New Insight into the Oxidation of Arsenite by the Reaction of Zerovalent Iron and Oxygen. Comment on “pH Dependence of Fenton Reagent Generation and As(III) Oxidation and Removal by Corrosion of Zero Valent Iron in Aerated Water”

Jiang, Jin; Pang, Shengyong; Ouyang, Feng

doi:10.1021/es9004015

Cited by 23 publications

(15 citation statements)

References 12 publications

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“…All of the above phenomena implied that As(III) was primarily removed by the oxide film coated on the pristine ZVI and/or the newly formed iron oxides without oxidizing to As(V) in the absence of WMF at pH ini 5.0−9.0. 27,37 Without WMF, more arsenic was removed at pH ini 7.0−9.0 in the process of As(III) removal by ZVI than from As(V), which is consistent with the phenomenon reported by Su and Puls. 13 It was elaborated that As(V) was more effectively removed by coprecipitation than As(III) was at an equilibrium pH lower than 7.4.…”

Section: ■ Results and Discussionsupporting

confidence: 88%

“…26,42,43 Other researchers believe that the oxidation of As(III) occurs on or near the solid surface, which involves surface-mediated redox transformations instead of adsorption of reaction products formed in the solution phase. 27,37,41,44 All of them agree that Fenton reactions can take place at a neutral pH range and are responsible for the As(III) oxidation.…”

Section: ■ Results and Discussionmentioning

confidence: 86%

“…In addition, with respect to the As(III) removal mechanism by ZVI, there is still a dispute on whether the As(III) oxidation occurs in solution or on the surface of iron oxides. 26,27 To address this issue, simultaneous analysis of the arsenic species in solution and solid phases versus reaction time will be helpful, and the application of WMF may provide new insight into this issue.…”

mentioning

confidence: 99%

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Effect of Weak Magnetic Field on Arsenate and Arsenite Removal from Water by Zerovalent Iron: An XAFS Investigation

Sun

Guan

Wang

et al. 2014

Environ. Sci. Technol.

138

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In this study, a weak magnetic field (WMF), superimposed with a permanent magnet, was utilized to improve ZVI corrosion and thereby enhance As(V)/As(III) removal by ZVI at pHini 3.0-9.0. The experiment with real arsenic-bearing groundwater revealed that WMF could greatly improve arsenic removal by ZVI even in the presence of various cations and anions. The WMF-induced improvement in As(V)/As(III) removal by ZVI should be primarily associated with accelerated ZVI corrosion, as evidenced by the pH variation, Fe(2+) release, and the formation of corrosion products as characterized with X-ray absorption fine structure spectroscopy. The arsenic species analysis in solution/solid phases at pHini 3.0 revealed that As(III) oxidation to As(V) in aqueous phase preceded its subsequent sequestration by the newly formed iron (hydr)oxides. However, both As(V) adsorption following As(III) oxidation to As(V) in solution and As(III) adsorption preceding its conversion to As(V) in solid phase were observed at pHini 5.0-9.0. The application of WMF accelerated the transformation of As(III) to As(V) in both aqueous and solid phases at pHini 5.0-9.0 and enhanced the oxidation of As(III) to As(V) in solution at pHini 3.0.

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Section: ■ Results and Discussionsupporting

confidence: 88%

Section: ■ Results and Discussionmentioning

confidence: 86%

mentioning

confidence: 99%

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Effect of Weak Magnetic Field on Arsenate and Arsenite Removal from Water by Zerovalent Iron: An XAFS Investigation

Sun

Guan

Wang

et al. 2014

Environ. Sci. Technol.

138

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“…This interpretation received support from several other groups, [32][33][34][35] but was questioned by Pang et al who proposed that surface interactions, and not Fe(IV), were responsible for the observed behavior in these inhomogeneous environments. 36,37 As part of our on-going interest in high-valent iron chemistry and the Fenton reaction, we conducted an in depth study of the kinetics and products of the reaction of Fe(H 2 O) 6…”

Section: Introductionmentioning

confidence: 99%

pH-induced mechanistic changeover from hydroxyl radicals to iron(iv) in the Fenton reaction

2012

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A major pathway in the reaction between Fe(II) and H 2 O 2 at pH 6-7 in non-coordinating buffers exhibits inverse kinetic dependence on [H + ] and leads to oxidation of dimethyl sulfoxide (DMSO) to dimethyl sulfone (DMSO 2 ). This step regenerates Fe(II) and makes the oxidation of DMSO catalytic, a finding that strongly supports Fe(IV) as a Fenton intermediate at near-neutral pH. This Fe(IV) is a less efficient oxidant for DMSO at pH 6-7 than is (H 2 O) 5 FeO 2+ , generated by ozone oxidation of Fe(H 2 O) 6 2+ , in acidic solutions. Large concentrations of DMSO are needed to achieve significant turnover numbers at pH $ 6 owing to the rapid competing reaction between Fe(II) and Fe(IV) that leads to irreversible loss of the catalyst. At pH 6 and #0.02 mM Fe(II), the ratio of apparent rate constants for the reactions of Fe(IV) with DMSO and with Fe(II) is $10 4 . The results at pH 6-7 stand in stark contrast with those reported previously in acidic solutions where the Fenton reaction generates hydroxyl radicals. Under those conditions, DMSO is oxidized stoichiometrically to methylsulfinic acid and ethane. This path still plays a role (1-10%) at pH 6-7.

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“…The fraction of As(V) increased progressively from 77.6% to 85.0% as the intensity of the MF for preparing Mag-ZVI increased from 0 to 500 mT, indicating that premagnetization facilitated oxidation of As(III) to As(V). Combining the results of arsenic removal behavior and arsenic speciation in solution and the solid phase, it could be confirmed that the transformation of As(III) to As(V) by ZVI was improved by applying premagnetization. ,− In summary, ZVI corrosion was accelerated due to premagnetization, and Mag-ZVI prepared in an MF with greater intensity corroded at a larger rate, which favored the Fenton reaction, conversion of As(III) to As(V), and generation of iron (hydr)oxides for incorporating arsenic. Although As(III) was oxidized at a greater rate in the system with Mag-ZVI, a drop in As(V) accumulation was observed, as compared to its counterpart in the system with Pri-ZVI, which could be explained by the quick generation of iron (hydr)oxides.…”

Section: Resultsmentioning

confidence: 83%

Improving the Reactivity of Zerovalent Iron by Taking Advantage of Its Magnetic Memory: Implications for Arsenite Removal

Shi

et al. 2015

Environ. Sci. Technol.

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Premagnetization was employed to enhance the reactivity of zerovalent iron (ZVI) toward As(III) sequestration for the first time. Compared to the pristine ZVI (Pri-ZVI), the rate of As(III) elimination by the premagnetized ZVI (Mag-ZVI) was greater over the pHini range of 4.0-9.0 and increased progressively with increasing intensity of the magnetic field for premagnetization. Mag-ZVI could keep its reactivity for a long time and showed better performance than Pri-ZVI for As(III) removal from synthetic groundwater in column tests. The Fe K-edge XAFS analysis for As(III)-treated ZVI samples unraveled that premagnetization promoted the transformation of ZVI to iron (hydr)oxides and shifted the corrosion products from maghemite and magnetite to lepidocrocite, which favored the arsenic sequestration. The arsenic species analysis revealed that premagnetization facilitated the oxidation of As(III) to As(V). ZVI pretreated with grinding was very different from Mag-ZVI with regard to As(III) removal, indicating that the improved reactivity of Mag-ZVI should not be associated with the physical squeezing effect of the ZVI grains during magnetization. The positive correlation between the remanence of Mag-ZVI and the rate constants of total arsenic removal indicated that the enhanced reactivity of Mag-ZVI was mainly ascribed to its magnetic memory, i.e., the remanence kept by Mag-ZVI.

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New Insight into the Oxidation of Arsenite by the Reaction of Zerovalent Iron and Oxygen. Comment on “pH Dependence of Fenton Reagent Generation and As(III) Oxidation and Removal by Corrosion of Zero Valent Iron in Aerated Water”

Cited by 23 publications

References 12 publications

Effect of Weak Magnetic Field on Arsenate and Arsenite Removal from Water by Zerovalent Iron: An XAFS Investigation

Effect of Weak Magnetic Field on Arsenate and Arsenite Removal from Water by Zerovalent Iron: An XAFS Investigation

pH-induced mechanistic changeover from hydroxyl radicals to iron(iv) in the Fenton reaction

Improving the Reactivity of Zerovalent Iron by Taking Advantage of Its Magnetic Memory: Implications for Arsenite Removal

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