Sulfide Phases Research Articles

Metal preconcentration for gold mineralization in arcs: Geophysical observations from Western Junggar, NW China

Previous studies showed that metal preconcentration in fluids and/or magma is critical to the formation of gold deposit in arcs and is closely related to the segregation of sulfide phases. However, the depth range and the magnitude of and associated mechanism by which the deep crust controls the metal preconcentration of arc mineralization remain enigmatic. Here we present geophysical observations of the medium-scale Baogutu porphyry copper–gold deposit and the large-scale Hatu epithermal gold deposit from the late Paleozoic arc in the western Junggar, NW China. During the closure of Paleo-Asian Ocean, Baogutu deposit formed at ∼313 Ma relating to the adakitic intrusions driven by the ridge-related subduction, and Hatu deposit formed at ∼300 Ma just before the subduction termination. The transcrustal structures of resistivity and shear-wave velocity would show the signatures of metal preconcentration by reasoning the cause of low-resistivity anomaly to the persisting sulfide phases and the change of shear-wave velocity to the garnet proportion, respectively. Our results showed that the sulfide phases persisted in the entire deep crust and thus the metal preconcentration could occur in the base cumulates and mush reservoir beneath Hatu deposit, but the signatures were not fully reflected beneath the Baogutu deposit. These observations suggest that the reduced permeability of brittle-ductile transition and the water flux associated with magma likely affect the rising rate of melt, resulting in different efficiency of the metal preconcentration. Thus, the endowments of mineralization in arcs are controlled by crustal structures and contemporaneous arc magmatism during subduction.

VIS-IR Spectroscopy of Mixtures of Water Ice, Organic Matter, and Opaque Mineral in Support of Small Body Remote Sensing Observations

Visual-to-infrared (VIS-IR) remote sensing observations of different classes of outer solar system objects indicate the presence of water ice and organics. Here, we present laboratory reflectance spectra in the 0.5–4.2 μm spectral range of binary particulate mixtures of water ice, organics analogue (kerite), and an opaque iron sulphide phase (pyrrhotite) to investigate the spectral effects of varying mixing ratios, endmember grain size, and mixing modality. The laboratory spectra are also compared to different implementations of the Hapke reflectance model (Hapke, 2012). We find that minor amounts (≲1 wt%) of kerite (investigated grain sizes of 45–63 μm and <25 μm) can remain undetected when mixed in coarse-grained (67 ± 31 μm) water ice, suggesting that organics similar to meteoritic insoluble organic matter (IOM) might be characterized by larger detectability thresholds. Additionally, our measurements indicate that the VIS absolute reflectance of water ice-containing mixtures is not necessarily monotonically linked to water ice abundance. The latter is better constrained by spectral indicators such as the band depths of water ice VIS-IR diagnostic absorptions and spectral slopes. Simulation of laboratory spectra of intimate mixtures with a semi-empirical formulation of the Hapke model suggests that simplistic assumptions on the endmember grain size distribution and shape may lead to estimated mixing ratios considerably offset from the nominal values. Finally, laboratory spectra of water ice grains with fine-grained pyrrhotite inclusions (intraparticle mixture) have been positively compared with a modified version of the Hapke model from Lucey and Riner (2011).

Mineralogical Criteria for Genetic Relationship of Igneous and Carbonatite Rocks of the Tomtor Massif (Siberian Platform)

The Tomtor massif, located in the north-east of the Siberian Platform, is a polychronous zonal-ring complex of alkaline ultrabasic rocks and carbonatites containing a unique deposit of Nb and REE. A comparative analysis of the typomorphic features of minerals of different types of silicate rocks and carbonatites of the Tomtor massif is given in order to establish their convergent features. In order to exclude the mutual influence of rocks formed at different times on each other, samples were taken from different dispersed independent pipe-like bodies of melteigites, a sheet body of alkaline picrites and a transverse dike of carbonatite located south of the Tomtor massif, as well as from alkaline syenites from the southern margin of the massif. It is shown that interesting convergent features are identified in the rock-forming and accessory minerals, including rare-metal ore minerals of different silicate igneous rocks and carbonatite formations. Rock-forming minerals - pyroxenes, micas, feldspars, feldspathopids, garnets, as well as basic and rare carbonates, oxide ore minerals, including Cr-containing spinelides, and sulfide and other exotic phases have such features. The confirmation of the convergence of a group of obvious high-temperature early magmatic elements-MgO, Cr, and Ni - with a group of CaO, CO2, H2O, P2O5, and Y components forming carbonatite derivatives was the most interesting nuance in this regard. Existence of such polychromous complicated ore-magmatic ring complexes as Tomtor massif indicates occurrence of intraplate deep large magma-generating hearths in lithosphere mantle. Such easily fusible hearths, conserved in lithosphere mantle of residual melts of kimberlite, alkali-picrites, carbonatite compositions, under the subsequent favorable geodynamic settings, are subject to rapid flotation, undergoing decompression melting and forming concentric-zonal platform complexes of alkali ultrabasic rocks with carbonatites

Epigenetic Copper Mineralization in Raipur-Mokhampura Area, Mangalwar Complex, Bhilwara District, Rajasthan

Abstract Rocks of the Mangalwar and Sandmata Complex of the Bhilwara Supergroup of Archaean age host copper mineralization in the form of chalcopyrite-bornite in Raipur-Mokhampura and Rajaji ka Karera areas of Bhilwara district, Rajasthan. The area forms a part of the dismembered granite-greenstone sequence of the Bhilwara Supergroup. Chalcopyrite and bornite form the dominant copper sulphides along with pyrite, digenite, chalcocite and some accessory Bi-telluride and Bi-Cu sulphide phases. These sulphides occur along the S2 foliation planes, veins and fractures within the amphibolites and calc-gneiss. Presence of Bi indicates hydrothermal epigenetic nature of the mineralization developed under highly acidic reducing condition and high sulphur fugacity.

Geochemical Studies of some Heavy Metals’ Toxicity in Groundwater with their Plausible Sources around Gondwana Supergroup, Wardha Valley Coalfields, Maharashtra

Abstract The study is designed for groundwater assessment in terms of some sorted heavy metals’ toxicity and their probable source in Wardha valley coalfields, Maharashtra. For both seasons, 45 groundwater samples were collected separately to assess Al, Cd, Cr, Cu, Fe, Ni, Pb and Zn by AAS. Among them, 22 were found contaminated as per BIS (2012) concerning Cd, Fe, Ni and Pb. The major contributors in both seasons were Fe, Zn, Cu and Al. The PCA study has shown sound relationships among Fe-Ni, Cd-Ni, and Al-Cu-Zn. The contamination intensities in various samples indicates that the mining region as a prime cause. The Kamthi and Barakar formations in the study area were considered as a contamination source. The significant role of lower pH environment in enhanced contamination was revealed in the correlation analysis. Accordingly, the probability of acid mine drainage was supposed. The EPMA and SEM-EDS/X studies reveal the presence of sulphide phases in Barakar Formation and sulphur in associated carboniferous strata confirming the source of lower pH. Accordingly, the acid mine drainage was anticipated to be responsible for heavy metals’ dissolution and migration to groundwater in mining areas.

Interfacial engineering effect and bipolar conduction of Ni- doped MoS2 nanostructures for thermoelectric application

Transition Metal Chalcogenides play an important role in the thermoelectric (TE) application due to their unique properties such as stability, easily tunable carrier transport and charge carrier mobility which enhance the power factor. Molybdenum disulphide (MoS2) is a hopeful TE material with a layered structure, but it possesses low electrical conductivity. Herein, our present work focuses to improve the electrical conductivity of MoS2 by Ni-doping and the effect of Ni-concentration was studied extensively. Undoped and Ni-doped MoS2 samples were successfully prepared by hydrothermal route. The hexagonal structured 2H-MoS2 and the formation of nickel sulphide (NiS) secondary phase at 10 at% of Ni-concentration was confirmed by XRD analysis. HRTEM confirmed the influence of Ni content in MoS2 layers which create the bonding between the layers and reduces the interlayer distance of MoS2. The reduced thermal conductivity was observed around 0.48 Wm−1K−1 for 7.5 at% of Ni-doped MoS2 which is two times lower than that of undoped MoS2. Meanwhile, the enhancement of electrical conductivity of Ni-doped samples from 0.012 S/cm to 0.049 S/cm observed for 7.5 at% of Ni-doped MoS2 sample. Because of NiS, the conduction behavior was changed from p-type to n-type Seebeck coefficient. The maximum zT was obtained as 0.28 × 10−3 for undoped sample. However, Ni-doping was experimentally proved to the simultaneous optimization of enhanced electrical conductivity and the suppressed thermal conductivity, the change in carrier type due to nickel sulphide (NiS) phase reduced the figure of merit.

Ancient Melt-Depletion in Fresh to Strongly Serpentinized Tonga Trench Peridotites

ABSTRACT Peridotites from the Tonga Trench are some of the deepest-derived and freshest ever obtained from the seafloor. This study reports new bulk-rock major-, trace-, highly siderophile-element (HSE) abundance and 187Os/188Os data, as well as major- and trace-element abundances of mineral phases for NOVA88D dredge peridotites. The samples are harzburgites that experienced varying degrees of serpentinization, recorded in their loss on ignition (LOI) values, from zero to 16.7%. Degree of serpentinization in samples is correlated with Na, B, K, Sr, Ca, Rb and U, and weakly correlated with W, Fe, Pb, Cs and Li abundances, but is uncorrelated with other lithophile elements, most especially the rare earth elements (REE). Serpentinization had no systematic effect on the HSE abundances or 187Os/188Os compositions in the harzburgites. NOVA88D harzburgites record >18% melt depletion which has resulted in heterogenous distribution of the HSE within the rocks, likely due to retention of these elements within sub-micron sized alloy or sulphide phases. Time of rhenium depletion (TRD) ages, recorded by Os isotopes, average ~ 0.7 ± 0.4 Ga and can be as ancient as 1.5 Ga. Some harzburgite compositions are consistent with minor melt infiltration processes modifying incompatible trace element compositions and Re abundances, with a possible melt infiltration event at ~120 Ma based on 187Re-188Os, prior to the inception of subduction at the Tonga Trench at ~52 Ma. Evidence for ancient melt depletion, combined with limited melt processing since inception of subduction suggests that NOVA88D harzburgites represent melt residues incorporated into the Tonga arc, rather than their geochemical signatures being produced beneath the recent arc. Estimates of fO2 (~ − 0.4 ± 0.4 ΔFMQ) and olivine-spinel equilibration temperatures for the Tonga Trench samples (830 ± 120 ̊C) are similar to abyssal peridotites and some Izu-Mariana-Bonin peridotites. These values are unlikely to relate directly to recorded degrees of melt depletion and melt depletion ages in the rocks. Refractory residues from prior melt depletion events are probably common in the convecting mantle, and those with high degrees of melt depletion (>18%) and relatively ancient melt depletion ages (<2 Ga) are likely to have been formed during prior melting processes rather than melting processes within their current tectonic setting. These refractory peridotites can be incorporated into a range of tectonic settings, including into mid-ocean ridges, succeeding arcs, or within the continental lithospheric mantle, where they may play a limited role in melt generation processes.

Advancing Li-ion storage performance with hybrid vertical carbon/Ni3S2-based electrodes

Conversion-reaction induced charge storage mechanisms of transition metal sulphides have received considerable interest in designing high-capacity electrodes for electrochemical energy storage devices. However, their low conductivity and structural degradation during cycling limit their applications as energy storage devices. A combination of different nickel sulphide phases tailored with carbon nanostructures is suggested to address these limitations. Herein, a facile, two-step approach is demonstrated for fabricating a hybrid electrode, consisting of trinickel disulphide (Ni3S2) formed on a metallic Ni nanoparticle supported by vertical carbon nanotubes (VCN) backbone in the form Ni3S2/Ni@VCN. Ni3S2/Ni@VCN electrodes were tested as anode for lithium-ion batteries, and the electrode featured outstanding lithium-storage capabilities with a high reversible capacity (1113 mAh g−1 after 100 cycles at 100 mA g−1), excellent long-term cycling stability (770 mAh g−1 after 500 cycles at 200 mA g−1), and good rate capability. The resulting electrode performance is one of the best Li-ion storage capabilities in the Ni3S2-type anode materials described. A unique “broccoli-like” structure of polycrystalline Ni3S2 capped on conductive VCN backbone helps the interface storage process and boosts lithium storage performance.

(Fe, Ni, Co) 9 S 8 @ CS catalyst decorated on N‐doped carbon as an efficient electrocatalyst for oxygen evolution reaction

Fe, Ni, and Co and their alloys are widely studied for oxygen evolution reaction and hydrogen evolution in electrocatalytic water splitting under alkaline conditions, and their pentlandite sulfide was found to enhance the catalytic activity for the reactions. In this study, the synthesis of pentlandite sulfide of Fe, Ni, and Co was tried by a ball milling and subsequent pyrolysis. It was proved that the ball milling method is a promising way for a pentlandite formation and simultaneous carbon encapsulation. An aniline monomer played a role of carbon source for carbon encapsulation, and ammonium persulfate provided sulfur for a sulfide formation. Three kinds of compounds were synthesized by varying the Ni/Co ratio, and their structural characteristics and electrochemical activity were investigated and compared each other. X-ray diffraction patterns showed that they consisted of pentlandite sulfide and metal alloy phase. Transmission electron microscopy revealed that nanoparticles enwrapped by carbon shell were uniformly distributed on N-doped carbon. Electrochemical activity was studied under alkaline condition, and the overpotential of 260 mV at 10 mA/cm2 was obtained in 1 M KOH solution for oxygen evolution reaction. After 500 cycles, the overpotential increased slightly to 310 mV. From this study, it was revealed that the electrochemical activity of (Fe, Ni, Co)9S8 depends on structural parameters not elemental composition.

Identification of magnetic enhancement at hydrocarbon-fluid contacts

Identifying the depths of the hydrocarbon-fluid contacts in a reservoir is important for determining hydrocarbon reserves and production planning. Using core samples from the Tay Sandstone reservoir in the central North Sea, we show that there is a magnetic enhancement at the hydrocarbon-fluid contacts that is detectable through both magnetic susceptibility measurements and magnetic hysteresis measurements. We observed this magnetic enhancement at both gas-oil and oil-water contacts, which have been independently identified using nonmagnetic methods; we did not consider gas-water contacts in this study. We demonstrate that this magnetic enhancement is caused by the precipitation of new nanometric iron oxide (magnetite) and iron sulfide (greigite) phases. The magnetic enhancement may be caused by diagenetic changes or preferential biodegradation at the top of the oil column during early filling and at the oil-water contact. Our findings have the potential to be used to identify paleo-hydrocarbon-fluid contact in both structurally modified fields and failed wells. The technique can also be used to infer the fill history of a basin and calibrate petroleum systems models. Magnetic susceptibility measurements have the advantage that they can easily and quickly be measured in the field on whole core material.

Tin sulfide nanoparticles as photocatalysts for the degradation of organic dyes

Tin sulfide (SnS) nanoparticles were prepared from tin(II) dithiocarbamate single source precursors. Powder X-ray diffraction patterns of the SnS nanoparticles confirmed orthorhombic herzenbergite phase of tin sulfide. High-resolution transmission electron microscope images show spherically shaped tin sulfide with particles size in the range 1.0–2.8 nm. The bandgap energy obtained from Tauc plots is in the range 2.95–3.32 eV. The as-prepared SnS nanoparticles were used as nano photocatalysts for the degradation of brilliant green (BG), crystal violet (CV), methylene blue (MB) and methyl red (MR) under visible light irradiation. The degradation efficiency of BG by the SnS nanoparticles after 180 min irradiation are 76%, 81% and 70% by SnS-1, SnS-2 and SnS-3. Degradation efficiency of 66%, 90% and 75% were obtained for SnS-1, SnS-2 and SnS-3, respectively, against CV dye. While the efficiency of 79%, 97% and 93% were obtained for SnS-1, SnS-2 and SnS-3, respectively, against MB dye. The results showed that the as-prepared SnS nanoparticles are efficient photocatalyst for the degradation of BG, CV, MB and MR dyes. Liquid chromatography-mass spectrometry was used to investigate the degradation pathway of the organic dyes. The effects of irradiation time, scavengers and photostability on the photocatalysis process were also evaluated.

Mineralization and hydrothermal alteration in the Mamão orogenic gold deposit, Andorinhas greenstone belt, Carajás Province, Brazil

The Mamão gold deposit, located in the eastern portion of the Amazonian Craton, northern Brazil, is hosted by mafic rocks of the Mesoarchean Andorinhas greenstone belt. An underground mine was operated in this area by Troy Resources Ltd., which produced approximately 350 koz of gold between 2008 and 2015. The hydrothermal alteration halos are characterized by a distal zone (10- to 80 m wide) with a chlorite-albite-epidote-actinolite assemblage, an intermediate zone (5- to 20 m wide) marked by calcite-albite-chlorite-actinolite-quartz, a proximal zone (0.5–5 m wide) composed of biotite-quartz-calcite-pyrite-(gold) and a quartz vein-hosted orebody zone (0.5- to 6 m wide) composed by quartz-calcite-pyrite-(gold). Geochemical data indicate that the metabasalt, metandesite and metadacite host rocks display a tholeiitic N-MORB signature, suggesting that they were formed in ancient oceanic spreading centers. Hydrothermal chlorite of the Mamão deposit is classified as ripidolite and brunsvigite. Biotite is the main mica and increases in modal content from the distal alteration to the vein zone, displaying compositions within the annite domain. Muscovite occurs as very fine lamellae and is generally located in the intermediate zone of the altered region. Amphiboles are calcium-rich and display compositions mostly varying from hornblende (Mg-hornblende to Fe-hornblende) in the distal zone, to actinolite in the intermediate zone. Sulfidation occurs in all hydrothermal alteration zones, with both fine- and coarse-grained pyrite as the main sulfide phase, and lesser amounts of chalcopyrite, pyrrhotite, cobaltite and sphalerite. Fine-grained pyrite contains many gold inclusions and is typical of the orebody zone preferentially in close contact with the proximal hydrothermal zone, whereas coarse-grained pyrite (without recoverable gold) occurs in the veins. From the edges to the core of the hydrothermal alteration halos, the As, Sb, Ag and Au contents in the pyrite increase, whereas Pb, Co and Mo decrease. Gold occurs as free crystals (2- to 0.1 mm) disseminated within the gangue or as inclusions in the fine-grained pyrite. Temperature estimated via chlorite geothermometer ranges from 284- to 320 °C, with pressure between 1.12 and 1.34 kbar according to biotite geobarometer calculations for the hydrothermal zones. The C–O–S isotope analyses of the calcite and pyrite from the orebody zone yielded δ13C, δ18O and δ34S values ranging from −4.23 to −3.54‰, 8.60–9.77‰ and 3.37–3.52‰ respectively, which suggests that the hydrothermal fluid is predominantly of metamorphic origin. The εNd (3.0) calculated using isotopic analyses of the metavolcanic host rocks varies between +0.11 and + 4.25. A whole-rock Sm–Nd isochron age of 2952 ± 14 Ma was obtained from the host rocks, while a post-mineralized pyrite yielded a Sm–Nd isochron age of 2446 ± 35 Ma. The deposit exhibits mineralogical and isotopic characteristics consistent with those of orogenic type containing gold-bearing, sulfide-rich quartz veins. The Mamão deposit's host rocks are among the oldest rocks described so far in the Carajás Province. The age of the mineralizing event is limited between 2.95 and 2.45 Ga (probably ca. 2.7 Ga), which is the major metallogenic event of gold-deposit formation in several granite-greenstone terrains worldwide.

Coordination agent-dominated phase control of nickel sulfide for high-performance hybrid supercapacitor

The property of an active material is not only influenced by its morphology and size, but also by its crystal phase. The present phase regulation of nickel sulfide is mainly achieved by controlling the participation of sulfur source in reaction. Thus, new perspectives direct at phase control need to be explored and supplemented. Herein, we proposed a novel coordination agent-dominated phase modulation strategy assisted by a hydrothermal process. It is found that increasing the amount of coordination agent can drove the phase transformation from the initial composite of β-NiS/α-NiS/Ni3S4 to β-NiS/α-NiS, and then to pure β-NiS. The mechanism of phase regulation has been proposed, and the general application of this method has been demonstrated. By employing coordination agent, the size of resulted products is reduced, and the morphology is optimized. As a result, all of the pure β-NiS electrodes indicate significantly enhanced specific capacity than the pristine β-NiS/α-NiS/Ni3S4 composite. Notably, the sample synthesized with 3 mmol of urea (S11) shows uniform morphology and smallest size, and it gives a highest specific capacity of 223.8 mAh g−1 at 1 A g−1, almost 1.5 times of the original sample. The fabricated S11//rGO device delivers a high energy density of 56.6 Wh·kg−1 at a power density of 407.5 W·kg−1, and keeps an impressive capacity retention of 84% after 20,000 cycles. This work put forwards a new prospect for controlling the phase and composition of nickel sulfide based on coordination chemistry.

Optimization and assessment of a sequential extraction procedure for calcium carbonate rocks

Sequential extraction analyses are widely used for the determination of element speciation in sediments and soils. Typical sequential extraction protocols were developed to extract from low-carbonate samples and therefore are not necessarily suitable for high-carbonate samples. In this study, we tested increased reagent to sample ratios to adjust an existing sequential extraction procedure to analyze high-CaCO3 samples with concentrations ranging from 70 to above 90 %. Complete dissolution of the CaCO3 phase, and a higher extraction efficiency of manganese associated with the carbonate phase, was achieved when using four times the original reagent to sample ratio in the 2nd extraction step. This increase of reagent did not compromise the extraction of subsequent phases as shown by unaffected Fe concentrations in a low-carbonate sample. Hence, an essential outcome was that increasing the solution to sample ratio did not lead to the dissolution of other sedimentary phases, such as hydrous and crystalline iron oxides or sulfides. Thus, compared to other extraction protocols that use a lower reagent to sample ratio in the carbonate dissolution step, the new protocol allowed the complete extraction of oxide and sulfide phases in the following extraction steps. Furthermore, the study demonstrated the benefit of replacing Na-acetate with NH4-acetate to extract exchangeable ions and carbonates. We observed increased intensities for several analytes, i.e., trace metals such as Mo and As, due to less suppression of the analyte signal by NH4-acetate than by Na-acetate during analysis by inductively coupled plasma optical emission spectrometry (ICP-OES).

Modifying the catalytic properties of hydrotreating NiMo–S phases by changing the electrodonor capacity of the support

The hydrogenation activity and physico-chemical characterization of a series of NiMo catalyst supported on materials with different acid-base properties (Al2O3, layered double hydroxides-derived MgAl oxides and MgO) have been investigated. The results show a clear correlation between the electrodonor capacity of the support, the negative charge density of the supported NiMo oxides and the intrinsic hydrogenation rate of the sulfided phase. Spectroscopic characterization ruled out any possible contribution derived from differences in the NiMoS2 stack or slab size distributions, as determined by high-resolution transmission electron microscopy. The experimental results obtained suggest the occurrence of an electron transfer phenomena from the support to the supported NiMoS2 slabs, being this effect stronger for supports with higher electrodonor capacity.This work presents a specific electronic support effect that goes beyond the classical dispersing and stabilizing role.

Mg isotope variations in microphases of unequilibrated enstatite chondrites

AbstractMagnesium, a major mineral‐forming element of the inner solar system, is partitioned between the silicate and the unique sulfidic phases (niningerite, MgS) of enstatite chondrites (ECs) owing to the formation of EC under exceptionally reducing conditions. In this study, we have carried out mineralogical characterization of the distinct Mg‐ and Si‐bearing phases of unequilibrated ECs (EH3). To evaluate the Mg isotope variations in such reduced planetary bodies, we have analyzed the Mg isotope composition of several enstatitic silicate phases, matrices (composed of mixed proportions of silicate and sulfidic phases), and bulk meteorite fractions micro milled from three EH3 chondrites. We found that the stable Mg isotope composition (expressed as δ25Mg) of the microphase separates of EH3 chondrites ranged from −0.216 ± 0.014‰ to −0.094 ± 0.014‰. Despite the dispersion in Mg isotope values, the average δ25Mg of the silicate fractions of the studied EH3 chondrites was similar to its matrix and bulk meteorite fractions. Mass‐dependent Mg isotope fractionation was evinced among the phase separates of EH3 chondrites with the slope of the fractionation line on a δ25Mg versus δ26Mg plot being closer to kinetic fractionation trend. Experimental and theoretical considerations hint that Mg isotope exchange between the silicate and sulfide phases might have generated the observed Mg isotope variations among the microphase separates of EH3 chondrites. Based on our Mg isotope data, in combination with the Si isotope composition obtained in the same aliquot of silicate–matrix fractions of EH3 chondrites and its subsolar Al/Si ratio, we suggest that the high abundance of Si in EC (due to the partitioning of Si among diverse silicates, silica, and metallic phases) and the loss of Mg and refractory components from EC‐forming regions could explain the lower Mg/Si ratio of EC compared to that of ordinary and carbonaceous chondrites.

Two Phases of Monolayer Tantalum Sulfide on Au(111).

We prepared monolayers of tantalum sulfide on Au(111) by evaporation of Ta in a reactive background of H2S. Under sulfur-rich conditions, monolayers of 2H-TaS2 formed, whereas under sulfur-poor conditions TaS2-x with 0 ≤ x ≤ 1 were found. We identified this phase as TaS, a structure that can be derived from 2H-TaS2 by removal of the bottom S layer.

Worth from Waste: Utilizing a Graphite-Rich Fraction from Spent Lithium-Ion Batteries as Alternative Reductant in Nickel Slag Cleaning

One possible way of recovering metals from spent lithium-ion batteries is to integrate the recycling with already existing metallurgical processes. This study continues our effort on integrating froth flotation and nickel-slag cleaning process for metal recovery from spent batteries (SBs), using anodic graphite as the main reductant. The SBs used in this study was a froth fraction from flotation of industrially prepared black mass. The effect of different ratios of Ni-slag to SBs on the time-dependent phase formation and metal behavior was investigated. The possible influence of graphite and sulfur contents in the system on the metal alloy/matte formation was described. The trace element (Co, Cu, Ni, and Mn) concentrations in the slag were analyzed using the laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) technique. The distribution coefficients of cobalt and nickel between the metallic or sulfidic phase (metal alloy/matte) and the coexisting slag increased with the increasing amount of SBs in the starting mixture. However, with the increasing concentrations of graphite in the starting mixture (from 0.99 wt.% to 3.97 wt.%), the Fe concentration in both metal alloy and matte also increased (from 29 wt.% to 68 wt.% and from 7 wt.% to 49 wt.%, respectively), which may be challenging if further hydrometallurgical treatment is expected. Therefore, the composition of metal alloy/matte must be adjusted depending on the further steps for metal recovery.

Trace-Element Geochemistry of Sulfides in Upper Mantle Lherzolite Xenoliths from East Antarctica

Sulfides in upper mantle lherzolite xenoliths from Cretaceous alkaline-ultramafic rocks in the Jetty Peninsula (East Antarctica) were studied for their major and trace-element compositions using SEM and LA-ICP-MS applied in situ. Modal abundance of sulfides is the lowest in Cpx-poor lherzolites ≤ Spl-Grt lherzolites << Cpx-rich lherzolites. Most sulfides are either interstitial (i-type) or inclusions in rock-forming minerals (e-type) with minor sulfide phases mostly present in metasomatic veinlets and carbonate-silicate interstitial patches (m-type). The main sulfide assemblage is pentlandite + chalcopyrite ± pyrrhotite; minor sulfides are polydymite, millerite, violarite, siegenite, and monosulfide solution (mss). Sulfide assemblages in the xenolith matrix are a product of the subsolidus re-equilibration of primary mss at temperatures below ≤300 °C. Platinum group elements (PGE) abundances suggest that most e-type sulfides are the residues of melting processes and that the i-type sulfides are crystallization products of sulfide-bearing fluids/liquids. The m-type sulfides might have resulted from low-temperature metasomatism by percolating sulfide-carbonate-silicate fluids/melts. The PGE in sulfide record processes are related to partial melting in mantle and intramantle melt migration. Most other trace elements initially partitioned into interstitial sulfide liquid and later metasomatically re-enriched residual sulfides overprinting their primary signatures. The extent of element partitioning into sulfide liquids depends on P, T, fO2, and host peridotite composition.

Triphenylphosphine-Assisted Transformation of NiS to Ni2P through a Solvent-Less Pyrolysis Route: Synthesis and Electrocatalytic Performance.

Straightforward synthetic routes to the preparation of transition metal phosphides or their chalcogenide analogues are highly desired due to their widespread applications, including catalysis. We report a facile and simple route for the preparation of a pure phase nickel phosphide (Ni2P) and phase transformations in the nickel sulfide (NiS) system through a solvent-less synthetic protocol. Decomposition of different sulfur-based complexes (dithiocarbamate, xanthate, and dithiophosphonate) of nickel(II) was investigated in the presence and absence of triphenylphosphine (TPP). The optimization of reaction parameters (nature of precursor, ratio of TPP, temperature, and time) indicated that phosphorus- and sulfur-containing inorganic dithiophosphonate complexes and TPP (1:1 mole ratio) produced pure nickel phosphide, whereas different phases of nickel sulfide were obtained from dithiocarbamate and xanthate precursors in the presence or absence of TPP. A plausible explanation of the sulfide or phosphide phase formation is suggested, and the performance of Ni2P was investigated as an electrocatalyst for supercapacitance and overall water-splitting reactions. The performance of Ni2P with the surface free of any capping agents is not well explored, as common synthetic methods are solution-based routes; therefore, the electrocatalytic performance was also compared with metal phosphides, prepared by other routes. The highest specific capacitance of 367 F/g was observed at 1 A/g, and the maximum energy and power density of Ni2P were calculated to be 17.9 Wh/kg and 6951 W/kg, respectively. The prepared nickel phosphide required overpotentials of 174 and 316 mV along with Tafel slopes of 115 and 95 mV/dec to achieve a current density of 10 mA/cm2 for the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER), respectively.