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Open AccessFeature PaperCommunication

Understanding the Operating Mode of Fe0/Fe-Sulfide/H2O Systems for Water Treatment

1
School of Earth Science and Engineering, Hohai University, Fo Cheng Xi Road 8, Nanjing 211100, China
2
Biosystems and Environmental Engineering Research Group, Department of Soil Science and Agricultural Engineering, Faculty of Agriculture, University of Zimbabwe, P.O. Box MP167, Mount Pleasant, Harare, Zimbabwe
3
Department of Applied Geology, University of Göttingen, Goldschmidtstraße 3, D-37077 Göttingen, Germany
4
Department of Water and Environmental Science and Engineering, Nelson Mandela African Institution of Science and Technology, P.O. Box 447, Arusha, Tanzania
*
Authors to whom correspondence should be addressed.
Processes 2020, 8(4), 409; https://doi.org/10.3390/pr8040409
Received: 9 March 2020 / Revised: 24 March 2020 / Accepted: 25 March 2020 / Published: 31 March 2020
The general suitability of water treatment systems involving metallic iron (Fe0) is well-established. Various attempts have been made to improve the efficiency of conventional Fe0 systems. One promising approach combines granular Fe0 and an iron sulfide mineral to form Fe0/Fe-sulfide/H2O systems. An improved understanding of the fundamental principles by which such systems operate is still needed. Through a systematic analysis of possible reactions and the probability of their occurrence, this study establishes that sulfide minerals primarily sustain iron corrosion by lowering the pH of the system. Thus, chemical reduction mediated by FeII species (indirect reduction) is a plausible explanation for the documented reductive transformations. Such a mechanism is consistent with the nature and distribution of reported reaction products. While considering the mass balance of iron, it appears that lowering the pH value increases Fe0 dissolution, and thus subsequent precipitation of hydroxides. This precipitation reaction is coupled with the occlusion of contaminants (co-precipitation or irreversible adsorption). The extent to which individual sulfides impact the efficiency of the tested systems depends on their intrinsic reactivities and the operational conditions (e.g., sulfide dosage, particle size, experimental duration). Future research directions, including the extension of Fe0/Fe-sulfide/H2O systems to drinking water filters and (domestic) wastewater treatment using the multi-soil-layering method are highlighted. View Full-Text
Keywords: contaminant removal; iron corrosion; pyrite oxidation; synergetic effects; zero-valent iron contaminant removal; iron corrosion; pyrite oxidation; synergetic effects; zero-valent iron
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MDPI and ACS Style

Xiao, M.; Hu, R.; Cui, X.; Gwenzi, W.; Noubactep, C. Understanding the Operating Mode of Fe0/Fe-Sulfide/H2O Systems for Water Treatment. Processes 2020, 8, 409. https://doi.org/10.3390/pr8040409

AMA Style

Xiao M, Hu R, Cui X, Gwenzi W, Noubactep C. Understanding the Operating Mode of Fe0/Fe-Sulfide/H2O Systems for Water Treatment. Processes. 2020; 8(4):409. https://doi.org/10.3390/pr8040409

Chicago/Turabian Style

Xiao, Minhui; Hu, Rui; Cui, Xuesong; Gwenzi, Willis; Noubactep, Chicgoua. 2020. "Understanding the Operating Mode of Fe0/Fe-Sulfide/H2O Systems for Water Treatment" Processes 8, no. 4: 409. https://doi.org/10.3390/pr8040409

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