Mn Hydroxides Research Articles

Speciation of Trace Metals in the Bottom Sediments of the Mozhaisk Reservoir and the Moskva River

The speciation of heavy metaf Geology, ls (Mn, Fe, Co, Ni, Cu, Zn, Cd, and Pb) in the bottom sediments of the Mozhaisk Reservoir and the Moskva River is described. They were characterized using the Tessier sequential selective extraction procedure trace element concentrations determined by inductively coupled plasma–mass spectrometry (ICP-MS). The bottom sediments of the Mozhaisk Reservoir are characterized by higher concentrations of the examined metals compared to the channel alluvium of the Moskva River. In this case, the most widespread metal compounds in the bottom sediments of the Mozhaisk Reservoir are firmly bound (stable form) to the mineral matrix. High concentrations of the firmly bound forms of metals (Co, Ni, Cu, Zn, Cd, Pb, and Fe) in the bottom sediments are due to an increased proportion of the silt fraction (0.1–0.01 mm) entering the reservoir due to abrasion of its shores. The only exceptions are Mn and Cd, which are present in labile compounds with carbonates and hydroxides of iron and manganese. In the bottom sediments of the Moskva River, strongly bound forms prevail for most metals—for Ni, Zn, and Cd, they are complex compounds with Fe and Mn hydroxides; for Co, Cu, Pb, and Fe, they are compounds with stable silicate minerals. The proportion of labile bioavailable forms of metals in the bottom sediments of the Moskva River is higher than in the reservoir due to anthropogenic input. Among the labile forms of the metal compounds, carbonates predominate. The proportion of elements in the most mobile exchange form and in compounds with organic matter is not large and does not exceed 14% for most elements. The only exceptions are Co and Cd, for which the concentration of the exchange form reaches 25%.

REE mineralization in alkaline rhyolites of the Pechalninsky ore field (North-East of Russia)

For the first time (by methods Scanning Electron microscopy, X-ray spectral microanalysis and cathodoluminescence method) REE mineralization studies have been conducted in alkaline rhyolites of the Pechalninsky ore field (North-East of Russia), a potentially larger-volume source of HREE. It is shown that in the direction of fluidity, thin interlayers composed of crystalline aggregates of pyroxenes and/or amphiboles impregnated with a silicate substance alternate in the rock, and ribbon-like thin strips and lace separations of Fe, Ti, and Mn hydroxides that have replaced titanomagnetite (relict secretions of which are partially preserved). Microcrystalline aggregates of pyroxenes and/or amphiboles contain the finest inclusions of REE secretions (5–7 microns), the determination of mineral species of the latter is difficult due to the small particle sizes. Scanning electron microscopy (EMF) has determined that these secretions are REE phosphates. Concentrically zonal and radially radiant REE secretions have been revealed in the relics of titanomagnetite crystals. The first ones are represented by silicates enriched with Yt and REE. In them, the content of REE varies unevenly from the center to the edge. Radially radiant aggregates are represented by oxides and/or carbonates containing REE (La, Ce and Nd predominate). The results obtained can be used in the development of enrichment technology.

Electrochemical Performance of LiNi0.5Mn0.5O2 Electrode in All-Solid-State Battery

IntroductionOxide-based all-solid-state batteries (Ox-ASSBs) have been attracting attention as next-generation secondary batteries because of their high safety and high energy density. Recently, Ox-ASSBs have been reported by use of LISICON-type Li3.5Ge0.5V0.5O4(LGVO) as a solid electrolyte and layered NaCl-type LiCoO2 and LiNi1/3Mn1/3Co1/3O2 as positive electrodes. We have focused on Li2MnO3-based positive electrodes without Co, as shown in Li4/3-2/3x Mn2/3-1/3x NixO2 (0<x<1/2). LiNi0.5Mn0.5O2(x=1/2, LNMO) combines high capacity and thermal stability. It is well known that disordering of Li and Ni in the layered NaCl-type structure occurs during sintering and that oxide ions involve in charge compensation at higher voltages. Accordingly, the electrochemical properties vary depending on the amount of Ni substitution and excess Li relative to the transition metal in conventional Li-ion battery. Therefore, we have investigated an Ox-ASSB battery using LNMOs as a positive electrode, specifically focusing on effects of both Li, Ni-disordering and their sintering temperatures on the performance while controlling chemical compositions precisely.ExperimentalLNMO were prepared by co-precipitation method. The precursor Ni and Mn hydroxides ware prepared from Ni(NO3)2･6H2O and Mn(NO3)2･6H2O. The precursor and LiOH･H2O were mixed to a specified chemical composition ratio, formed under pressure, and calcined at 1073, 1173, 1273 K to obtain LNMO. The solid electrolyte LGVO was synthesized by sintering a mixture of Li4GeO4 and Li3VO4 at 973 K. The LNMO composite cathode layer on LGVO was prepared by applying a composite LNMO cathode slurry, drying, and sintering at 1023K for 6 hours The solid electrolyte LGVO and cathode material LNMO contain 5 % Li3BO3 as a sintering aid. The crystalline phase was identified by powder X-ray diffraction measurement by CuKα radiation. The chemical bonding state was analyzed by X-ray photoelectron spectroscopy Electrochemical testing was performed by LNMO/ LGVO / sulfide solid electrolyte Li10GeP2S12 / In-Li cell (Φ10mm) at 323 K. The rate of constant current was 1/100 C in the 2.0-(3.6~4.0) V.Results and discussionThe samples sintered at 1073, 1173, and 1273 K showed a single phase of LiNi0.5Mn0.5O2. The I (003)/I (104) intensity ratio of Bragg peak, which is an index of the degree of disordering of Li and Ni, increased with increasing sintering temperature. The disordering of Li and Ni in the layered NaCl-type structure occurred with increasing sintering temperature. Fig. 1 shows the charge-discharge measurement results of Ox-ASSB using LNMO (x=1/2) sintered at 1173 K. Followed by a single phasic reaction, a plateau is observed around 3.9 V, the discharge capacities are 175 mAhg-1 at the end-of-charge voltage of 3.6 V and more than 250 mAhg-1 at 4.0 V. Compared to conventional LiB using a liquid electrolyte, this LNMO shows a higher specific capacity, suggesting a possibility to have stable charge-discharge behaviors with LGVO solid electrolyte. These results will be discussed based on the analysis of the cell resistance and the chemical bonding states by XPS measurements before and after charging and discharging. We will present results of other Li-rich positive electrodes in Ox-ASSBs while focusing on a role of oxide ions during and charging-discharging. Figure 1

Structure–reactivity relationships in the removal efficiency of catechol and hydroquinone by structurally diverse Mn-oxides

Structure–reactivity relationships in the removal efficiency of catechol and hydroquinone by structurally diverse Mn-oxides

Modes of occurrence of tungsten in coals: a review

Relevance. The necessity to know the conditions and forms of W concentration in coals for solving a number of scientific and engineering problems at complex development of coal deposits. Aim. Complex estimation of W modes of occurrence in coal for development of measures for rational ecologically safe use of coal. Methods. Correlation analysis, scanning electron microscopy, infrared spectroscopy, coal group analysis, inductively coupled plasma mass spectrometry, instrumental neutron activation analysis. Results and conclusions. The modes of occurrence of W in coal were studied by a complex of methods. In the majority of W-enriched coal deposits, a negative significant correlation of its content in coal and coal ash with ash yield was found, indicating its association with organic matter. Using the method of coal group composition analysis, it was found that the main carrier and concentrator of W in the studied lignite deposits is organic matter. The contribution of the mineral phase in general in W-rich coals and in coals with its normal content does not exceed 20%, usually less than 5%. These conclusions are also confirmed by infrared spectroscopy data, according to which no more than 15% of the metal in the samples studied is associated with mineral phases. The association of W with high molecular humic acids predominates. In anomalously W-enriched lignites, the humic acid phase represents 76 to 88% of the gross metal content. The role of bitumen and low-molecular-weight humic acids in the balance of W is marginal at their different levels in the coals. Mineral phases of W are not characteristic of coal. Nano-microinclusions of scheelite, wolframite, hubnerite and ferberite were recorded as isolated occurrences. The main mineral phases are associated with Fe and Mn hydroxides, in which W is presented as a trace element in the amount of 1–5% together with other elements (Ge, As, etc.). In more metamorphosed bituminous and anthracite coals, authigenic mineral formations were found, represented by tungstite, phyllotungstite, native W and complex Fe-Mn-Ca-W-O mineral phases.

Alterations of High-Carbon (Shungite) Rocks by the Lake Onega Waters: Mineralogy and Geochemistry of the Process

Abstract ––Carbonaceous (shungite) rocks have high contents of trace elements, which can get to the environment through natural weathering. Shungite rocks are a group of Precambrian carbonaceous rocks of volcanic and sedimentary genesis in Karelia. In this work we present results of studying the mineral and geochemical compositions of shungite rocks at their outcrops on the shoreline of Lake Onega. The interaction of the Onega waters with shungite rocks led to: (1) the removal of most elements, except for K, Mn, Ba, and Mg, whose contents in the rocks increased; (2) the formation of an assemblage of secondary minerals, such as hematite, jarosite, goethite, chalcocite, anglesite, brookite, and Mn hydroxides. Based on the results obtained, we propose a model of the transformation of high-carbon (shungite) rocks by the Onega waters.

Ultraselective enrichment of trace elements in seawater by Co-rich ferromanganese nodules

Ultraselective enrichment of trace elements in seawater by Co-rich ferromanganese nodules

Assessment of anthropogenic pollution in Guanabara Bay (SE Brazil) through biogeochemical data and stable isotope mixing models.

This work intends to identify pollution sources along the margins of Guanabara Bay (GB; SE Brazil) through a multiproxy approach and Bayesian stable isotopic mixture model (BSIMM). For this purpose, 33 surface sediment samples were collected and analyzed for granulometry, geochemistry (heavy metals, total organic carbon-TOC, stable isotopes of carbon and nitrogen-δ13C and δ15N, Rock-Eval pyrolysis parameters-REPP), and physicochemical parameters. Metal concentrations (E) dissolved in water (EW), adsorbed by organic matter (EOM) and by Mn hydroxides (EMn), and total extracted concentrations (ET) were analyzed. Sampling was conducted in 2018 after an oil spill from Reduc Oil Refinery. Potential Ecological risk index (PERI), based on metals, classified 85% of the analyzed stations as having moderate to considerable ecological risk. The metals with the potential to cause the highest ecological risk were CdW, CdOM, PbOM, and HgOM. The combination of BSIMM and REPP data was an effective proxy for oil spill detection by indicating the presence of polycyclic aromatic hydrocarbons (PAHs). Relatively high TOC contents suggested that the analyzed stations are eutrophicated environments. BSIMM discriminated three groups of stations with different sources of organic matter (OM), endorsing the result previously shown by the cluster analysis: (A) Niterói region, Botafogo marina, Glória marina, Fiscal and Fundão islands with diffuse sources of OM, including marine phytoplankton and material of continental origin from highly polluted rivers and domestic sewage; (B) region near Fundão and Governador islands and Mangue Channel outlet with OM (≃70%) supplied by highly polluted streams and a small contribution of PAHs; (C) Duque de Caxias and Botafogo-Urca inlet with significant contributions of PAHs, materials from C-3 plants and rivers polluted by urban sewage. Results of linear regressions in conjunction with BSIMM indicate that HgMn and PbOM mainly affect Group A's stations. Although the eastern margin of GB (Niterói; Group A) showed greater oceanic interaction than the other groups, it presented substantial concentrations of metals, potentially harmful (i.e., Hg and Pb) to marine biota and human health.

A facile route for decoration of hematite photoanodes by transition metal hydroxide co‐catalysts

AbstractEarth‐abundant α‐Fe2O3 (hematite) is a convincing photoanode for photoelectrochemical (PEC) water splitting; however, its intrinsic properties of inferior charge transfer and sluggish water oxidation kinetics limit its performance. Here, we report a straightforward decoration method for transition metal hydroxides to accelerate the oxygen evolution reaction (OER) of hematite photoanodes grown by electric field‐assisted liquid phase deposition (EA‐LPD). The investigations revealed that Co(OH)2 acts as a superior co‐catalyst compared with hydroxides of Mn, Fe, Co, Ni, and Zn. EA‐LPD‐grown hematite photoanode loaded with cobalt hydroxide exhibited an excellent PEC performance. A photocurrent density of 0.93 mA.cm−2 at 1.23 V versus reversible hydrogen electrode was achieved for the modified hematite, ∼3 times more than that of pristine hematite, and a cathodic shift of 100 mV for the onset potential was observed. The proposed simple and cost‐effective co‐catalyst loading strategy provides a high degree of freedom in the design of co‐catalysts with a complex chemical composition comprising transition metal oxyhydroxides and hydroxides on different photoanodes for more efficient charge carrier separation for the PEC applications.

Understanding seasonal variations in As and Pb river fluxes and their regulatory mechanisms through monitoring data.

The Doce River Basin (DRB) suffers with the adverse impacts of mining activities, due to its high level of urbanization and numerous industrial operations. In this study, we present novel insights into contaminant flow dynamics, seasonal variations, and the primary factors driving concentration levels within the region. We conducted an extensive analysis using a database sourced from the literature, which contained data on the contamination of arsenic (As) and lead (Pb) in the Doce River. Our primary aim was to investigate the patterns of As and Pb flow throughout the entire basin, their response to seasonal fluctuations, and the key parameters influencing their concentration levels. The results showed significant seasonal fluctuations in As and Pb fluxes, peaking during the rainy season. The 2015 Fundão dam breach in the DRB led to notable changes, elevating elemental concentrations, particularly As and Pb, which were subsequently transported to the Atlantic Ocean. These increased concentrations were primarily associated with iron and manganese oxides, hydroxides, and sulfates, rather than precipitation, as evidenced by regressions with low R2 values for both As (R2 = 0.07) and Pb (R2 < 0.001), concerning precipitation. The PCA analysis further supports the connection between these elements and the oxides and hydroxides of Fe and Mn. The approach employed in this study has proven to be highly effective in comprehending biogeochemical phenomena by leveraging data from the literature and could be a model for optimizing resources by capitalizing on existing information to provide valuable insights for drainage basin management, particularly during crises.

Constructing a 3D multichannel structure to enhance performance of Ni–Co–Mn hydroxide electrodes for flexible supercapacitors

Constructing a 3D multichannel structure to enhance performance of Ni–Co–Mn hydroxide electrodes for flexible supercapacitors

Nonthermal plasma-activated polyvalent cerium-manganese bimetallic (hydro)oxide-functionalized nanographene for the removal of thallium(I) contaminants and mechanism exploration

Nonthermal plasma-activated polyvalent cerium-manganese bimetallic (hydro)oxide-functionalized nanographene for the removal of thallium(I) contaminants and mechanism exploration

Mineralogy of apatite-aegirine-mesoperthite pegmatites of mine no. 243 Of the ilmeny state reserve (South Ural)

The paper describes mineralogy of apatite-aegirine-mesoperthite pegmatites, which are located in a fenite halo at the southeastern contact of the Selyankino syenite block (Ilmeny State Reserve, South Urals). Two pegmatite veins are exposed by mines. The pegmatites differ from the known veins of the Ilmeny State Reserve in a high amount of apatite and the presence of the best collection aegirine druses. The pegmatites contain albite, microcline, aegirine, hydroxyapatite, fuorapatite, calcite, titanite, chevkinite-(Ce), magnetite, ilmenite, hematite, rutile, Fe and Mn hydroxides, monazite-(Ce), rhabdophane-(Ce), rhabdophane-(La), and dalnegorskite. Keywords: aegirine, apatite, mesoperthite, dalnegorskite, syenite pegmatites, phenite, South Urals.

Composition, distribution and enrichment of trace metals in sediments from the muddy area off the southern Shandong Peninsula in the Northwestern South Yellow Sea of China since 10,000 years

Composition, distribution and enrichment of trace metals in sediments from the muddy area off the southern Shandong Peninsula in the Northwestern South Yellow Sea of China since 10,000 years

Economic and Environmental Sustainability of an Innovative Cryo-Mechano-Hydrometallurgical Process Validated at Pilot Scale for the Recycling of Li Batteries

An innovative cryo-mechano-hydrometallurgical process (named LIBAT) was demonstrated at pilot scale for the treatment of EOL lithium primary batteries with chemistry Li(0)-MnO2. The process allowed the recycling of steel scraps from external cases after cryomechanical dismantling, and the recovery of Mn and Li products after hydrometallurgical processing. During demonstration activities, about nine tons of batteries were treated in the cryomechanical section, and one ton of black mass was treated in the hydrometallurgical section for the recovery of Mn hydroxides and Li2CO3. The environmental impacts of the process were evaluated in comparison with an innovative pyrometallurgical approach allowing Li recovery, confirming the benefits of the proposed process due to a reduction in energy consumption. Process simulations were performed considering different mixture feeds (only Li primary, or mixture with Li-ion batteries) and process options (only the cryomechanical section of the integral process) to assess the lower limits of potentiality that would ensure economic sustainability.

Determination of Arsenic Species Distribution in Arsenide Tailings and Leakage Using Geochemical and Geophysical Methods

This study describes the distribution of arsenic mobile species in the tailings of Cu–Co–Ni–arsenide using the sequential extraction and determining the contents of arsenate (AsV) and arsenite (AsIII). The object of this study is the tailings ponds of the Tuvakobalt plant, which contains waste from the hydrometallurgical arsenide ore processing of the Khovu-Aksy deposit (Republic of Tuva, Russia). A procedure of sequential extraction for arsenic was applied, and it includes the extraction of the following forms: water-soluble, potentially water-soluble and exchangeable, easily sorbed on the surface of carbonates, associated with Fe/Mn oxides/hydroxides, associated with easily oxidized minerals, and accounted for by non-oxidized arsenic minerals. This procedure, which takes into account the peculiarities of the physical and chemical composition of the waste, was supplemented by the analytical determination of the arsenite and arsenate content by using the methods of inductively coupled plasma atomic emission spectrometry (ICP-AES) combined with the hydride generation technique (HG-ICP-AES). The content of the most mobile forms of arsenic, which are water-soluble, potentially water-soluble, and exchangeable species, is equal to 56% of the total arsenic content, 23% and 33% of which are arsenite and arsenate, respectively. Unlike arsenic, the mobile forms of metals have been determined in small quantities. The largest proportion of water-soluble and exchangeable forms is formed by Mg, Ca, and Sr at 11, 9.4, and 20%, respectively (residual and redeposited carbonates). The proportion of water-soluble forms of other metals (Cu, Zn, Co, and Ni) is &lt; 1% or 0. The main part of the metals is adsorbed on the surface of Fe and Mn hydroxides, enclosed in easily and hardly oxidized minerals. In addition to geochemical studies, the presence of leaks from the tailing ponds into ground waters was determined by using electrical resistivity tomography. The data obtained indicate a high environmental hazard of tailings and the possibility of water-soluble and highly toxic arsenic compounds entering ground waters and aquifers.

Excellent catalytic performance of mechanically alloyed AlCrFeMnTiZr0.5 high-entropy alloy for malachite green degradation

Excellent catalytic performance of mechanically alloyed AlCrFeMnTiZr0.5 high-entropy alloy for malachite green degradation

Geology, mineralogy, geochemistry and deposit model of iron and manganese in Bouarfa mine, Eastern High Atlas, Morocco

The Bouarfa Iron and Manganese Deposits are contained in the Sinemurian carbonate formations in the eastern High Atlas. It is a large deposit which has allowed the exploitation of more than 1.5 million tons of manganese and which still contains millions of tons of reserves. The mapping carried out shows the extension of the mineralization with oxides and hydroxides of Mn and Fe. The definition of types of mineralization shows that they are essentially stratiform deposits with some bodies and veins in the fault zones. The result of the mineralogical identification and geochemical analyses shows that it is a sedimentary deposit resulting from at least two mineralizing events with a high Fe-Mn content during the installation of the Sinemurian shallow carbonate platform. This is an environment of rapid oxidation and relatively sufficient sulphide inputs under redox conditions.

Clarifying and quantifying the immobilization capacity of cement pastes on heavy metals

Clarifying and quantifying the immobilization capacity of cement pastes on heavy metals

Molybdenum–Manganese hydroxide microcubes based electrode via hydrothermal method for asymmetric supercapacitor

Molybdenum–Manganese hydroxide microcubes based electrode via hydrothermal method for asymmetric supercapacitor