Sulfide Complex Research Articles

In Situ Observation of Precipitation Behavior of MnS during Solidification of Steel Melt Intended for Production of Nonquenched and Tempered Steel

Two heats of steel are melted using a vacuum induction furnace in the laboratory, with one heat undergoing magnesium treatment and the other being subjected to a combined magnesium–calcium treatment. The precipitation and agglomeration behaviors of inclusions of these two steel samples are observed using a high‐temperature confocal laser scanning microscopy. MnS precipitates form around oxide cores and undergo rapid growth during the solidification process of molten steel, and these MnS precipitates with oxide cores react with the cores, resulting in the transformation of the MnS into complex sulfides. In comparison with Al2O3 inclusions, MgO·Al2O3 inclusions have a lower critical velocity (V c), making them more susceptible to being engulfed by the solid–liquid interface. As the size of colliding inclusions increases, the coalescence–collision frequency (E 0) initially decreases until it reaches a minimum value. After that, with further size increments, the frequency starts to increase. During the inclusions growth process through collision, there is a distinct zone where coalescence–collision frequency is low. Inclusions that reach this zone struggle to grow further due to reduced collision coalescence, consequently leading to a predominance of inclusions with diameters in this zone.

Combined effect of magmatic fluid–seawater mixing and host rock alteration on the formation of gold-enriched massive sulfides in the Forecast vent field, southern Mariana Trough

Massive sulfides and sulfide-bearing breccia were collected from the Forecast vent field in the southern Mariana Trough. These samples exhibit varying degrees of hydrothermal alteration and/or mineralization, with the former type having significant enrichments in Au (up to 101 ppm). In this study, detailed analyses of mineralogy, geochemistry, S isotope, and fluid inclusion were conducted to understand the unusual Au-rich mineralization. Mineralogical investigations and geochemical analyses (LA–ICP–MS and EPMA) of dominant sulfide minerals indicate that electrums, the main phase of Au mineralization, are characterized by two different generations based on mineralogical relationships and fineness. Early-stage high fineness electrums (930–981 ‰) are associated with sphalerite under relatively high-temperature fluid conditions, whereas galena is main host mineral related to late-stage low fineness electrums (773–868 ‰). Sphalerite geothermometry (231–264 °C), the occurrence of colloform textured sulfides, and microthermometric characteristics of fluid inclusions (Th = 220–304 °C; Salinity = 1.4–6.6 wt% NaCl equivalent; a general trend of decreasing salinity with decreasing Th) indicate that significant decreases in H2S activity, attributed to seawater dilution and rapid precipitation of sulfide minerals, facilitated the efficient destabilization and deposition of Au transported as sulfide complexes from hydrothermal fluids. In particular, the lower 34S values (+0.2 ‰ to + 1.3 ‰) of sulfides compared to those of arc/back-arc lavas (δ34S = +5‰ to + 11 ‰), along with the prevalence of CO2 in the vapor phase of fluid inclusions, reflect that the significant contribution of magmatic volatile influx supplied most of the sulfur and metals (including Au) to the Forecast hydrothermal fluids. Additionally, the abundance of montmorillonite and varying proportions of sulfide and gangue minerals observed in hydrothermal samples suggest that the chemical buffering of fluids by associated substrates and/or sediments could be another significant factor in promoting Au-rich mineralization. Therefore we conclude that the combination of magmatic fluid–seawater mixing and host rock alteration plays an important role in the formation of Au-enriched massive sulfides in the Forecast vent field.

Development of an alternative method to quantify H2S: application in wine fermentation.

A colorimetric method for the quantification of hydrogen sulfide (H₂S) produced in microbial fermentations was developed using lead gelled alginate microparticles packed in glass columns. The formation of a lead sulfide complex, between H₂S and lead ion (Pb2+) immobilized on the microparticles, allowed simple and accurate quantification by colorimetry. The microparticle-loaded columns were calibrated and showed significant analytical sensitivity. The calibration curve of the system showed a correlation coefficient (r2) of 0.995 and a detection limit of 1.29 ± 0.02 μg L-1. The application of the columns in laboratory wine fermentations was able to detect variations in H2S production from 10.6 to 23.5 μg L-1 by increasing the sugar content in the medium, and from 10.6 to 3.2 μg L-1 with decreasing nitrogen content in the medium. Validation of the proposed method was carried out by determining H₂S in a vinic fermentation model, the results of which were compared with those obtained using a reference chemical method. The data obtained showed no statistically significant differences between the two methods, confirming the reliability and accuracy of the developed system. © 2024 Society of Chemical Industry.

Gold in sulfide fluids revisited

Gold solubility was measured at temperatures of 350, 400, 450, and 490 °C and pressures of 500 and 1000 bar in an ’oxidized sulfide’ system, as a function of pHT (2 – 10) and sulfur concentration (m(Stotal) = 0.03 – 1.2 [mol·(kg H2O)-1]). In this system, sulfur primarily exists as H2S, H2SO3, H2SO4, their dissociation products, and radical species such as S2- and S3-. The complexes Au(HS)2-, Au2S22-, AuHS(aq), AuHS(H2S)3(aq), and AuOH(aq) were identified as the primary gold species in the experimental fluids, varying with pH and m(Stotal). The solubility constants for Au(HS)2-, a critical (hydro)sulfide complex, align excellently with literature for ’reduced sulfide’ fluids, where sulfur predominantly exists in the 2- oxidation state. New experimental data from the ’oxidized sulfide’ system were regressed along with reliable literature data from ’reduced sulfide’ systems to calculate standard thermodynamic properties and parameters of the Helgeson-Kirkham-Flowers (HKF) model. The solubility constants for charged complexes, Au(HS)2- and Au2S22-, increase sharply with temperature, whereas those for neutral species, AuHS(aq) and AuHS(H2S)3(aq), show a pronounced peak near 300 °C. These (hydro)sulfide complexes account for gold solubility ranging from a few tens of ppb to a few tens of ppm in natural sulfide fluids, depending on the fluid pH. Thermodynamic calculations also indicate that, in addition to (hydro)sulfide species and the hydroxide complex, AuCl2- significantly contributes to Au mobility in high-temperature acidic chloride fluids. Based on new experimental data and prior studies using solubility and X-ray absorption spectroscopy methods, other gold complexes including mixed Au-HS-Cl, Au-HS-S3- species, and complexes with alkali metal cations, are deemed redundant. Above 250 °C, the influence of chloride salts on gold solubility can be accurately modeled using a simple extended Debye-Hückel equation with the term bγ·I = 0. The Setchenov coefficient bn = 0 suffices for calculating the activity coefficients of neutral species. This streamlined thermodynamic model aligns closely with earlier experimental work by Terry Seward and his team, effectively describing the state of Au in all types of natural fluids where Au exists in the 1+ oxidation state, under any set of P-T-f(O2)-f(S2)-compositional parameters.

The anatomy, micromorphology, and essential oils of the Turkish endemic and endangered species Alchemilla orduensis

In this study, the anatomical and micromorphological characteristics of the vegetative organs and the essential oil constituents of the aerial and underground parts of the local and endangered endemic species A. orduensis Pawł. were evaluated. For anatomical study, sections of root, rhizome, stem, leaves and petiole were excised and stained with safranin/fast green mixture. Leaf and petiole structures were examined micromorphologically. Essential oil contents were determined by headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry (HS-SPME/GC-MS) analysis. The results showed that rectangular meristematic cells were present in the root. The leaf is of the bifacial and amphistomatic type. Stomata cells are of the anomocytic type. The stomatal index for the upper surface of the leaves is 0.04, while the stomatal index for the lower surface is 0.17. Druse crystals were found in the rhizome, stem and leaves. Among the various compounds identified, the most abundant groups in the aboveground parts are alcohols (39.81%) and ketones (14.99%) with 1-Octen-3-ol, 1-octan-3-one and borane- methyl sulfide complex as the main compounds. Terpenes (23.44%) and alcohols (11.82%), in which myrtenolis was the main compound, were most abundant in the underground parts.

Enhancing flotation beneficiation efficiency of complex ores using ionometry methods

Flotation beneficiation plays a leading role in the processing most ores. The efficiency of this process is ensured by the correct selection of operating modes, which involves choosing the most selective reagents and determining their optimal consumption. Despite the significance of this issue, the classic approach to determining beneficiation parameters involves testing followed by the processing of the results obtained and the determination of the reagent consumption. However, such studies do not reveal the essence of the physicochemical processes occurring within the pulp, and the results of testing one sample may not correspond to the optimum when the properties of the sample change.The purpose of this work is to develop and implement a methodological approach to the study of ore flotation beneficiation using ionometry methods. The data obtained from ion-selective sensors significantly deepen our insight into the transformations occurring during the flotation process and allow for consideration of possible adverse factors that hinder effective process progression.To achieve this goal, a comparative analysis of two approaches to flotation beneficiation testing was performed using complex sulfide ores as examples. In the first stage, a flotation beneficiation study was conducted through D-optimal factor testing, which included 20 individual tests to determine the optimal consumption of modifying reagents, yielding qualitative indicators. In the second stage, flotation tests were conducted using electrochemical monitoring with pH, Ag2S, Pt, and membrane electrodes. A universal flowchart for flotation studies with ion-selective sensors has been developed, facilitating the application of this approach to various ores. The implementation of the results from this comparative analysis has led to a 7.8% increase in beneficiation efficiency while reducing reagent consumption. Additionally, the insights gained into the electrochemical processes occurring allowed for assumptions about the adverse factors affecting flotation outcomes. In conclusion, a model for the potential application of this approach at existing enterprises was proposed, including the implementation of an “intelligent assistant” for flotation operators based on the developed electrochemical models.

Characteristics of epithermal gold-base metals prospect in the Anggai block, northern Obi Island, Indonesia

The Obi island, located in the North Moluccas Au-Ag-Cu province, hosts several mineral prospects, one of which is gold-base metals in the Anggai block. Several companies have historically explored the area since the end of the 1900s. The ore bodies are white to smoky and brownish-white, banded, laminated, colloform, crustiform, and massive quartz vein structures or textures, trending north northwest to south southeast. The ore bodies consist of gold and base metals hosted in the Bacan Formation and are enveloped by dominantly argillic alteration and the addition of silicic alteration. In this study, we provide several analyses, namely petrography, measurements using Portable Infrared Mineral Analyser (PIMA), Atomic Absorption Spectrometry (AAS), and fluid inclusion analysis, to understand geological and geochemical characteristics related to formation of gold-base metals in the Anggai block. Under the microscope, gold (i.e., electrum) is freely observed and closely occurs with argentite. While galena, chalcopyrite, sphalerite, covellite, chalcocite, and pyrite are mainly observed together. The correlation coefficient between Au and other metals shows a strong positive correlation with Zn (r = 0.810188) and a weak positive correlation with Ag (r = 0.459857). Ag shows only a weak positive correlation to Au, while the other elements show a strong positive correlation. In addition, Cu, Pb, and Zn show a strong positive correlation with each other. The micro-thermometry analysis of fluid inclusions shows two modes of homogenization temperature (Th) and salinity: 180-200 °C and 240-280 °C, and 1.4-1.6 and 1.9-2.2 wt% NaCl eq., respectively, suggesting overprinting evidence to enrich the ore bodies with occurrences of gold and base metals in the quartz veins. Gold-base metals were probably carried by the sulfide complex, which later precipitated during the cooling of the hydrothermal fluid.

Mineralized structures from the Alhué mining district, Chile: Using fluid inclusions and textures

The Alhué mining district (AMD) of the Coastal Range in Central Chile is situated approximately 70 km southwest of the city of Santiago and hosted in stratified Jurassic and Early Cretaceous sequences which are common in central Chile. More than 79 faults and veins are recognized in the AMD hosted in andesites and tuffs with clear structural control showing two distinct trends. Precious‐metal mineralization locally extends over strike lengths of up to 1000 m along these structures with grades averaging at 5 ppm gold and 23 ppm of silver. In this study, a University of Chile – YAMANA GOLD joint research project was created to better understand this particular deposit and explore the origin of gold anomalies found in the district using drill core, mine, and surface samples. Wide internal variations in homogenization temperature and electrolytes were observed at all scales: on the district scale, in mineralized structures intersected in drill core, and in hand specimens. This variability may reflect the diversity of ore-forming conditions in the mining district in addition to the different processes (including fault motion over time) and geochemical components within the district. Textural analyses and fluid inclusion assemblages (FIA) provide evidence for boiling and flashing mechanisms at several localities. Raman spectroscopy and LA-ICP-MS techniques allowed a better characterization of the fluid composition and mineral paragenesis. The presence of gold (∼3.8 ppm) and silver (∼1424 ppm) in both vapor-rich only FIAs (i.e. that contain 99 % vapor) hosted in quartz and liquid-rich FIA hosted in sphalerite implies that gold was transported as sulfide and chloride complexes. The AMD shows a transition from a high temperature environment (sometimes containing calc-silicate minerals) to a low temperature (epithermal) system. This mineralization depended on the type of vein system which tend to be mineralized in strike slip faults e.g. Maqui and Lorena structures. The consequence of flashing documented at dilational jogs, structural intersections and fault bends was likely an important outcome leading to the precipitation of metals at the AMD.Coexisting liquid-rich and vapor-rich fluid inclusions contained in a FIA were observed at the deepest levels in the Chilco vein and the proportion of samples showing boiling increases with depth, indicating that additional precious metal resources may be present below current exploration depths. In summary, our new results reveal that gold, silver and base metal veins found at the AMD in Chile are unique hydrothermal polymetallic ore deposits that are structurally controlled and related to an orogenic environment. A general model for the AMD is one where high temperature fluids from deep crustal mafic magmatic systems, probably as products of a devolatilization and far-from-equilibrium conditions, reach subsurface conditions along faults and are mineralized along these faults. Because having a truly unique ore deposit in the geologic record is very unlikely, the AMD forms an important case study that helps understand structurally controlled ore deposits. Thus our work can form a model for future exploration in the AMD and provide insight into exploration in other sites in Chile and along continental margin settings worldwide, in both poorly characterized known deposits and at greenfield sites.

Characteristics and Formation Mechanism of Oxide–Sulfide Complex Inclusions in High-Speed Railway Wheel Steel

Characteristics and Formation Mechanism of Oxide–Sulfide Complex Inclusions in High-Speed Railway Wheel Steel

A quantitative analysis method of complex sulfide components for understanding initial capacity degradation mechanism in lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries are a strong contender for the new-generation battery system to meet the growing energy demand due to their significantly high energy density (2600 Wh/kg) and cost-effectiveness. However, the practical operating conditions yield an initial capacity of less than 80 % of the theoretical capacity, resulting in a limited lifespan and hindering broader application. What's worse, current mechanism, especially the evolution process of sulfides for the initial capacity degradation is not clear due to the practical difficulties of effective separation and detection of sulfur-containing components. Herein, we have developed an instrumental analysis method enabling graded leaching and quantitative determination of sulfur-containing components. This technology achieves a detection precision surpassing 99.11 %, addressing the inherent deficiency in calculating sulfur-containing components using the decrement method. Applying this method reveals that the presence of lithium polysulfides in the electrolyte (26.34 wt%) after discharging is the primary factor causing insufficient capacity utilization in Li-S batteries. This work not only demonstrates the unique behavior of Li-S batteries at high sulfur loading but also provides a systematic evaluation method to guide further research on high-energy-density batteries, and provides theoretical and technical support to promote the development of high-energy, long-life Li-S batteries.

Tricoordinate Beryllium Radicals and Their Reactivity.

The one-electron reduction of [(CAAC)Be(Dur)Br] (CAAC = cyclic alkyl(amino)carbene, Dur = 2,3,5,6-tetramethylphenyl = duryl) with lithium sand in diethyl ether yields the first neutral, tricoordinate, and moderately stable beryllium radical, [(CAAC)(Et2O)BeDur]• (2-Et2O), which undergoes a facile second one-electron reduction concomitant with the insertion of the beryllium center into the endocyclic C-NCAAC bond and a cyclopropane-forming C-H bond activation of an adjacent methyl group. In situ generation of 2-Et2O and addition of PMe3 yield the stable analogue, [(CAAC)(Me3P)BeDur]• (2-PMe3), which serves as a platform for PMe3-ligand exchange with stronger donors, generating the radicals [(CAAC)LBeDur]• (2-L, L = isocyanides, pyridines, and N-heterocyclic carbenes). X-ray structural analyses show trigonal-planar beryllium centers and strong π backbonding from the metal to the CAAC ligand. The EPR signals of all six isolated [(CAAC)LBeDur]• radicals display significant, albeit small, hyperfine coupling to the 9Be nucleus. DFT calculations show that the spin density is mostly delocalized over the CAAC π framework and, where present, the isocyanide CN moiety, with only a small proportion (3-6%) on the beryllium center. 2-PMe3 proved thermally unstable at 80 °C, first undergoing radical hydrogen abstraction with the solvent, followed by insertion of beryllium into the endocyclic C-NCAAC bond and PMe3 transfer to the former carbene carbon atom. The reactions with diphenyl disulfide and phenyl azide occur at the beryllium center and yield the corresponding Be(II) phenyl sulfide and amino complexes, respectively, the latter concomitant with radical transfer and hydrogen abstraction by the beryllium-bound nitrogen center.

Polymer‐Derived Ceramic Coatings with Excellent Thermal Cycling Stability

In the present work, transition metal‐containing preceramic silicon polymers were synthesized via chemical modification of a commercially available organopolysilazane with Hf and Ta amido complexes as well as with borane dimethyl sulfide complex. The incorporation of transition metals into the polymer structure, their influence on ceramization and processability were thoroughly investigated. Moreover, the prepared preceramics were coated onto silicon wafers via spin coating and converted into crack‐free, amorphous SiHfTa(B)CN‐based ceramic coatings with excellent adhesion to the substrate. The composition of the ceramic coatings was investigated via X‐ray photoelectron spectroscopy (XPS) and their high‐temperature behavior was studied via oxidation tests performed at 1100 °C. Moreover, a thermal cycling procedure to temperatures above 1250 °C with rapid heating and cooling rates (i.e., in the range of 100–120 K s−1) was applied to the ceramic coating, which showed no damage even after ten thermal cycles, indicating their outstanding performance and their potential for use as environmental barrier coatings at high temperatures.

Fe-containing sphalerite as a co-catalyst for degradation of Congo red dye

Complex sulfide ores are associated with various sulfide minerals, characterized by their impurity content and physical defects. Sphalerite, a well known Zn-bearing mineral, consists of sulfides and inevitably contains various impurities. In this regard, minor metals in Zn concentrate complicate the flotation process or hydrometallurgical process. Nevertheless, the Fe-containing sphalerite is regarded as an efficient inorganic co-catalyst due to its surface properties with unsaturated S atoms and Fe atoms. Typically, the Fe(III) reduction determines the overall efficiency of the Fenton process, necessitating a stoichiometric excess of H2O2 and catalysts. To address the limitations of the Fenton process, this study proposes the use of Fe-containing sphalerite (ZnS) as co-catalysts to enhance the Fe(III)-H2O2 system. The redox reactions between ZnS and Fe(III) can efficiently decompose H2O2, which promotes the reaction between Fe(III) and Fe(II). Therefore, in this study, ZnS was evaluated as a co-catalyst to enhance the Fenton-like system for the degradation of Congo red (CR). The CR degradation was examined using different processes involving a single factor (ZnS, H2O2), dual factor (ZnS-H2O2, Fe(II)-H2O2, Fe(III)-H2O2), and triple factor (ZnS-Fe(III)-H2O2), to demonstrate co-catalyst effect. It was confirmed that both ZnS and Fe(III) were introduced into the system. Remarkably, 98.9% of ZnS-Fe(III)-H2O2 was degraded within 5 min, underscoring the effectiveness of ZnS as a co-catalyst in enhancing the activating of H2O2. When ZnS-Fe(III)-H2O2 system was used, CR degradation was affected by Fe(III) and H2O2 concentration, ZnS doses, and solution pH. During the reuse experiments, CR could be completely degraded, and Co-catalytic efficiency of ZnS was maintained for three reuse cycles.

Contrasting a series of bidentate amido phosphine oxide, sulfide, or selenide ligands and complexes of dimethyl aluminum and indium.

A series of EP(V)-imine phosphine-imine ligands (Dipp-NC(CH3)-(CH2)-PE(Ph2)) (Dipp = 2,6-diisopropylphenyl, E = O, S, Se) and corresponding dimethyl aluminum and indium complexes were prepared and characterized using multi-nuclear NMR spectroscopy and SC-XRD. Solution-state 1H and 31P NMR spectroscopy indicate a mixture of isomers in solution (C6D6, CDCl3, and CD3CN). Solid state structures of both the imine and (E)-enamine isomers of the oxygen-based ligand have been observed. These three ligands (L) were then deprotonated with M(CH3)3 (M = Al or In), with methane loss forming a 6-membered ring via bidentate chelation ((κ2-L)M(CH3)2). The indium/oxide complex also crystallized as a 12-membered ring.

Hydrosulphide-methaemoglobin-albumin cluster: a hydrogen sulphide donor.

Methaemoglobin (metHb) possesses inherent characteristics that facilitate reversible binding to hydrogen sulphide. Exogenous hydrogen sulphide supplementation imparts beneficial bioactive effects, including antioxidant and anti-inflammatory; hence, we hypothesized that the metHb-hydrogen sulphide complex could act as a hydrogen sulphide donor for medication. In this study, we prepared a hydrosulphide-metHb-albumin (H2S-metHb-albumin) cluster and examined its applicability as a hydrogen sulphide donor in the mice model of hepatic ischemia-reperfusion injury. Structural analysis revealed that the H2S-metHb-albumin cluster exhibited a nanostructure wherein one metHb was wrapped by an average of three albumins, and hydrogen sulphide was bound to the haem. Additionally, the H2S-metHb-albumin cluster exhibited low-pH responsiveness, leading to sustained release of hydrogen sulphide. Owing to these structural and pharmaceutical characteristics, the severity of hepatic ischemia-reperfusion injury was alleviated via antioxidant and anti-inflammatory effects of the H2S-metHb-albumin cluster treatment. The protective effects were more potent in the H2S-metHb-albumin cluster compared to that in a conventional hydrogen sulphide donor (sodium hydrogen sulphide). No abnormal signs of toxic and biological responses were observed after the H2S-metHb-albumin cluster administration, confirming high biological compatibility. These results successfully establish the proof of concept that the H2S-metHb-albumin cluster is a promising hydrogen sulphide donor. To the best of our knowledge, this is the first report demonstrating the remarkable potential of metHb as a biomaterial for hydrogen sulphide donors.

Water Splitting Reaction Mechanism on Transition Metal (Fe-Cu) Sulphide and Selenide Clusters-А DFT Study.

The tetracarbonyl complexes of transition metal chalcogenides M2X2(CO)4, where M = Fe, Co, Ni, Cu and X = S, Se, are examined by density functional theory (DFT). The M2X2 core is cyclic with either planar or non-planar geometry. As a sulfide, it is present in natural enzymes and has a selective redox capacity. The reduced forms of the selenide and sulfide complexes are relevant to the hydrogen evolution reaction (HER) and they provide different positions of hydride ligand binding: (i) at a chalcogenide site, (ii) at a particular cation site and (iii) in a midway position forming equal bonds to both cation sites. The full pathway of water decomposition to molecular hydrogen and oxygen is traced by transition state theory. The iron and cobalt complexes, cobalt selenide, in particular, provide lower energy barriers in HER as compared to the nickel and copper complexes. In the oxygen evolution reaction (OER), cobalt and iron selenide tetracarbonyls provide a low energy barrier via OOH* intermediate. All of the intermediate species possess favorable excitation transitions in the visible light spectrum, as evidenced by TD-DFT calculations and they allow photoactivation. In conclusion, cobalt and iron selenide tetracarbonyl complexes emerge as promising photocatalysts in water splitting.

Atom-Economical Synthesis of Lewis Acidic Boron Containing Porous Organic Polymers via Hydroboration Polymerization for Basic Chemical Capture.

Atom economy is one of the main concerns for material synthesis. Here, the facile synthesis of Lewis acidic boron-containing porous organic polymers (B-POPs) via hydroboration polymerization reaction of commercially available borane dimethyl sulfide complex (BH3 ∙SMe2 ) with multi-alkynes under mild reaction conditions is presented. This new synthetic method for B-POPs has the advantage of high atom economy. The resulted porous alkenyl borane polymers (PABPs) have unique features such as high boron content, strong Lewis acidity, and high surface areas. Owing to the strong Lewis acid-base interactions, PABPs exhibit excellent adsorptive capacity toward triethylamine (up to 841mgg-1 ) and pyridine (up to 1396mgg-1 ) vapor.

Characterization of solids obtained from calcium and magnesium precipitation by sodium carbonate addition

The addition of sodium carbonate (Na2CO3) to the flotation water of complex sulfide ores is a strategy implemented to mitigate the adverse effect of calcium and magnesium present in the process water of complex sulfide flotation. These contaminating agents are due to the use of lime as pH regulator and to the presence in the ore of magnesium species. Na2CO3 is added with the aim of precipitating Ca2+ and Mg2+ as carbonates. In the case of calcium, it precipitates CaCO3, which has been identified by XRD as calcite and vaterite. In the case of magnesium, the precipitating solid is of amorphous nature. In order to identify the chemical nature of magnesium precipitates, thermogravimetric analysis was carried out. Additionally, the solids were analyzed by SEM–EDS to support the observations. The results suggest that the amorphous solid may consist of a hydrated basic magnesium carbonate, precursor of hydromagnesite (Mg5(CO3)4(OH)2·4H2O).Graphical abstract

Sequential Nitrile Amidination-Reduction as a Straightforward Procedure to Selective Linear Polyamine Preparation.

A straightforward strategy toward the efficient synthesis of linear saturated polyamines containing 1,2-diaminoethane and/or 1,3-diaminopropane fragments has been developed. The procedure is based on the chemistry of 5- and 6-membered cyclic amidines, including their efficient synthesis from nitrile precursors and subsequent chemoselective reductive-opening by a borane-dimethyl sulfide complex. This two-step procedure provides a robust methodology for the synthesis of linear polyamine skeletons under nonharsh conditions and free of using selective protective groups or tedious workups.

A kinetic and thermodynamic study of the removal of calcium and magnesium from aqueous solutions similar to those of complex sulphide flotation by the addition of sodium carbonate

ABSTRACT The use of recycled water in flotation has a negative impact on flotation of sulphide mineral species because these waters contain chemical species that affect the recovery and selectivity of the process. This study aims to study the reaction mechanism between aqueous calcium and magnesium sulphate contained in the water released by complex sulphide flotation process, and the carbonate ions added to the water as sodium carbonate (Na2CO3). The addition of Na2CO3 has been shown to have a positive effect on the recovery and grade of the final Pb-Cu concentrate obtained, but the reasons of this are not yet fully understood. The present study was conducted by adding Na2CO3 to a saturated gypsum solution containing Mg(II). Analytical techniques such as XRD, TGA and zeta potential measurements were used to characterise the obtained solids. It was observed that the addition of Na2CO3 favoured the precipitation of the Ca(II) as calcite and vaterite. The reaction kinetics was found to be of second-order. In the case of magnesium alone, the precipitates are amorphous. This study provides new information on the reaction mechanism between metal ions and carbonates. The information collected can help design processes for the removal of ions from flotation water.