Reduction of carbon tetrachloride by nanoscale palladized zero-valent iron@ graphene composites: Kinetics, activation energy, effects of reaction conditions and degradation mechanism

Ma, Yuanhui; Lv, Xiaofan; Yang, Qi; Wang, Yeyao; Chen, Xiao

doi:10.1016/j.apcata.2017.05.028

Cited by 43 publications

(11 citation statements)

References 53 publications

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“…The nitrate removal was 91.9% after 15 min at 313 K compared with only 45.4% at 283 K. The nitrate was gradually reduced as the reaction progressed, and after 90 minutes of reaction, the removal rate reached 92.2%, 96.5%, 98.2%, and 99.5% for the temperatures of 283 K, 293 K, 303 K, and 313 K, respectively. A higher reaction temperature probably increases the percentage of activated molecules and the collision probability between the nitrate ions and materials, producing better removal efficiencies with increasing temperature 29 . Contrarily, a decreasing temperature caused a smaller nitrate reduction, which is typical for an endothermic reaction, with a similar trend reported in nitrate reduction systems where zero-valent iron acted as the reductant 17,50,55 .…”

Section: Resultsmentioning

confidence: 99%

“…pollutant transformation 27,28 . Embedded noble metals also show potential for protecting nZVI from passivation 29 . Moreover, regarding catalytic removal of nitrate, noble metals have been intensively studied for their selectivity towards end products 14,30 .…”

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confidence: 99%

“…Studies also revealed its capacity to provide sites for the precipitation of iron (hydr)oxides during the reaction process 22 . More importantly, the conjugate structure of graphene enhances the adsorption capacity of reactant molecules, with the high electron mobility facilitating the transfer of electrons in the catalytic reaction, thereby improving the catalytic activity of nZVI particles 29 .…”

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confidence: 99%

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Effect and mechanism of graphene structured palladized zero-valent iron nanocomposite (nZVI-Pd/NG) for water denitration

Huang

Zhang

Peng

et al. 2020

Sci Rep

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Nitrate reduction by zero-valent iron-based materials has been extensively studied. However, the aggregation of nanoparticles and the preference for unfavored ammonia products limit the application of this technology. To overcome this issue, this study introduced a novel synthesized nanoscale palladized zero-valent iron graphene composite (nZVI-Pd/NG) and explored its nitrate reduction efficiency. A nitrate removal rate of 97.0% was achieved after 120 min of reaction for an initial nitrate concentration of 100 mg N/L. The nitrogen gas selectivity was enhanced from 0.4% to 15.6% at the end point compared to nanoscale zero-valent iron (nZVI) particles under the same conditions. Further analyses revealed that zero-valent metal nanoparticles spread uniformly on the graphene surface, with a thin layer of iron (hydr)oxides dominated by magnetite. The nZVI-Pd/NG exhibited good catalytic activity with the associated activation energy of 17.6 kJ/mol being significantly lower than that with nZVI (42.8 kJ/mol). The acidic condition promoted a higher nZVI utilization rate, with the excess dosage of nZVI-Pd/NG ensuring a high nitrate removal rate for a wide pH range. This study demonstrates an improvement in nitrate reduction efficiency in a nZVI system by combining the exceptional properties of graphene and palladium. Nitrate is a major environmental pollutant in surface and ground water systems 1,2. Nitrate overload in water causes eutrophication and poses a threat on human health when consumed 3-5. Several onsite and offsite methods, including biological denitrification 6,7 , reverse osmosis 8 , adsorption 9,10 , chemical reduction 3,11 , and electrolysis 12,13 , serve for nitrate removal. Among these treatment methods, chemical reduction is considered among the most promising due to its high efficiency and stability 14,15. Recently, the zero-valent iron (ZVI) has been intensively studied as a reductive material due to its non-toxicity, low cost, and wide availability. Previous studies demonstrate that nitrate is significantly reduced by metallic iron under anoxic and anaerobic conditions 2,16. The surface area of iron used for denitration is vital in accelerating the reaction rate 17. Therefore, nanoscale zero-valent iron (nZVI) with high surface area and nanoscale particle size are utilized for nitrate removal. The reaction rate of the nZVI is largely improved compared with the microscale ZVI, with the reaction time dropping from several days to 1-2 hours 16,18. However, in practice, the agglomeration and passivation of nZVI particles reduce their effectiveness. The attraction between nZVI particles causes aggregation into microscale particles, thereby reducing their mobility and lowering the effective surface area 19. The microscale particles formed are considered to behave like the microscale ZVI 20. It has also been reported in many studies that as reaction proceeds, iron corrosion products (such as maghemite, lepidocrocite, magnetite, akaganeite, goethite) may cover the core-shell structure of nZVI, preventing subseq...

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Section: Resultsmentioning

confidence: 99%

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confidence: 99%

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confidence: 99%

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Effect and mechanism of graphene structured palladized zero-valent iron nanocomposite (nZVI-Pd/NG) for water denitration

Huang

Zhang

Peng

et al. 2020

Sci Rep

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“…Batch experiments on the effect of different temperatures were conducted to evaluate the activation energy ( E a ) for the dechlorination of CT with nZVIs and nZVI@SN‐rGO. According to the Arrhenius equation, the functional relationship between the temperature and the rate constant is

k_{obs} = A \times e^{- E_{a} / italicRT}

where k obs is the measured first‐order rate constant, E a is the activation energy, A is a pre‐exponential factor, R is the ideal gas constant and T is the temperature. Integrating equation results in

ln k_{obs} = - \frac{E_{normala}}{R} \times \frac{1}{T} + ln A

…”

Section: Resultsmentioning

confidence: 99%

“…As a result, the novel iron‐based catalyst (i.e. nZVI@SN‐rGO) could not only avoid magnetic nanoparticle agglomeration during the CT degradation process but also significantly increase the specific surface area, which might in turn provide more effective surface‐active sites for CT degradation . Furthermore, due to the fact that the redox couple formed by ZVI and dissolved aqueous ferrous ions had a standard reduction potential of −0.44 eV, the nZVI@SN‐rGO combining nZVIPs with S/N dual‐doped r‐GO under acidic condition made up many microscopic galvanic cells, which might promote the yield of nascent state active [H].…”

Section: Resultsmentioning

confidence: 99%

Degradation of carbon tetrachloride using ultrasound‐assisted nanoscaled zero‐valent iron particles@sulfur/nitrogen dual‐doped reduced graphene oxide composite: Kinetics, activation energy, effects of reaction conditions and degradation mechanism

Meng

Wang

2019

Applied Organom Chemis

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We report a study of the synthesis of nanoscale zero-valent iron particles stabilized by sulfur/nitrogen dual-doped reduced graphene oxide (i.e. nZVI@SN-rGO) and their applications as major reactants for the dechlorination of carbon tetrachloride (CT) by combining sonolysis with consideration of several operation parameters such as pH, temperature, catalyst dosage, as well as in the presence of common inorganic anions. The experimental results showed that the modified technology could remain effective for up to 180 min of reaction time under optimal conditions. Especially, there was no significant reduction in the removal efficiency toward CT even after five cycles, which was indicative of good stability. A study of the effects of common inorganic anions revealed that the presence of Clˉand HCO 3ˉe xhibited different positive effects in the following order: Clˉ> HCO 3ˉ; NO 3ˉa nd SO 4 2ˉs howed inhibition effects on CT removal. The structure and properties of nZVI@SN-rGO were characterized using X-ray diffraction, scanning electron microscopy, surface area analysis, Raman spectroscopy and X-ray photoelectron spectroscopy. Additionally, the corresponding activation energy was approximately 31.04 kJ mol −1 , suggesting that the surface chemical reaction rather than diffusion was the ratelimiting step in the CT decomposition process. More importantly, the possible reaction mechanism and dechlorination pathway of CT using the ultrasoundassisted nZVI@SN-rGO system were also investigated.

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Dechlorination of carbon tetrachloride by Nanoscale Nickeled Zero‐Valent Iron @ Multi‐Walled Carbon Nanotubes: Impact of reaction conditions, kinetics and mechanism

Xiao

Yang

et al. 2018

Applied Organom Chemis

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The nanoscale nickeled zero‐valent iron @ multi‐walled carbon nanotubes (NF@MWCNTs) were synthesized, characterized and used to dispose carbon tetrachloride (CT) in aqueous solution. Scanning electron microscopy (SEM), X‐ray energy dispersive spectroscopy (EDS), X‐ray diffraction (XRD) and Brunauer–Emmett–Teller (BET) gas sorptometry measurements were conducted to characterize the microstructure of the NF@MWCNTs. And batch experiments under different operation parameters were conducted to investigated the activity of NF@MWCNTs on degrading CT, including the content of NF@MWCNTs composites, temperature, catalyst dosage, initial pH and different anions. The experimental results showed that 4% nickel content of Ni/Fe bimetal and 2:1 doping ratio of Fe/MWCNTs were the wise choices in this study, which provided excellent degradation efficiency of CT when compared with nanoscale zero‐valent iron (nZVI) (97.44% and 55.28%, respectively). That was benefited from the fact that MWCNTs as an excellent support material could reduce the activation energy of 7.952 kJ/mol, and the nickel metal further reduced the reaction activation energy of 11.022 kJ/mol as presented in the conceptual model. Beyond that, NF@MWCNTs showed good reusability after five times consecutive reaction. Based on these, the reaction mechanism and degradation pathway also had been discussed.

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Reduction of carbon tetrachloride by nanoscale palladized zero-valent iron@ graphene composites: Kinetics, activation energy, effects of reaction conditions and degradation mechanism

Cited by 43 publications

References 53 publications

Effect and mechanism of graphene structured palladized zero-valent iron nanocomposite (nZVI-Pd/NG) for water denitration

Effect and mechanism of graphene structured palladized zero-valent iron nanocomposite (nZVI-Pd/NG) for water denitration

Degradation of carbon tetrachloride using ultrasound‐assisted nanoscaled zero‐valent iron particles@sulfur/nitrogen dual‐doped reduced graphene oxide composite: Kinetics, activation energy, effects of reaction conditions and degradation mechanism

Dechlorination of carbon tetrachloride by Nanoscale Nickeled Zero‐Valent Iron @ Multi‐Walled Carbon Nanotubes: Impact of reaction conditions, kinetics and mechanism

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