Iron Sulfide Compounds Research Articles

Interaction Study of Oxygen and Iron-Sulfur Clusters Based on the Density Functional Theory

For the petrochemical industry, the spontaneous burning of iron sulfide compounds has been a major issue. In this study, XRD characterization of samples of iron sulfide compounds with spontaneous combustion tendency revealed that amorphous FeS was the primary constituent of the samples. A molecular simulation was used to build an amorphous FeS cluster model, and the density functional theory was used to examine the adsorption and reactivity characteristics of Fe4S4 clusters with O2. Different adsorption structures are generated by considering different adsorption sites and the electronic characteristics of each adsorption structure are evaluated. The results show that O2 prefers to adsorb around Fe atoms and has repulsion with S atoms, and the adsorption energy is maximum when two O atoms are co-adsorbed around Fe atoms, which is 198.13 kJ/mol. After adsorption charge, oxygen is in the superoxide state. The calculation of the reaction path divides the reaction process into different stages and considers different reaction routes. A thorough evaluation of the energy barriers and reaction energies of the two exothermic reactions leads to the conclusion that reaction path 1 is the optimal reaction path, and the reaction can release a total of 582.76 kJ/mol of heat. According to calculations, dimeric sulfur S2 must absorb a large part amount of energy in order to conduct the oxidation process. However, because S2 is present in the Fe4S4 reaction system, it may start the oxidation reaction by absorbing heat from the system and releasing 470.94 kJ/mol of heat. As a result, we conclude that this spontaneous exothermic reaction is a major cause of iron sulfide compounds spontaneous combustion. The thermal oxidation of the dimeric sulfur S2 generated in the reaction system releases heat that aggregates with the heat from the Fe4S4 cluster’s oxidation reaction system, eventually causing spontaneous combustion as a result of the heat’s continual buildup. In this study, we explore the reason for the extremely easy oxidation and spontaneous burning of iron sulfide compounds from a microscopic perspective to provide a theoretical foundation for the prevention and control of iron sulfide compound spontaneous combustion in the petrochemical sector.

Coal-based sulfur hybrid sorbent for removal of Hg0 from flue gas. Part 1. High inorganic sulfur coal

A novel sulfur hybrid mercury sorbent was successfully prepared by chemically activating high inorganic sulfur coal using potassium hydroxide (KOH). The optimal conditions for preparing the sorbent are at 800 °C with the ratio of KOH/coal at 2:4 by mass. The prepared sorbent, named ZY-2:4-800, containing 0.92% sulfur with a high specific surface area of 353 m2·g−1, has a wide temperature range for mercury removal. Between 60 and 180 °C, the Hg0 removal efficiencies of this sorbent keep above 95% within 2 hr under N2+O2+NO+SO2+H2O. This is because that O2 can slightly improve the mercury removal ability of the sorbent, and it shows great resistance to acid gas (NO and SO2) and H2O. The calculated Hg0 adsorption capacity of ZY-2:4-800 is 214.7 μg·g−1, which is much higher than that of activated carbon sorbent (ACs) reported in the literature. Based on XPS and Hg-TPDD analysis, it is revealed that the iron sulfide compounds in coal can be converted into active sites as S0, S22–, and C-S during the preparation of the sorbents, and Hg interacts with these active sites and forms β-HgS (metacinnabar). The excellent mercury removal performance and the low cost indicate that the as-prepared sorbent from the blend of the high inorganic-sulfur coal and KOH is a promising sorbent for mercury removal from flue gas. It is expected that this method could be applicable in converting other high-inorganic sulfur coals into efficient mercury sorbents.

The effect of natural inhibitor concentration of Fumaria officinalis and temperature on corrosion protection mechanism in API X80 pipeline steel in 1 M H2SO4 solution

In this investigation, the effect of Fumaria officinalis concentration, as a natural inhibitor, and the medium temperature on the corrosion prevention mechanism of an API X80 pipeline steel alloy in the solution of 1 M H2SO4 is studied. For this purpose, corrosion behavior of the pipeline steel in the solution of 1 M H2SO4 at the presence of 0, 2, 4 and 6 g/L Fumaria officinalis inhibitor at medium temperatures of 20 °C, 40 °C and 60 °C was assessed. To assess the corrosion protection mechanism of the API X80 pipeline steel under these conditions, Open Circuit Potential (OCP), Potentiodynamic Polarization and Electrochemical Impedance Spectroscopy (EIS) tests were conducted. As well, Scanning Electron Microscopy (SEM) equipped with Energy Dispersive Spectroscopy (EDS) detector was used to analyze the corrosion products formed on the surface of the pipeline specimens. Results of OCP and potentiodynamic polarization tests showed that Fumaria officinalis reduces the speed of both anodic and cathodic reactions. Also, ΔGads0calculation showed that Fumaria officinalis led to the reduction of anodic and cathodic reactions through its physical-chemical adsorption on the surface and blocking of corrosion active locations. The results of EIS tests indicated that with increasing the Fumaria officinalis inhibitor, the corrosion resistance of the API X80 pipeline steel increased. As well, corrosion products analysis showed that Iron sulfide compounds were formed on the surface of the specimens. In terms of the medium temperature, results showed that increasing the temperature of the solution from 20 °C to 60 °C has led to an increased corrosion rate and efficiency reduction of Fumaria officinalis. Moreover, it was defined that the adsorption process of Fumaria officinalis on the surface of the API X80 pipeline steel at the temperature of 40°Cin the 1 M H2SO4 solution followed adsorption isotherm of Langmuir.

Speciation of iron sulfide compounds by means of X-ray Emission Spectroscopy using a compact full-cylinder von Hamos spectrometer.

We present experimental and theoretical X-ray emission spectroscopy (XES) data of the Fe Kβ line for Iron(II)sulfide (FeS) and Iron(II)disulfide (FeS2). In comparison to X-ray absorption spectroscopy (XAS), XES offers different discrimination capabilities for chemical speciation, depending on the valence states of the compounds probed and, more importantly in view of a a broader, laboratory-based use, a larger flexibility with respect to the excitation source used. The experimental Fe Kβ XES data was measured using polychromatic X-ray radiation and a compact full-cylinder von Hamos spectrometer while the calculations were realized using the OCEAN code. The von Hamos spectrometer used is characterized by an energy window of up to 700 eV and a spectral resolving power of E/ΔE = 800. The large energy window at a single position of the spectrometer components is made profit of to circumvent the instrumental sensitivity of wavelength-dispersive spectrometers to sample positioning. This results in a robust energy scale which is used to compare experimental data with ab initio valence-to-core calculations, which are carried out using the ocean package. To validate the reliability of the ocean package for the two sample systems, near edge X-ray absorption fine structure measurements of the Fe K absorption edge are compared to theory using the same input parameters as in the case of the X-ray emission calculations. Based on the example of iron sulfide compounds, the combination of XES experiments and ocean calculations allows unravelling the electronic structure of different transition metal sulfides and qualifying XES investigations for the speciation of different compounds.

Study on Friction Behavior of Ferroalloy and Wet Granulation Sulfur under Low Normal Load Conditions

To study the friction behavior of ferroalloy and wet granulation sulfur under low normal load conditions, a series of experiments were performed using a homemade rotating test apparatus. Scanning electron microscopy with an energy dispersive spectrometer (SEM-EDS) and X-ray diffraction (XRD) were utilized to examine the friction products. The experimentally monitored friction coefficient data were used to develop a finite element model to simulate the temperature field and a theoretical model to calculate the flash temperature of the contact area of the friction surface. The experimental, simulation, and theoretical results showed that the flash temperature of the friction surface is much higher than the average temperature of the friction surface and allows the reaction of iron and sulfur to form iron–sulfide compounds.

Growth-promoting effects of the hydrogen-sulfide compounds produced by Desulfovibrio desulfuricans subsp. desulfuricans co-cultured with Escherichia coli (DH5α) on the growth of Entamoeba and Endolimax species isolates from swine.

Certain Desulfovibrio sp. (anaerobic sulfate-reducing bacteria) are indigenous to swine cecum and colon, which are also common habitats for parasitic amoebae such as Entamoeba polecki and Entamoeba suis. In this study, we evaluated the growth-promoting effects of D. desulfuricans co-cultured with Escherichia coli (DH5α) and its products [e.g., hydrogen sulfide (H2S) and certain iron-sulfide (FeS) compounds] using Robinson's medium, on the 4 amoeba isolates from swine-Entamoeba polecki subtype (ST)-1, E. polecki ST-3, Entamoeba suis, and Endolimax sp., and, consequently, a continuous culture system for these amoebae was established. However, this novel culture system was required to regulate the excess H2S dissolved in the medium by increasing air space as amoeba isolates thrive only in large air spaces (30-40%). The effects of air space and H2S and FeS compounds on the growth of E. polecki ST-1 (TDP-5) were determined. E. polecki ST-1 (TDP-5) thrived well in culture bottles with an air space of 30-40% (aerobic) (H2S: ~250-400 μmoles/L), but did not grow at all in an air space < 5% (microaerobic) ( H2S:~800 μmoles/L) and in anaerobic vessels (H2S: 20-30 μmoles/L). In both H2S-depleted and FeS compound-depleted conditions, the amoebae sp. could not thrive either. It was hypothesized that an appropriate concentration of H2S and FeS compounds might function as important physiologically active components of electron carriers such as FeS and ferredoxin.

Tribological property study of mercaptobenzothiazole‐containing borate derivatives and its synergistic antioxidative effects with N‐phenyl‐α‐naphthylamine

AbstractThe synthesised mercaptobenzothiazole‐containing borate ester (MTEB) and mercaptobenzothiazole‐containing borate (MTES) have good tribological performances in rapeseed oil (RSO). At 0.5 wt% concentration, MTEB and MTES can increase the extreme pressure value of RSO by 60.7% and 67.6%, respectively. The wear scar diameters (WSDs) of oil samples decrease with increase of MTEB (MTES) contents, and the antiwear effect of MTES is better than MTEB at the same condition, because of their polarity is different. There are similar results in the friction reduction performance. The X‐ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) analysis results have shown that MTEB and MTES can form protective films on the metal surfaces that contain boron oxide, iron oxide, ferrous sulfate, iron sulfide (MTEB additive), and other organic nitrogen compounds. The different reaction films formed in the complex boundary possess extreme pressure and antiwear capability. MTES possessed good synergistic antioxidation effect with N‐phenyl‐α‐ naphthylamine (T531), because it increased the oxidation activation energy than RSO by 97.13% when 0.025 wt% MTES is mixed with 0.25% T531.

The effect of temperature, CO2, H2S gases and the resultant iron carbonate and iron sulfide compounds on the sour corrosion behaviour of ASTM A-106 steel for pipeline transportation

In this investigation, extracted products corrosion behaviour of sour environment in oil and gas industry was studied. Of the important aspects of these products is the presence of significant amounts of CO2 and H2S in the solution of the sour products. The corrosion mechanism could also be involved during the extraction, transportation and purification of the sour products. Therefore, the corrosion behaviour of ASTM A-106 Grade A carbon steel, used for the transportation of oil and gas, in the presence of H2S and CO2 and at different temperatures, was studied by potentiodynamic polarization, electrochemical impedance spectroscopy techniques, and Scanning Electron Microscope (SEM) equipped with Electron Dispersive Spectroscope (EDS). Corrosion tests were conducted on the alloy in solutions with 3 wt% NaCl saturated with CO2 gas in the presence/absence of 200 ppm H2S gas at temperatures of 25 °C, 45 °C, 65 °C, 85 °C. Results showed that increasing the temperature of the solution substantially increased the corrosion rate of the steel under investigation. As well, the presence of both gases of CO2 and H2S enhanced the corrosion rate. EDS results also showed that iron carbonate and iron sulfide compounds do not have sufficient stability at high temperatures to protect the metal surface against corroding agents. And they could not form a uniform coating on the steel surface.

Oxidation of iron sulfide and surface-bound iron to regenerate granular ferric hydroxide for in-situ hydrogen sulfide control by persulfate, chlorine and peroxide

Hydrogen sulfide emission from sediments in storm drainage networks, estuaries and marine seafloor is a nuisance. The regeneration of the GFH for reuse is crucial to make dosing granular ferric hydroxide (GFH) an effective, long-lasting solution than doing liquid oxidants to the control of sedimentary hydrogen sulfide. This paper investigated the oxidation of iron sulfide and surface-bound iron compounds to regenerate GHF using persulfate, chlorine and peroxide for the in-situ control of hydrogen sulfide. The hydrogen sulfide removal capacities of virgin, persulfate-, chlorine- and peroxide-regenerated GFH were 68.34, 77.49, 67.87 and 57.59 mg S/g, respectively. The recovery of the capacities was mainly attributed to the oxidation of iron sulfide, surface-bound Fe(II) and released Fe2+ to amorphous ferric hydroxides. Iron sulfide was mainly oxidized to sulfate (SO42−) (97.8%) by persulfate, and to elemental sulfur (S(0)) (5.8 and 25%), thiosulfate (S2O32−) (27.7 and 11.3%) and SO42− (66.5 and 63.7%) by chlorine and peroxide, respectively. In addition to the oxidation by persulfate, the reaction between persulfate and the surface Fe(II) compounds also generated sulfate radicals and hydroxyl radicals, which enhanced the oxidation of the iron sulfide and surface-bound iron compounds on the GFH surface and regenerated GFH more completely.

Experimental study on ignition mechanisms of wet granulation sulfur caused by friction

It is common to see fire accidents caused by friction during the storage and transportation of wet granulation sulfur. To study the sulfur ignition mechanism under friction conditions, a new rotating test apparatus is developed to reproduce friction scenes at lab scale. A series of experiments are performed under different normal loads. The SEM-EDS and the XRD were utilized to examine the morphologies and compositions of the tested specimens and the friction products. Experimental results show that these two methods are mostly in agreement with each other. The iron-sulfide compounds are produced and the proportion of iron-sulfide compounds is reduced with normal loads increasing, compared to the total number of the friction products. The facts implied by the integration analysis of friction products with the temperature changes of the near friction surface unveil an underlying mechanism that may explain sulfur ignition by friction in real scenarios. The sulfur ignition may be mainly caused by the spontaneous combustion of iron sulfide compounds produced by friction under low normal load with 200N. With the increase of normal loads, the resulting iron-sulfide compounds are decreasing and the high temperature from friction heat begins to play a major role in causing fire.

Analysis of the chemical or bacterial origin of iron sulfides on steel by time of flight secondary ion mass spectrometry (ToF-SIMS)

We report here on ToF-SIMS measurements of the 34S/32S isotopic ratio on three different iron sulfide compounds, a Pyrite substrate, a troilite layer prepared by thermal sulfidation of iron in H2S gas, and an iron sulfide prepared by interaction of a steel sample with a medium containing Sulfate-Reducing Bacteria (SRB). The measurements performed on the three kinds of surfaces show that ToF-SIMS is perfectly suitable, after fine tuning of its performance, to distinguish the origin (chemical or bacterial) of the sulfide formed on Fe based substrates from the measurement of the 34S/32S intensity ratio. This opens the way to quick and clear determination of the origin of sulfide degradation in many industrial areas.

Electrochemical characteristics of the early corrosion stages of API X52 steel exposed to H2S environments

Electrochemical impedance spectroscopy (EIS) and polarization curve techniques were used to study the early stages of hydrogen sulfide (H2S) corrosion. Results revealed the formation of different iron sulfide compounds during the early stages of corrosion. Meanwhile, Warburg impedance characteristics were determined through EIS. Numerous flake-like mackinawites were observed after 15 h. The diffusion-controlled mechanism gradually disappeared during the process. After immersion for 15 h to 7 d in aqueous H2S, the flake-like mackinawites grew larger and adhered, which increased the thickness of corrosion product films. The EIS and polarization curve tests proved that the increase in thickness of corrosion product films enhances corrosion resistance.

Formation mechanisms of pyrite (FeS2) nano-crystals synthesized by colloidal route in sulfur abundant environment

Pyrite (FeS2) nano-crystals (NCs) were synthesized in an excess sulfur environment using a colloidal hot-injection method, and the phase change behavior of the iron sulfide compounds was investigated. As the growth time increased, the phase of the iron sulfide NCs transformed from mackinawite (FeS) via greigite (Fe3S4) to pyrite (FeS2). Thus, Fe3S4 phases was considered as intermediate precursors on the pathway of FeS2 phases in the reaction between FeS phases and excess sulfur. The elemental ratio of [S/Fe] increased from 1.1 to 2.1 during the phase change, and the shape of the NCs changed from a hexagonal nano-sheet (Fe3S4), via cubic (FeS2), to a cubic-hedral structure (FeS2). Strong absorption peaks in the UV–Vis spectra were observed in the FeS2 phase, and its optical band gap was estimated to be ∼0.9 eV, indicating the semiconducting nature of pyrite. Consequently, the synthesis of FeS2 in sulfur abundant environment was suitable method to acquire a pure semiconducting FeS2 phases. The reason was thought that the depletion of Fe-element after the formation of FeS2 phases led to the decrease of intermediate phases and the gradual changes from intermediate phases to FeS2 resulted in pure phases.

Impact of Oyster Farming on Diagenetic Processes and the Phosphorus Cycle in Two Estuaries (Brittany, France)

This study aims to compare the impact of oyster cultures on diagenetic processes and the phosphorus cycle in the sediments of the Aber Benoît and the Rivière d’Auray, estuary of Brittany, France. Our results showed clear evidence of the seasonal impact of oyster cultures on sediment characteristics (grain size and organic matter parameters) and the phosphorus cycle, especially in the Aber Benoît. At this site, seasonal variations in sulfide and Fe concentrations in pore waters, as well as Fe–P concentrations in the solid phase, highlighted a shift from a system governed by iron reduction (Reference) to a system governed by sulfate reduction (beneath oyster). This could be partly explained by the increase in labile organic matter (i.e., biodeposits) beneath oysters, whose mineralization by sulfate led to high sulfide concentrations in pore waters (up to 4,475 µmol l−1). In turn, sulfide caused an enhanced release of phosphate in the summer, as adsorption sites for phosphate decreased through the formation of iron–sulfide compounds (FeS and FeS2). In the Aber Benoît, dissolved Fe/PO4 ratios could be used as an indicator of phosphate release into oxic water. Low Fe/PO4 ratios in the summer indicated higher effluxes of phosphate toward the water column (up to 47 µmol m−2 h−1). At other periods, Fe/PO4 ratios higher than 2 mol/mol indicated very low phosphate fluxes. In contrast, in the Rivière d’Auray, the occurrence of macroalgae, stranding regularly all over the site, clearly masked the impact of oyster cultures on sediment properties and the phosphorus cycle and made the use of Fe/PO4 ratios more difficult in terms of indicators of phosphate release.

Microscopic characteristic of biological iron sulfide composites during the generation process and the association with treatment effect on heavy metal wastewater

Heavy metal pollution is a serious environmental concern worldwide, resulting in both environmental and human harm. Recently, studies have shown that environmental biotechnologies based on sulfate reduction offer a potential for removal of toxic heavy metals. Biological iron sulfide composites are iron sulfide compounds generated in situ by sulfate-reducing bacteria. In this study, microscopic morphological changes during the composites' generation process were studied, and the effect of biological iron sulfide composites in different generation phases on treatment of heavy metal wastewater was investigated to establish the correlation between macro-effect and micro-properties. The results revealed that the generation process of biological iron sulfide composites occurs in three phases: the formation phase, stationary phase, and agglomeration phase. The stationary phase can be divided into a pre-stationary phase and post-stationary phase. It was found that the best treatment time for Cr(6+) is in the pre-stationary phase, while the best treatment time for Cu(2+)and Cd(2+) is in the post-stationary phase. The results of this study further prove the benefits of treatment of heavy metal wastewater using biological sulfide composites and provide theoretical guidance in practical applications.

Intrinsic Peroxidase Catalytic Activity of Fe7 S8 Nanowires Templated from [Fe16 S20 ]/Diethylenetriamine Hybrid Nanowires.

Iron sulfide compounds are emerging as an important family of functional materials owing to their important properties and their applications in different technical fields. Well-defined Fe7 S8 nanowires templated by thermal decomposition of [Fe16 S20 ]/diethylenetriamine hybrid nanowires under an argon atmosphere are reported. As-prepared Fe7 S8 nanowires show typical Michaelis-Menten kinetics and good affinity to both H2 O2 and 3,3',5,5'-tetramethylbenzidine. At pH 7.0, the constructed UV/Vis sensor showed a linear range for the detection of H2 O2 from 0.5 to 150 μM with a correlation coefficient of 0.9998. The H2 O2 sensor based on the Fe7 S8 nanowires shows a highly sensitive response and has better stability than horseradish peroxidase when exposed to solutions with different pH values and temperatures. These excellent properties make the as-prepared Fe7 S8 nanowires powerful tools for potential applications as an "artificial peroxidase" in biosensors and biotechnology.

Effects of sulfate amendments on mineralization and phosphorus release from South Florida (USA) wetland soils under anaerobic conditions

Abstract We investigated the potential effects of elevated water-column sulfate (SO 4 ) levels on heterotrophic microbial respiration and net phosphorus (P) release for soils collected from impacted and unimpacted Everglades wetlands in south Florida. Soils from three sites, ranging from low P and low SO 4 to high P and high SO 4 environments, were examined under controlled laboratory conditions. The soils were subjected to anaerobic incubations to evaluate net P release and organic matter decomposition in response to SO 4 amendments of 32 or 96 mg l −1 (0.33 and 1.0 mM). Three processes have been described in the literature to explain why SO 4 enrichment may lead to P release from soils under anaerobic conditions. First, alkalinization can lead to a more favorable pH environment for decomposition. For the soils examined here, alkalinization due to the hydrogen ion-consuming reaction of SO 4 reduction was not a prominent mechanism. We found that pH decreased in the incubation vessels, and that increases in alkalinity were more likely attributable to calcium carbonate dissolution than SO 4 reduction. Moreover, all the soils exhibited near circum-neutral pH levels, with moderate to high concentrations of native alkalinity. Second, formation of iron sulfide (FeS x ) compounds has been shown to mobilize iron (Fe)-associated P. Soils from only one of the study sites had Fe concentrations that would be expected to be high enough to influence P mobility. Relatively high porewater Fe:soluble reactive P (SRP) ratios (>83:1) were observed at this site, which suggests that Fe could theoretically exert control over the release of P from the soil. However, soil P levels at this site were too low to measure any substantial influence of Fe on net P mobilization. Finally, availability of electron acceptors such as SO 4 is a major determinant of decomposition rate, and thus rate of organic P release. Amending the soils with SO 4 did not result in either more heterotrophic microbial respiration as measured by carbon dioxide (CO 2 ) and methane (CH 4 ) production, or increased net P mobilization. In two of the SO 4 -amended soils where post-incubation total sulfide concentrations were as high as 23.4 mg l −1 , SO 4 addition reduced production of respiratory carbon end products, suggesting hydrogen sulfide inhibition. Moreover, limitations imposed by substrate quality and low P contributed to the lack of meaningful enhanced decomposition of organic matter with the addition of 32 or 96 mg SO 4 l −1 to the oligotrophic wetland soils. Even though P release did occur under anaerobic conditions for the more enriched site, addition of SO 4 did not enhance P release.

Electrolytic iron sulfides in prototype lithium batteries with gel electrolytes based on poly(vinyliden fluoride) and its derivatives

Electrolytic thin-film iron sulfide compounds were studied in prototype lithium batteries with gel electrolytes based on poly(vinyliden fluoride) and its derivatives by the method of galvanostatic cycling at room temperature. A discharge capacity of 200–280 mA h g−1 in 80–180 cycles was obtained.

Soil solution sulfide control by two iron-oxide minerals in a submerged microcosm

Under reduced conditions, commonly experienced at the bottom of aquaculture ponds, sulfate is reduced to sulfide. Sulfide in the form ‘H 2S’ is highly toxic to aquatic organisms. Iron oxides have the capacity to regulate the formation of sulfide by poising the redox sequence and to form insoluble iron sulfide compounds, further decreasing the activity of sulfides in solution. Ferrihydrite, a poorly crystallized, high surface area hydrous iron oxide, and hematite, a highly crystallized, low surface iron oxide, were separately added to a synthetic soil composed of bentonite, kaolinite, and quartz sand in a microcosm study. Bermuda grass was added to the soil as an organic matter source to induce reducing conditions. The soils were flooded with artificial seawater diluted to salinity levels of 1, 14, and 34 ppt. Concentration solutions of total dissolved sulfide and iron in interstitial; and of oxygen and pH in the water column were measured 25, 46 and 72 days after flooding the soil. Concentrations of sulfide in treatments with hematite and ferrihydrite were significantly lower than those of treatments without iron oxides. On all sampling dates, ferrihydrite was up to eight times more effective than hematite in regulating the accumulation of sulfides in solutions with salinity levels of 14 and 34 ppt. Mean dissolved-oxygen concentrations in treatments with ferrihydrite were higher than those of treatments with hematite. At the intermediate salinity level, adding either hematite or ferrihydrite at rates higher than 4 g kg −1 did not significantly improve the effectiveness of sulfide removal from solution. At the highest salinity level, increasing the concentration of hematite from 4 to 13 g kg −1 may have some practical merit, while higher rates may not be justifiable. There appears to be no advantage in applying ferrihydrite at rates higher than 4 g kg −1 at the highest salinity level.

Electrolytic Iron Sulfide Products in Lithium Batteries

A technology for electrolytic production of iron sulfide compounds applicable in thin-layer lithium batteries is developed. Physicochemical and structural properties and the surface morphology of compounds are studied by x-ray diffraction and thermal analyses, absorption IR spectroscopy, and atomic force microscopy. Specific discharge characteristics of compounds in thin-layer compact nonballast and paste electrodes of model lithium power sources are determined. The discharge capacity of compounds in thin layers weighing 1.0–7.5 mg cm–2 galvanostatically cycled in electrolyte PC, DME, 1 M LiClO4 at room temperature stays at 200–320 mA h g–1 for 40–50 cycles.