Reductive Dechlorination Of Carbon Tetrachloride Research Articles

New Mechanism via Dichlorocarbene Intermediate for Activated Carbon-Mediated Reductive Dechlorination of Carbon Tetrachloride by Sulfide in Aqueous Solutions.

Although activated carbon (AC) is widely used as an adsorbent and barrier for contaminated sediment remediation, little attention has been paid to its mediation effects on reductive dechlorination of chlorinated solvents by commonly presenting sulfide. Here, we reported that highly porous, graphitized AC (250 mg L-1) suspended in deoxygenated aqueous solutions could increase the pseudo-first-order rate constant of sulfide-induced dechlorination of carbon tetrachloride (CCl4) by more than 1 order of magnitude. Carbon disulfide (CS2) was the only main product, with no production of chloroform or dichloromethane. The minimum promotion of CCl4 reduction observed with electro-conductive but nonporous graphite and a microporous but electro-insulative resin (XAD-4) indicates that graphitic carbons and micropores both play key roles in AC-mediated dechlorination of CCl4 by sulfide. The detection of dichlorocarbene (:CCl2) by free radical trapping experiments combined with the high suitability of the Langmuir-Hinshelwood model led us to propose a new mediation mechanism: CCl4 molecules adsorbed within the deep regions of AC micropores formed by graphitic carbons accept two electrons transferred from sulfide to form :CCl2, which is impeded from hydrolysis and hydrogenolysis by the hydrophobic micropore and further reacts with sulfide to generate CS2. Consistently, the production of :CCl2 was very low when AC was replaced with graphite or XAD-4. The proposed mechanism was further validated by the enhanced mediation effects of another two carbonaceous materials (template-synthesized mesoporous carbon and covalent triazine-based framework) that are electro-conductive and have well-developed micropore structures. These findings highlight the importance of pore properties of carbonaceous materials as mediators or catalysts for reductive dechlorination reactions and shed light on the development of coupled adsorption-reaction systems for remediation.

Hydroxyl groups bridge the electron transfer from Fe(II) to carbon tetrachloride

Reductive dechlorination of chlorinated organic pollutants (COPs) by Fe(II) occurs in natural environments and engineered systems. Fe(II) ions undergo hydroxylation in aqueous solutions to form Ferrous Hydroxyl Complex (FHC), which plays an essential role in Fe(II)-mediated reductive dechlorination. However, how hydroxyl groups of FHC bridge the electron transfer from Fe(II) to COPs is still not fully understood. This work shows that the rate of reductive dechlorination of carbon tetrachloride (CT) by FHC increased with increasing OH− dosage. XRD data shows the increase of OH− dosage transform FHC from Fe2(OH)3Cl to Fe(OH)2, which leads to increased reductive strength of FHC. More non-hydrogen bonded hydroxyl groups coordinate with Fe(II) in FHC with increasing the OH− dosage, which stabilizes the octahedral structure of Fe(II) as shown by Mössbauer data. Electrochemical analysis reveals that the increase of OH− dosage enhances the reductive activity of FHC, which is also confirmed by the decreased HOMO-LUMO gap. It was found that FHC dechlorinated CT to methane, which was attributed to the stabilization of trichlorocarbene anion(˸CCl3−) by [surface-O-Fe(II)-OH]+. This work deepens our understanding on the bridge effect of hydroxyl groups on the electron transfer from Fe(II) to COPs, and provides a theoretical foundation for the reductive dechlorination of COPs in both natural environments and engineered systems.

Enhanced dechlorination of carbon tetrachloride by Ni-doped zero-valent iron nanoparticles @ magnetic Fe3O4 (Ni4/Fe@Fe3O4) nanocomposites

A bimetallic nanocomposite, named as Ni4/Fe@Fe3O4, which was prepared via loading Fe/Ni bimetallic onto magnetite (Fe3O4), was applied to the reductive dechlorination of carbon tetrachloride (CT) for the first time and was identified by scanning electron microscopy (SEM), X‐ray energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) to explore its structure and properties. The effects of the Ni loading (weight ratio of Fe/Ni), CT concentration, initial solution pH, temperature and Ni4/Fe@Fe3O4 dosage on the reaction system were studied. The experimental results showed that the nanoscale Ni/Fe@Fe3O4 bimetallic particles with a mass ratio of 4% of Ni/Fe exhibited excellent performance for CT degradation. The removal efficiency of CT can reach 96.3% within 35 min with only 0.2 g/L of Ni4/Fe@Fe3O4. The degradation kinetics of CT by Ni4/Fe@Fe3O4 nanocomposites was conformed to the pseudo first-order kinetics and the activation energies (Ea) was 25.87 kJ/mol. Moreover, Ni4/Fe@Fe3O4 presented good reusability and stability after four cycles. Based on the detection results of CT degradation products by gas chromatography (GC), a possible degradation mechanism was discussed, which can be divided into the following ways: (1) Migration and adsorption of CT molecules. (2) Direct reductive dechlorination of CT molecules by nano zero-valent iron (nZVI). (3) Reduction dechlorination of CT by Fe2+ released by Ni4/Fe@Fe3O4. (4) Ni0 might induce the conversion of H2 to active atomic hydrogen (·H) to degrade chloromethane. These results exhibited that Ni4/Fe@Fe3O4 will be a nanocomposite with great application potential for CT degradation from aqueous solutions.

Application of nano‐scale zero‐valent iron adsorbed on magnetite nanoparticles for removal of carbon tetrachloride: Products and degradation pathway

Nano‐scale zero‐valent iron (nZVI) attached to Fe3O4 nanoparticles (Fe0@Fe3O4), which has better dispersibility and a larger specific surface area than the nanoparticles alone, were prepared and applied to the reductive dechlorination of carbon tetrachloride (CT). CT removal efficiencies by Fe0@Fe3O4 composites with different ratios of the two components were compared. Under optimum conditions, when the Fe0/Fe3O4 ratio was 1:2, almost no CT was detected after 50 min and it took only about 30 min to reach a removal efficiency of 90%, compared with 120 min for an Fe0/Fe3O4 ratio of 1:4. An increase in the amount of nZVI in the catalyst effectively improved the removal of CT and accelerated the reaction rate. Chloroform was the main product. Compared with Fe3O4 alone, a significant increase in the solution concentrations of ferrous and ferric ions occurred in the Fe0@Fe3O4 system: both Fe2+ and Fe3+ reached their maximum concentrations at 60 min and then tended to decline over the next 60 min. The increase in Fe2+ concentration was attributed to the reaction between nZVI and CT, which produces ferrous ions when electrons transfer from Fe0 to organic chlorides. Synergistic effects between the composite constituents promoted the relative rates of mass transfer to reactive sites and Fe2+ generated in solution facilitated the reduction of chlorinated organic pollutants by magnetite. Thus, Fe0@Fe3O4 nanoparticles effectively achieved reductive dechlorination of CT and provide an improved nZVI catalyst for the remediation of chlorinated organic compounds.

Ultrafast reductive dechlorination of carbon tetrachloride by amorphous Fe78Si9B13 alloy

Amorphous Fe78Si9B13 ribbons and zero-valent iron (ZVI) powder were used to remove carbon tetrachloride (CTC) in the neutral oxic environment. The amorphous Fe78Si9B13 ribbons showed significantly better dechlorination performance than the ZVI powder, and the CTC could be degraded nearly completely within 3 h. The recyclability of amorphous Fe78Si9B13 ribbons was investigated, and the results confirmed their effectiveness and stability to remove the CTC for at least ten times. Our work demonstrates the application potential of amorphous alloys as an alternative to ZVI in the dechlorination of chlorinated organic compounds, and can provide new ideas for designing efficient dechlorinating agent in the actual field groundwater remediation.

EDDS enhanced Shewanella putrefaciens CN32 and α-FeOOH reductive dechlorination of carbon tetrachloride

S,S-ethylenediamine-N,N-disuccinic acid (EDDS) enhanced reductive dissolution of α-FeOOH by Shewanella putrefaciens CN32 (CN32), resulting in formation of surface-bound Fe(II) species (FeIIEDDS) to improve reductive dechlorination of carbon tetrachloride (CT). The pseudo-first-order rate constants for bio-reduction extents of α-FeOOH by CN32 in the presence of 1.36 mM EDDS was 0.023 ± 0.0003 d−1 which was higher than without EDDS. The enhancement mechanism of bio-reduction was attributed to the strong complexation ability of EDDS to formed FeIIIEDDS, which could be better utilized by CN32. The dechlorination kinetic of CT by FeIIEDDS (2.016 h−1) in the presence of 1.36 mM EDDS was 24 times faster than without EDDS. Chloroform were detected as main products for the degradation of CT. The chemical analyses and morphological observation showed that combination between EDDS and Fe2+ produced FeIIEDDS complex, which had a reductive potential of −0.375 V and significantly enhanced CT dechlorination. The results showed that EDDS played an important role in enhancing the bio-reduction of α-FeOOH to accelerate reductive dechlorination of CT.

Degradation of Carbon Tetrachloride by nanoscale Zero‐Valent Iron @ magnetic Fe3O4: Impact of reaction condition, Kinetics, Thermodynamics and Mechanism

Nano‐scale zero‐valent Iron (nZVI) attached on the Fe3O4 nanoparticles were prepared and creatively applied in the reductive dechlorination of Carbon Tetrachloride (CT). The characterization results of the synthesized composite indicated a main component of nZVI particles assembled on the surface of Fe3O4 with a layer of iron‐oxide film on the periphery, of which the dispersibility was better and the specific surface area was larger. The effects of different reaction conditions like temperature, initial pH values, Fe0@Fe3O4 dosage and initial CT concentrations on the removal of CT were evaluated. Under the optimum conditions, the Fe0@Fe3O4 composites showed a CT removal efficiency of 89.1% in 60 min, which was much greater than that of nZVI (61.7%) and Fe3O4 particles (14.3%). The removal process obeyed the pseudo‐first‐order kinetic model. Synergy effects of the constituents in the composite which can promote the relative rates of mass transfer to reactive sites were proposed to be existed and the magnetism of Fe3O4 could help to overcome the aggregation and surface passivation problem of nZVI. Thus, Fe0@Fe3O4 nanoparticles in our study can effectively complete the reductive dechlorination of CT and an improved nZVI catalyst is provided for the remediation of chlorinated organic compounds.

Reductive dechlorination of carbon tetrachloride by bioreduction of nontronite

Reductive dechlorination of carbon tetrachloride (CT) was investigated during bioreduction of iron-containing clay mineral (i.e., nontronite) by iron-reducing bacteria (Shewanella putrefaciens CN32 (CN32)). In the absence of CT, the production of Fe(II) significantly increased in nontronite suspension with CN32 in 124 d (11.1% of Fe(III) reduction), resulting in formation of new secondary Fe(II) mineral phase (i.e., vivianite (FeII3(PO4)2·8H2O)). In the presence of CT, an acceleration of CT dechlorination was observed after 13 d and it reached almost 68% of removal efficiency at 32 d in nontronite suspension with CN32, which was 1.8 times higher than that by CN32 alone (37%). Significant amounts of formate (30.1%) and CO (2.4%) were measured during the CT dechlorination in the nontronite suspension with CN32. Results obtained from Fe(II) measurement and X-ray diffraction (XRD) showed the acceleration of Fe(II) production after 13 d and the formation of vivianite in the range of 13–25 d, suggesting that the biogenic vivianite enhanced the CT dechlorination in this study. Experimental results from batch kinetic tests, Fe(II) measurements, XRD analysis, and by-product study suggested that the formation of vivianite can play a crucial role for the enhanced reductive dechlorination of CT in phosphorous enriched subsurface environments with iron-containing clay minerals.

Iron-Sulfide-Associated Products Formed during Reductive Dechlorination of Carbon Tetrachloride.

This paper investigated the mackinawite (FeS)-associated products formed during reaction between FeS and carbon tetrachloride (CT) at pH 7 and 8. At pH 8, reaction of FeS with CT led to formation of abundant spherical particles with diameters between 50 and 400 nm on the FeS surface and in solution; far fewer such particles were observed at pH 7. Analysis of the FeS surface by energy dispersive X-ray spectroscopy after reaction with CT at pH 8 showed decreased sulfur and elevated oxygen compared to unreacted FeS. The spherical particles that formed upon FeS reaction with CT were mostly amorphous with localized areas of poorly crystalline two-line ferrihydrite. X-ray photoelectron spectroscopy indicated that the predominant Fe surface species after reaction with CT at pH 8 was Fe(III)-O, consistent with ferrihydrite and other amorphous iron (hydr)oxides as major products. Powder X-ray diffraction analysis suggested formation of greigite upon reaction of FeS with CT at pH 7. Both ferrihydrite and Fe(2+), which is a product of greigite dissolution, can react with dissolved HS(-) to form FeS, suggesting that, after oxidation by chlorinated aliphatics, FeS can be regenerated by addition or microbial generation of sulfide.

Carbon Tetrachloride Degradation by Alkaline Ascorbic Acid Solution

Ascorbic acid (AA) mediated electron transfer may induce reductive dechlorination of carbon tetrachloride (CCl(4)). This study investigated the role of AA in conjunction with the presence of iron minerals over a wide pH range for the reduction of CCl(4) in aqueous systems. The results indicate that CCl(4) was reduced by AA at a pH of 13 (>pKa(2, AA) of 11.79) and chloroform (CHCl3) was a transformation byproduct of CCl(4). When CCl(4) levels were reduced to near complete disappearance, the decrease of CHCl(3) was then observed. The degradation rate of CCl(4) and also the formation rate of CHCl(3) increased with increased AA concentrations. Analysis of reaction kinetics between CCl(4) and AA revealed an overall second-order reaction with a rate constant of 0.253 ± 0.018 M(-1) s(-1). Furthermore, the reduction rate of CCl(4) by AA at pH of 13 could be enhanced with the presence of iron minerals (Fe(3)O(4), Fe(2)O(3), FeOOH, and FeS2). In the absence or presence of iron minerals, the fraction of CCl(4) transformed to CHCl(3) was less than 1, indicating simultaneous one- and two-electron transfer processes. The end-products of AA at a pH of 13 included threonic acid and oxalic acid. This study highlights the potential of an alkaline AA solution for remediating chlorinated solvents.

Efficient Dechlorination of Carbon Tetrachloride by Hydrophobic Green Rust Intercalated with Dodecanoate Anions

The reductive dechlorination of carbon tetrachloride (CT) by Fe(II)-Fe(III) hydroxide (green rust) intercalated with dodecanoate, Fe(II)(4)Fe(III)(2)(OH)(12)(C(12)H(23)O(2))(2) · yH(2)O (designated GR(C12)), at pH ~ 8 and at room temperature was investigated. CT at concentration levels similar to those found in heavily contaminated groundwater close to polluted industrial sites (14-988 μM) was reduced mainly to the fully dechlorinated products carbon monoxide (CO, yields >54%) and formic acid (HCOOH, yields >6%). Minor formation of chloroform (CF), the only chlorinated degradation product, was also detected (yields <6.3%). Reactions carried out with excess GR followed pseudo first-order kinetics with respect to CT with rate constants ranging from 6.5 × 10(-2) to 0.47 h(-1). These rate constants are comparable to those measured for CT dechlorinations mediated by zerovalent iron. Reduction of the highest concentration of CT (1.4 mM) proceeds until 56% of the Fe(II) sites of GR(C12) was consumed. This reaction ceased after 10 h due to surface passivation of GR(C12).

Enhanced reductive degradation of carbon tetrachloride by biogenic vivianite and Fe(II)

We demonstrated that reductive dechlorination of carbon tetrachloride (CT) can be enhanced by iron-bearing soil minerals (IBSMs) in the presence of Shewanella putrefaciens CN32 (CN32) due to the formation of biogenic vivianite and Fe(II). The bioreduction efficiency of magnetite was the highest (51.1%), followed by lepidocrocite (25.7%), goethite (3.6%), and hematite (1.8%). The dechlorination kinetic of CT by lepidocrocite (0.043d−1) in the presence of CN32 was three times faster than that by microbial transformation with CN32 (0.014d−1). Chloroform (16.1–29.4%), carbon monoxide (2.4–23.8%), and formate (0–58.0%) were measured as main products for the degradation of CT by magnetite and lepidocrocite in the presence of CN32. X-ray diffraction and electron microscope analyses revealed that the biogenic vivianite can form during the CT degradation in magnetite and lepidocrocite suspensions with CN32. The dechlorination kinetics of CT by chemogenic vivianite was much faster than that by magnetite and lepidocrocite with CN32. The highest formate production (84.2%) was observed during a full degradation of CT by the chemogenic vivianite. The experimental results showed that biogenic vivianite and sorbed Fe(II) formed during the bioreduction of IBSMs played a pivotal role for the reductive dechlorination of CT.

Dechlorination of Environmental Contaminants Using a Hybrid Nanocatalyst: Palladium Nanoparticles Supported on Hierarchical Carbon Nanostructures

This paper demonstrates the effectiveness of a new type of hybrid nanocatalyst material that combines the high surface area of nanoparticles and nanotubes with the structural robustness and ease of handling larger supports. The hybrid material is made by fabricating palladium nanoparticles on two types of carbon supports: as-received microcellular foam (Foam) and foam with carbon nanotubes anchored on the pore walls (CNT/Foam). Catalytic reductive dechlorination of carbon tetrachloride with these materials has been investigated using gas chromatography. It is seen that while both palladium-functionalized carbon supports are highly effective in the degradation of carbon tetrachloride, the rate of degradation is significantly increased with palladium on CNT/Foam. However, there is scope to increase this rate further if the wettability of these structures can be enhanced in the future. Microstructural and spectroscopic analyses of the fresh and used catalysts have been compared which indicates that there is no change in density or surface chemical states of the catalyst after prolonged use in dechlorination test. This implies that these materials can be used repeatedly and hence provide a simple, powerful, and cost-effective approach for dechlorination of water.

Enhanced Dechlorination of Carbon Tetrachloride by Immobilized Fulvic Acids on Alumina Particles

Fulvic acids (FA) were immobilized on alumina particles in order to evaluate their catalytic effect as solid-phase redox mediator (RM) during the reductive dechlorination of carbon tetrachloride (CT) by anaerobic sludge. FA were extracted from three different soil samples and two commercial composts. Electron carrying capacity (ECC) was determined in all FA samples in order to select the appropriate source of redox-mediating compounds for CT dechlorination. TiO2, Al(OH)3, and γ-Al2O3 particles were tested as immobilizing materials for the extracted FA. FA extracted from a temperate pine forest soil showed the highest ECC (291.72 μmol g−1). The highest adsorption capacity of FA, measured as total organic carbon (TOC), was achieved by alumina (γ-Al2O3) particles (12 mg TOC-FA g−1). Results suggest that the transfer of electrons rather than their microbial generation through glucose fermentation was the rate-limiting factor during dechlorination of CT. Immobilized FA increase up to 10.4-fold the rate of CT dechlorination as compared with the control lacking FA. Immobilization of FA on alumina particles was very stable, and spectrophotometric screening did not detect any detachment of FA during dechlorination of CT, thus confirming that the enhanced dechlorination achieved could exclusively be linked to the redox-mediating capacity of immobilized FA. The present study constitutes the first demonstration that immobilized FA on alumina particles could serve as a solid-phase RM in dechlorination reactions.

Facile fabrication of nanostructured Pd–Fe bimetallic thin films and their electrodechlorination activity

A series of nanostructured Pd–Fe bimetallic thin films with the performance of fast and high-efficiency electrochemical reductive dechlorination were directly formed on glassy carbon electrodes (GCEs) through galvanic replacement of partial Fe 0 nanoparticles by Pd(II) ions. The composition and morphology of such Pd–Fe thin films are strongly dependent on the sacrificial Fe film templates fabricated by a template-free, double-potential step electrodeposition technique. The size, shape and morphology of the Fe nanoparticles that constitute the Fe thin films can be controlled well by adjusting the concentration of Fe 2+ ions in electrolyte solutions. Due to the good synergistic effect between Pd and Fe, the as-prepared Pd–Fe thin films with the novel microstructure display a high reactivity towards the electrochemical reductive dechlorination of carbon tetrachloride (CT), which closely related to the composition of Pd–Fe thin films, applied potential and temperature. The dechlorination reaction of CT complied with pseudo-first-order kinetics.

Reductive dechlorination of carbon tetrachloride in acidic soil manipulated with iron(II) and bisulfide ion

Batch and column tests were conducted to investigate the effect of reductant concentration, reductant contact time, and suspension pH on reductive dechlorination of carbon tetrachloride (CT) by soil manipulated with Fe(II) and HS −. Kinetic rate constants for the reductive dechlorination increased as the reductant concentrations increased. Fe(II) was more effective reductant than HS −, resulting in higher rate constants. The contact time of 1 day for the soil with HS − and that of 4 h with Fe(II) showed the highest reaction rates, respectively. The kinetic rate constants increased as the pH of soil suspensions with Fe(II) (5.2–8.0) and HS − (8.3–10.3) increased. Soil column with Fe(II) showed larger bed volumes (13.8) to reach a column breakthrough than that with HS − (4.0). Fe(II) treatment showed better removal of CT in the soil column with the addition of CaO than HS − treatment did. In contrast, HS − treatment not producing toxic products could be considered as an environmentally favorable reductant.

Reductive dechlorination of carbon tetrachloride by zero-valent iron and related iron corrosion

Electrochemical corrosion behavior of iron in aqueous solutions with and without carbon tetrachloride (CT) was investigated in a wide pH range from 0.4 to 14 using steady-state polarization curves and electrochemical impedance spectroscopy (EIS). It was found that the presence of CT significantly accelerated the hydrogen evolution reaction (HER) on the iron surface in strong acidic solutions, causing severe corrosion of iron; in return, the iron corrosion was helpful for the reductive dechlorination of CT. The inherent relationship between the dechlorination of CT and the corrosion of iron is attributed to the fact that the adsorbed hydrogen atoms produced during the iron corrosion process are necessary for the dechlorination process of CT. As a result, the removal efficiency of CT is strongly dependent on the extent of iron corrosion in aqueous solutions at different pH values.

The Relative Importance of Abiotic and Biotic Transformation of Carbon Tetrachloride in Anaerobic Soils and Sediments

The relative contributions of abiotic and microbial processes and the role of dissolved species in the reductive dechlorination of carbon tetrachloride (CT) by natural soils and sediments were investigated. Microcosms were constructed using soils or sediments and site water from three locations, and then amended with electron acceptors and/or donors to stimulate the growth of iron- and sulfate-reducing bacteria and to promote the formation of minerals that can react with CT. Before spiking with CT, half the replicate microcosms were sterilized in order to measure the rates of abiotic CT transformation without any direct contribution from microbial dechlorination. Abiotic reaction rates were significantly greater than microbial rates for a range of initial CT concentrations, and for both iron- and sulfate-reducing conditions. In most cases, abiotic reaction rates were indistinguishable from total reaction rates (abiotic plus microbial), indicating a negligible microbial contribution to CT transformation. While in most microcosms the soil/sediment acted as the abiotic reductant, under certain conditions the supernatant was more reactive with CT than was the solid phase. For these conditions, we propose that the reactive species in the supernatant consisted of aqueous natural organic matter that underwent reduction or other transformation by S(-II) generated by sulfate-reducing bacteria.

Ex-situ Reductive Dechlorination of Carbon Tetrachloride by Iron Sulfide in Batch Reactor

Ex-situ reductive dechlorination of carbon tetrachloride (CT) by iron sulfide in a batch reactor was characterized in this study. Reactor scaled-up by 3.5 L was used to investigate the effect of reductant concentration on removal efficiency and process optimization for ex-situ degradation. The experiment was conducted by using both liquid-phase and gas-phase volume at pH 8.5 in anaerobic condition. For 1 mM of initial CT concentration, the removal of the target compound was 98.9% at 6.0 g/L iron sulfide. Process optimization for ex-situ treatment was performed by checking the effect of transition metal and mixing time on synthesizing iron sulfide solution, and by determining of the regeneration time. The effect of Co(II) as transition metal was shown that the reaction rate was slightly improved but the improvement was not that outstanding. The result of determination on the regeneration time indicated that regenerating reductant capacity after 1 st treatment of target compound was needed. Due to the high removal rates of CT, ex-situ reductive dechlorination in batch reactor can be used for basic treatment for the chlorinated compounds.

Electrochemical reductive dechlorination of carbon tetrachloride on nanostructured Pd thin films

The nanostructured Pd thin films prepared via cyclic voltammetric deposition method are proved to be a promising electrocatalyst for electrochemical reductive dechlorination of carbon tetrachloride (CT). The use of as-prepared Pd thin films as the working electrode material provides a possibility to separately study the role of various forms of hydrogen in the dechlorination reactions. Electrochemical characterization and gas chromatography analysis clearly indicate for the first time that the adsorbed hydrogen has excellent ability to remove CT from acidic solutions through the surface reaction with the chemisorbed CT molecules, which is of fundamental importance to have a better understanding of the reaction mechanism of electrochemical dechlorination.