered on high-efficiency Fe0/biochar and utilizing pre-reduction and PMS reactivation strategies to synergistically degrade 2,4-D, which had strong environmental relevance. By elucidating the synergistic removal mechanism, the research provided valuable insights into removing emerging pollutants, thus promoting environmental sustainability and safeguarding ecosystem health. Overall, it is of high importance to provide a feasible and efficient method for removing hazardous 2,4-D from water environments, which contributes to addressing pressing environmental problems.

Enhanced reductive degradation of trichloroethylene by ball milled nitridation of bimetallic Ni-ZVI: Combination effect of electron transfer and catalytic hydrogenation

The performance optimization of zerovalent iron (ZVI) based materials for reductive dechlorination is critical but remains challenging. Combining the advantages of bimetallic and heteroatomic modification may lead to a novel strategy for reductive dechlorination of chlorinated ethenes (CEs) pollution. In this study, three different types of dual-modified micron ZVI (mZVI) composite particles, namely, pre-bimetallic modified mZVI (Ni/mZVI-N), pre-nitrogen modified mZVI (N/mZVI-Ni), and simultaneously modified mZVI (Ni/N-mZVI), were prepared by adjusting the order of ball milling modification of nickel and melamine, in which ball milling mechanical-chemical interactions contributed to the generation of enriched M-N structures. In terms of combined reactivity and selectivity, Ni/N-mZVI exhibited the best performance, with trichloroethylene (TCE) dechlorination rate (kobs,TCE) and electron efficiency (εe) of 0.14 h−1 and 8.9 %, respectively, which were 10.7 and 7.5 times higher than those of mZVI. The distribution and percentage of degradation products further illustrated the reductive dechlorination of nickel-nitrogen dual-modified mZVI via both electron transfer and atomic hydrogen (H*) pathways. A series of characterization and mechanistic analyses showed that the enhancement of TCE reductive dechlorination performance could be attributed to the combined effect of Fe−N to accelerated electron transfer and Ni-N to enhance catalytic hydrogenation. In addition to decreased H2 accumulation, Ni/N-mZVI reduced leaching ions thus mitigating secondary contamination. This double-modification strategy employed to enhance the optimization of mZVI for groundwater remediation establishes a foundation for ongoing progress in the synthesis of reactive materials.

Unveiling the Mechanistic Role of Surface Nitrogen and Sulfur in Boosting the Dechlorination Performance of Zero-Valent Iron

Unveiling the Mechanistic Role of Surface Nitrogen and Sulfur in Boosting the Dechlorination Performance of Zero-Valent Iron

Interlayer Structure Manipulation of FeOCl/MXene with Soft/Hard Interface Design for Safe Water Production Using Dechlorination Battery Deionization

AbstractSuffering from the susceptibility to decomposition, the potential electrochemical application of FeOCl has greatly been hindered. The rational design of the soft‐hard material interface can effectively address the challenge of stress concentration and thus decomposition that may occur in the electrodes during charging and discharging. Herein, interlayer structure manipulation of FeOCl/MXene using soft‐hard interface design method were conducted for electrochemical dechlorination. FeOCl was encapsulated in Ti3C2Tx MXene nanosheets by electrostatic self‐assembly layer by layer to form a soft‐hard mechanical hierarchical structure, in which Ti3C2Tx was used as flexible buffer layers to relieve the huge volume change of FeOCl during Cl− intercalation/deintercalation and constructed a conductive network for fast charge transfer. The CDI dechlorination system of FeOCl/Ti3C2Tx delivered outstanding Cl− adsorption capacity (158.47 ± 6.98 mg g−1), rate (6.07 ± 0.35 mg g−1 min−1), and stability (over 94.49 % in 30 cycles), and achieved considerable energy recovery (21.14 ± 0.25 %). The superior dechlorination performance was proved to originate from the Fe2+/Fe3+ topochemical transformation and the deformation constraint effect of Ti3C2Tx on FeOCl. Our interfacial design strategy enables a hard‐to‐soft integration capacity, which can serve as a universal technology for solving the traditional problem of electrode volume expansion.

Interlayer Structure Manipulation of FeOCl/MXene with Soft/Hard Interface Design for Safe Water Production Using Dechlorination Battery Deionization.

Suffering from the susceptibility to decomposition, the potential electrochemical application of FeOCl has greatly been hindered. The rational design of the soft-hard material interface can effectively address the challenge of stress concentration and thus decomposition that may occur in the electrodes during charging and discharging. Herein, interlayer structure manipulation of FeOCl/MXene using soft-hard interface design method were conducted for electrochemical dechlorination. FeOCl was encapsulated in Ti3C2Tx MXene nanosheets by electrostatic self-assembly layer by layer to form a soft-hard mechanical hierarchical structure, in which Ti3C2Tx was used as flexible buffer layers to relieve the huge volume change of FeOCl during Cl- intercalation/deintercalation and constructed a conductive network for fast charge transfer. The CDI dechlorination system of FeOCl/Ti3C2Tx delivered outstanding Cl- adsorption capacity (158.47 ± 6.98 mg g-1), rate (6.07 ± 0.35 mg g-1 min-1), and stability (over 94.49% in 30 cycles), and achieved considerable energy recovery (21.14 ± 0.25%). The superior dechlorination performance was proved to originate from the Fe2+/Fe3+ topochemical transformation and the deformation constraint effect of Ti3C2Tx on FeOCl. Our interfacial design strategy enables a hard-to-soft integration capacity, which can serve as a universal technology for solving the translational problem of electrode volume expansion.

HCl removal from cement bypass flue gas at medium-high temperatures using cement bypass dust: Performance, mechanism, and adsorption kinetics

The use of alternative fuels is a growing trend in the cement industry, and it may lead to issues with HCl emissions. This study investigated the HCl removal performance of cement bypass dust (CBPD) at medium-high temperatures (500–700℃). This is not only of great significance for controlling HCl emissions from cement kilns but also alleviates the disposal pressure of this industrial solid waste. The results show that HCl adsorption capacity increased first and then decreased with increasing temperature, reaching a maximum of 676 mg/g at 600°C. The HCl concentrations significantly influenced the reaction rate, yet its impact on the uptake chlorine capacity is comparatively minimal. CBPD without size separation showed the best dechlorination performance and highest final chlorine capacity compared with CBPD of size 0–48 μm and 48–75 μm. Blending inert SiO2 particles into CBPD can greatly increase the breakthrough time. The longest breakthrough time is 7580 seconds, approximately 35 times that of CBPD without dispersion. CaO is the primary substance in CBPD to remove HCl, and the reaction produces CaCl2 and its hydrate. A shrinking core model was used to analyse the experimental data, suggesting a combination control of the chemical reaction and the product diffusion.

Carboxymethyl cellulose stabilization induced changes in particle characteristics and dechlorination efficiency of sulfidated nanoscale zero-valent iron

Polymer stabilization, exemplified by carboxymethyl cellulose (CMC), has demonstrated effectiveness in enhancing the transport of nanoscale zero-valent iron (nZVI). And, sulfidation is recognized for enhancing the reactivity and selectivity of nZVI in dechlorination processes. The influence of polymer stabilization on sulfidated nZVI (S-nZVI) with various sulfur precursors remains unclear. In this study, CMC-stabilized S-nZVI (CMC-S-nZVI) was synthesized using three distinct sulfur precursors (S2−, S2O42−, and S2O32−) through one-step approach. The antioxidant properties of CMC significantly elevated the concentration of reduced sulfur species (S2−) on CMC-S-nZVIs, marking a 3.1–7.0-fold increase compared to S-nZVIs. The rate of trichloroethylene degradation (km) by CMC-S-nZVIs was observed to be 2.2–9.0 times higher than that achieved by their non-stabilized counterparts. Among the three CMC-S-nZVIs, CMC-S-nZVINa2S exhibited the highest km. Interesting, while the electron efficiency of CMC-S-nZVIs surged by 7.9–12 times relative to nZVI, it experienced a reduction of 7.0–34% when compared with S-nZVIs. This phenomenon is attributed to the increased hydrophilicity of S-nZVI particles due to CMC stabilization, which inadvertently promotes the hydrogen evolution reaction (HER). In conclusion, the findings of this study underscores the impact of CMC stabilization on the properties and dechlorination performance of S-nZVI sulfidated using different sulfur precursors, offering guidance for engineering CMC-S-nZVIs with desirable properties for contaminated groundwater remediation.

Enhanced electrocatalytic hydrodechlorination of 2,4-dichlorophenol over palladium nanoparticles loading on dendrite-like Ni-Cu-P interlayer

A new electrode with high electrocatalytic hydrodechlorination activity was prepared by pulse electrodeposition of Pd nanoparticles on a dendrite-like Ni-Cu-P interlayer with foam nickel as the substrate. The physical and chemical properties of the composite electrode were systematically investigated by various characterizations. The dechlorination performance was evaluated with 2,4-dichlorophenol as the model pollutant. The results indicated that in 150 min the dechlorination efficiency over the electrode without the Ni-Cu-P interlayer was only 52.7 %, while 100 % of 2,4-dichlorophenol could be removed by the composite electrode. The enhanced dechlorination performance was mainly attributed to the synergic effect between Pd nanoparticles and the Ni-Cu-P interlayer. The dendrite morphology of Ni-Cu-P facilitated Pd nanoparticle dispersion, thus providing more active sites and reducing the consumption of Pd. Furthermore, the Ni-Cu-P interlayer assisted Pd0 to produce more active hydrogen and increased the content of Pd2+ to promote CCl bond cleavage. Consequently, the dechlorination performance was improved.

Minor chromium passivation of S-ZVI enhanced the long-term dechlorination performance of trichlorethylene: Effects of corrosion and passivation on the reactivity and selectivity

The corrosion and surface passivation of sulfidized zero-valent iron (S-ZVI) by common groundwater ions and contaminants are considered to be the most challenging aspects in the application of S-ZVI for remediation of chlorinated contaminants. This study investigated the impacts of corrosive chloride (Cl−) and passivation of hexavalent chromium (Cr(VI)) on the long-term reactivity, selectivity, corrosion behavior, and physicochemical properties during the 60-day aging process of S-ZVI. Although the co-existing of Cl− promoted the initial reactivity of S-ZVI, the rapid consumption of Fe° content shortened the reactive lifetime owing to the insufficient electron capacity. Severe passivation by Cr(VI) (30 mg L−1) preserved the Fe° content but significantly interfered with the reductive sulfur species, resulting in an increase in electron transfer resistance. In comparison, minor passivated S-ZVI (5.0 mg L−1 Cr(VI)) inhibited the hydrogen evolution while concurrently mitigating the further oxidation of the reductive iron and sulfur species, which significantly enhanced the long-term reactivity and selectivity of S-ZVI. Furthermore, the enhancement effect of minor passivation could be detected in the aging processes of one-step, two-step, and mechanochemically synthesized S-ZVI particles with different S/Fe ratios and precursors, which further verified the advantages of minor passivation. This observation is inspirable for the development of innovative strategies for environmental remediation by S-ZVI-based materials.

Low-temperature catalytic dechlorination of model plastic pyrolytic oil over zeolite catalysts

Catalytic dechlorination of model plastic pyrolytic oil was investigated over different types of zeolites and ion-exchanged 13X zeolites at the low temperatures of 20–120 °C. Among different types of parent zeolites (13X, β, MCM-41), 13X had the highest catalytic dechlorination performance. After ion exchange of 13X with Ag+, its catalytic dechlorination performance was significantly enhanced, and the chlorine removal over Ag-13X reached 97.2 % after reaction for 5 h at 120 °C. The characterization results indicated that the acidity of the zeolite governed its catalytic dechlorination performance, and higher acid amount and stronger acid strength are preferred. Different types of chlorinated compounds followed different dechlorination mechanisms. The primary chlorinated alkanes (e.g., 1-chlorooctane) underwent nucleophilic substitution by the surface –OH groups or H2O to form alcohols and HCl, or dehydrochlorination reaction to produce olefins and HCl, while higher chlorinated alkanes with adjacent hydrogen (e.g., chlorocyclohexane) mainly underwent dehydrochlorination reaction to produce olefins and HCl. Chlorinated aromatics (e.g., chlorobenzene) was removed mainly by physical adsorption. Ag-13X showed good stability, and the chlorine removal still retained 72.1 % after 102 h on stream. After four dechlorination-regeneration cycles, the chlorine removal had only a slight decrease due to the partial collapse of its structure and slight loss of its acid amount.

Biochar as an electron shuttle loaded with Fe/Ni bimetallic nanoparticles for efficient removal of 2,4-dichlorophenols: Performance, degradation pathway and mechanism

Biochar can be served as a substrate for immobilizing bimetallic particles and applied in the pollutant removal, however, its specific role and mediated electron shuttle mechanism against 2,4-dichlorophenol (2,4-DCP) have not been elucidated. In this study, biochar loaded with Fe/Ni bimetallic nanoparticles (BC@Fe/Ni) was optimally synthesized, and its dechlorination performance, pathway and mechanism towards 2,4-DCP were investigated. The results showed that BC@Fe/Ni was more effective compared to Fe/Ni nanoparticles in the 2,4-DCP removal due to its well-dispersed Fe/Ni nanoparticles and increased electron-shuttling capability. The optimal parameters for 2,4-DCP removal by BC@Fe/Ni were assessed, the highest removal efficiency equivalent to 50 mg L−1 of 2,4-DCP was achieved at pH 4.0 with a dosage of 2 g L−1. The 2,4-DCP removal was an adsorption-dechlorination-adsorption pathway, primarily through para-Cl elimination, ortho-Cl elimination and finally phenol adsorption. The removal mechanism of 2,4-DCP by BC@Fe/Ni may involve the 2,4-DCP reductive dechlorination by nZVI, atomic hydrogen and biochar-mediated electron transfer, and final adsorption by biochar. In summary, this study demonstrates that biochar is a promising electron shuttle for immobilizing bimetallic particles and serves as a reference for the dechlorination mechanism of chlorinated organic pollutants by biochar-based bimetallic nanomaterials.

CaO hydrated with ethanol solution for flue gas HCl immobilization. Part II: Influences of gas components

The injection of alkaline adsorbent into flue gas for HCl removal technology is greatly impacted by the complex flue gas components. The newly developed ethanol-modified Ca-based adsorbent was demonstrated a superior dechlorination performance. In this work, the effect of flue gas components on the dechlorination was comprehensively studied by experiments, micro-insight characterization and mechanism analyses. The results showed that the high initial HCl concentration boosts the reaction rate but lowers the Ca/Cl mole ratio. O2 promotes the HCl adsorption efficiency by impelling the reaction between HCl and adsorbent to generate Ca(ClO)2 that enhances the chlorination and converting CaClOH to CaO. The presence of SO2 and CO2 hinders the removal of HCl in both physical and chemical aspects. The product layers of CaSO3 and CaCO3 may cover the adsorbent active sites that deteriorates the pore structure and seriously inhibits the adsorption of HCl on the adsorbent surface and prevents mass diffusion into the inner pores. It was discovered that HCl, SO2 and CO2 have an affinity to the Ca site, so there exists nonnegligible competitive adsorption between them that reduces the number of basic sites to which HCl can adhere. The HCl removal efficiency falls from 72.33% to 41.34% as SO2 concentration rises from 0 ppm to 1600 ppm. While it decreases from 72.33% to 51.17% as CO2 concentration changes from 0% to 20%.

Pd nanoparticles supported on microflower NiMOF modified roughed nickel foam with the enhanced active site for electrochemical dechlorination of trichloroacetic acid

Electrocatalytic hydrodechlorination (ECH) has been considered as an effective method to convert refractory chlorinated organics into biodegradable chlorine-free organics under mild conditions. In this work, a composite electrode of Pd/NiMOF/roughed nickel foam (Pd/NiMOF/RNF) with excellent dechlorination performance was prepared by electrodeposition of Pd nanoparticles on the flower-shaped NiMOF interlayer grown in-situ. Benefiting from the high specific surface area of NiMOF structure and excellent dispersion of Pd facilitated, the Pd/NiMOF/RNF offered abundant active hydrogen and larger open channels for the easy diffusion of reactants and products in the electrochemical dechlorination process. 97% of 6 μmol/L trichloroacetic acid (TCAA) was dechlorinated at a cathodic potential of −1.2 V within 90 min. The corresponding palladium mass activity was calculated to be 0.39 μg min−1 cm−2 mg−1 Pd, which was approximately 3.5 times greater than other report on ECH cathode. Moreover, the Pd/NiMOF/RNF cathode remained stable even after five consecutive cycle tests. Toxic assessment results indicated that the dechlorination process was beneficial to the detoxification of TCAA at the end of reaction. The hydrodechlorination mechanism of TCAA was proposed by density functional theory (DFT) analysis and electrochemical characterization on the Pd/NiMOF/RNF electrode. The findings of this study have the potential to contribute to the development of electrocatalytic treatment methods for chlorinated organic compounds in drinking water.

Dechlorination of waste polyvinyl chloride (PVC) through non-thermal plasma

Dechlorination is essential for the chemical recycling of waste polyvinyl chloride (PVC) plastics. This study investigated the use of non-thermal plasma (NTP) for chlorine removal, with a focus on the effects of treatment time and discharge power on dechlorination efficiency. The results showed that longer treatment times and higher discharge powers led to better dechlorination performance. The maximum efficiency (98.25%) and HCl recovery yield (55.72%) were achieved at 180 W power after 40 min of treatment where 96.44% of Cl existed in the form of HCl gas, 1.44% in the liquid product, and 2.12% in the solid residue product. NTP at a discharge power of 150 W showed better dechlorination performance compared to traditional thermal pyrolysis treatment in temperatures ranging from 200 to 400 °C. The activation energy analysis of the chlorine removal showed that compared to pyrolysis-based dechlorination (137.09 kJ/mol), NTP-based dechlorination (23.62 kJ/mol) was more easily achievable. This work presents a practical method for the dechlorination of waste PVC plastic using a novel technology without requiring additional thermal and pressure input.

Unlocking the potential of resuscitation-promoting factor for enhancing anaerobic microbial dechlorination of polychlorinated biphenyls

Microbial dechlorination of polychlorinated biphenyls (PCBs) is limited by the slow growth rate and low activity of dechlorinators. Resuscitation promoting factor (Rpf) of Micrococcus luteus, has been demonstrated to accelerate the enrichment of highly active PCB-dechlorinating cultures. However, it remains unclear whether the addition of Rpf can further improve the dechlorination performance of anaerobic dechlorination cultures. In this study, the effect of Rpf on the performance of TG4, an enriched PCB-dechlorinating culture obtained by Rpf amendment, for reductive dechlorination of four typical PCB congeners (PCBs 101, 118, 138, 180) was evaluated. The results indicated that Rpf significantly enhanced the dechlorination of the four PCB congeners, with residual mole percentages of PCBs 101, 118, 138 and 180 in Rpf-amended cultures being 16.2–29.31 %, 13.3–20.1 %, 11.9–14.4 % and 9.4–17.3 % lower than those in the corresponding cultures without Rpf amendment after 18 days of incubation. Different models were identified as appropriate for elucidating the dechlorination kinetics of distinct PCB congeners, and it was observed that the dechlorination rate constant is significantly influenced by the PCB concentration. The supplementing Rpf did not obviously change dechlorination metabolites, and the removal of chlorines occurred mainly at para- and meta- positions. Analysis of microbial community and functional gene abundance suggested that Rpf-amended cultures exhibited a significant enrichment of Dehalococcoides, Dehalogenimonas and Desulfitobacterium, as well as non-dechlorinators belonging to Desulfobacterota and Bacteroidetes. These findings highlight the potential of Rpf as an effective additive for enhancing PCB dechlorination, providing new insights into the survival of functional microorganisms involved in anaerobic reductive dechlorination.