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AbstractPresently huge operation costs arising from aeration and high electron donor requirements accompanied by low metal recovery rates are some impediments to the large-scale application of bioleaching for low-grade ores. The current study investigates key parameters for scaling up anoxic bioleaching, which overcomes some of the above shortcomings, on polymetallic manganese nodules using soil-based manganese-reducing bacterial consortia in a stirred bioreactor. Operating conditions such as carbon source concentration and pulp density were optimized. Parameters like pH, oxidation–reduction potential (ORP), and microbial growth were monitored in the bioreactor in both stirred and non-stirred conditions. The Mn(IV) reduction and dissolution in the bioreactor was 27 (±2.8)% over 30 days, which significantly enhanced to 43 (±1.5)% and 42 (±0.35)% in the presence of humic acid and anthraquinone sulfonic acid, respectively, in 15 days. A maximum dissolution of 21 (±4.1)% Cu, 10 (±3.0)% Ni, 18 (±4.7)% Co and 7 (±3.9)% Fe were also obtained with 100 µM humic acid from the agitated bioreactor in 15 days. The corresponding specific glucose consumption rate per unit mass of ore was found to be 27 mg g−1 day−1, which is 10 times lower than the rates reported previously for aerobic bioleaching methods. The investigation shows that mild agitation can significantly improve the anoxic bioleaching, especially with added electron shuttles, to enable better ore-bacteria interaction and prevent ore compaction during scale-up. The pH and ORP of the system point toward a reductive dissolution of Mn by the organisms. [ABSTRACT FROM AUTHOR]

Electric reduction furnaces cannot be fed fines in the production of manganese ferroalloy as they hinder gas permeability. Thus, agglomeration techniques can be used to minimize the environmental and economic impacts of storing fines. Among these techniques, briquetting is advantageous because it allows for cold agglomeration of the particles and is flexible in terms of particle sizes. Therefore, this work aimed to develop self-reductor briquettes composed of ore manganese fines, dust ferromanganese, charcoal fines, and three different binders. The compaction pressure, curing time, and % binder were optimized to enhance briquette strength through a multivariate experimental design consisting of a screening study using a 23 full factorial design followed by response surface methodology with a spherical central composite design. The results were assessed by analysis of variance, and a regression model was established. The study found that briquettes elaborated with bentonite exhibited an optimized compressive strength of 4.02 MPa, achieved with a compaction pressure of 67.55 MPa and 12.71% bentonite. For briquettes elaborated with pregelatinized starch, a compressive strength of 7.04 MPa was obtained with a compaction pressure of 67.52 MPa, a curing time of 19.51 days, and 8.07% pregelatinized starch. For briquettes agglomerated using slaked lime and molasses, an optimized compaction pressure of 27.09 MPa and a curing time of 23.27 days resulted in a compressive strength of 1.63 MPa. These results suggest that briquettes containing bentonite and pregelatinized starch are feasible substitutes for lump ore in electric furnaces. [ABSTRACT FROM AUTHOR]

Bark paintings represent a unique artform that originated in Australia and continues to this day. This paper presents a scientific investigation into both the pigments and binders used by Aboriginal artists from across the Northern Territory (NT) and the Kimberley region in Western Australia (WA) and represents the first major study dedicated to identifying these materials in samples taken from paintings. Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS), Fourier transform infrared (FTIR) and Raman spectroscopy were used to identify the pigments in the four colors commonly associated with works by Aboriginal artists: red, yellow, black, and white. Iron oxides are used for red and yellow. Typically, kaolin is used for white and carbon or natural manganese ores are used for black, although the use of other pigments such as huntite (white) and battery black were seen in paintings from specific locations. Evidence of trade could not be established during this study; however, analysis shows that artists may use different pigments based on location and availability. A combination of FTIR and pyrolysis-gas chromatography-mass spectrometry (pyrolysis-GC-MS) was utilized to investigate the presence of a binder in the paint. Plant-based materials were identified as the binder in the majority of the paintings. The use of orchid juice was common, both as a preparatory layer on the bark substrate and as a paint binder. The presence of synthetic resins was more widespread than anticipated, attributed to both conservation efforts and more modern painting practices. [ABSTRACT FROM AUTHOR]

Manganese dioxide in pyrolusite was directly reduced to manganese sulfate by high-temperature roasting with ammonium sulfite as reducing agent, so as to achieve efficient extraction of pyrolusite. The effects of mass ratio of ammonium sulfite to pyrolusite, roasting temperature and time, leaching temperature and time on the extraction rate of manganese were investigated, and the optimum process conditions were determined. The results show that the optimal conditions are the mass ratio of ammonium sulfite to pyrolusite of 0.75:1, roasting temperature of 500 °C, roasting time of 1.5 h, leaching temperature of 25 °C, leaching time of 30 min. Under the conditions, the leaching rate of manganese and iron is about 93% and about 9.5%, respectively. The extraction effect of manganese is good. [ABSTRACT FROM AUTHOR]

This study develops briquettes from fines generated in the processing of manganese ore from a strategic manganeferous district of Minas Gerais–Brazil. The briquettes were produced based on the following variables: compaction pressure (20 and 25MPa), curing time (7 and 28 days), percentage by mass of binder (5% and 10%), and replacement with tailings (0% and 10%). Technological tests evaluated the compressive, abrasion, impact strength and water absorption. The best conditions for briquette included 10% Portland cement, 10% Mn tailings, compaction pressure of 25MPa and 7 days of curing, as well as 10% Portland cement, compaction pressure of 25MPa and 28 days of curing. The briquettes primarily contained the spessartine, todorokite, quartz, and pyrolusite minerals. The storage time tests indicated that the briquettes responded satisfactorily to storage for three months in a dry environment and at room temperature. Through crackling tests, the briquettes have potential to be commercially used. [ABSTRACT FROM AUTHOR]

Manganese is widely used in the iron and steel industry, batteries and other fields. The amount of the manganese oxide ores existing in China coeval with iron and their manganese-to-iron ratio is low. A study was conducted on a synchronous reduction roasting-magnetic separation of a ferromanganese ore with high content of iron taken from South Africa using CO as reductant. Under the conditions of 750°C roasting temperature, 40 min roasting time, 30% CO concentration roasting atmosphere and − 0.074 mm accounting for 82.56% grinding fineness, the iron removal rate was close to 70% through magnetic separation, with the grade and manganese recovery of manganese concentrate reaching 49% and 72.50% and the manganese-to-iron ratio increasing from 2.5 to 5.92. The X-ray diffraction analysis indicated that Mn2O3 and Fe2O3 in the raw ore was reduced to MnO and Fe3O4, respectively, without forming the intermediate product Mn3O4 in a weak reducing atmosphere. The SEM-EDS analysis of the roasted product showed that the simultaneous reduction of manganese and iron oxides could be achieved when the roasting temperature reaches 750°C. The crystal forms of MnO and Fe3O4 were more perfect, and the coexisting grains of Ca, Si and Al clustered further with increasing roasting temperature. [ABSTRACT FROM AUTHOR]

Rare earth elements (REE) of the host rocks (Fe-siliceous rocks) and manganese ores of the Nchwaning Mine (Hotazel Formation, Kalahari manganese field) were studied. An important feature of manganese ores and host rocks (Fe-silicites) is the presence of negative and positive cerium (Ce/Ce*) and europium (Eu/Eu*) anomalies. This testifies to the complex and long history of the formation of manganese ores. Initial metal-bearing (Mn, Fe) sediments of a shallow-water basin with a negative cerium anomaly (Ce/Ce*) were enriched in europium (positive Eu/Eu*) at different stages of lithogenesis both during sedimentation (underwater discharge of hydrothermal fluids), and subsequent processes of hydrothermal transformation of the ore-bearing strata. The source of manganese could be basaltic andesites of the underlying Ongeluk Formation. [ABSTRACT FROM AUTHOR]

Potentially toxic elements (PTEs) pose a significant threat to aquatic ecosystems. This study investigated the content and potential sources of PTEs (Cr, Mn, Ni, Cu, Zn, Cd, Pb) in water, sediment, and dominant aquatic plants (Hydrilla verticillata and Spirogyra varians) in the Xiaojiang River, located near the Zhaiying manganese mine in Guizhou Province, China. Correlation analysis, principal component analysis (PCA), and cluster analysis were employed to assess PTE distribution and potential sources. Water PTE concentrations complied with the Class II standard (GB3838-2002), indicating no water pollution. However, sediment PTE levels exceeded background values, particularly Mn, which exhibited moderate to strong contamination. Cd also showed moderate contamination, posing a considerable ecological risk. Cd was the main potential pollutant with the highest contribution rate. Mn and Cd were therefore identified as priority pollutants requiring targeted abatement strategies. Mining activities likely represent the primary source, but combined pollution from vehicle traffic and agriculture might also contribute. Hydrilla verticillata demonstrated a higher capacity for PTE enrichment from sediment compared to Spirogyra varians, suggesting its potential for sediment remediation (except for Cu). A significant correlation existed between both plant species and sediment PTE content. PCA supported the association between S. varians and sediment PTEs. Linear regression analyses revealed better correlations between S. varians and sediment Mn, Ni, Cu, and Zn (0.77, 0.68, 0.82, and 0.79, respectively). Taken together, these findings suggest that S. varians serves as an effective bioindicator for monitoring sediment contamination with PTEs. [ABSTRACT FROM AUTHOR]

The pre-reduction of manganese ore using elemental sulfur under an inert atmosphere at temperatures above 600 °C is required for maximum MnO formation. Under atmospheric conditions, SO2 formation via sulfur oxidation leads to MnSO4, which again will dissociate to lower Mn oxides. Thus, excess energy is required for this conversion, thereby decreasing the overall energy efficiency. The optimum pre-reduction condition obtained is 800 °C, with a holding time of 4 hours at 0.5 S/Mn ratio. [ABSTRACT FROM AUTHOR]

The Middle Permian manganese deposit in Zunyi, northern Guizhou is one of the major manganese mining areas in South China. However, the age of this manganese deposit has not been accurately constrained. Previous studies have generally concluded that the formation of Zunyi manganese ores was linked with the early activities of the Emeishan Large Igneous Province (ELIP). In this study, we investigated the lithology and mineralization age of the Mn-bearing rocks in the study area and explored the connections between ELIP and the genesis of these rocks. Zircon samples from the Mn-bearing tuff in the Tuanxi section of Zunyi were used for zircon U-Pb chronological analysis by LA-ICP-MS method. The results constrain the deposition age of Mn-bearing rocks in Member 3 of the Maokou Formation was older than 266 ± 3 Ma, this age was closely related to the early stage of ELIP, but it was 5–10 Ma earlier than the main eruption of the Emeishan basalt. Combined with the regional paleogeography, we believe that the mantle plume activities prior to the main eruption of ELIP provided the tectonic stress, manganese source, and mineralization environment for manganese ore formation in the rift basin of the study area. [ABSTRACT FROM AUTHOR]

The world-class deposits of the Kalahari Manganese Field (KMF) in South Africa constitute a key resource of manganese (Mn) ore for the global steel industry. Many aspects of the origin of high metal-grade ores in the northernmost KMF remain unresolved, especially with respect to the complex hydrothermal history of these ores and the source/s of fluids responsible for epigenetic metal enrichment. In this study, the geochemistry of boron (B) is employed as a potential proxy for such processes, and the results are contextualised against an assumed low metalgrade precursor. Samples collected from the northern part of the Kalahari Manganese Deposit allow for the distinction of three Mn ore types, of which the precursor ore is the closest candidate, petrographically and geochemically, to primary/diagenetic Mn deposition. This precursor ore is dominated by Mn-carbonate and braunite, and records B concentrations in the order of a few 100s to 1 000s ppm and positive δ11B values at an average of 11 ± 6?. Ferruginous Mn ores appear to have formed from decarbonation of precursor ore and metasomatic ferric iron addition, particularly in the stratigraphically upper Mn ore bed, which is closest to the overlying Olifantshoek and Kalahari unconformities. Ferruginous Mn ores appear depleted in B (ca. 500 ppm on average) and have lower boron isotope values (δ11B: 0 ± 3?). Hydrothermally Mn-enriched ores, in contrast, are dominated by hausmannite, braunite-II and bixbyite and record highest B concentrations (up to 10 000s ppm) and δ11B values as high as 41?, pointing to metasomatic introduction of B by circulating evaporitic brines. While further research is needed to comprehensively unravel the geochemical intricacies of B within the complex interplay of fluids and rocks in the Hotazel region, the findings of this study still strongly suggest that B holds promise as a tracer for alteration processes in the KMF. [ABSTRACT FROM AUTHOR]

The present research explores the potential of manganese oxide waste ore in energy storage applications, focusing on supercapacitors. The investigation assesses the electrochemical capabilities of natural manganese oxides obtained from the Drama region, which has been the main mining center of Greece for manganese ore, especially that of battery-grade quality. Samples were collected from abandoned mining sites in the Kato Nevrokopi area, Drama. The structure and composition of the manganese minerals were determined by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Electrochemical tests involved the preparation of electrodes using natural nsutite and heat-treated nsutite (hausmannite). Then, the designed electrodes were subjected to cyclic voltammetry tests and charge–discharge measurements. The hausmannite electrode exhibited a higher specific capacitance of 667 F/g at a current density of 0.2 A/g, and the electrode material retained 98.3% of its initial capacitance after 1000 cycles. This study provides new perspectives on simple and efficient methods for transforming natural nsutite material from mining waste to hausmannite with greater structural homogeneity and better electrochemical behavior. [ABSTRACT FROM AUTHOR]

China's manganese ore import sources are relatively single, with an external dependency exceeding 90%. Despite China is rich in manganese ore resources, they are predominantly characterized by low-grade manganese ores with excessive iron content. The mineral composition is complex, the coexistence is close, the selectivity difference between minerals is small, and separation is difficult. In order to better develop and utilize ferromanganese ore, chemical composition analyses, SEM, MLA, X-ray diffraction analysis and other testing methods were used to conduct process mineralogy research on a overseas ferromanganese ore, and a separation and recovery exploration test was conducted on the ore. The results indicate that the TFe grade is 31.31%, the Mn grade is 9.09%, and the main impurity element Si02 content is 28.73% in the ore. The main valuable minerals in the ore are limonite, coronadite, and psilomelane, with contents of 49.57%, 8.60%, and 6.44% respectively; the main gangue minerals are quartz and barite, with contents of 29.01 and 6.24% respectively. The particle sizes of coronadite and psilomelane in the ore are restively line, with the -38µm particle size distribution reaching 74.59% and 62.54% respectively. Their monomer dissociation degrees are low, only 16.75% and 15.12%. Coronadite and psilomelane mainly exist in intergrowth, with the content of both poor and rich intergrowth above 40%. The two are more closely embedded with limonite. Most of the coronadite particles exist in limonite as tine-grained inclusions. Similarly, most of the psilomelane particles exist in limonite as inclusions or disseminated forms. These make it more challenging to dissociate the iron and manganese mineral monomers. Therefore, it is difficult to achieve effective separation of iron and manganese minerals by traditional mineral processing methods. With the process of "hydrogen-based mineral phase transformatiom magnetic separation", the ore can be treated. And the technical indexes of iron ore concentrate with yield of 54.08%, Fe grade of 58.35%, Fe recovery of 91.47% can be obtained. [ABSTRACT FROM AUTHOR]

The paper reports original data on the isotopic composition (δ13С, δ18О) and major and rare earth element (REE) geochemistry of manganese ores in the Rodinauli section of the Kvirila deposit (Georgia). The δ13С (V-PDB) and δ18О (V-SMOW) values vary from –19.6 to –6.6‰ and from 21.1 to 29.1‰, respectively, in the carbonate ores; and from ‒14.9 to ‒5.5‰ and from 21.8 to 28.4‰, respectively, in the carbonate substance of cement of oxide ores. The studied ores are characterized by the presence of negative Ce anomaly ( up to 0.51) in majority of samples (both carbonate and oxide ores); the prominent Eu anomaly is absent. A conclusion has been made that the ores were formed both under conditions of early diagenesis of sediments and later, during catagenesis, with the participation of metal-bearing elisional solutions. [ABSTRACT FROM AUTHOR]

The world has moved into an era of hidden ore body exploration, necessitating the development of new prospecting and exploration methods. One promising approach is to use the deep convolutional neural network (DCNN) algorithm to extract spatial and correlation characteristics of multiple two-dimensional elements related to hidden ores. This paper explores this method on Datangpo manganese (Mn), constructing prediction datasets that includes geological, geochemical, geophysical and aeromagnetic features. Analyzing metallogenic conditions and control factors of Mn ores, we construct a Mn ore prediction model (Geo-DCNN) based on multiple geographical knowledge and DCNN. The Geo-DCNN model reaches ore-bearing accuracy of 79.11%, non-ore-bearing accuracy of 99.01%, overall accuracy of 95.35%, and loss value of 0.0227 after training. Based on analysis of ROC curve, P-R curve, field investigation, and target area verification, we discover that the prediction results of the Geo-DCNN model in northeast Guizhou have a high correspondence rate with known manganese deposits. This provides valuable insight for further ore exploration in the area. Additionally, the results indicate that the Geo-DCNN model is robust and portable, suggesting that it can be applied to metallogenic prediction practices for manganese ore in similar regions. [ABSTRACT FROM AUTHOR]

• First colorimetric and chemical characterisation performed on the chromatic evolution Portuguese azulejos (glazed tiles) comprising a timespan of ca. 250 years. • The methodology followed a non-invasive approach that can and will be replicated on other sets of tiles. • While basic pigments remained the same, their chemical composition changed over time and the colour palette exhibited different hues in specific chronologies. • A modified Naples yellow pigment with zinc was characteristic of 17th-century Portuguese azulejos. • The mixture of Naples yellow with cobalt blue to obtain olive green is also characteristic of Portuguese azulejos , but rarely mentioned in the literature for coeval maiolica/faience productions. This work provides an overview of the pigments used by Portuguese azulejo painters through the study of 34 glazed tiles belonging to the National Azulejo Museum in Lisbon, Portugal. The tiles are dated from the late 16th century to the early 19th century, with most samples attributed to the 17th and 18th centuries. Building on a previous study where the chemical composition of the 17th-century colour palette was characterised [1] , we used a non-invasive methodology to further identify compositional differences among groups of colours spanning a wider timeframe. Blue, white, yellow, orange, purple, green and brown decorations were analysed by EDXRF to obtain qualitative and (in some samples) quantitative information on their chemical composition. µ-Raman spectroscopy was used to identify the main colouring agents. Finally, colorimetric measurements of the different hues of each colour were performed to address the relation between colour and chemical composition. Our results show that greens could be obtained through a copper-based pigment or by mixing lead-antimonate with cobalt-blue pigment. Although cobalt is the colouring agent of all blue decorations, compositional differences suggest the use of different types of raw materials or the addition of specific reagents to modify the hue. On the other hand, yellow hues ranging from lemon yellow to orange were manufactured by adding zinc, tin, or iron oxide to a lead antimonate base. Finally, a manganese ore was used to make the purple pigment. Overall, we noted that while the basic pigments remained the same, the colour palette was progressively widened during the 18th century. This was done by using more pure pigments (i.e., with less iron), by changing the ratio in pigment mixtures (i.e., blue and yellow), or by overlapping colour layers for artistic effects. Finally, the results of the chemical and colorimetric analyses are always influenced by the concentration of the pigment in the glaze, its thickness and the overlapping of pigments used by azulejo painters to expand the shades available for the final artistic composition. [ABSTRACT FROM AUTHOR]

Corrosion of mild steel in sodium sulfate solutions (1000 mg SO42- L-1) in the presence of various phosphate inhibitors was studied gravimetrically. Studies were performed under static conditions at room temperature. The known sodium polyphosphate inhibitor has been found to have low efficacy under these conditions. The inhibitor efficiency of its does not exceed 30.5 % at a concentration of 100 mg P2O5 L-1. It has been shown that a more effective inhibitor is calcium-manganese polyphosphate (Са, Mn)(PO3)2 obtained on the basis of manganese ore enrichment wastes of the Zhayrem deposit. The inhibitor efficiency of its already at a concentration of 20 mgP2O5 L-1 is 47.3 %. At a concentration of 100 mgP2O5 L-1, the inhibitor efficiency (Са, Mn)(PO3)2 is 96.2 %. Electrochemical tests confirmed the results of the gravimetric study. Infrared spectroscopic analysis showed that phosphate protective coatings were formed on the steel surface in solutions of sodium sulfate with additives of calcium-manganese polyphosphate. [ABSTRACT FROM AUTHOR]

The Imini mining district (southern foreland of the intraplate Atlasic belt of Morocco) hosts the largest Mn resources of North Africa, consisting of two laterally extensive bodies of high-grade pyrolusite-rich manganese ore and a third discontinuous medium-grade coronadite-rich Mn ore in a ~ 10–15-m-thick Cenomanian–Turonian dolostone unit. Until now, the origin and timing of the Mn ore have been poorly constrained. New Pb isotopic ratios show that Triassic series (basalts and ferruginous sandstone) are likely the source of the metals. 40Ar/39Ar dating of K-Mn oxides shows that the Mn-rich orebodies formed during at least three periods: late Cretaceous to late Paleocene (> 58 Ma), late Eocene (ca. 36.3 Ma), and early Burdigalian to early Serravalian probably in two pulses at ca. 19–20 Ma and ca. 13 Ma. These periods coincide with three known building phases of the Atlasic relief during late Cretaceous, late Eocene, and the Early(?)-Middle Miocene. We therefore propose the Atlasic tectonics as the first-order control of the Mn mineralization. Periods with regionally high elevations modified the climate to wetter conditions that supplied meteoric water to feed temporary aquifers. Relief building created the required hydraulic head to sustain (1) fluid-rock interaction between O2-poor acidic fluids and the Triassic series, (2) migration of the metal-rich fluid, and (3) to overpressure fluid in the Imini depositional site. The decreasing thickness of Triassic series in front of the Imini anticline forced these low-temperature (< 100 °C) fluids to mix with oxygenated and alkaline ground waters in the karst system and precipitate Mn oxides. The N70°-oriented Atlasic tectonic structure controls the orientation of the Mn deposits. The late Eocene–Early/Middle Miocene uplifts generated additional supplies and/or in situ remobilization of the primary late Cretaceous medium-grade ore to form the high-grade pyrolusite-rich ore. [ABSTRACT FROM AUTHOR]

The research investigated the potential of natural ore with a low manganese content gradient, imported from the Tiouine region of Morocco, as an adsorbent of cadmium ions in a phosphoric acid medium. For the first time, the ore was prepared and used as adsorbent in three different sizes (60, 315, and 500 µm), and characterized by X-ray diffraction, fluorescence spectroscopy, Fourier transform infrared, and scanning electron microscopy. The chemical activation of raw ore by HCl and KOH at different temperatures was necessary to enhance the removal capacity of Cd(II) ions. The removal capacity was evaluated by studying the ore's particle size and different reaction parameters such as contact time, temperature, and cadmium ions concentration. The activation process improved the adsorption performance of the raw ore in a concentrated phosphoric acid medium. The very low quantity of manganese released by the natural ore during the phosphoric acid purification process proves its high stability. This work suggests the possibility of using manganese oxide ore in the treatment of liquid effluents contaminated by metal ions and more precisely to purify or reduce the cadmium content in industrial phosphoric acid. [ABSTRACT FROM AUTHOR]

This study provides for the first time details of the mineralogy, petrography and mineral paragenetic relationships of manganese ores of the Avontuur deposit, a prominent northern outlier of the Kalahari Manganese Field in the Northern Cape Province of South Africa. Using a combination of light and electron microscopy and X-ray powder diffractometry on an extensive suite of exploration drill core samples, it is shown that the manganese ores comprise an exceptionally fine-grained assemblage of Mn2+-silicates (friedelite, tephroite, gageite), Mn2+/Mn3+-oxides (jacobsite, hausmannite) and Mn2+-carbonates (rhodochrosite, kutnahorite, Mn-dolomite and Mn-calcite). This mineral assemblage is a product of diagenesis and very low-grade regional metamorphism. Locally, this assemblage is overprinted by contact metamorphism or supergene alteration. Despite close geochemical and textural similarities, the manganese ores of the Avontuur deposit are surprisingly different in their mineralogy compared to the carbonate- and braunite-dominated mangano-lutites of the main Kalahari deposit. Distinctly higher concentrations of both SiO2 and Fe2O3 in the manganolutites of the Avontuur deposit as compared to the main Kalahari Deposit provide the reason for the markedly different mineralogy. Such marked differences in bulk chemistry are tentatively attributed to systematic lateral variations in the physicochemical conditions of mineral precipitation during the deposition of the Hotazel Formation. [ABSTRACT FROM AUTHOR]

Currently exploited iron ores have high-manganese content. Conventional leaching of manganese takes about 2 h at 80 ̊C followed by precipitation. Thus, it consumes high energy and a relatively long-time. In this paper, the mechanochemical method was investigated for reducing manganese in iron ore at a shorter time and at room temperature. The number and size of balls were studied during the milling process in the presence of sulfuric and/or oxalic acid either as a single acid or as a mixture. The higher the ball's number and size the higher the iron and manganese dissolution. The sulfuric-oxalic acid mixture is better than the usage of single acid for reducing the manganese at about 10 min. The iron concentrate, containing 54% Fe and 2.9% Mn from a feed containing 57% Fe and 7.5% Mn, is obtained using 15 balls of size 3.3 cm and 2%:4% sulfuric to oxalic ratio and dosage. Moreover, the mechanochemical is advantageous over conventional leaching as it continuously cleans the surface, creates new surfaces, controls iron dissolution, is conducted at room temperature and shorter time (about 10% of the time needed for the leaching process), and direct production of iron concentrate without subsequent processes like precipitation. [ABSTRACT FROM AUTHOR]

Methylene blue is widely used in various industries. The discharge of industrial effluents with methylene blue residues may have hazardous effects on living systems. In this paper, the low-cost, eco-friendly, and abundant geoadsorbent natural manganese ore sand was used as an attractive material to remove methylene blue. The results indicated that the poorly crystalline manganese ore sand could simultaneously adsorb and degrade methylene blue. The pseudo-first-order and MnOII (I) kinetic models could describe the decolorization, but the latter had better predictive characteristics. The kinetics were affected by coexisting substances, but a decolorization efficiency of greater than 80% still could be achieved in actual water matrices. Characterization of manganese ore sand before and after use indicated that the degradation processes that occurred at pH values of 2, 3, 5, 7, and 10 included direct and indirect redox reactions. Specifically, the manganese ore sand behaved primarily as an oxidant at acidic pH, as a catalyst at alkaline pH, and simultaneously as oxidant and catalyst at a neutral pH. Possible degradation routes were proposed based on the suggested intermediates. The main behavior of the oxidant was demethylation of C–CH3 from methylene blue, and the degree of demethylation increased with decreased pH. As the catalyst, the C–N and C–S bonds on the central heterocycle could be further broken by manganese ore sand after demethylation. The performance of manganese ore sand is related to the content of high-valent Mn species. [ABSTRACT FROM AUTHOR]

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A new member of the epidote supergroup, ferriandrosite-(Ce), ideally MnCeFe3+AlMn2+(Si2O7)(SiO4)O(OH), was found at the Július manganese ore occurrence near Betliar, Rožňava Co., Košice Region, Slovakia. It occurs as subhedral grains and polycrystalline aggregates, up to 0.3 mm in size, enclosed in pyroxmangite. Other associated minerals are spessartine, rhodochrosite, quartz, baryte and pyrosmalite-(Mn). Ferriandrosite-(Ce) is dark brown, with a light brown streak and vitreous lustre. The Mohs hardness is ~6½ to 7 and tenacity is brittle with no observable cleavage or fracture. The calculated density is 4.321 g⋅cm–3. Ferriandrosite-(Ce) is optically biaxial (+), with weak pleochroism, high surface relief and the mean calculated refractive index is 1.832. The empirical structural formula of ferriandrosite-(Ce), based on 13 anions per formula unit, is A1(Mn2+0.63Ca0.35Ce0.02)Σ1.00A2(Ce0.53La0.27Nd0.14Pr0.05REE*0.01)Σ1.00M1(Fe3+0.41Al0.12V3+0.01Mg0.40Ti0.05)Σ0.99M2Al1.00M3(Mn2+0.75Fe2+0.22Mg0.03)Σ1.00T1–3Si3.00O11O4(O0.67F0.33)(OH), where REE* are minor rare earth elements. Ferriandrosite-(Ce) is monoclinic, space group P 21/ m , a = 8.8483(4) Å, b = 5.7307(3) Å c = 10.0314(5) Å, β = 113.3659(15)°, V = 466.95(4) Å3 and Z = 2. The crystal structure of ferriandrosite-(Ce) was refined to a final R 1 = 0.0210 for 1910 reflections with F o > 4σ(F o) and 127 refined parameters. Structural features of ferriandrosite-(Ce) are discussed and compared with other members of the androsite-series. [ABSTRACT FROM AUTHOR]

The beginning of human settlement in the Hami Basin, located in the eastern part of Xinjiang, has been a focal question for the academic community in China. In particular, the thesis that the immigrating population from the Hexi Corridor since the late Neolithic founded the Tianshanbeilu culture has riveted the attention of scholars. Pottery wares, abundantly discovered at the synonymous cemetery of this culture, have played a key role in extrapolating population migration and cultural interaction. This paper aims to test the thesis by characterizing the chemical composition, painting pigment, and carburizing technique of 70 pottery samples from the cemetery with various scientific methods. It shows that the chemical compositions of the coarse pottery in the three colors of red, yellow, and gray, painted and unpainted alike, are remarkably different from those of fine pottery in black and red, indicating that the raw materials for the coarse and fine pottery samples are possibly procured from different sources; the pigments of the red slip and black paint are derived from hematite, black manganese ore, and carbon black; carburizing and polishing techniques are further applied to the gray coarse pottery; In combination with the compositional data of pottery samples from the Yaer cemetery also in the Hami Basin and the Xichengyi settlement in the Hexi Corridor, this paper finds that some pottery wares of the Tianshanbeilu culture were exchanged within the Hami Basin, but each site had its own production facility. No direct exchange of pottery wares with Xichengyi is attested; the similar style of pottery wares between the two sites may have resulted from population migration and technological exchange. [ABSTRACT FROM AUTHOR]

The transition from an open-pit to an underground space is inevitable to exploit deposits from greater depth. Crown pillar, a remnant ore usually left in between open-pit to underground mining that supports the terrain and aids in carrying out underground mining operations safely and its stability is vital. The design of crown pillar is majorly influenced by its thickness, span, slope angle, ore dip, depth of open-pit mining, rock mass quality, cohesion and friction angle. When the crown pillar is situated near the surface (shallow depth), it is synonymously named as the surface crown. The behaviour of the crown pillar is different from the surface crown due to variation in geo-mining conditions. As underground mining progresses, displacements around the crown pillar are generated and stresses reorients around it. This can be assessed through numerical simulation. To have a better understanding, this paper concentrates on crown pillar's stability and geometrical parameters influence on its stability. The field study is carried out at Ramrama manganese ore mine, where the transitioning takes place at shallower depth and FLAC3D 5.0 is used for numerical simulation work to analyse the behaviour of the crown pillar. From the results interpreted, it is found that the maximum amount of principal stresses decreases for the lower span, 8 m, of crown pillar with increase in slope angle and for the larger span as in case of 22 m span; the stresses generated are reduced in case of 38° slope angle and increased for 45° slope angle. Higher dip of orebody generates high amount of stresses in the pillar and with an increase in the depth of mining, high amount of displacements and stresses are observed around the crown pillar. [ABSTRACT FROM AUTHOR]

This study was carried out to investigate the production of manganese nanomaterials by enriching fine and low-grade manganese ores. Fine and low-grade manganese ore sample was obtained from Balıkesir-Mezit-Tumanpınarı region in Turkey. Experimental studies were processed in two different routes. In the first method, optimum enrichment conditions were determined by enriching the ore with a two-stage column flotation method. The optimum flotation time obtained for fine and low-grade manganese ore is 10 minutes. The optimum variables obtained from 10 min column flotation are 60 g/dm3 collector (sodium oleate), 1 g/dm3 depressant (sodium silicate), 3 g/dm3 frother (pine oil) and pH 7 (natural pH of manganese ore). Higher-grade MnO2 was obtained at the natural pH value of manganese ore. Under the optimum conditions, the concentrate of 76.55% MnO2 could be recovered by two-stage column flotation from the ore containing 29.9% MnO with the recovery of 90.25%. In the other route, the enriched sample was dissolved and MnCO3 was obtained by using Na2CO3. Then, 400 nm manganese oxide nanorods were produced by roasting MnCO3. [ABSTRACT FROM AUTHOR]

Results of studies for preparing complex Fe–Si–Mn–Al master alloy are presented. High-silicon lean manganese ores of the West Kamys ore deposit (18–30% Mn and 35–45% SiO2) and high-ash coal of the Saryadyr deposit (Kazakhstan) with an ash content of 45–55% are used as charge materials. Technological studies are conducted in an ore-thermal electric furnace with a capacity of 250 kVA. An experimental batch of master alloy with an average chemical composition is obtained, %: Mn — 20; Si — 42; Al — 16; P — 0.03; Fe balance. Dependences of aluminum, silicon and manganese content in final alloy on ratios Mnox + Feox + SiO2 + Al2O3)/Cso and Mnox/(Mnox + Feox + SiO2 + Al2O3) in an initial charge are revealed. The fundamental possibility and expediency of obtaining an aluminum silicon manganese master alloy of a new composition by a slag-free method with integrated use of all useful components of lean manganese ore and high-ash coal is demonstrated. An X-ray diffraction pattern of prototypes indicates that alloy phase composition is presented in the form of intermetallics — MnSi, Mn15Si26, Al2Fe3Si4, Al5Fe2, FeSi, and structurally free silicon. The resulting master alloys of selected composition are not subject to self-dispersal reactions. [ABSTRACT FROM AUTHOR]

The utilisation of mine waste/low-grade ores has become a major concern for the mining and metallurgical industries. Day by day, high-grade ores are rapidly depleted and fines/low-grade ores are dumped in the mining site, becoming a source of pollution and taking up a lot of area. To overcome the above problem, a novel smelting reduction technology was directly used to utilise low-grade/mine waste as an alternative raw material for the production of crude alloy and further for stainless steel. In this work, Fe-Cr-Ni-Mn crude alloy was directly produced from the mine waste/low-grade ores by a high-temperature arc smelting process. The dried composite pellets were prepared using chromite overburden (COB), chrome ore fines (Cr ore fines), and leangrade manganese ore (LG-Mn ore) in the ratio 4:3:3 at a 500 g scale. The effect of slag basicity (0.1-0.8) on metal concentration and recovery was studied and optimised for maximum metal recovery (Fe, Cr, Ni, and Mn) in the direct smelting experiments. The Fe-Cr-Ni-Mn crude alloy having 71.6% Fe, 22.69% Cr, 1.02% Ni, 0.972% Mn, and 2.41% C at 0.4 basicity was successfully produced with a metal recovery of 63.1% at ~1700°C. [ABSTRACT FROM AUTHOR]

A new X-ray fluorescence technique is proposed as an alternative to the labor-consuming volumetric method for the estimation of manganese valence state in ferromanganese nodules. The approach is based on the measurement of the relative intensities of some X-ray fluorescence spectrum characteristic spectral lines and satellites (MnKβ5 and MnKβ′) preconditioned by electron transfer from the valence shell. Calibration curves were created using manganese oxide samples (MnO, Mn2O3, MnO2) and 12 certified reference materials of ferromanganese nodules, cobalt-bearing ferromanganese crusts, and manganese ores with certified (or determined by approved methods) total and tetravalent manganese content. The presence of high iron content was taken into account. A set of oceanic ferromanganese nodules samples collected in the Magellan Seamounts (Pacific Ocean) were analyzed. Differences between the results of the X-ray fluorescence method and volumetric techniques for tetravalent manganese content were 4.9 rel.%, which is comparable with the accuracy of the volumetric technique (3.6 rel.%). [ABSTRACT FROM AUTHOR]

The low-cost Fe(II) reductants used in the leaching of pyrolusite usually cause high concentrations of iron ions in the leaching solution, which are difficult to treat and recover. Herein, a green cyclic leaching process for pyrolusite with recycling and reusing of Fe(II) reductants was developed. Sodium sulfide was introduced to reduce and precipitate iron ions in the leaching solution. Ep-H diagrams show that Fe3+ can be reduced to Fe2+ by S2− and form a precipitate with the high efficiency of 93.09%. Since the main component of the precipitate was ferrous disulfide with reducibility, it was used as a reducing agent for low-grade manganese oxide ores. A total of 97.96% of the manganese was highly reductively leached by the obtained precipitate of 0.28 g·g−1 ore. Furthermore, the leaching efficiency was almost unchanged after five iterations of cyclic experiments. The cyclic leaching process enables the efficient leaching of manganese and the recycling of iron, which provides a green and economic method for the efficient utilization of low-grade pyrolusite resources. [ABSTRACT FROM AUTHOR]

Ferromanganese smelting in electric arc furnaces is an energy-intensive process with corresponding CO2 emissions and environmental impacts. Upgrading the furnace charge can improve process efficiency and decrease electricity consumption. An oxide manganese ore, consisting mainly of pyrolusite, calcite and goethite, was thermally upgraded by calcination and solid-state reduction. During calcination of the ore at 900-1100°C, carbonates and hydroxides were decomposed and a considerable amount of oxygen was removed. The manganese content of the run-of-mine ore was increased from 39.86% to 47% after calcination. Carbothermic reduction of the ore at 1250°C resulted in almost all of the iron oxide and some of the manganese oxide passing into the metallic form. The results showed that a significant part of the endothermic reactions during the solid-state treatment of the ore can be carried out with low-cost fossil fuels. This leads to enrichment of the electric arc furnace charge, lower electricity consumption in the furnace, lower overall processing costs and a more efficient smelting process. [ABSTRACT FROM AUTHOR]

In this article, a novel efficient and environmental reductive roasting-acid leaching technique was proposed by a combined pretreatment of the microwave heating and reduction of alkali lignin. Factors influencing the leaching of manganese from manganese oxide ores were investigated, such as heating modes (microwave heating and conventional heating), microwave roasting parameters and acid leaching parameters. The results indicated that the leaching ratio of manganese by microwave heating was significantly higher than that by conventional heating under the same conditions. The reduction of manganese oxide ores by microwave heating was completed at a roasting temperature of 150°C and a roasting time of 5 min with the addition of 50% alkali lignin with the reduction sequence of MnO2 → Mn2O3 → Mn3O4 → MnO. A 97.43% leaching ratio of manganese was obtained from the roasted ore, which was leached by a 1.5 mol/L concentration of sulfuric acid at a 50°C leaching temperature, 50 rpm stirring speed and a 10:1 liquid-to-solid ratio for 5 min. Compared to the conventional reductive roasting-acid methods, the proposed technique was performed at a considerably lower temperature and shorter time, with higher reducing agent utilization ratio to processing the different manganese oxide ores. [ABSTRACT FROM AUTHOR]

The rare earth elements (REE) geochemistry and the isotope (δ13C, δ18O) composition of manganese ores of the Chiatura (Georgia) deposit were studied. One of the major features of all types of manganese ores is negative cerium (Ce/Ce*PAAS) anomaly and the absence of europium (Eu/Eu*PAAS) anomaly. Oxide oolitic manganese ores were formed in oxic shallow marine environments. The content and distribution of REEs (in particular Ce and Eu) in these ores are connected mainly with ferrous oxides. The performed C- and O-isotope research in Mn-carbonates (oolitic and massive) has indicated that carbonate ores were formed by the participation of isotopically light CO2 which is a result of the oxidation of organic matter in the sediment strata by reducing environments of early diagenesis (and, partially, catagenesis) zone. Obtained negative cerium anomalies in the studied carbonate ores reflect the specific REE patterns in pore waters of sediments of earlier isdiagenesis zone of the Oligocene Chiatura's basin. The deficiency of cerium in this zone remains debatable and requires further study.Formation of manganese carbonates took place multistage by the input of incisional solutions of different chemistry into sea bottom waters and sediments. The absence of europium anomaly indicates about lack of hydrothermal solution input. [ABSTRACT FROM AUTHOR]

[Display omitted] • A memristor with the Ag/CuMnO 2 /Ti sandwich structure was developed. • The resistance levels of the Ag/CuMnO 2 /Ti device can be regulated by magnetic field. • The magnetic field controlled memristor towards implantable detector was designed. • The magnetic-responsive memristor can be used in the multi-levels information storage. • The magnetic field controlled resistance switching behavior should be attributed to the influence of Loren magnetic force on moving charge. Memristors, which combine the behaviors of memory and resistive switching (RS), have a wide application prospect in information processing and artificial neural networks. The RS memory behaviors of memristors are primarily determined by the functional layer materials, device structure, and working conditions. Herein, a CuMnO 2 nanomaterial with the manganese copper ore structure was prepared on a Ti substrate by hydrothermal method, and a memristor with the Ag/CuMnO 2 /Ti sandwich structure was developed. The RS memory behavior of the as-prepared memristor can be regulated through a low magnetic field (MF), and thus the resistance value of device shows a multi-level resistance states. Compared with other regulation factors, the MF can remotely adjust and control the RS characteristics of memristor, which is a non-invasive and non-destructive regulatory means. The MF regulated memristor can not only be used for multi-level high-density information storage, but also it can protect the health of special populations by identifying the MF intensity of the surrounding environment. When the device is operated in an MF environment, the change of resistance value of the device in both high resistance state (HRS) and low resistance state (LRS) is mainly attributed to the influence of Loren magnetic force on conductive ions. [ABSTRACT FROM AUTHOR]

Increasing demand for manganese and rapid depletion of high-grade manganese ores grow attention to other resources. However, environmental impacts and techno-economic issues are the main challenges regarding manganese extraction from low-grade ores. This study investigated the environmental impacts of manganese recovery from low-grade ores and the synthesis of magnetic manganese ferrite. Two methods of synthesis were selected, a high-temperature synthesis using a furnace and a low-temperature method where the aging process compensates for the absence of a high-temperature regime. Life cycle analysis was conducted through the collected data to quantify and compare the environmental impacts. The high-temperature synthesis method surpassed the other process in almost all environmental categories adopted in the TRACI model. Additionally, sodium hydroxide has almost the highest contribution in both synthesis methods, while in the recovery process, electricity was the major contributor to all environmental categories. Besides electricity, sulfuric acid and sulfur dioxide play essential roles in the environmental impacts of the recovery process. Therefore, the low-temperature synthesis of manganese ferrite as a novel method is cost-effective and warrants the least environmental footprint. [ABSTRACT FROM AUTHOR]

Economic growth in developing countries, China in particular, has led to an increase in steel production and consumption in recent years. This trend is stimulating the demand for manganese ferroalloys. High-grade manganese ores from Australia, Africa, and South America are being supplied in larger quantifies to Asian ferroalloy plants, which used to consume low-grade manganese ores. Most experts believe that the future of the manganese industry will depend on the dynamics of steel production. In other economic areas, manganese consumption is expected to grow immensely due to the use of manganese for manufacturing lithium-ion and nickel–metal hydride batteries for electric vehicles. More than 90% of the manganese produced globally is utilized by the iron and steel industry in the form of various manganese ferroalloys. Manganese consumption in steelmaking in different countries depends on the range of smelted metal (oxygen-converter or electric steelmaking), the scientific and technical level of technological processes, and other factors. In the CIS countries, specific consumption of manganese amounts to 9 kg per 1 ton of steel, which is an impressive figure. In this research, we investigate the possibility of phosphorus removal into the gas phase during production of manganese ferroalloys. This will make it possible to involve domestic phosphorus-containing manganese ores in production for obtaining high-grade manganese ferroalloys. [ABSTRACT FROM AUTHOR]

The effect of raw materials on the temperature development and prereduction behavior of Comilog and Nchwaning manganese ores (3.33–4.00 mm or 11.20–15.00 mm) were investigated in a CO-CO2 atmosphere. Experiments were conducted at a heating rate of 6 °C/min from room temperature to 1000 °C where the ore was mixed with inert material (quartz) in various ratios. A similar heating program gave dissimilar temperature development for Comilog and Nchwaning ores due to differences in oxygen levels and reduction rates. The temperature development, and thus reduction rate, decreased with the increasing amount of inert material in the mix for Comilog ore in size 3.33–4.00 mm. The peak reaction rates observed during reduction were 2.4 wt%/min, 1.0 wt%/min, and 0.8 wt%/min for an ore:quartz weight ratio of 1:0, 1:1, and 1:3, respectively. For Comilog ore in size 11.20–15.00 mm, and Nchwaning ore in both sizes, the temperature development and reduction rates were slightly or insignificantly affected. It was suggested that the effect was low for reactions under a diffusion-controlled kinetic regime. [ABSTRACT FROM AUTHOR]

The purpose of this article will be to show how the Brazilian manganese exploration contracts in Amapá between 1946 and 1954 signed with the mining company Icomi were an instrument of capital appreciation on an international scale, since a significant part of the income was compromised in external agreements with Bethlehem Steel and the Eximbank. Methodologically, we will read the main issues in the specific legislation that involved the manganese exploration contracts in Amapá and their effects, dialoguing with the studies that analyzed this institutional framework. The main institutional regimes researched are: i)- Decree-Law n° 5.812 (09/13/1943) creating the territory of Amapá; ii)- Decree-Law No. 9,858 (09/13/1946) creating the national manganese reserve in Amapá; iii)- Decree No. 24,156 (12/04/1947) which governed the contract signed with Icomi for manganese exploration; iv)- Decree No. 28,162 (05/31/1950) revising the contract with Icomi; v)- Law No. 1,235 (11/14/1950) which established the guarantee of the National Treasury for a loan to be contracted by Icomi abroad; vi)- and, lastly, Ordinance No. 247 (04/29/1953) which allowed the amendment to the lease agreement of manganese ore deposits in Serra do Navio - Amapá. After making a detailed investigation of the exploration contracts, the article concludes that the extraction of manganese in Amapá was a true model of enclave economy, in which a large part of the income generated by the enterprise did not radiate throughout the region. [ABSTRACT FROM AUTHOR]

Total reflection X-ray fluorescence (TXRF) has been widely considered as an effective analytical tool for the analysis of a great variety type of polymetallic deposits, because it has many advantages of extremely high sensitivity, high accuracy, minor sample preparation, and the ability of multielement simultaneous analysis. Sample preparation is quite important for TXRF quantitative analysis. Since pretreatment factors, such as sample amount, dispersant type, sample particle size and sample physicochemical properties, are seriously impact the accuracy of results. Based on this reason, investigating an appropriate sample pretreatment strategy is fundamental for accurate assessment of strategic metal elements in polymetallic deposits. This review presents a comprehensive overview of TXRF applications in the field of mineral analysis, including apatite, manganese ore, K-feldspars, granite, copper-nickel sulfide ore, etc. Moreover, the accurate evaluation of TXRF quantitative analysis is detailedly discussed, and the relevant sample preparation methods and preparation factors are also addressed. [ABSTRACT FROM AUTHOR]

Peroxymonosulfate‐based advanced oxidation processes (PMS‐AOPs) for in situ persistent organic pollutant (POP) remediation in aqueous solutions can be a promising technology. However, this technology is constrained by its high toxicity and cost of metal oxide and non‐metal catalysts for PMS activation. Here, we investigated the catalytic performance of a widely available natural mineral, manganese ore (MO), for PMS activation. A series of natural MO samples in an aqueous solution were prepared via the Fenton‐like reaction. The samples' crystalline structure, surface morphology, textural properties, and other surface characteristics of the selected MO were systematically characterized. The effects of PMS concentration and process parameters on the degradation performance of four chosen model pollutants, that is, phenol, tetrabromobisphenol A (TBBPA), rhodamine B (RhB), and methylene blue (MB), were evaluated. The experimental results showed that natural MO increased catalytic activity and enhanced the PMS oxidation processes, with 98%, 90%, and 75% removal efficiencies on phenol, TBBPA, and RhB, respectively, within 1.5 h. The reduction in the initial pH solution from 10 to 7 and the increase in temperature from 15 to 45°C enhanced the MB degradation rate (decolorization) by 55 and 46%, respectively, within 2 h. During the PMS activation process, SO4•−, •OH, and 1O2 species were generated, but only SO4•− and •OH radicals with strong oxidative potentials contributed to the catalytic degradation. The dissolved metals from the experiments were found well within the limit of drinking water standards, verifying that the MO + PMS catalytic system is suitable for commercial applications. This work provides insights into the development potential and prospects of using natural minerals for PMS activation and POP degradation, which can accelerate their industrial applications. [ABSTRACT FROM AUTHOR]

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