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Cárdenas-Hernández PA, Hickey K, Di Toro DM, Allen HE, Carbonaro RF, Chiu PC. Linear Free Energy Relationship for Predicting the Rate Constants of Munition Compound Reduction by the Fe(II)-Hematite and Fe(II)-Goethite Redox Couples. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2023; 57:13646-13657. [PMID: 37610109 DOI: 10.1021/acs.est.3c04714] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/24/2023]
Abstract
Abiotic reduction by iron minerals is arguably the most important fate process for munition compounds (MCs) in subsurface environments. No model currently exists that can predict the abiotic reduction rates of structurally diverse MCs by iron (oxyhydr)oxides. We performed batch experiments to measure the rate constants for the reduction of three classes of MCs (poly-nitroaromatics, nitramines, and azoles) by hematite or goethite in the presence of aqueous Fe2+. The surface area-normalized reduction rate constant (kSA) depended on the aqueous-phase one-electron reduction potential (EH1) of the MC and the thermodynamic state (i.e., pe and pH) of the iron oxide-Feaq2+ system. A linear free energy relationship (LFER), similar to that reported previously for nitrobenzene, successfully captures all MC reduction rate constants that span 6 orders of magnitude: log ( k S A ) = ( 1.12 ± 0.04 ) [ 0.53 E H 1 59 m V - ( p H + p e ) ] + ( 5.52 ± 0.23 ) . The finding that the rate constants of all the different classes of MCs can be described by a single LFER suggests that these structurally diverse nitro compounds are reduced by iron oxide-Feaq2+ couples through a common mechanism up to the rate-limiting step. Multiple mechanistic implications of the results are discussed. This study expands the applicability of the LFER model for predicting the reduction rates of legacy and emerging MCs and potentially other nitro compounds.
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Affiliation(s)
- Paula A Cárdenas-Hernández
- Department of Civil and Environmental Engineering, University of Delaware, Newark, Delaware 19716, United States
| | - Kevin Hickey
- Department of Civil and Environmental Engineering, University of Delaware, Newark, Delaware 19716, United States
| | - Dominic M Di Toro
- Department of Civil and Environmental Engineering, University of Delaware, Newark, Delaware 19716, United States
| | - Herbert E Allen
- Department of Civil and Environmental Engineering, University of Delaware, Newark, Delaware 19716, United States
| | - Richard F Carbonaro
- Department of Chemical Engineering, Manhattan College, Riverdale, New York 10471, United States
- Mutch Associates LLC, Ramsey, New Jersey 07446, United States
| | - Pei C Chiu
- Department of Civil and Environmental Engineering, University of Delaware, Newark, Delaware 19716, United States
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2
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Puigserver D, Herrero J, Carmona JM. Mobilization pilot test of PCE sources in the transition zone to aquitards by combining mZVI and biostimulation with lactic acid. THE SCIENCE OF THE TOTAL ENVIRONMENT 2023; 877:162751. [PMID: 36921871 DOI: 10.1016/j.scitotenv.2023.162751] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/25/2022] [Revised: 02/05/2023] [Accepted: 03/05/2023] [Indexed: 05/06/2023]
Abstract
The potential toxic and carcinogenic effects of chlorinated solvents in groundwater on human health and aquatic ecosystems require very effective remediation strategies of contaminated groundwater to achieve the low legal cleanup targets required. The transition zones between aquifers and bottom aquitards occur mainly in prograding alluvial fan geological contexts. Hence, they are very frequent from a hydrogeological point of view. The transition zone consists of numerous thin layers of fine to coarse-grained clastic fragments (e.g., medium sands and gravels), which alternate with fine-grained materials (clays and silts). When the transition zones are affected by DNAPL spills, free-phase pools accumulate on the less conductive layers. Owing to the low overall conductivity of this zone, the pools are very recalcitrant. Little field research has been done on transition zone remediation techniques. Injection of iron microparticles has the disadvantage of the limited accessibility of this reagent to reach the entire source of contamination. Biostimulation of indigenous microorganisms in the medium has the disadvantage that few of the microorganisms are capable of complete biodegradation to total mineralization of the parent contaminant and metabolites. A field pilot test was conducted at a site where a transition zone existed in which DNAPL pools of PCE had accumulated. In particular, the interface with the bottom aquitard was where PCE concentrations were the highest. In this pilot test, a combined strategy using ZVI in microparticles and biostimulation with lactate in the form of lactic acid was conducted. Throughout the test it was found that the interdependence of the coupled biotic and abiotic processes generated synergies between these processes. This resulted in a greater degradation of the PCE and its transformation products. With the combination of the two techniques, the mobilization of the contaminant source of PCE was extremely effective.
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Affiliation(s)
- Diana Puigserver
- Department of Mineralogy, Petrology and Applied Geology. Faculty of Earth Sciences, University of Barcelona (UB), Water Research Institute (IdRA-UB), Serra Húnter Tenure-elegible Lecturer, C/ Martí i Franquès, s/n, E-08028 Barcelona, Spain.
| | - Jofre Herrero
- Department of Mineralogy, Petrology and Applied Geology, Faculty of Earth Sciences, University of Barcelona (UB), Water Research Institute (IdRA-UB), C/ Martí i Franquès, s/n, E-08028 Barcelona, Spain.
| | - José M Carmona
- Department of Mineralogy, Petrology and Applied Geology, Faculty of Earth Sciences, University of Barcelona (UB), Water Research Institute (IdRA-UB), C/ Martí i Franquès, s/n, E-08028 Barcelona, Spain.
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3
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Yin X, Hua H, Dyer J, Landis R, Fennell D, Axe L. Degradation of chlorinated solvents with reactive iron minerals in subsurface sediments from redox transition zones. JOURNAL OF HAZARDOUS MATERIALS 2023; 445:130470. [PMID: 36493644 DOI: 10.1016/j.jhazmat.2022.130470] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2022] [Revised: 11/08/2022] [Accepted: 11/23/2022] [Indexed: 06/17/2023]
Abstract
Reactive iron (Fe) mineral coatings found in subsurface reduction-oxidation transition zones (RTZs) contribute to the attenuation of contaminants. An 18.3-m anoxic core was collected from the site, where constituents of concern (COCs) in groundwater included chlorinated solvents. Reactive Fe mineral coatings were found to be abundant in the RTZs. This research focused on evaluating reaction kinetics with anoxic sediments bearing ferrous mineral nano-coatings spiked with either tetrachloroethylene (PCE), trichloroethylene (TCE), or 1,4-dichlorobenzene (1,4-DCB). Reaction kinetics with RTZ sediments followed pseudo-first-order reactions for the three contaminants with 90% degradation achieved in less than 39 days. The second-order rate constants for the three COCs ranged from 6.20 × 10-4 to 1.73 × 10-3 Lg-1h-1 with pyrite (FeS2), 4.97 × 10-5 to 1.24 × 10-3 Lg-1h-1with mackinawite (FeS), 1.25 × 10-4 to 1.89 × 10-4 Lg-1h-1 with siderite (FeCO3), and 1.79 × 10-4 to 1.10 × 10-3 Lg-1h-1 with magnetite (Fe3O4). For these three chlorinated solvents, the trend for the rate constants followed: Fe(II) sulfide minerals > magnetite > siderite. The high reactivity of Fe mineral coatings is hypothesized to be due to the large surface areas of the nano-mineral coatings. As a result, these surfaces are expected to play an important role in the attenuation of chlorinated solvents in contaminated subsurface environments.
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Affiliation(s)
- Xin Yin
- Department of Civil and Environmental Engineering, New Jersey Institute of Technology, Newark, NJ 07032, USA
| | - Han Hua
- Department of Civil and Environmental Engineering, New Jersey Institute of Technology, Newark, NJ 07032, USA; Department of Civil, Construction & Environmental Engineering, University of New Mexico, Albuquerque, NM 87131, USA
| | - James Dyer
- Savannah River National Laboratory, Aiken, SC 29808, USA
| | | | - Donna Fennell
- Rutgers University, Department of Environmental Sciences, 14 College Farm Road, New Brunswick, NJ 08901, USA
| | - Lisa Axe
- Otto H. York Department of Chemical and Materials Engineering, New Jersey Institute of Technzhaology, Newark, NJ 07032, USA.
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4
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Lawrinenko M, Kurwadkar S, Wilkin RT. Long-term performance evaluation of zero-valent iron amended permeable reactive barriers for groundwater remediation - A mechanistic approach. GEOSCIENCE FRONTIERS 2023; 14:1-13. [PMID: 36760680 PMCID: PMC9903902 DOI: 10.1016/j.gsf.2022.101494] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
Permeable reactive barriers (PRBs) are used for groundwater remediation at contaminated sites worldwide. This technology has been efficient at appropriate sites for treating organic and inorganic contaminants using zero-valent iron (ZVI) as a reductant and as a reactive material. Continued development of the technology over the years suggests that a robust understanding of PRB performance and the mechanisms involved is still lacking. Conflicting information in the scientific literature downplays the critical role of ZVI corrosion in the remediation of various organic and inorganic pollutants. Additionally, there is a lack of information on how different mechanisms act in tandem to affect ZVI-groundwater systems through time. In this review paper, we describe the underlying mechanisms of PRB performance and remove isolated misconceptions. We discuss the primary mechanisms of ZVI transformation and aging in PRBs and the role of iron corrosion products. We review numerous sites to reinforce our understanding of the interactions between groundwater contaminants and ZVI and the authigenic minerals that form within PRBs. Our findings show that ZVI corrosion products and mineral precipitates play critical roles in the long-term performance of PRBs by influencing the reactivity of ZVI. Pore occlusion by mineral precipitates occurs at the influent side of PRBs and is enhanced by dissolved oxygen and groundwater rich in dissolved solids and high alkalinity, which negatively impacts hydraulic conductivity, allowing contaminants to potentially bypass the treatment zone. Further development of site characterization tools and models is needed to support effective PRB designs for groundwater remediation.
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Affiliation(s)
- Michael Lawrinenko
- Center for Environmental Solutions and Emergency Response, U.S. Environmental Protection Agency, 919 Kerr Research Drive, Ada, OK 74820, USA
| | - Sudarshan Kurwadkar
- Department of Civil and Environmental Engineering, California State University, 800 N. State College Blvd., Fullerton, CA 92831, USA
| | - Richard T. Wilkin
- Center for Environmental Solutions and Emergency Response, U.S. Environmental Protection Agency, 919 Kerr Research Drive, Ada, OK 74820, USA
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Brumovský M, Micić V, Oborná J, Filip J, Hofmann T, Tunega D. Iron nitride nanoparticles for rapid dechlorination of mixed chlorinated ethene contamination. JOURNAL OF HAZARDOUS MATERIALS 2023; 442:129988. [PMID: 36155299 DOI: 10.1016/j.jhazmat.2022.129988] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2022] [Revised: 08/24/2022] [Accepted: 09/13/2022] [Indexed: 06/16/2023]
Abstract
Sulfidation and, more recently, nitriding have been recognized as promising modifications to enhance the selectivity of nanoscale zero-valent iron (nZVI) particles for trichloroethene (TCE). Herein, we investigated the performance of iron nitride (FexN) nanoparticles in the removal of a broader range of chlorinated ethenes (CEs), including tetrachloroethene (PCE), cis-1,2-dichloroethene (cis-DCE), and their mixture with TCE, and compared it to the performance of sulfidated nZVI (S-nZVI) prepared from the same precursor nZVI. Two distinct types of iron nitride (FexN) nanoparticles, containing γ'-Fe4N and ε-Fe2-3N phases, exhibited substantially higher PCE and cis-DCE dechlorination rates compared to S-nZVI. A similar effect was observed with a CE mixture, which was completely dechlorinated by both types of FexN nanoparticles within 10 days, whereas S-nZVI was able to remove only about half of the amount, most of which being TCE. Density functional theory calculations further revealed that the cleavage of the first C-Cl bond was the rate-limiting step for all CEs dechlorinated on the γ'-Fe4N(001) surface, with the reaction barriers of PCE and cis-DCE being 29.9, and 40.8 kJ mol-1, respectively. FexN nanoparticles proved to be highly effective in the remediation of PCE, cis-DCE, and mixed CE contamination.
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Affiliation(s)
- Miroslav Brumovský
- University of Natural Resources and Life Sciences, Vienna, Department of Forest, and Soil Sciences, Institute of Soil Research, Peter-Jordan-Straße 82, 1190 Vienna, Austria; Department of Environmental Geosciences (EDGE), Centre for Microbiology and Environmental Systems Science, University of Vienna, Josef-Holaubek-Platz 2, UZA II, 1090 Vienna, Austria; Regional Centre of Advanced Technologies and Materials, Czech Advanced Technology and Research Institute (CATRIN), Palacký University, Šlechtitelů 27, 779 00 Olomouc, Czech Republic.
| | - Vesna Micić
- Department of Environmental Geosciences (EDGE), Centre for Microbiology and Environmental Systems Science, University of Vienna, Josef-Holaubek-Platz 2, UZA II, 1090 Vienna, Austria
| | - Jana Oborná
- Regional Centre of Advanced Technologies and Materials, Czech Advanced Technology and Research Institute (CATRIN), Palacký University, Šlechtitelů 27, 779 00 Olomouc, Czech Republic
| | - Jan Filip
- Regional Centre of Advanced Technologies and Materials, Czech Advanced Technology and Research Institute (CATRIN), Palacký University, Šlechtitelů 27, 779 00 Olomouc, Czech Republic
| | - Thilo Hofmann
- Department of Environmental Geosciences (EDGE), Centre for Microbiology and Environmental Systems Science, University of Vienna, Josef-Holaubek-Platz 2, UZA II, 1090 Vienna, Austria
| | - Daniel Tunega
- University of Natural Resources and Life Sciences, Vienna, Department of Forest, and Soil Sciences, Institute of Soil Research, Peter-Jordan-Straße 82, 1190 Vienna, Austria
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Robinson T, Latta DE, Leddy J, Scherer MM. Redox Potentials of Magnetite Suspensions under Reducing Conditions. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2022; 56:17454-17461. [PMID: 36394877 PMCID: PMC9730839 DOI: 10.1021/acs.est.2c05196] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Predicting the redox behavior of magnetite in reducing soils and sediments is challenging because there is neither agreement among measured potentials nor consensus on which Fe(III) | Fe(II) equilibria are most relevant. Here, we measured open-circuit potentials of stoichiometric magnetite equilibrated over a range of solution conditions. Notably, electron transfer mediators were not necessary to reach equilibrium. For conditions where ferrous hydroxide precipitation was limited, Nernstian behavior was observed with an EH vs pH slope of -179 ± 4 mV and an EH vs Fe(II)aq slope of -54 ± 4 mV. Our estimated EHo of 857 ± 8 mV closely matches a maghemite|aqueous Fe(II) EHo of 855 mV, suggesting that it plays a dominant role in poising the solution potential and that it's theoretical Nernst equation of EH[mV] = 855 - 177 pH - 59 log [Fe2+] may be useful in predicting magnetite redox behavior under these conditions. At higher pH values and without added Fe(II), a distinct shift in potentials was observed, indicating that the dominant Fe(III)|Fe(II) couple(s) poising the potential changed. Our findings, coupled with previous Mössbauer spectroscopy and kinetic data, provide compelling evidence that the maghemite/Fe(II)aq couple accurately predicts the redox behavior of stoichiometric magnetite suspensions in the presence of aqueous Fe(II) between pH values of 6.5 and 8.5.
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Affiliation(s)
- Thomas
C. Robinson
- Department
of Civil and Environmental Engineering, University of Iowa, Iowa City, Iowa52242, United States
| | - Drew E. Latta
- Department
of Civil and Environmental Engineering, University of Iowa, Iowa City, Iowa52242, United States
| | - Johna Leddy
- Department
of Chemistry, University of Iowa, Iowa City, Iowa52242, United States
| | - Michelle M. Scherer
- Department
of Civil and Environmental Engineering, University of Iowa, Iowa City, Iowa52242, United States
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7
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Puigserver D, Herrero J, Nogueras X, Cortés A, Parker BL, Playà E, Carmona JM. Biotic and abiotic reductive dechlorination of chloroethenes in aquitards. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 816:151532. [PMID: 34752872 DOI: 10.1016/j.scitotenv.2021.151532] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/07/2021] [Revised: 11/03/2021] [Accepted: 11/04/2021] [Indexed: 06/13/2023]
Abstract
Chlorinated solvents occur as dense nonaqueous phase liquid (DNAPL) or as solutes when dissolved in water. They are present in many pollution sites in urban and industrial areas. They are toxic, carcinogenic, and highly recalcitrant in aquifers and aquitards. In the latter case, they migrate by molecular diffusion into the matrix. When aquitards are fractured, chlorinated solvents also penetrate as a free phase through the fractures. The main objective of this study was to analyze the biogeochemical processes occurring inside the matrix surrounding fractures and in the joint-points zones. The broader implications of this objective derive from the fact that, incomplete natural degradation of contaminants in aquitards generates accumulation of daughter products. This causes steep concentration gradients and back-diffusion fluxes between aquitards and high hydraulic conductivity layers. This offers opportunities to develop remediation strategies based, for example, on the coupling of biotic and reactive abiotic processes. The main results showed: 1) Degradation occurred especially in the matrix adjacent to the orthogonal network of fractures and textural heterogeneities, where texture contrasts favored microbial development because these zones constituted ecotones. 2) A dechlorinating bacterium not belonging to the Dehalococcoides genus, namely Propionibacterium acnes, survived under the high concentrations of dissolved perchloroethene (PCE) in contact with the PCE-DNAPL and was able to degrade it to trichloroethene (TCE). Dehalococcoides genus was able to conduct PCE reductive dechlorination at least up to cis-1,2-dichloroethene (cDCE), which shows again the potential of the medium to degrade chloroethenes in aquitards. 3) Degradation of PCE in the matrix resulted from the coupling of reactive abiotic and biotic processes-in the first case, promoted by Fe2+ sorbed to iron oxides, and in the latter case, related to dechlorinating microorganisms. The dechlorination resulting from these coupling processes is slow and limited by the need for an adequate supply of electron donors.
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Affiliation(s)
- Diana Puigserver
- Department of Mineralogy, Petrology and Applied Geology, Faculty of Earth Sciences, University of Barcelona (UB), Water Research Institute (IdRA-UB), Serra Húnter Tenure-elegible Lecturer, C/ Martí i Franquès, s/n, E-08028 Barcelona, Spain.
| | - Jofre Herrero
- Department of Mineralogy, Petrology and Applied Geology, Faculty of Earth Sciences, University of Barcelona (UB), Water Research Institute (IdRA-UB). C/ Martí i Franquès, s/n, E-08028 Barcelona, Spain.
| | - Xènia Nogueras
- Department of Mineralogy, Petrology and Applied Geology, Faculty of Earth Sciences, University of Barcelona (UB). C/ Martí i Franquès, s/n, E-08028 Barcelona, Spain; Health Section of the City Council of Mataró (Barcelona), Specialized Support Technician, Carrer de la Riera, 48, 08301 Mataró, Barcelona, Spain.
| | - Amparo Cortés
- Department of Biology, Health and Environment, Faculty of Pharmacy, University of Barcelona, Av. Joan XXIII, 27-31, E-08028 Barcelona, Spain.
| | - Beth L Parker
- School of Engineering, University of Guelph, 50, Stone Road East, Guelph, N1G 2W1, Ontario, Canada.
| | - E Playà
- Department of Mineralogy, Petrology and Applied Geology, Faculty of Earth Sciences, University of Barcelona (UB). C/ Martí i Franquès, s/n, E-08028 Barcelona, Spain.
| | - José M Carmona
- Department of Mineralogy, Petrology and Applied Geology, Faculty of Earth Sciences, University of Barcelona (UB), Water Research Institute (IdRA-UB). C/ Martí i Franquès, s/n, E-08028 Barcelona, Spain.
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8
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Deng J, Zhan X, Wu F, Gao S, Huang LZ. Fast dechlorination of trichloroethylene by a bimetallic Fe(OH)2/Ni composite. Sep Purif Technol 2021. [DOI: 10.1016/j.seppur.2021.119597] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
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9
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Hua H, Yin X, Fennell D, Dyer JA, Landis R, Morgan SA, Axe L. Roles of reactive iron mineral coatings in natural attenuation in redox transition zones preserved from a site with historical contamination. JOURNAL OF HAZARDOUS MATERIALS 2021; 420:126600. [PMID: 34271444 DOI: 10.1016/j.jhazmat.2021.126600] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2021] [Revised: 06/26/2021] [Accepted: 07/05/2021] [Indexed: 06/13/2023]
Abstract
In this study, a protocol was developed to identify reduction-oxidation (redox) transition zones in an effort to exploit natural source zone depletion processes. A sediment core with a total length of 18-m was collected from a site with historical contamination that includes chlorinated benzenes where the redox condition was preserved. In the four redox transition zones investigated, reactive iron coatings are characterized with a suite of analyses under anaerobic conditions. To distinguish surface coating mineralogy, X-ray diffraction, X-ray fluorescence, and field-emission scanning electron microscopy with an energy dispersive X-ray analyzer were applied along with a six-step sequential extraction process. The cycling of Fe and S, as an important contribution and indicator of ongoing natural attenuation processes for constituents of concern (COC), was delineated by using data from multiple and complementary analyses for isolating and identifying iron phases. Along with groundwater chemistry, contaminant concentrations, and microbial genera, attenuation of COCs is expected to be active and sustainable in redox transition zones, where there is an abundance of reactive iron mineral coatings cycling through biogeochemical reactions. Reactions in other redox transition zones may be limited where iron mineral coatings are not dominant.
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Affiliation(s)
- Han Hua
- Department of Civil and Environmental Engineering, New Jersey Institute of Technology, Newark, NJ 07102, United States
| | - Xin Yin
- Department of Civil and Environmental Engineering, New Jersey Institute of Technology, Newark, NJ 07102, United States
| | - Donna Fennell
- Rutgers University, Department of Environmental Sciences, 14 College Farm Rd., New Brunswick, NJ 08901, United States
| | - James A Dyer
- Savannah River National Laboratory, Aiken, SC 29808, United States
| | | | | | - Lisa Axe
- Department of Chemical and Materials Engineering, New Jersey Institute of Technology, Newark, NJ 07102, United States.
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10
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Schaefer CE, Ho P, Berns E, Werth C. Abiotic dechlorination in the presence of ferrous minerals. JOURNAL OF CONTAMINANT HYDROLOGY 2021; 241:103839. [PMID: 34052750 DOI: 10.1016/j.jconhyd.2021.103839] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2020] [Revised: 05/19/2021] [Accepted: 05/21/2021] [Indexed: 06/12/2023]
Abstract
Laboratory batch experiments were performed to assess the reduction of trichloroethene (TCE) and oxygen via natural ferrous minerals. TCE reduction under anoxic conditions was measured via the generation of reduced gases, while oxygen reduction via the generation of hydroxyl radicals was measured as a surrogate for potential TCE oxidation. Results showed that TCE reduction under anoxic conditions was observed for ankerite, siderite, and illite, but not for biotite; acetylene was the primary identified dechlorination product. With the exception of biotite, first-order dechlorination rate constants increased with increasing ferrous content of the mineral, with rate constants ranging from 3.1 × 10-8 to 4.8 10-7 L g-1 d-1. Measured reduction potentials (mV vs SHE) ranged from -104 for illite to +84 for biotite. When normalizing measured first-order dechlorination rate constants to the estimated ferrous iron mineral specific surface area (where surface area was based on nitrogen adsorption analysis of the minerals), TCE dechlorination rate constants increased with increasing reduction potentials. Under oxic conditions, hydroxyl radicals were generated with each of the four minerals. However, mineral activity showed no readily apparent correlation to ferrous content or mineral surface area. In terms of TCE and oxygen reduced per mole of ferrous iron initially present in each mineral, illite was the most reactive of the four minerals. Together, these results suggest that several ferrous minerals may contribute to abiotic dechlorination in the natural environment, and (at least for TCE reduction under anoxic conditions) measurement of ferrous mineral content and reduction potential may serve as useful tools for estimating TCE first-order abiotic dechlorination rate constants.
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Affiliation(s)
- Charles E Schaefer
- CDM Smith, 110 Fieldcrest Avenue, #8, 6(th) Floor, Edison, NJ 08837, United States of America.
| | - Paul Ho
- CDM Smith, 14432 SE Eastgate Way # 100, Bellevue, WA 98007, United States of America
| | - Erin Berns
- University of Texas at Austin, Civil, Architectural, and Environmental Engineering, 301 E. Dean Keeton St., Stop C1786, Austin, TX 78712, United States of America
| | - Charles Werth
- University of Texas at Austin, Civil, Architectural, and Environmental Engineering, 301 E. Dean Keeton St., Stop C1786, Austin, TX 78712, United States of America
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11
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Huang J, Jones A, Waite TD, Chen Y, Huang X, Rosso KM, Kappler A, Mansor M, Tratnyek PG, Zhang H. Fe(II) Redox Chemistry in the Environment. Chem Rev 2021; 121:8161-8233. [PMID: 34143612 DOI: 10.1021/acs.chemrev.0c01286] [Citation(s) in RCA: 147] [Impact Index Per Article: 49.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Iron (Fe) is the fourth most abundant element in the earth's crust and plays important roles in both biological and chemical processes. The redox reactivity of various Fe(II) forms has gained increasing attention over recent decades in the areas of (bio) geochemistry, environmental chemistry and engineering, and material sciences. The goal of this paper is to review these recent advances and the current state of knowledge of Fe(II) redox chemistry in the environment. Specifically, this comprehensive review focuses on the redox reactivity of four types of Fe(II) species including aqueous Fe(II), Fe(II) complexed with ligands, minerals bearing structural Fe(II), and sorbed Fe(II) on mineral oxide surfaces. The formation pathways, factors governing the reactivity, insights into potential mechanisms, reactivity comparison, and characterization techniques are discussed with reference to the most recent breakthroughs in this field where possible. We also cover the roles of these Fe(II) species in environmental applications of zerovalent iron, microbial processes, biogeochemical cycling of carbon and nutrients, and their abiotic oxidation related processes in natural and engineered systems.
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Affiliation(s)
- Jianzhi Huang
- Department of Civil and Environmental Engineering, Case Western Reserve University, 2104 Adelbert Road, Cleveland, Ohio 44106, United States
| | - Adele Jones
- UNSW Water Research Centre, School of Civil and Environmental Engineering, University of New South Wales, Sydney, New South Wales 2052, Australia
| | - T David Waite
- UNSW Water Research Centre, School of Civil and Environmental Engineering, University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Yiling Chen
- Institute of Environmental and Ecological Engineering, Guangdong University of Technology, Guangzhou 510006, China
| | - Xiaopeng Huang
- Physical Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99352, United States
| | - Kevin M Rosso
- Physical Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99352, United States
| | - Andreas Kappler
- Geomicrobiology, Center for Applied Geosciences, University of Tuebingen, 72076 Tuebingen, Germany
| | - Muammar Mansor
- Geomicrobiology, Center for Applied Geosciences, University of Tuebingen, 72076 Tuebingen, Germany
| | - Paul G Tratnyek
- School of Public Health, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Portland, Oregon 97239, United States
| | - Huichun Zhang
- Department of Civil and Environmental Engineering, Case Western Reserve University, 2104 Adelbert Road, Cleveland, Ohio 44106, United States
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Mangayayam MC, Alonso-de-Linaje V, Dideriksen K, Tobler DJ. Effects of common groundwater ions on the transformation and reactivity of sulfidized nanoscale zerovalent iron. CHEMOSPHERE 2020; 249:126137. [PMID: 32058137 DOI: 10.1016/j.chemosphere.2020.126137] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/03/2019] [Revised: 01/29/2020] [Accepted: 02/05/2020] [Indexed: 06/10/2023]
Abstract
Sulfidized nanoscale zerovalent iron (S-nZVI) is an Fe-based reactant widely studied for its potential use for groundwater remediation. S-nZVI reactivity has been widely investigated testing various contaminants in various water matrices, but studies on S-nZVI corrosion behaviour and reactivity upon exposure to complex groundwater chemistries are limited. Here, we show that anoxic aging of S-nZVI for 7 days in the absence and presence of key groundwater solutes (i.e., Cl-, SO42-, Mg2+, Ca2+, HCO3-, CO32-, NO3-, or HPO42-) impacts Fe0 corrosion extent, corrosion product and reduction rates with trichloroethene (TCE). White rust was the dominant corrosion product in ultrapure water and in SO42-, Cl-, Mg2+ or Ca2+ solutions; green rust and/or chukanovite formed in HCO3- and CO32- solutions; magnetite, formed in NO3- solutions and vivianite in HPO42- solutions. The aged S-nZVI materials expectedly showed lower reactivities with TCE compared to unaged S-nZVI, with reaction rates mainly controlled by ion concentration, Fe0 corrosion extent, type(s) of corrosion product, and solution pH. Comparison of these results to observations in two types of groundwaters, one from a carbonate-rich aquifer and one from a marine intruded aquifer, showed that S-nZVI corrosion products are likely controlled by the dominant GW solutes, while reactivity with TCE is generally lower than expected, due to the multitude of ion effects. Overall, these results highlight that S-nZVI corrosion behaviour in GW can be manifold, with varied impact on its reactivity. Thus, testing of S-nZVI stability and reactivity under expected field conditions is key to understand its longevity in remediation applications.
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Affiliation(s)
- Marco C Mangayayam
- Nano-Science Center, Department of Chemistry, University of Copenhagen, Universitetsparken 5, 2100, Copenhagen, Denmark.
| | - Virginia Alonso-de-Linaje
- AECOM Environment, Madrid, Spain; GIR-QUESCAT, Departamento de Quimica Inorgánica, Universidad de Salamanca, Salamanca, Spain
| | - Knud Dideriksen
- Geological Survey of Denmark & Greenland (GEUS), Øster Voldgade 10, 1350, Copenhagen, Denmark
| | - Dominique J Tobler
- Nano-Science Center, Department of Chemistry, University of Copenhagen, Universitetsparken 5, 2100, Copenhagen, Denmark.
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Entwistle J, Latta DE, Scherer MM, Neumann A. Abiotic Degradation of Chlorinated Solvents by Clay Minerals and Fe(II): Evidence for Reactive Mineral Intermediates. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2019; 53:14308-14318. [PMID: 31802666 DOI: 10.1021/acs.est.9b04665] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
For decades, there has been evidence that Fe-containing minerals might contribute to abiotic degradation of chlorinated ethene (CE) plumes. Here, we evaluated whether Fe(II) in clay minerals reduces tetrachloroethene (PCE) and trichloroethene (TCE). We found that structural Fe(II) in both low (SWy-2) and high (NAu-1) Fe clay minerals did not reduce PCE or TCE under anoxic conditions. There was also no reduction of PCE or TCE after adding 5 mM dissolved Fe(II) to the clay mineral suspensions. In the presence of high Fe(II) concentrations (20 mM), however, PCE and TCE reduction products were observed in the presence of low Fe-content clay mineral SWy-2. Mössbauer spectroscopy results indicate that a mixed-valent Fe(II)-Fe(III) precipitate formed in the reactive SWy-2 suspensions. In contrast, in suspensions containing 20 mM Fe(II) alone or Fe-free clay mineral (Syn-1), we observed a purely Fe(II)-containing precipitate (Fe(OH)2) and also PCE and TCE reduction products. Interestingly, the amount of CE products decreased in the order of Fe-free clay mineral Syn-1 > Fe(OH)2 > low Fe-content clay mineral SWy-2, suggesting that clay mineral Fe controlled the formation of the reactive mineral phase. Additional experiments with hexachloroethane (HCA) revealed that faster HCA reduction occurred with decreasing clay mineral Fe content. Kinetic modeling yielded invariable second-order rate constants and increasing concentrations of reactive Fe(II) as the Fe(II)/Fe(total) content of the precipitates increased. Our data suggest that clay mineral Fe(III) is a sink for electrons from added Fe(II) that otherwise might have reduced the CEs. Furthermore, our findings are consistent with the hypothesis that active precipitation of Fe(II)-containing reactive mineral intermediates (RMI) may be important to CE reduction and suggest that RMI formation depends on clay mineral presence and Fe content.
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Affiliation(s)
- James Entwistle
- School of Engineering , Newcastle University , Newcastle upon Tyne , NE1 7RU , U.K
| | - Drew E Latta
- Civil and Environmental Engineering , The University of Iowa , Iowa City , Iowa 52242 , United States
| | - Michelle M Scherer
- Civil and Environmental Engineering , The University of Iowa , Iowa City , Iowa 52242 , United States
| | - Anke Neumann
- School of Engineering , Newcastle University , Newcastle upon Tyne , NE1 7RU , U.K
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Murray AM, Ottosen CB, Maillard J, Holliger C, Johansen A, Brabæk L, Kristensen IL, Zimmermann J, Hunkeler D, Broholm MM. Chlorinated ethene plume evolution after source thermal remediation: Determination of degradation rates and mechanisms. JOURNAL OF CONTAMINANT HYDROLOGY 2019; 227:103551. [PMID: 31526529 DOI: 10.1016/j.jconhyd.2019.103551] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/07/2019] [Revised: 08/28/2019] [Accepted: 08/30/2019] [Indexed: 06/10/2023]
Abstract
The extent, mechanism(s), and rate of chlorinated ethene degradation in a large tetrachloroethene (PCE) plume were investigated in an extensive sampling campaign. Multiple lines of evidence for this degradation were explored, including compound-specific isotope analysis (CSIA), dual C-Cl isotope analysis, and quantitative real-time polymerase chain reaction (qPCR) analysis targeting the genera Dehalococcoides and Dehalogenimonas and the genes vcrA, bvcA, and cerA. A decade prior to this sampling campaign, the plume source was thermally remediated by steam injection. This released dissolved organic carbon (DOC) that stimulated microbial activity and created reduced conditions within the plume. Based on an inclusive analysis of minor and major sampling campaigns since the initial site characterization, it was estimated that reduced conditions peaked 4 years after the remediation event. At the time of this study, 11 years after the remediation event, the redox conditions in the aquifer are returning to their original state. However, the DOC released from the remediated source zone matches levels measured 3 years prior and plume conditions are still suitable for biotic reductive dechlorination. Dehalococcoides spp., Dehalogenimonas spp., and vcrA, bvcA, and cerA reductive dehalogenase genes were detected close to the source, and suggest that complete, biotic PCE degradation occurs here. Further downgradient, qPCR analysis and enriched δ13C values for cis-dichloroethene (cDCE) suggest that cDCE is biodegraded in a sulfate-reducing zone in the plume. In the most downgradient portion of the plume, lower levels of specific degraders supported by dual C-Cl analysis indicate that the biodegradation occurs in combination with abiotic degradation. Additionally, 16S rRNA gene amplicon sequencing shows that organizational taxonomic units known to contain organohalide-respiring bacteria are relatively abundant throughout the plume. Hydraulic conductivity testing was also conducted, and local degradation rates for PCE and cDCE were determined at various locations throughout the plume. PCE degradation rates from sampling campaigns after the thermal remediation event range from 0.11 to 0.35 yr-1. PCE and cDCE degradation rates from the second to the third sampling campaigns ranged from 0.08 to 0.10 yr-1 and 0.01 to 0.07 yr-1, respectively. This is consistent with cDCE as the dominant daughter product in the majority of the plume and cDCE degradation as the time-limiting step. The extensive temporal and spatial analysis allowed for tracking the evolution of the plume and the lasting impact of the source remediation and illustrates that the multiple lines of evidence approach is essential to elucidate the primary degradation mechanisms in a plume of such size and complexity.
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Affiliation(s)
- Alexandra Marie Murray
- Department of Environmental Engineering, Technical University of Denmark, Kgs. Lyngby DK-2800, Denmark.
| | - Cecilie B Ottosen
- Department of Environmental Engineering, Technical University of Denmark, Kgs. Lyngby DK-2800, Denmark
| | - Julien Maillard
- Laboratory for Environmental Biotechnology, ENAC-IIE, Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland
| | - Christof Holliger
- Laboratory for Environmental Biotechnology, ENAC-IIE, Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland
| | - Anders Johansen
- Department of Environmental Science, Aarhus University, Frederiksborgvej 399, 4000 Roskilde, Denmark
| | - Lærke Brabæk
- Department of Environmental Engineering, Technical University of Denmark, Kgs. Lyngby DK-2800, Denmark
| | - Inge Lise Kristensen
- Department of Environmental Engineering, Technical University of Denmark, Kgs. Lyngby DK-2800, Denmark
| | - Jeremy Zimmermann
- Centre for Hydrogeology & Geothermics (CHYN), University of Neuchatel, Rue Emile Argand 11, CH 2000 Neuchatel, Switzerland
| | - Daniel Hunkeler
- Centre for Hydrogeology & Geothermics (CHYN), University of Neuchatel, Rue Emile Argand 11, CH 2000 Neuchatel, Switzerland
| | - Mette M Broholm
- Department of Environmental Engineering, Technical University of Denmark, Kgs. Lyngby DK-2800, Denmark
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Berns EC, Sanford RA, Valocchi AJ, Strathmann TJ, Schaefer CE, Werth CJ. Contributions of biotic and abiotic pathways to anaerobic trichloroethene transformation in low permeability source zones. JOURNAL OF CONTAMINANT HYDROLOGY 2019; 224:103480. [PMID: 31006532 DOI: 10.1016/j.jconhyd.2019.04.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/08/2018] [Revised: 03/12/2019] [Accepted: 04/09/2019] [Indexed: 06/09/2023]
Abstract
Low permeability source zones sustain long-term trichloroethene (TCE) groundwater contamination. In anaerobic environments, TCE is transformed by both biological reductive dechlorination and abiotic reactions with reactive minerals. Little is known about the relative contribution of these two pathways as TCE diffuses from low permeability zones (LPZs) into high permeability zones (HPZs). This study combines a flow cell experiment, batch experiments, and a diffusion-reaction model to evaluate the contributions of biotic and abiotic TCE transformation in LPZs. Natural clay (LPZ) and sand (HPZ) from a former Air Force base were used in all experiments. In batch, the LPZ material transformed TCE and cis-1,2-dichloroethene (cis-DCE) to acetylene with pseudo first-order rate constants of 8.57 × 10-6 day-1 and 1.02 × 10-6 day-1, respectively. Biotic and abiotic pathways were then evaluated together in a bench-scale flow cell (16.5 cm × 2 cm × 16.5 cm) that contained a LPZ layer, with a source of TCE at the base, overlain by a HPZ continuously purged with lactate-amended groundwater. Diffusion controlled mass transfer in the LPZ, while advection controlled migration in the HPZ. The mass discharge rate of TCE and its biotic (cis-DCE and vinyl chloride) and abiotic (acetylene) transformation products were measured over 180 days in the flow cell effluent. Depth profiles of these compounds through the LPZ were determined after terminating the experiment. A one-dimensional diffusion-reaction model was used to interpret the effluent and depth profile data and constrain reaction parameters. Abiotic transformation rate constants for TCE to acetylene, normalized to in situ solids loading, were approximately 13 times greater in batch than in the flow cell. Slower transformation rates in the flow cell indicate elevated TCE concentration and/or further degradation of acetylene to other reduced gas compounds in the flow cell LPZ (thereby partially masking TCE abiotic transformation). Biotic and abiotic parameters used to interpret the flow cell data were then used to simulate a field site with a 300 cm thick LPZ. Abiotic processes contributed to a 2% reduction in TCE flux after 730 days. When abiotic rate constants were changed to that observed in batch, or to rate constants previously reported for a pyrite rich mudstone, the TCE flux reduction was 21% and 53%, respectively, after 730 days. Though biotic processes dominated TCE transformation in the flow cell experiment, the simulations indicate that abiotic processes have potential to significantly contribute to TCE attenuation in electron donor limited environments provided suitable reactive minerals are present.
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Affiliation(s)
- Erin C Berns
- The University of Texas at Austin, Department of Civil, Architectural, and Environmental Engineering, 301 E. Dean Keeton St., Stop C1786, Austin, TX 78712, USA
| | - Robert A Sanford
- University of Illinois at Urbana-Champaign, Department of Geology, 1301 West Green St., Urbana, IL 61801, USA
| | - Albert J Valocchi
- University of Illinois at Urbana-Champaign, Department of Civil and Environmental Engineering, 205 North Mathews Ave., Urbana, IL 61801, USA
| | - Timothy J Strathmann
- Colorado School of Mines, Department of Civil and Environmental Engineering, 1500 Illinois St., Golden, CO 80401, USA
| | | | - Charles J Werth
- The University of Texas at Austin, Department of Civil, Architectural, and Environmental Engineering, 301 E. Dean Keeton St., Stop C1786, Austin, TX 78712, USA.
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Mangayayam M, Dideriksen K, Ceccato M, Tobler DJ. The Structure of Sulfidized Zero-Valent Iron by One-Pot Synthesis: Impact on Contaminant Selectivity and Long-Term Performance. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2019; 53:4389-4396. [PMID: 30859830 DOI: 10.1021/acs.est.8b06480] [Citation(s) in RCA: 62] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Sulfidized zerovalent iron (sZVI) is widely studied because of its remarkable reactivity with a number of groundwater contaminants. Nonetheless, its nanoscale structure is not well understood. As such, there is an uncertainty on how sZVI structure controls its reactivity and fate in the subsurface environment. Using pair distribution function analyses, we show that sZVI made from one-pot synthesis using dithionite as sulfur precursor consists of an Fe0 core with a shell composed dominantly of short-range ordered Fe(OH)2 and FeS having coherent scattering domains of less than 8 Å. Reactivity experiments show that increasing shell material significantly decreases rate for cis-dichloroethene (cis-DCE) reduction, whereas the opposite is observed for trichloroethene (TCE). The results are consistent with a conceptual model wherein cis-DCE reduction requires active Fe0 sites, which become largely inaccessible when shell material is abundant. Conversely, an increase in FeS shell volume led to faster TCE reduction via direct electron transfer. Aging experiments showed that sZVI retained >50% of its TCE removal efficiency after 30-day exposure to artificial groundwaters. The decline in sZVI reactivity due to long-term exposure to groundwater, is attributed to Fe0 oxidation from water reduction coupled by reorganization and recrystallization of the poorly ordered shell material, which in turn reduced access to reactive FeS sites.
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Affiliation(s)
- Marco Mangayayam
- Nano-Science Center, Department of Chemistry , University of Copenhagen , Universitetsparken 5 , 2100 Copenhagen , Denmark
| | - Knud Dideriksen
- Nano-Science Center, Department of Chemistry , University of Copenhagen , Universitetsparken 5 , 2100 Copenhagen , Denmark
- Geological Survey of Denmark & Greenland (GEUS) , Øster Voldgade 10 , 1350 Copenhagen , Denmark
| | - Marcel Ceccato
- Nano-Science Center, Department of Chemistry , University of Copenhagen , Universitetsparken 5 , 2100 Copenhagen , Denmark
- iNANO-Kemi , Aarhus University , Langelandsgade 140 , Aarhus , Denmark
| | - Dominique J Tobler
- Nano-Science Center, Department of Chemistry , University of Copenhagen , Universitetsparken 5 , 2100 Copenhagen , Denmark
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Qin H, Guan X, Bandstra JZ, Johnson RL, Tratnyek PG. Modeling the Kinetics of Hydrogen Formation by Zerovalent Iron: Effects of Sulfidation on Micro- and Nano-Scale Particles. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2018; 52:13887-13896. [PMID: 30381947 DOI: 10.1021/acs.est.8b04436] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The hydrogen evolution reaction (HER) that generates H2 from the reduction of H2O by Fe0 is among the most fundamental of the processes that control reactivity in environmental systems containing zerovalent iron (ZVI). To develop a comprehensive kinetic model for this process, a large and high-resolution data set for HER was measured using five types of ZVI pretreated by acid-washing and/or sulfidation (in pH 7 HEPES buffer). The data were fit to four alternative kinetic models using nonlinear regression analysis applied to the whole data set simultaneously, which allowed some model parameters to be treated globally across multiple experiments. The preferred model uses two independent reactive phases to match the two-stage character of most HER data, with rate constants ( k's) for each phase fitted globally by iron type and phase quantities ( S's) fitted as fully local (independent) parameters. The first, faster stage was attributed to a reactive mineral intermediate (RMI) phase like Fe(OH)2, which may form in all experiments during preequilibration, but is rapidly consumed, leaving the second, slower stage of HER, which is due to reaction of Fe0. In addition to providing a deterministic model to explain the kinetics of HER by ZVI over a wide range of conditions, the results provide an improved quantitative basis for comparing the effects of sulfidation on ZVI.
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Affiliation(s)
- Hejie Qin
- State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering , Tongji University , Shanghai 200092 , P. R. China
- Shanghai Institute of Pollution Control and Ecological Security , Shanghai 200092 , P.R. China
| | - Xiaohong Guan
- State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering , Tongji University , Shanghai 200092 , P. R. China
- Shanghai Institute of Pollution Control and Ecological Security , Shanghai 200092 , P.R. China
| | - Joel Z Bandstra
- Department of Mathematics, Engineering, and Computer Science , Saint Francis University , P.O. Box 600, Loretto , Pennsylvania 15940 , United States
| | - Richard L Johnson
- OHSU-PSU School of Public Health , Oregon Health & Science University , 3181 SW Sam Jackson Park Road , Portland , Oregon 97239 , United States
| | - Paul G Tratnyek
- OHSU-PSU School of Public Health , Oregon Health & Science University , 3181 SW Sam Jackson Park Road , Portland , Oregon 97239 , United States
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