Activity Of FeO Research Articles

Stability and dissolution of single-crystalline iron oxide thin films in electrochemical environments

The stability of single-crystalline monolayer FeO(111) and 10 nm thin Fe3O4(111) films on Pt(111) upon exposure to environments of increasing chemical complexity has been studied with X-ray photoelectron spectroscopy, temperature-programmed desorption, in-situ scanning tunneling microscopy, and cyclic voltammetry. The well-defined oxide films, which were prepared under ultrahigh-vacuum conditions, were exposed to aqueous solutions of different pH and electrochemical cycling in pure and catechol-containing electrolyte. The films are stable in neutral (pH 7) and alkaline (pH 13) solutions both at open circuit conditions and during electrochemical cycling within the limits of hydrogen and oxygen evolution potentials. Also in strongly acidic (pH 1) perchlorate solution the films remain intact under open circuit conditions, but they quickly dissolve on application of electrochemical potential. Especially for the ultrathin FeO(111) films, catechol enhances the dissolution at neutral pH during electrochemical cycling. A comparison of Pt(111), FeO(111) and Fe3O4(111) substrates in the electrochemical catechol oxidation reaction reveals enhanced and sustained activity of FeO in alkaline environment, while strong deactivation occurs on Pt(111) and Fe3O4(111). This is explained by the weaker interaction between catechol and FeO(111) compared to the other substrates, which hampers the formation of a barrier layer on the electrode surface.

Effect of EDTA and Citric Acid Additive on the Polymorph, Morphology, and Photocatalytic Activity of Iron Oxyhydroxide.

Iron oxyhydroxide [FeO(OH)] is a promising photocatalyst owing to its simple synthesis at mild temperatures and narrow band gap, which allows for the efficient harvesting of visible light. The selective production of FeO(OH) polymorphs and the modulation of their morphology by changing the iron salts, salt concentration, and additives have been widely reported. This study focuses on overcoming fast charge-carrier recombination by developing FeO(OH)-based heterostructure materials. The role of a chelating ligand (EDTA and citrate) in determining the polymorph type, morphology, and photocatalytic activity of FeO(OH) was studied. The findings revealed the additive produced of nanosized α-FeO(OH)/EDTA and layered γ-FeO(OH)/citrate with superior catalytic activities.

Effect of MgO on phase equilibria of copper matte and SiO2-saturated iron silicate slag in smelting complicated copper resources

The effect of MgO on the phase equilibria between matte and tridymite-saturated FeOx−SiO2−MgO slag was investigatedusing high-temperature equilibration and microanalysis technique. The results showed that at 1300 °C and p(SO2) of 10 kPa, the presence of MgO reduced the FeO activity of the slag, leading to the decrease in the oxygen partial pressure (p(O2)) over the slag and the Cu solubility in the slag. Due to the lower FeO activity, FeS was oxidized from matte into slag, increasing the Cu concentration of the matte. In high-SiO2 concentrationslags, excessive MgO in the liquid slag recrystallized as solid olivine (Mg2SiO4−Fe2SiO4), increasing the slag viscosity and copper losses in the slag. The maximum MgO solubility in the FeOx−SiO2−MgO slag increased from 3 wt.% to 8 wt.% when the temperature raised from 1200 to 1300 °C under p(O2) of 10−6 kPa. At higher MgO content, the slag composition could be optimized by increasing temperature and adding SiO2 flux to maintain a fully molten slag or avoid high proportions of solids.

Sulfide Capacity and Activity of Iron Oxide in CaO–SiO<sub>2</sub>–FeO Ternary System at 1573 K

The knowledge of sulfide capacities of FeO-containing slags is necessary for better understanding the resulfurization reaction in hot metal pre-treatments. In this study, copper-iron-sulfur liquid alloy was equilibrated with CaO–SiO2–FeO ternary slag to measure sulfide capacities and FeO activities simultaneously at temperature below the melting point of pure iron. The experimental result that the sulfide capacity increased with increasing FeO content could be explained by the fact that FeO was a basic oxide, and the sulfide capacity of the CaO–SiO2–FeO ternary system was significantly larger than those of the CaO–SiO2–MgO, CaO–SiO2–AlO1.5 and CaO–SiO2–CaF2 ternary systems. Although the FeO activity and oxygen potential were raised by the FeO addition, the calculated value for sulfur distribution ratio between CaO–SiO2–FeO slag and hot metal increased with an increase in FeO content.

Solubility and Activity of Iron Oxide in Solid Solutions between Ca<sub>2</sub>SiO<sub>4</sub> and Ca<sub>3</sub>P<sub>2</sub>O<sub>8</sub> at 1573 K

Towards better understanding of fundamental dephosphorization slags of the FeO-CaO-SiO2-P2O5 quaternary system, this study aimed at clarifying the thermochemical properties of iron oxide in Ca2SiO4-Ca3P2O8 solid solutions. The solubility and activity of FeO in the solid solutions coexisting with CaSiO3 at 1573 K were determined by SEM-EDX analysis and a gas equilibrium method, respectively. Based on the present experimental results, the phase relationships could be explained that the solid solution of high FeO solubility coexists with CaSiO3 and liquid slag of low FeO content, while the solid solution of low FeO solubility coexists with CaO and liquid slag of high FeO content.

Thermodynamic Nature of SiO2 and FeO in Flux O Potential Control Subject to Submerged Arc Welding Process

SiO2 and MnO are the essential components dictating flux O potential subject to submerged arc welding. Due to the lack of thermodynamic data on the flux properties in early trials, the roles of SiO2 and FeO in the determination of the flux O potential remain nebulous, and conclusions are often conflicting with each other. Within this framework, through the analysis of the fluxes of 23 formulas at the full coverage of acid and basic fluxes with a basicity index spanning from 0.5 to 5.6, attempts are made to obtain a better understanding of the thermodynamic interconnection between oxides (SiO2 and FeO) and the flux O potential, and to clarify the controversial conclusions raised by different investigators. In particular, a thermodynamic approach has been proposed to simulate the equilibrium FeO activity, during which no measurement of the slag composition is needed. It is revealed that the simulated equilibrium FeO activity is feasible to evaluate the flux potential for both acid and basic fluxes, which may pave a vital way to save the experimental resources on the flux design and analysis.

Effect of Impurities on Spinel Precipitation Behavior in Molten Fayalite Slag

The effects of alumina (Al2O3) and magnesia (MgO) impurities on the precipitation of spinels such as magnetite (Fe3O4) due to the oxidation of fayalite (Fe2SiO4) slag in copper smelters were investigated. Molten fayalite slag was oxidized in alumina, magnesia, and quartz sample boats, and spinel precipitation behaviors were compared. The inclusion of Al2O3 and MgO as impurities promoted the precipitation and growth of spinel crystals. It was assumed that this effect was attributed to the rapid formation of hercynite at the interface between the alumina sample boat and slag, growth of spinel due to the substitution of Al and Fe(III) in hercynite, and the solid solution of Mg in spinels. However, as the experiments with quartz sample boats were conducted unavoidably with SiO2 saturated slag, the possibility of suppression of solute diffusion due to increased viscosity and decreased FeO activity in the slag cannot be ignored. Therefore, it is considered that the effects of Al2O3 and MgO on spinel precipitation must be further investigated.

Metal Saturated Cumulates from Siberia — Lunar Basalt Analogues?

Abstract It is not well known which chemical differentiation pathways basaltic melts will take when they are iron metal saturated. Thermodynamically, the pathway seems predictable. So long as Fe metal is a stable liquidus phase and relative oxygen fugacity (fO2) is not subject to major fluctuations, the activity of FeO (aFeOmelt) is buffered by the iron–wüstite (IW) equilibrium 2Femetal + O2 → 2FeOmelt. Metallic Fe also stabilizes olivine through the equilibrium 2Femetal + O2 + SiO2 melt → Fe2SiO4 olivine. That equilibrium tends to suppress the enrichment in bulk SiO2 when Fe saturated basaltic melts differentiate. We document the differentiation history of tholeiitic cumulates from the Siberian craton that carry up to 30 modal % metallic Fe. Our study is complemented by differentiation experiments at two redox states, one set in Fe metal capsules at 1.6 log units below IW (IW-1.6) and a second set in graphite capsules at IW + 1.5. Iron saturated differentiation pathways do not show enrichments in FeO nor in bulk SiO2 because olivine remains stable along the entire liquid line of descent. By contrast, melts equilibrated at IW + 1.5, that is, outside metallic Fe saturation, crystallize pigeonite as first silicate and follow a normal (terrestrial) differentiation pathway involving marked SiO2 enrichment. The Fe-saturated path duplicates in detail the liquid line of descent we derive for the cumulates. Iron-saturated experiments have limited applicability to the Earth because there are so few terrestrial basalts saturated with metallic Fe; however, they might apply to the Moon. Many lunar basalts appear to have been saturated with an Fe-Ni phase during their emplacement on the lunar surface, and potentially during generation within the lunar mantle.

Ice nucleation activity of iron oxides via immersion freezing and an examination of the high ice nucleation activity of FeO.

Heterogeneous ice nucleation is a common process in the atmosphere, but relatively little is known about the role of different surface characteristics on the promotion of ice nucleation. We have used a series of iron oxides as a model system to study the role of lattice mismatch and defects induced by milling on ice nucleation activity. The iron oxides include wüstite (FeO), hematite (Fe2O3), magnetite (Fe3O4), and goethite (FeOOH). The iron oxides were characterized by X-ray diffraction (XRD) and Brunauer-Emmett-Teller (BET) surface area measurements. The immersion freezing experiments were performed using an environmental chamber. Wüstite (FeO) had the highest ice nucleation activity, which we attribute to its low lattice mismatch with hexagonal ice and the exposure of Fe-OH after milling. A comparison study of MnO and wüstite (FeO) with milled and sieved samples for each suggests that physical defects alone result in only a slight increase in ice nucleation activity. Despite differences in the molecular formula and surface groups, hematite (Fe2O3), magnetite (Fe3O4), and goethite (FeOOH) had similar ice nucleation activities, which may be attributed to their high lattice mismatch to hexagonal ice. This study provides further insight into the characteristics of a good heterogeneous ice nucleus and, more generally, helps to elucidate the interactions between aerosol particles and ice particles in clouds.

Use of computational thermodynamics software to determine the influence of CaO, FeO and SiO2 on hot metal dephosphorization efficiency

The properties of the mixtures used in hot metal dephosphorization, such as solid and liquid fraction phases, CaO and FeO activity and viscosity, are determinant for the process efficiency. The influence of these properties on hot metal dephosphorization were studied for CaO–FeO–SiO2 mixtures. The experiments were carried out at 1400 °C, in MgO-C crucibles, where the mixtures were added to the hot metal. Metal samples were taken at different times to measure the variation of phosphorus (P) content over time. The initial mixtures and final slags properties were determined by computational thermodynamics software FactSage 7.2. A parameter named Dephosphorization Factor (FDeP), that measures the efficiency of the initial mixtures and final slag, in hot metal dephosphorization was used. It was found that the FDeP presents a high correlation (R2) with the dephosphorization efficiency and can be used to predict which slag will be the most efficient.

Influence of Desulfurization with Fe2O3 on the Reduction of Nickel Converter Slag.

Generally in the nickel converter slag, metals are mainly in the form of sulfides, which are difficult to separate from slag. Although metal oxides in the slag, such as NiO, CoO, and Cu2O, are easily reduced into metal using carbon, the presence of sulfur inhibits the reduction reaction. In this study, the addition of Fe2O3 to nickel converter slag produced desulfurized slag, which enhanced the carbothermal reduction process. Increasing the desulfurization rate promoted the conversion of sulfides into oxides in slag, which significantly increased the activity of NiO, Cu2O, and Fe2O3. However, the residual sulfur content had no significant effect on the activity of FeO and CoO, due to the high initial FeO content and cobalt existing mainly in the form of oxides. The optimum addition of Fe2O3 was 15.0 g per 100 g nickel slag, while the desulfurization ratio was 36.84% and the rates of nikel, cobalt and copper recovery were 95.33%, 77.73%, and 73.83%, respectively.

Improving the production efficiency of high-titania slag in Ti extraction process: fluxing effect on formation of pseudobrookite

We investigated the carbothermic reduction process of ilmenite ore at 1873 K with flux addition. Without flux, the pseudobrookite phase with a high melting temperature was precipitated during ilmenite smelting. This could be the main reason for decreased reduction of iron in ilmenite. To accelerate reduction of ilmenite, two factors were considered. One is increasing the reduction driving force during smelting. Activity of FeO is the major factor to control reduction in driving force. The other factor is delay in formation of the pseudobrookite phase, a high-melting point precipitation phase. In this system, MgO in ilmenite could be used to form pseudobrookite. To control these factors, in this study, flux agent (i.e., Na2O or SiO2) addition was considered. The thermochemical simulation program, FactSageTM7.0 was used to calculate the viscosity of slag and the activity of components as fluxing agents were added. High-temperature experiments using an induction furnace were also conducted to confirm the computational results. To determine the composition of final products, i.e., titanium slag, X-ray fluorescence analysis was executed. As a result of Fe and Ti behaviours in slag, SiO2 addition showed no significant difference from the slag without flux. However, Fe reduction in ilmenite, i.e. TiO2-enrichment, was more accelerated when Na2O was added. X-ray diffraction, scanning electron microscopic and transmission electron microscopic analyses results also showed that even 1 wt% Na2O addition significantly influenced the titanium slag production compared to no flux addition.

Oxygen transfer phenomenon between slag and molten steel for production of IF steel

FeO-containing slag originated from the basic oxygen furnace to the ladle is a major reoxidation source during the following secondary refining. Ladle slag reduction treatment (slag treatment) is one of the common countermeasures adopted to eliminate the steel contamination by FeO reoxidation. The oxygen transfer phenomenon between molten steel and slag was studied during the industrial production of interstitial-free (IF) steel, the measured and calculated oxygen activities in steel were compared, and the Fe–O equilibrium at the slag–molten steel interface was investigated by thermodynamic analysis. With slag treatment, the oxygen potential is higher in the molten steel than in the pre-deoxidation slag; this causes oxygen transfer from the molten steel to the slag, decreasing the efficiency of slag treatment. Based on this, a two-step slag deoxidation process was optimized. The second step further reduced the FeO content. On the other hand, the CaO/Al2O3 (C/A) ratio in the refining slag must be controlled, because it affects the FeO activity and inclusion absorption capacity of the slag. The results suggest that the C/A ratio of 1.2–1.5 and the FeO content of < 6% are beneficial to refine IF steel.

Effects of Slag Composition on H2 Generation and Magnetic Precipitation from Molten Steelmaking Slag–Steam Reaction

In this paper, the effects of slag composition (slag basicity CaO/SiO2 and FeO concentration) on the amounts of H2 gas generated and the magnetic spinel phase precipitated as a result of the reaction between synthetic steelmaking slag and steam at 1873 K (1600 °C) were studied by thermodynamic simulation (using Thermodynamic Package FactSage 7.0) and laboratory experiments. The thermodynamic calculation showed that, upon increasing slag basicity (CaO/SiO2) from 1.0 to 2.5, for the reaction of 100 g of slags with 100 g of H2O gas, the accumulated amount of the produced H2 gas increased from 0.17 to 0.27 g, while the amount of magnetic spinel phase first increased and then decreased, with the maximum precipitation of 16.71 g at the basicity of 1.5. When the FeO concentration increased from 15 to 30 pct for the slag with basicity of 2.0, the accumulated amount of the produced H2 gas increased from 0.17 to 0.28 g, and the amount of magnetic spinel phase increased from 5.88 to 10.59 g. The laboratory experiments were conducted in confocal laser scanning microscope to verify the reaction between 0.2 g of slag and 3.75 L of H2O-Ar gas $$ \left( {P_{{{\text{H}}_{2} {\text{O}}}} \, = 0.2\,{\text{atm}}} \right) $$ . The results indicated that, for 100 g of slags, upon increasing slag basicity (CaO/SiO2) from 1.0 to 2.5, both the produced H2 gas and magnetic spinel phase first increased and then decreased, with the maximum amounts being 0.09 g of gas and 37.00 g of magnetic spinel phase at the slag basicity of 1.50. For the FeO concentration increasing from 15 to 30 pct, the amounts of both the produced H2 gas and magnetic spinel phase increased from 0.04 to 0.10 g and from 18.00 to 27.00 g, respectively. The reaction rate between the molten CaO-SiO2-FeO-MnO-Al2O3-MgO slag and the moisture $$ \left( {P_{{{\text{H}}_{2} {\text{O}}}} \, = 0.2\,{\text{atm}}} \right) $$ increased with the increasing FeO activity in the slag. The dependence of the reaction rate (mol/cm2/s) on FeO content can be expressed as $$ r \, = (7.67\left( {a_{\text{FeO}} } \right) - 2.99) \times 10^{ - 7} $$ .

Enhancing the Reduction of High-Aluminum Iron Ore by Synergistic Reducing with High-Manganese Iron Ore

How to utilize low grade complex iron resources is an issue that has attracted much attention due to the continuous and huge consumption of iron ores in China. High-aluminum iron ore is a refractory resource and is difficult to upgrade by separating iron and alumina. An innovative technology involving synergistic reducing and synergistic smelting a high-aluminum iron ore containing 41.92% Fetotal, 13.74% Al2O3, and 13.96% SiO2 with a high-manganese iron ore assaying 9.24% Mntotal is proposed. The synergistic reduction process is presented and its enhancing mechanism is discussed. The results show that the generation of hercynite (FeAl2O4) and fayalite (Fe2SiO4) leads to a low metallization degree of 66.49% of the high-aluminum iron ore. Over 90% of the metallization degree is obtained by synergistic reducing with 60% of the high-manganese iron ore. The mechanism of synergistic reduction can be described as follows: MnO from the high-manganese ore chemically combines with Fe2SiO4 and FeAl2O4 to generate Mn2SiO4, MnAl2O4 and FeO, resulting in higher activity of FeO, which can be reduced to Fe in a CO atmosphere. The main products of the synergistic reduction process consist of Fe, Mn2SiO4, and MnAl2O4.

Effects of CaO Addition on the Iron Recycling from Nickel Slags by Oxidation-Magnetic Separation

To recover iron from water-quenched nickel slags, CaO was added. Thermodynamic analysis showed that CaO promotes the reaction between fayalite (Fe2SiO4) and O2. Phase diagrams of the FeO-SiO2-MgO-CaO slag with various CaO contents in an air atmosphere drawn by FactSage 7.1 showed that the phase components can be significantly affected by the CaO contents. With increasing CaO content, the fusion characteristic temperatures decreased rapidly to a minimum and subsequently increased slightly. The oxidization of Fe2SiO4 in nickel slags was accelerated significantly by the addition of CaO, which led to an increase of FeO activity and decrease of Fe2O3 activity to promote the formation of MgFe2O4. Excess addition of CaO led to the formation of more silicates. In addition, the crystallization temperature was also reduced with increasing CaO content, causing less spinel to crystalize. With increasing CaO content, the iron recovery and yield of concentrate first increased and subsequently decreased, while the total iron (TFe) content was almost not influenced and maintained a relatively stable value.

Calculation Model for Activity of FeO in Quaternary Slag System SiO2-CaO-Al2O3-FeO

According to the coexistence theory of slag structure, a calculation model for the activity of FeO in the quaternary system SiO2-CaO-Al2O3-FeO of depleted copper slag was established. The model was used to calculate and analyze the effects of temperature (T), basicity (B), and Al2O3 content on the activity of FeO (NFeO). The results show that temperature has little impact on NFeO. With increased basicity, NFeO first increased slightly, then increased sharply, and finally decreased. It is easier for CaO to combine with SiO2 than FeO to form calcium silicate, which replaces FeO in 2FeO·SiO2 and increases NFeO. However, when basicity is higher than 2.0, CaO not only reacts with SiO2, but also combines with FeO to form calcium ferrate compounds to decrease NFeO. In addition, the activity of FeO decreases with increased Al2O3 content because of the reaction between CaO and Al2O3. The results can be used as a theoretical basis to guide the carbothermal reduction process of copper slag.

Evaluating the hot metal dephosphorization efficiency of different synthetic slags using phosphorus partition ratio, phosphate capacity and computational thermodynamics

Abstract Phosphate capability (CP) and phosphorus partition ratio (LP) are usually used to evaluate the thermodynamic efficiency of dephosphorization slags with different compositions in hot metal pretreatment. However, these parameters are only useful in equilibrium conditions, and they are not accurate when they are used to evaluate slag efficiency in industrial processes. The current study evaluated the hot metal dephosphorization efficiency of different synthetic slags in experimental tests at 1400oC. This evaluation was made by using CP and LP, and by the computational thermodynamic software FactSage 6.4. This software allows to calculate the amount of liquid and solid present in the slag, which directly affects kinetic reactions. Therefore, even the computational thermodynamic software calculations are from considering the equilibrium, which in these cases can be used to explain the kinetic behavior of the processes. The obtained results allow concluding that CP and LP are valid, but only when they are used for equilibrium calculations; and that they should not be used to measure slag efficiency in industrial processes. A parameter named Dephosphorization Factor (FDeP) was developed based on data determined by computational thermodynamics. It was developed to be related to the dephosphorization efficiency. The results obtained in the current study allow to conclude that the initial synthetic slags, which presented higher CaO activity value, higher liquid quantity and FeO activity, will be the most efficient ones. And allow to conclude too, that the higher the factor, the greater the slag dephosphorization efficiency.

Novel method for iron recovery from hazardous iron ore tailing with induced carbothermic reduction-magnetic flocculation separation

In this paper, a novel method to recover iron from iron ore tailing (IOT) was studied. The method was induced with carbothermic reduction, followed by magnetic flocculation separation (MFS) and conventional magnetic separation (CMS). The effects of reduction temperature, as well as the amount of coal and sodium carbonate on iron recovery efficiency, were chiefly introduced according to the experimental mechanism. Results of carbothermic reduction showed that iron minerals in the IOT were transformed to metallic iron at the reduction temperature of 1100 °C for 120 min, with a C/Ore mass ratio of 25% and a mass ratio of Na2CO3 to ore of 8%. The reduction activity of FeO increased and a deep reduction from FeO to metallic iron was observed with the addition of Na2CO3. The metallization mean of induced reduction ores reached 32.53%. Results of magnetic separation showed that the MFS concentrate grade was 74.02% Fe, with the recovery rate at 79.51% when the reduced samples were ground to 87.4% below 38 μm. This iron recovery increased by 4.19% compared with that of CMS, whereas the iron concentrate grade slightly changed. In addition, the microstructure and phase transformation of the carbothermic reduction process were studied by X-ray powder diffraction, scanning electron microscope, and energy-disperse spectroscopy, thereby complying with the main force analysis of magnetic flocculation in the MFS to help understand the mechanism of the novel method.

New high pressure experiments on sulfide saturation of high-FeO∗ basalts with variable TiO2 contents – Implications for the sulfur inventory of the lunar interior

In order to constrain sulfur concentration in intermediate to high-Ti mare basalts at sulfide saturation (SCSS), we experimentally equilibrated FeS melt and basaltic melt using a piston cylinder at 1.0–2.5 GPa and 1400–1600 °C, with two silicate compositions similar to high-Ti (Apollo 11: A11, ∼11.1 wt.% TiO2, 19.1 wt.% FeO∗, and 39.6 wt.% SiO2) and intermediate-Ti (Luna 16, ∼5 wt.% TiO2, 18.7 wt.% FeO∗, and 43.8 wt.% SiO2) mare basalts. Our experimental results show that SCSS increases with increasing temperature, and decreases with increasing pressure, which are similar to the results from previous experimental studies. SCSS in the A11 melt is systematically higher than that in the Luna 16 melt, which is likely due to higher FeO∗, and lower SiO2 and Al2O3 concentration in the former. Compared to the previously constructed SCSS models, including those designed for high-FeO∗ basalts, the SCSS values determined in this study are generally lower than the predicted values, with overprediction increasing with increasing melt TiO2 content. We attribute this to the lower SiO2 and Al2O3 concentration of the lunar magmas, which is beyond the calibration range of previous SCSS models, and also more abundant FeTiO3 complexes in our experimental melts that have higher TiO2 contents than previous models’ calibration range. The formation of FeTiO3 complexes lowers the activity of FeO∗, aFeO∗silicate melt, and therefore causes SCSS to decrease. To accommodate the unique lunar compositions, we have fitted a new SCSS model for basaltic melts of >5 wt.% FeO∗ and variable TiO2 contents. Using previous chalcophile element partitioning experiments that contained more complex Fe-Ni-S sulfide melts, we also derived an empirical correction that allows SCSS calculation for basalts where the equilibrium sulfides contain variable Ni contents of 10–50 wt.%. At the pressures and temperatures of multiple saturation points, SCSS of lunar magmas with compositions from picritic glasses, mare basalts, to young lunar meteorites vary from 2600 to 4800 ppm for basalt equilibration with a pure FeS melt and from 1400 to 2600 ppm for basalt equilibration with a Fe-rich sulfide melt containing 30 wt.% Ni. The measured S contents in these proposed near-primary lunar magmas are lower than the predicted SCSS at the conditions of their last equilibration with the lunar mantle, indicating no sulfide retention in the lunar mantle source during partial melting. Sulfide exhaustion during partial melting in the lunar mantle also supports the notion that the bulk silicate moon is depleted in highly siderophile elements. Based on the measured S contents and the estimated degree of melting, the estimated S contents for the mantle source of A15 green glass and A15 mare basalts is 10–23 ppm; for A17 orange glass is 25–62 ppm, for A12 mare basalts is 27–92 ppm, and for A11 basalt is 35–120 ppm. Consideration of SCSS decrease due to the presence of Ni in the sulfide melt does not change these mantle S abundance estimates for <30 wt.% Ni in the sulfide. The inferred S contents suggest that the lunar mantle is heterogeneous in terms of S. Although variable among different groups, the inferred S abundance of up to 120 ppm in the lunar mantle falls near the lower end of the S content of the depleted terrestrial mantle such as the MORB source.