Nanoparticulate Nickel-Hosting Phases in Sulfidic Environments: Effects of Ferrous Iron and Bacterial Presence on Mineral Formation Mechanism and Solid-Phase Nickel Distribution

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dc.contributor.authorManson, Muammaren
dc.contributor.authorWinkler, Christopheren
dc.contributor.authorHochella, Michael F. Jr.en
dc.contributor.authorXu, Jieen
dc.date.accessioned2019-10-25T12:59:34Zen
dc.date.available2019-10-25T12:59:34Zen
dc.date.issued2019-06-26en
dc.description.abstractThe precipitation of nickel with sulfide is an important process governing the bioavailability of Ni in natural waters, and this process has the potential to effectively remove aqueous Ni contaminants in near-surface environments. In this study, we use experimental approaches to investigate the diversity of Ni-hosting phases precipitated in sulfidic environments across a range of aqueous Ni-to-Fe ratios ([Ni](aq)/[Fe](aq)) and in the presence or absence of the sulfate-reducing bacteria (SRB), Desulfovibrio vulgaris. In the absence of Fe(II), the initial precipitates in abiotic experiments are found to consist primarily of polyphasic Ni-sulfides (average sizes <20 nm) with millerite (trigonal NiS) cores and amorphous shells. The precipitates' crystallinity is enhanced noticeably over a period of similar to 6 days, forming larger-sized hexagonal alpha-NiS, and observations of defects such as twinning and stacking faults implicate a formation pathway via reassembly of fine nanoparticulate precursors. By comparison, in the presence of SRB and in the absence of Fe, more crystalline phases such as polydymite (Ni3S4 ) and vaesite (NiS2) are also precipitated in addition to the monosulfide phases. The observed difference suggests that the presence of SRB enables the transformation of polyphasic precursors to more crystalline structures through the combined effects of bacterial metabolites and localized precipitation within a low pH micro-environment around the cell walls. The addition of Fe(II) (i.e., [Ni](aq)/[Fe](aq) = 5:1) leads to formation of less crystalline Ni-sulfides in both biotic and abiotic systems, indicating crystal structure distortion caused by substitution of Ni with Fe. With decreasing [Ni](aq)/[Fe](aq), Ni-sulfides become rarer, mixed Ni-Fe phases start to appear, and finally Ni-rich mackinawite (FeS) becomes the primary Ni-hosting phase at the lowest ratio tested ([Ni](aq)/[Fe](aq) = 1:5). We propose that whether aqueous Ni forms discrete Ni-S phases or is incorporated into dominantly Fe-S phases is primarily determined by the precipitation kinetics, and our experiments at [Ni](aq)/[Fe](aq) = 1:1 suggest that Ni-sulfide precipitation kinetics is comparable or higher than Fe-sulfides at this condition. Overall, our study allows for prediction on the phases and biogeochemical factors controlling Ni removal and availability in sulfidic environments.en
dc.description.notesThis study was funded by the grant DOE-BES DE-FG02-06ER15786 bestowed by the United States Department of Energy to MH, Mitsu Murayama, and JX, and also by the start-up package provided to JX by The University of Texas at El Paso.en
dc.description.sponsorshipUnited States Department of EnergyUnited States Department of Energy (DOE) [DOE-BES DE-FG02-06ER15786]; University of Texas at El Pasoen
dc.format.mimetypeapplication/pdfen
dc.identifier.doihttps://doi.org/10.3389/feart.2019.00151en
dc.identifier.issn2296-6463en
dc.identifier.otherUNSP 151en
dc.identifier.urihttp://hdl.handle.net/10919/95053en
dc.identifier.volume7en
dc.language.isoenen
dc.publisherFrontiersen
dc.rightsCreative Commons Attribution 4.0 Internationalen
dc.rights.urihttp://creativecommons.org/licenses/by/4.0/en
dc.subjectnickel sulfidesen
dc.subjectmilleriteen
dc.subjectpolydymiteen
dc.subjectvaesiteen
dc.subjectsulfate-reducing bacteriaen
dc.subjectpolyphasicen
dc.subjectsulfidic environmentsen
dc.subjectmackinawiteen
dc.titleNanoparticulate Nickel-Hosting Phases in Sulfidic Environments: Effects of Ferrous Iron and Bacterial Presence on Mineral Formation Mechanism and Solid-Phase Nickel Distributionen
dc.title.serialFrontiers in Earth Scienceen
dc.typeArticle - Refereeden
dc.type.dcmitypeTexten
dc.type.dcmitypeStillImageen

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