Organic Sulfur Products and Peroxy Radical Isomerization in the OH Oxidation of Dimethyl Sulfide
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37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
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Suppressing Atmospheric Degradation of Sulfide-Based Solid Electrolytes via Ultrathin Metal Oxide Layers
Sulfide-based solid-state electrolytes (SSEs) are promising materials with superior Li-ion conductivity; however, their poor atmospheric stability limits commercial manufacturing at scale. Here, we investigate the impact of ultrathin metal oxide layers deposited via atomic layer deposition (ALD) on the stability of Li 6 PS 5 Cl (LPSCl). Al 2 O 3 layers grown directly on LPSCl particles significantly stabilize the surface chemistry and Li-ion transport properties relative to uncoated material upon exposure to both an ambient atmosphere (22% relative humidity, RH) and humidified O 2 (100% RH). Detailed investigations indicate that coatings impede the surface and bulk degradation kinetics of exposed materials, even for coatings as thin as ∼1 Å. Furthermore, this suggests that stabilization is due to more than just a physical barrier. Shifts in valence band edge positions of coated LPSCl indicate that ALD coatings alter the surface electronic structure and resulting oxidation tendency of underlying LPSCl, suggesting new avenues to improving the environmental stability of sulfide SSEs.
Atmospheric chemistry↗
Probing the Cl-initiated oxidation of dimethyl sulfide using synchrotron VUV photoionization mass spectrometry
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Sheps, Leonid [Sandia National Laboratories (SNL-C↗
Organic Sulfur Products and Peroxy Radical Isomerization in the OH Oxidation of Dimethyl Sulfide
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54 ENVIRONMENTAL SCIENCES↗
Percolative Sulfide Core Formation in Oxidized Meteorite Parent Bodies
Most models of planetary differentiation involve the formation of metallic cores during or after extensive silicate melting, but some volatile-rich reservoirs in the protoplanetary disk did not accrete substantial amounts of Fe,Ni-metal. Instead, their potential core-forming assemblages were dominated by Fe,Ni-sulfides and oxides due to high ƒ O 2 and ƒ S 2 . Derivative melts from these assemblages may have been capable of percolative migration leading to core formation prior to silicate melting. However, no direct evidence for this process has been reported in meteoritic literature. Similarly, while many iron meteorites are thought to represent cores of their respective parent bodies, no direct evidence for Fe,Ni-sulfide/oxide cores have been reported to-date. The most promising potential for such evidence may be found in the anomalous noble metal trace element proportions of restitic oxidized primitive achondrites (i.e., brachinites, log ƒ O 2 ~IW-1), which are similar to those found in sulfides of Rumuruti-type chondrites (RCs) that contain only trace amounts of Fe,Ni-metal at log ƒ O 2 ≥ IW-1. This work addresses the following outstanding questions: (1) Are molten sulfides in oxidized meteorite assemblages capable of percolative melt migration? (2) How is this process recorded in the noble metal (i.e., siderophile/chalcophile) trace element geochemistry of relevant meteorites? (3) Did O,S-rich meteorite parent bodies form sulfide cores?
S. D. Crossley↗
Formation of Fe(III) (hydr)oxides from Fe(II) sulfides: Implications for akaganeite detection on Mars
Akaganeite (β-FeO(OH,Cl)) is a Fe(III) (hydr)oxide with a tunnel structure typically occupied by chloride. This mineral was first proposed to be present in Meridiani Planum and Gusev crater on Mars and akaganeite was subsequently detected by X-ray diffraction in Yellowknife Bay and Vera Rubin Ridge locations in Gale crater. Akaganeite in Gale crater has been proposed to form from Fe(II) sulfides but formation conditions remain unconstrained. We investigated akageneite formation by oxidative alteration of natural Fe(II) sulfide pyrrhotite exposed to HCl and oxidation-hydrolysis of Fe(II) HCl-leached from pyrrhotite at initial pH0 1.5, 2, 3, and 4. X-ray diffraction and Mössbauer analyses revealed formation of poorly-crystallized akageneite in oxidative alteration experiments. Air-exposure of the HCl-reacted dry pyrrhotite led to an increase in akageneite formation and precipitation of Fe(II) hydrated sulfates, goethite, and hydronium jarosite. Iron(II) oxidation-hydrolysis was sensitive to Si dissolved from phyllosilicates in one pyrrhotite sample. Akaganeite and goethite formed at pH0 1.5 and 2 with akageneite more abundant at dissolved Si/Fe ratio of 0.08 and goethite more abundant at Si/Fe of 0.01. Akaganeite formed together with hematite, ferrihydrite, and goethite at pH0 3, and formation was suppressed at pH0 4. Well-crystallized akageneite precipitated at pH0 1.5 while akaganeite of poorer crystallinity formed at pH0 2 and 3. Akageneite in Gale crater could form from sulfides by both mechanisms: oxidative alteration of sulfide minerals and oxidation-hydrolysis of leached Fe(II). The processes likely occurred during late diagenetic events triggered by interactions of acidic Cl-bearing groundwater with Fe(II) sulfides. Akaganeite in Yellowknife Bay, Gale crater could have formed by Fe(II) oxidation-hydrolysis either as a sole Fe(III) (hydr)oxide at pH<2 or along with ferrihydrite and hematite at 2<pH<4 in Si-enriched conditions. Akaganeite formation at Vera Rubin Ridge, Gale crater could have occurred through oxidative alteration of sulfides in Cl-bearing pH 1.2-1.5 solutions. The presence of well-crystalline akageneite in Vera Rubin Ridge indicates that Fe(II) oxidation-hydrolysis contributed to akageneite formation.
Mars gale crater akaganeite↗
Formation of Fe(III) (hydr)oxides from Fe(II) Sulfides: Implications for Akaganeite Detection on Mars
Akaganeite (Cl-bearing Fe(III) (hydr)oxide) was identified by the Chemistry and Mineralogy X-ray diffraction (XRD) instrument onboard the Mars Science Laboratory (MSL) Curiosity Rover in mudstones drilled at Yellowknife Bay and Vera Ru-bin Ridge in Gale crater [1,2]. The mineral likely formed in chloride-bearing solutions of variable pH[3]but progenitor Fe-bearing phases for martian akaganeite are not well constrained. Akaganeite in Gale crater has been proposed to form through oxidation of Fe(II) sulfide minerals [2,3]. The objectives of this study was to constrain akaganeite formation conditions from Fe(II) sulfide pyrrhotite.
Mars↗
Overexpression of sulfide:quinone reductase (SQR) in Acidithiobacillus ferrooxidans enhances sulfur, pyrite, and pyrrhotite oxidation
ABSTRACT Hydrogen sulfide is produced during the dissolution of some sulfidic minerals and during the microbial metabolism of reduced sulfur compounds. The sulfide:quinone reductase (SQR) enzyme is able to oxidize H 2 S, and the bioleaching cells Acidithiobacillus ferrooxidans have two SQR genes, only one of which has been characterized. We cloned and overexpressed the two SQR genes in A. ferrooxidans and show that they both have SQR activity. Both AFE_0267 and AFE_1792 are active under anaerobic conditions, but only AFE_1792 is active under aerobic conditions. The effect of the SQR overexpression and the expression of related genes on sulfur metabolism was investigated. The overexpression of SQR improved cell growth and sulfur oxidation, suggesting enhanced SQR activity led to a reduction in H 2 S toxicity as well as providing additional energy through H 2 S oxidation. Additionally, the impact on the oxidation of pyrite and pyrrhotite was investigated. The rate of oxidation of pyrite by the engineered cells was enhanced, and, furthermore, the rate of pyrrhotite oxidation was more than doubled. IMPORTANCE H 2 S is a toxic sulfur intermediate, and the SQR enzyme has evolved to oxidize H 2 S in A. ferrooxidans . In addition to detoxification, H 2 S oxidation provides energy, and overexpression of SQR enhanced aerobic and anaerobic growth on sulfur. The SQR overexpression also enhanced pyrite and pyrrhotite oxidation, which may facilitate the pyrometallurgical processing of a number of critical materials including copper, nickel, and the platinum group metals.
Jung, Heejung↗
Coordinated Mineralogical and Isotopic Analysis of a Cosmic Symplectite Identified in a Stardust Terminal Particle
Comet Wild-2 samples returned by the Stardust spacecraft contain a chemically diverse mixture of material, underscoring the complex nature of comets. Studies of entire Stardust aerogel tracks afford the opportunity to examine the fine-grained particle fragments distributed along the length of the track as well as the terminal particles. Previous TEM characterization of a terminal particle (TP) in track #147 revealed a symplectically intergrown iron sulfide and oxide assemblage. Mineralogically similar assemblages, known as cosmic symplectites (COS, formerly termed "new-PCP"), have only been identified in the primitive carbonaceous chondrite Acfer 094. Meteoritic COS have isotopically heavy O compositions (delta (sup 17), O-18 = 180per mille) that point to interactions with early solar system primordial water. In this study we report mineralogical and O isotopic measurements of the Wild-2 COS assemblage. Experimental: Track #147 is a "bulbous"-type track (4600 microns long) containing 7 terminal particles. The TPs were removed from the track, embedded in epoxy, and ultramicrotomed. A JEOL 2500SE 200 keV field-emission scanning-transmission electron microscope was used to obtain quantitative elemental maps and detailed mineralogical characterization. Following TEM analysis, two thin sections of TP4 (12 microns) were analyzed for O isotopes by raster ion imaging with the JSC NanoSIMS 50L. All three O isotopes were measured simultaneously using electron multipliers. San Carlos olivine grains were used as isotopic standards. Results and Discussion: The COS in the Wild-2 track #147 TP4 sample consists of symplectically intergrown pentlandite and nanocrystalline maghemite which coexists with high-Ca pyroxene with Na and Cr (kosmochlor component). This kosmochlor component could have a nebular origin and be precursors to type II chondrules in ordinary chondrites. Yet pentlandite is not a stable phase in the nebula. The COS in Acfer 094 also consists of pentlandite, but contains magnetite [4] rather than the more oxidized maghemite observed in the Wild-2 COS. The Acfer 094 COS display heavy O isotopic compositions that are the result of sulfidization and oxidation of Fe, Ni-metal grains and sulfides by O-17- and O-18-rich water in the solar nebula or possibly on the parent body. The O isotopic composition of the Wild-2 COS, however, is indistinguishable from terrestrial, indicating it was not altered by the same primordial aqueous reservoir as the Acfer 094 COS. The alteration could have occurred on the parent body by isotopically equilibrated ice. The mineralogy and petrography of Wild-2 samples suggests an incomplete or nascent hydration process. In future work we will analyze S isotopes in the track #147 TP4 COS and search for additional COS in Stardust samples.
Nguyen, A. N.↗
Theoretical studies of the low-lying states of ScO, ScS, VO, and VS
Bonding in the low-lying states of ScO, ScS, VO, and VS is theoretically studied. Excellent agreement is obtained with experimental spectroscopic constants for the low-lying states of ScO and VO. The results for VS and ScS show that the bonding in the oxides and sulfides is similar, but that the smaller electronegativity in S leads to a smaller ionic component in the bonding. The computed D0 of the sulfides are about 86 percent of the corresponding oxides, and the low-lying excited states are lower in the sulfides than in the corresponding oxides. The CPF method is shown to be an accurate and cost-effective method for obtaining reliable spectroscopic constants for these systems.
Bauschlicher, Charles W., Jr.↗
Sonochemical oxidation and stabilization of liquid elemental mercury in water and soil
Over 3000 mercury (Hg)-contaminated sites worldwide contain liquid metallic Hg [Hg(0) 1 ] representing a continuous source of elemental Hg(0) in the environment through volatilization and solubilization in water. Currently, there are few effective treatment technologies available to remove or sequester Hg(0) 1 in situ. We investigated sonochemical treatments coupled with complexing agents, polysulfide and sulfide, in oxidizing Hg(0) 1 and stabilizing Hg in water, soil and quartz sand. Results indicate that sonication is highly effective in breaking up and oxidizing liquid Hg(0) 1 beads via acoustic cavitation, particularly in the presence of polysulfide. Without complexing agents, sonication caused only minor oxidation of Hg(0) 1 but increased headspace gaseous Hg(0) g and dissolved Hg(0) aq in water. However, the presence of polysulfide essentially stopped Hg(0) volatilization and solubilization. As a charged polymer, polysulfide was more effective than sulfide in oxidizing Hg(0) 1 and subsequently stabilizing the precipitated metacinnabar (β-HgS) nanocrystals. Sonochemical treatments with sulfide yielded incomplete oxidation of Hg(0) 1 , likely resulting from the formation of HgS coatings on the dispersed µm-size Hg(0) 1 bead surfaces. Sonication with polysulfide also resulted in rapid oxidation of Hg(0) 1 and precipitation of HgS in quartz sand and in the Hg(0) 1 -contaminated soil. This research indicates that sonochemical treatment with polysulfide could be an effective means in rapidly converting Hg(0) 1 to insoluble HgS precipitates in water and sediments, thereby preventing its further emission and release to the environment. We suggest that future studies are performed to confirm its technical feasibility and treatment efficacy for remediation applications.
36 MATERIALS SCIENCE↗
Iron and sulfur in the pre-biologic ocean
Tentative geochemical cycles for the pre-biologic Earth are developed by comparing the relative fluxes of oxygen, dissolved iron, and sulfide to the atmosphere and ocean. The flux of iron is found to exceed both the oxygen and the sulfide fluxes. Because of the insolubility of iron oxides and sulfides the implication is that dissolved iron was fairly abundant and that oxygen and sulfide were rare in the atmosphere and ocean. Sulfate, produced by the oxidation of volcanogenic sulfur gases, was the most abundant sulfur species in the ocean, but its concentration was low by modern standards because of the absence of the river-borne flux of dissolved sulfate produced by oxidative weathering of the continents. These findings are consistent with the geologic record of the isotopic composition of sedimentary sulfates and sulfides. Except in restricted environments, the sulfur metabolism of the earliest organisms probably involved oxidized sulfur species not sulfide.
Review↗
Microbiological and geochemical characterization of As-bearing tailings and underlying sediments
Over the past 100 years, extensive oxidation of As-bearing sulfide-rich tailings from the abandoned Long Lake Gold Mine (Canada) has resulted in the formation of acid mine drainage (pH 2.0-3.9) containing high concentrations of dissolved As (similar to 400 mg L -1 ), SO 4 2- , Fe and other metals. Dissolved As is predominantly present as As(III), with increased As(V) near the tailings surface. Pore-gas O 2 is depleted to < 1 vol% in the upper 30-80 cm of the tailings profile. The primary sulfides, pyrite and arsenopyrite, are highly oxidized in the upper portions of the tailings. Elevated proportions of sulfide-oxidizing prokaryotes are present in this zone (mean 32.3% of total reads). The tailings are underlain by sediments rich in organic C. Enrichment in δ 34 S-SO 4 in pore-water samples in the organic C-rich zone is consistent with dissimilatory sulfate reduction. Synchrotron-based spectroscopy indicates an abundance of ferric arsenate phases near the impoundment surface and the presence of secondary arsenic sulfides in the organic-C beneath the tailings. The persistence of elevated As concentrations beneath the tailings indicates precipitation of secondary As sulfides is not sufficient to completely remove dissolved As. The oxidation of sulfides and release of As is expected to continue for decades. The findings will inform future remediation efforts and provide a foundation for the long-term monitoring of the effectiveness of the remediation program.
54 ENVIRONMENTAL SCIENCES↗
Dynamic Responses of Trace Metal Bioaccessibility to Fluctuating Redox Conditions in Wetland Soils and Stream Sediments
Natural aquatic systems undergo fluctuating redox conditions due to microbial activity, varying water saturation levels, and nutrients dynamics. With fluctuating redox conditions, trace metals can mobilize or sequester in response to changes in iron and sulfur speciation and the concentrations and lability of organic carbon. This study examined the effect of redox fluctuations on trace metal mobility in samples collected from two different natural aquatic systems: riparian wetlands and a stream. The wetland soils contained low sulfur and total Fe contents as compared to stream sediments. The mineral composition at both sites was dominated by quartz. We incubated water-saturated soils under three cycles of anoxic-oxic conditions (τanoxic:τoxic = 3) spanning 24 days and monitored the change in dissolved and bioavailable metal concentrations. For both natural systems, reduction of iron oxides under anoxic conditions caused Co and Zn release. In contrast, oxidation of sulfides mobilized Cu under oxic conditions in both sites. In wetland soils, dissolution of Fe (hydr)oxides increased Ni solubility; however, in stream sediments, Ni release occurred when sulfides or organic matter were oxidized. For stream sediments, each subsequent redox cycle increased the bioavailability of trace metals. Redox fluctuations in wetland soils increased bioavailable Zn and Cu and decreased bioavailable Ni and Co. This study illustrates that different trace metals display distinct bioavailability patterns during redox fluctuations in natural environments. The biogeochemical cycling of nutrients in systems with redox fluctuations may be influenced by these trace metal availability patterns in addition to the availability of electron donors and acceptors.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Insights into Spontaneous Solid Electrolyte Interphase Formation at Magnesium Metal Anode Surface from Ab Initio Molecular Dynamics Simulations
Spontaneous chemical reactivity at multivalent (Mg, Ca, Zn, Al) electrode surfaces is critical to solid electrolyte interphase (SEI) formation, and hence, directly affects the longevity of batteries. Here, we report an investigation of the reactivity of 0.5 M Mg(TFSI)2 in 1,2-dimethoxyethane (DME) solvent at a Mg(0001) surface using ab initio molecular dynamics (AIMD) simulations and detailed Bader charge analysis. Based on the simulations, the initial degradation reactions of the electrolyte strongly depend on the structure of the Mg(TFSI)2 species near the anode surface. At the surface, the dissociation of Mg(TFSI)2 species occurs via cleavage of the N-S bond for the solvent separated ion pair (SSIP) and via cleavage of the C-S bond for the contact ion pair (CIP) configuration. In the case of the CIP, both TFSI anions undergo spontaneous bond dissociation reactions to form atomic O, C, S, F, and N species adsorbed on the surface of the Mg anode. These products indicate that the initial SEI layer formed on the surface of the pristine Mg anode consists of a complex mixture of multiple components such as oxides, carbides, sulfides, fluorides, and nitrides. We believe that the atomic level insights gained from these simulations will lay the groundwork for the rational design of tailored and functional interphases that are critical for the success of multivalent battery technology.
Agarwal, Garvit↗
Lanthanum induced lattice strain improves hydrogen sulfide capacities of copper oxide adsorbents
This work probes the effects of La on reactions involving CuO sorbents and H 2 S in gaseous streams. La-CuO sorbents with nominal La/Cu atomic ratios of 1:2 achieved higher capacities (27 and 36 g H 2 S per 100 g sorbent) compared to CuO sorbents (25 g H 2 S per 100 g sorbent). Here, comparison of the La-CuO sorbents using energy dispersive x-ray spectroscopy and La L 3 -edge XAS suggested that increased capacity resulted from more uniform dispersion of La within the CuO phase (3.3 wt.% vs. 1.0 wt.% La). X-Ray absorption near edge structure analysis suggested more electron-rich Cu species in La-CuO samples, while extended X-ray absorption fine structure modeling showed an increase in single-scattering path lengths for neighboring and near-neighbor atoms. These changes suggest that La induces strain in the Cu-O lattice, thereby increasing H 2 S capacity by reducing energy barriers associated with surface reactions between oxygen atoms and adsorbed H 2 S molecules.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Atomic insights into the oxidative degradation mechanisms of sulfide solid electrolytes
Not Available
25 ENERGY STORAGE↗
Interstellar and Solar System Organic Matter Preserved in Interplanetary Dust
Interplanetary dust particles (IDPs) collected in the Earth's stratosphere derive from collisions among asteroids and by the disruption and outgassing of short‐period comets. Chondritic porous (CP) IDPs are among the most primitive Solar System materials. CP‐IDPs have been linked to cometary parent bodies by their mineralogy, textures, C‐content, and dynamical histories. CP‐IDPs are fragile, fine‐grained (less than um) assemblages of anhydrous amorphous and crystalline silicates, oxides and sulfides bound together by abundant carbonaceous material. Ancient silicate, oxide, and SiC stardust grains exhibiting highly anomalous isotopic compositions are abundant in CP‐IDPs, constituting 0.01 - 1 % of the mass of the particles. The organic matter in CP‐IDPs is isotopically anomalous, with enrichments in D/H reaching 50x the terrestrial SMOW value and 15N/14N ratios up to 3x terrestrial standard compositions. These anomalies are indicative of low T (10‐100 K) mass fractionation in cold molecular cloud or the outermost reaches of the protosolar disk. The organic matter shows distinct morphologies, including sub‐um globules, bubbly textures, featureless, and with mineral inclusions. Infrared spectroscopy and mass spectrometry studies of organic matter in IDPs reveals diverse species including aliphatic and aromatic compounds. The organic matter with the highest isotopic anomalies appears to be richer in aliphatic compounds. These materials also bear similarities and differences with primitive, isotopically anomalous organic matter in carbonaceous chondrite meteorites. The diversity of the organic chemistry, morphology, and isotopic properties in IDPs and meteorites reflects variable preservation of interstellar/primordial components and Solar System processing. One unifying feature is the presence of sub‐um isotopically anomalous organic globules among all primitive materials, including IDPs, meteorites, and comet Wild‐2 samples returned by the Stardust mission.
Messenger, Scott↗