Overlooked Role of Fe(IV) and Fe(V) in Organic Contaminant Oxidation by Fe(VI)

Zhu, Jiahui; Yu, Fulu; Meng, Jiaoran; Shao, Bin; Dong, Hongyu; Chu, Wenhai; Cao, Tongcheng; Wei, Guannan; Wang, Hejia; Guan, Xiaohong

doi:10.1021/acs.est.0c03212

Cited by 140 publications

(132 citation statements)

References 50 publications

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“…However, our previous study reported that the plots of −ln([EOC] t /[EOC] 0 ) versus Fe(VI) exposure displayed auto-accelerating trends (Case 1) when methyl phenyl sulfoxide (PMSO), carbamazepine (CBZ), and caffeine (CAF) were degraded by excess Fe(VI) at [EOC] 0 /[Fe(VI)] 0 < 1:5 . Moreover, the auto-accelerating trend of the EOCs oxidation by Fe(VI) at a specific pH was highly consistent with that of Fe(VI) decay.…”

Section: Introductionsupporting

confidence: 68%

Three Kinetic Patterns for the Oxidation of Emerging Organic Contaminants by Fe(VI): The Critical Roles of Fe(V) and Fe(IV)

Wang

Deng

Shao

et al. 2021

Environ. Sci. Technol.

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For the first time, this study showed that the apparent secondorder rate constants (k app ) of six selected emerging organic contaminants (EOCs) oxidation by Fe(VI) increased, remained constant, or declined with time, depending on [EOC] 0 /[Fe(VI)] 0 , pH, and EOCs species. Employing excess caffeine as the quenching reagent for Fe(V) and Fe(IV), it was found that Fe(V)/Fe(IV) contributed to 20−30% of phenol and bisphenol F degradation by Fe(VI), and the contributions of Fe(V)/Fe(IV) remained nearly constant with time under all the tested conditions. However, the contributions of Fe(V)/Fe(IV) accounted for over 50% during the oxidation of sulfamethoxazole, bisphenol S, and iohexol by Fe(VI), and the variation trends of k app of their degradation by Fe(VI) with time displayed three different patterns, which coincided with those of the contributions of Fe(V)/Fe(IV) to their decomposition with time. Results of the quenching experiments were validated by simulating the oxidation kinetic data of methyl phenyl sulfoxide by Fe(VI), which revealed that the variation trends of k app with time were significantly determined by the change in the molar ratio of Fe(V) to Fe(VI) with time, highlighting the key role of Fe(V) in the oxidative process. This study provides comprehensive and insightful information on the roles of Fe(V)/Fe(IV) during EOC oxidation by Fe(VI).

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Section: Introductionsupporting

confidence: 68%

Three Kinetic Patterns for the Oxidation of Emerging Organic Contaminants by Fe(VI): The Critical Roles of Fe(V) and Fe(IV)

Wang

Deng

Shao

et al. 2021

Environ. Sci. Technol.

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“…Although methyl phenyl sulfoxide (PMSO) has been used as the probe compound for identifying Fe(IV), 16 Mossbauer spectroscopy) was still less explored because Fe(IV) was a short-lived species. 17,18 Also, researchers hypothesized that surface-mediated electron transfer might be the origins of nonradical oxidation pathways in the ironloaded catalysts. 19 In the electron-transfer process, the catalyst serves as a conductive bridge to facilitate the electron migration from the electron donor of the pollutant to the acceptor of reactive complex intermediates (catalyst−PS*).…”

Section: ■ Introductionmentioning

confidence: 99%

“…The inhibitory effects by the reactions between radical ROS and the background substrates such as Cl – and dissolved organics could be mitigated by the nonradical pathways, which could limit the spectrum of oxidizable pollutants and avoid the undesired consumption of the reactive oxidant by the reaction with background substances. , Recently, iron-loaded catalysts have demonstrated potential as PS activators for pollutant degradation without relying on typical radical ROS. ,, The high reactivity of the iron-loaded catalyst/PS system was due to the generation of powerful high-valent iron species [e.g., Fe(IV)], which abstracted electrons directly from organic pollutants to fulfil the degradation. Although methyl phenyl sulfoxide (PMSO) has been used as the probe compound for identifying Fe(IV), direct spectroscopic techniques (e.g., Mössbauer spectroscopy) was still less explored because Fe(IV) was a short-lived species. , Also, researchers hypothesized that surface-mediated electron transfer might be the origins of nonradical oxidation pathways in the iron-loaded catalysts . In the electron-transfer process, the catalyst serves as a conductive bridge to facilitate the electron migration from the electron donor of the pollutant to the acceptor of reactive complex intermediates (catalyst–PS*) .…”

Section: Introductionmentioning

confidence: 99%

Persulfate Oxidation of Sulfamethoxazole by Magnetic Iron-Char Composites via Nonradical Pathways: Fe(IV) Versus Surface-Mediated Electron Transfer

Liang

Duan

et al. 2021

Environ. Sci. Technol.

191

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Despite the vital roles of reactive radical species in the coupled iron–carbon composite/persulfate (PS) system for eliminating pollutants, nonradical contributions are typically overlooked. Herein, we developed two efficient magnetic iron–char composites via low-temperature (BCFe-400) and high-temperature (BCFe-700) pyrolysis. The two composites activated PS through nonradical pathways for sulfamethoxazole (SMX) degradation. In the BCFe-400/PS system, high-valent iron Fe(IV) was the dominant active species for the oxidation, evidenced by methyl phenyl sulfoxide-based probe tests, Mössbauer spectroscopy, and in situ Raman analyses with kinetic evaluation. In the BCFe-700/PS system, surface-mediated electron transfer dominated the oxidation, and the nonradical regime was probed by the electrochemical test and in situ Raman analysis. Furthermore, the BCFe-400/PS system maintained high efficiency in continuous degradation of SMX due to the feasible Fe2+generation toward Fe(IV) formation. In the BCFe-700/PS system, the stability of the system was limited due to the hindered electron transfer between the surface reactive complex (i.e., BCFe-700–PS*) and SMX, and thermal treatment would help recover the reactivity. Both BCFe-400/PS and BCFe-700/PS systems exhibited high performances for SMX removal in the presence of chloride and humic acid and in real water matrixes (e.g., seawater, piggery wastewater, and landfill leachate), exhibiting the great merits of the nonradical system. Overall, the study would provide new insights into PS activation by iron-loaded catalysts to efficiently degrade pollutants via nonradical pathways.

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“…3) Determination of the contribution of Fe(V)/Fe(IV) and the reactivities of ferrates toward various organic contaminants. Our recent study revealed that methyl phenyl sulfoxide (PMSO) was mainly degraded by Fe (IV) and Fe(V) rather than by Fe(VI) per se and Fe(V) played a dominant role when PMSO was degraded by Fe (VI) (Zhu et al, 2020). The contributions of Fe(IV) and Fe (V) were previously underemphasized, and Fe(VI) was less reactive toward organic contaminants than what we expected.…”

Section: Replacement Of Fe(vi) With Fe(v)/fe(iv)mentioning

confidence: 68%

“…- (Huang et al, 2016;Zhu et al, 2020). With regard to I-DBPs, although H 2 O 2 can reduce HOI, the regenerated Iand the difficulty in forming stable IO 3…”

Section: Potential Environmental Risks Associated With the Halide Ionsmentioning

confidence: 99%

Application of Fe(VI) in abating contaminants in water: State of art and knowledge gaps

Wang

Shao

Qiao

et al. 2020

Front. Environ. Sci. Eng.

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The past two decades have witnessed the rapid development and wide application of Fe(VI) in the field of water de-contamination because of its environmentally benign character. Fe(VI) has been mainly applied as a highly efficient oxidant/disinfectant for the selective elimination of contaminants. The in situ generated iron(III) (hydr)oxides with the function of adsorption/coagulation can further increase the removal of contaminants by Fe(VI) in some cases. Because of the limitations of Fe(VI) per se, various modified methods have been developed to improve the performance of Fe(VI) oxidation technology. Based on the published literature, this paper summarized the current views on the intrinsic properties of Fe(VI) with the emphasis on the self-decay mechanism of Fe(VI). The applications of Fe (VI) as a sole oxidant for decomposing organic contaminants rich in electron-donating moieties, as a bi-functional reagent (both oxidant and coagulant) for eliminating some special contaminants, and as a disinfectant for inactivating microorganisms were systematically summarized. Moreover, the difficulties in synthesizing and preserving Fe(VI), which limits the large-scale application of Fe (VI), and the potential formation of toxic byproducts during Fe(VI) application were presented. This paper also systematically reviewed the important nodes in developing methods to improve the performance of Fe(VI) as oxidant or disinfectant in the past two decades, and proposed the future research needs for the development of Fe(VI) technologies.

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Overlooked Role of Fe(IV) and Fe(V) in Organic Contaminant Oxidation by Fe(VI)

Cited by 140 publications

References 50 publications

Three Kinetic Patterns for the Oxidation of Emerging Organic Contaminants by Fe(VI): The Critical Roles of Fe(V) and Fe(IV)

Three Kinetic Patterns for the Oxidation of Emerging Organic Contaminants by Fe(VI): The Critical Roles of Fe(V) and Fe(IV)

Persulfate Oxidation of Sulfamethoxazole by Magnetic Iron-Char Composites via Nonradical Pathways: Fe(IV) Versus Surface-Mediated Electron Transfer

Application of Fe(VI) in abating contaminants in water: State of art and knowledge gaps

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