Mn Deposits Research Articles

Manganese Electrochemistry in a Deep Eutectic Solvent: The Effects of KBr

AbstractThis work reports the effects of potassium bromide (KBr) on the electrodeposition of manganese on copper from a DES consisting of a stoichiometric 1:2 mix of choline chloride and ethylene glycol (Ethaline 200). The speciation of MnCl2.4H2O in Ethaline 200 has been investigated using UV–vis spectroscopy, in particular with regard to the addition of KBr to the plating bath, for which no apparent change in the Mn species was noted. This said, the physical properties of the manganese deposits themselves were found to have been considerably improved in comparison to when KBr was omitted from the bath; indeed, the actual adhesion of Mn was achieved for the first time on a copper substrate, somewhat remarkably producing a coating of some considerable thickness. Given its clear electrochemical behavior of the Mn liquid were subsequently determined via cyclic voltammetry method. A reduction in the peak current of Mn was noted on addition of KBr. The mechanism of Mn deposition has been examined via chronocoulometry and chronoamperometry. Surface analyses of Mn deposits have been conducted via SEM/EDX, AFM, and XRD, from which improvements to the Mn surface coatings in depositions performed from an electrolyte containing 0.1 M KBr were noted.

Welding techniques and manganese concentrations in blood and brain: Results from the WELDFUMES study

This study used whole-brain mapping to investigate the effect of different welding processes on manganese (Mn) accumulation in the brain. Exposure measurements were performed at the welders’ workplaces about 3 weeks before a magnetic resonance imaging (MRI) examination. The welders were categorized into three main groups based on welding method, and the T1-relaxation rate (R1) was measured using quantitative MRI (qMRI). Welders using shielded metal arc welding (SMAW) were found to have lower accumulations of total Mn in clusters encompassing white matter, thalamus, putamen, pallidum, and substantia nigra compared with welders using inert gas tungsten arc welding (GTAW) or continuous consumable electrode arc welding (CCEAW). A positive correlation was found between Mn in red blood cells (Mn-RBC) and R1 in a region encompassing pre-and post-central gyri. The results of this study show that the accumulation of free, bound, or compartmentalized Mn ions in the brain differed depending on the welding method used. These differences were predominately located in the basal ganglia but were also found in regions encompassing white matter. The level of Mn-RBC was correlated to the deposition of Mn in the left primary somatosensory and motor cortex and may therefore be linked to neurological and neurobehavioral symptoms.

Mineralisation controls for the diverse Cape manganese occurrences, South Africa

Abstract The Cape Fold Belt, comprising folded sedimentary sequences from predominantly the Palaeozoic Cape Supergroup, hosts a multitude of manganese occurrences and mineral deposits, many of which were subject to historical mining activity. Although size, grade and quality issues negate their modern-day exploitation for the steel-making process, the mechanisms by which Mn has enriched at these sites holds scientific value for our understanding of low-temperature Mn (bio-)geochemical cycling. Deposits located within the Cape Fold Belt comprise structure-hosted Mn deposits and a little described class of Mn mound deposits associated with chalybeate thermal springs (temperature = 41 to 48°C). Although the relationships between the two remain tenuous, detailed study of both classes provides insight into the conditions that favour Mn accumulation in the near-surface and sub-aerial environments. Comparisons between the physicochemistry of manganiferous- and non-manganiferous thermal springs suggest that manganese solubility is favoured by warm, acidic and slightly reducing fluids with elevated salinity. Transport, and associated fluid focusing typically within highly permeable sandstone units, serves to locate Mn mineralisation in near-surface structurally-complex trap sites that provide both accommodation space and conditions that are sufficiently oxidising. Where manganiferous spring waters spill out at surface, oxidation is caused by contact with atmospheric O2 to form Mn mound deposits, and ambient Mn-oxidising microbiota (e.g., genus Ramlibacter, and members of Burkholderiales, Rhodocyclaceae, and Oxalobacteraceae) are likely to play a role in enhancing the kinetics of this process. Relative to the structure-hosted deposits, these Mn mound deposits are typically lower grade (higher iron content) and relatively friable (high porosity and fine grain sizes). Supergene and diagenetic processes can lead to localised upgrade of the Mn mound material, although typically not to ore grade.

New Mn Electrochemistry for Rechargeable Aqueous Batteries: Promising Directions Based on Preliminary Results

Aqueous batteries with metal anodes exhibit robust anodic capacities, but their energy densities are low because of the limited potential stabilities of aqueous electrolyte solutions. Current metal options, such as Zn and Al, pose a dilemma: Zn lacks a sufficiently low redox potential, whereas Al tends to be strongly oxidized in aqueous environments. Our investigation introduces a novel rechargeable aqueous battery system based on Mn as the anode. We examine the effects of anions, electrolyte concentration, and diverse cathode chemistries. Notably, the ClO4‐based electrolyte solution exhibits improved deposition and dissolution efficiencies. Although stainless steel (SS 316 L) and Ni are stable current collectors for cathodes, they display limitations as anodes. However, using Ti as the anode resulted in increased Mn deposition and dissolution efficiencies. Moreover, we evaluate this system using various cathode materials, including Mn‐intercalation‐based inorganic (Ag0.33V2O5) and organic (perylenetetracarboxylic dianhydride) cathodes and an anion‐intercalation‐chemistry (coronene)‐based cathode. These configurations yield markedly higher output potentials compared to those of Zn metal batteries, highlighting the potential for an augmented energy density when using an Mn anode. This study outlines a systematic approach for use in optimizing metal anodes in Mn metal batteries, unlocking novel prospects for Mn‐based batteries with diverse cathode chemistries.

Effect of manganese amino acid complexes on growth performance, meat quality, breast muscle and bone development in broilers

ABSTRACT 1. This study was conducted to investigate the effects of dietary supplementation of manganese (Mn) amino acid complexes on growth performance, Mn deposition, meat quality, breast muscle and bone development of broilers. 2. A total of 504, one-day-old male Arbor Acres broilers were randomly divided into seven treatments; control diet (CON; basal diet, no extra Mn addition), manganese diet (MnN as Numine®-Mn; CON + 40, 80, 120 or 160 mg Mn/kg), manganese-S group (MnS; CON + 120 mg Mn/kg as MnSO4·H2O), manganese-A diet (MnA as Mn from hydrolysed feather meal; CON + 40 mg Mn/kg as MnA). 3. There were no significant differences for average daily gain (ADG) or feed intake (ADFI) among diets during the feed phases (p > 0.05). The FCR in the starter and over the whole period were quadratically affected by dietary MnN dosage and gave the lowest FCR at 80 mg/kg (p < 0.05). The Mn content of thigh muscle, jejunum, heart, pancreas, liver and tibia increased linearly with MnN addition (p < 0.05). 4. For meat quality, MnN significantly increased colour (a*), pH45 min and pH24 h, reduced shear force, drip loss and pressure loss of breast muscle (p < 0.05). 5. Moreover, MnN significantly upregulated MYOD expression at d 21 and SOD expression at d 42, decreased MuRF1 and Atrogin-1 mRNA level at d 42 in breast muscle. Transcriptome analysis revealed that the regulating effect of MnN on muscle development significantly enriched signalling pathways such as adhesion, ECM-receptor, MAPK, mTOR and AMPK. Furthermore, dietary MnN significantly affected tibia length and growth plate development (p < 0.05) and promoted growth plate chondrocytes by increasing SOX-9, Runx-2, Mef2c, TGF-β, Ihh, Bcl-2 and Beclin1 and decreasing Bax and Caspase-3 (p < 0.05) expression which affect longitudinal tibial development. 6. In conclusion, Mn amino acid complexes could improve growth performance, tissue Mn deposition, breast muscle development, meat quality and bone development.

Mannose-Binding Lectin Deposition in Membranous Nephropathy and Differentiation of Primary from Secondary Forms.

We investigated the lack of mannose-binding lectin (MBL) deposition in patients with secondary MNs (sMNs) with the presence of IgG4 deposition in relation to the presence of MBL deposition in patients with primary MNs (pMNs). We also established a connection between the stage of MN and MBL deposition. Materials from 72 renal biopsies with proven MN were used for immunohistochemistry staining (IHC) for the phospholipase A2 receptor (PLA2R), immunoglobulin subtype IgG4, and MBL. Patients were separated into one of the following three groups: primary MN (pMN), idiopathic MN (iMN), and secondary MN (sMN). Serum antibodies for PLA2R and thrombospondin type-I-domain-containing 7A (THSD7A) were also used for the precise evaluation of the type of MN, as well as for detecting positivity for PLA2R using IHC. Which stage of MN was present in relation to the deposition of MBL was evaluated. In total, 50 patients were positive for IgG4, 34 with pMN, 12 with iMN, and 4 with sMN. A total of 20 patients were positive for MBL, 14 with pMN and 6 with iMN; no MBL deposits were found in patients with sMN. MBL positivity was predominantly present in the first two stages of MN, with a gradual reduction in the later stages. The activation of the lectin-complement pathway occurs in the early stages of the disease and is associated with the deposition of IgG4; IgG4 deposition is present in sMN, but there is no MBL deposition. IgG4 cannot be used for the differentiation of primary from secondary MNs, but the lack of MBL can be used as a marker for sMN in the early stages of the disease.

Gluconic acid as the supplementary additive realizing high-efficiency production of metal manganese with decreased dosage of toxic selenium dioxide

Minimizing the dosage of toxic SeO2 additive in electrolyte for electrochemical deposition of metal manganese without compromising the current efficiency has long been the desire for electrolytic manganese industry. Herein, by combinative usage of SeO2 and gluconic acid (GlcA) as the composite additives, 50 % of SeO2 dosage can be cut down while the current efficiency can be increased from 67 % to 90 % at the same time, realizing the energy consumption being reduced by 23 % at the optimized concentration of 1.84 g/L GlcA. The electrochemical tests and electrode surface characterizations as well as density functional theory calculations jointly imply that the addition of GlcA can greatly increase the diffusion coefficient of Mn2+ from 1.5 × 10−6 cm2/s to 5.6 × 10−5 cm2/s, accelerating the approaching of Mn2+ towards the electrode surface by decreasing the diffusion barrier energy from 17.93 kJ/mol to 11.51 kJ/mol. On the electrode surface, the SeO32− is responsible for facilitating the electrochemical deposition of metal Mn by forming the MnSe intermediate while GlcA is in charge of restraining the activation of H2O molecule for inhibiting H2 generation, synergistically contributing to the efficient production of electrolytic metal manganese. The results can provide new insights for the environmentally friendly and high-efficiency upgrading of manganese industry.

Accumulation analysis and overall measurement to represent airborne toxic metals with passive tree bark biomonitoring technique in urban areas.

Authorities have long proved the utility of bioindicators in monitoring the state of environmental pollution. Some biological indicators can measure environmental pollutant levels, and many tree species have been tested for suitability for monitoring purposes. The differences in morphological characteristics in the trees have demonstrated the effects of human activities on different materials. Measuring bark and wood biomass from contaminated sites was identified and directly compared with those from a clean site or areas characterized by distinct contamination sources. However, preliminary results demonstrate the approach's potential in the realization of strategies for disease control and promoting health to reduce environmental and health inequalities in at-risk urban areas. Picea orientalis L. and Cedrus atlantica Endl., especially their bark, can be regarded as a more robust storage of Cu (37.95 mg/kg) and Mn (188.25 mg/kg) than Pinus pinaster, Cupressus arizonica, and Pseudotsuga menziesii, which and is therefore a better bioindicator for Cu and Mn pollution. Considering the total concentrations as a result of the study, the pollution is thought to be caused by environmental problems and traffic in the region. The deposition of Cu, Mn, Ni, and Zn elements was found P. menziesii (60, 443, 58, and 258 mg/kg) and P. orientalis (76, 1684, 41, and 378 mg/kg) and seems to reflect atmospheric quite clearly compared to P. pinaster, C. arizonica, and C. atlantica. Ni and Zn concentrations have significantly increased since 1983, and P. menziesii and P. orientalis can be potentially valuable bioindicators for emphasizing polluted fields.

LiMn2O4/Graphite Cell Degradation Mechanisms Studying How Mn Deposition Accelerates Lithiated Graphite Reactivity with Electrolyte

In this work, pouch cells of spinel LiMn2O4 (LMO) / artificial graphite (AG) were tested under varying conditions to investigate degradation mechanisms. Mn dissolution from the positive electrode and deposition onto the graphite negative electrodes immediately after formation was found to be significantly suppressed by operating cells at −10 °C during the formation cycle and limiting the upper cutoff voltage. A formation cycle at an elevated temperature of 70 °C greatly increases the Mn deposition and gas generation from electrolyte reduction after just a single cycle and had long term effects at increasing lifetime gassing and Mn deposition. The cold formation advantage disappeared once all cells were cycled at 40 °C, with similarly terrible cycle life (60–200 cycles) regardless of formation conditions. Studying fully lithiated graphite (LiC6) extracted from LMO cells in an isothermal microcalorimeter (IMC), we found that the parasitic heat flow associated with electrolyte reduction and graphite delithiation increased for anodes with significant Mn deposition. Therefore, Mn deposition on the negative electrode causes cell failure by compromising the anode passivation, increasing lithiated graphite-electrolyte reactivity and thereby accelerating the lithium inventory loss due to electrolyte reduction on the Mn sites on the negative electrode.

Laser melting deposition of Mn–Cu-based alloy: Microstructure, mechanical properties and damping capacities

Mn–Cu-based alloys are promising structural materials for noise and vibration reduction, and Mn–Cu-based alloys with medium Mn content offer significant advantages in formability and corrosion resistance. The preparation of Mn–Cu-based alloys using traditional processes has disadvantages such as the ease of defects and long preparation cycles. Laser melting deposition was employed to fabricate the Mn-36.53Cu-4.30Al-3.07Fe-2.46Ni-0.64Zn (wt. %) alloy thin wall sample, and the microstructure, mechanical characteristics, and damping capacity of the as-deposited samples were investigated. The microstructure of the as-deposited alloy revealed randomly dispersed fine γ-(Mn, Cu) dendrites and a small quantity of α-Mn phase across different sections. The as-deposited samples along the scanning direction (AD-S) exhibited an ultimate tensile strength (UTS) of 584 ± 6 MPa, while those along the deposition direction (AD-D) showed a UTS of 578 ± 6 MPa. The elongation of AD-S samples measured at 40 ± 0 %, and for AD-D samples, it was 31 ± 1 %. At ambient temperature, the as-deposited alloy displayed high damping properties with a frequency of 1 Hz and a strain amplitude ranging from 30 to 100 × 10−6. The findings contribute to the practical applications of Mn–Cu-based alloys, particularly those with a medium Mn concentration.

Microbial contribution to the formation of the Carboniferous sedimentary manganese deposits in northwestern China

There is an increasing consensus that microbes play a critical role in the genesis of sedimentary manganese (Mn) carbonate deposits. However, compelling evidence for the microbial involvement during sedimentary Mn metallogenesis remains insufficient, and the specific effects of microbial mediation need to be further elucidated. To advance our understanding of the microbial Mn metallogenesis, multi-scale petrographic observations and high-resolution mineralogical analyses (mainly based on Fourier transform infrared spectrometer and Raman spectroscopy) were conducted on the Carboniferous black shale-hosted Malkansu and limestone-hosted Zhaosu Mn ore deposits in northwestern China. Results show that the Mn ore samples are characterized by finely laminated texture with μm-scale cyclic variations of microbe-associated minerals including rhodochrosite, apatite, quartz, and organic matter as well. These features indicate the ubiquity of microbial mats during Mn mineralization. Microbial involvement is also supported by Mn carbonate aggregates with variable morphologies (filamentous with pearl necklace-like inner forms resembling vermiform morphologies and spheroidal, coccoid-like forms), as well as the annular organic matter that resembles bacterial cells. The cyclic occurrence of trace amounts of remnant Mn oxides verify that primary Mn accumulation took place under oxic bottom waters. The negative co-variation between Mn carbonates and organic matter on Raman profiles suggests that the former was formed during diagenesis via organic matter decomposition coupled with Mn oxide reduction. Combined with previous experimental simulations and natural observations, a two-step microbially mediated Mn metallogenic model is tentatively proposed for the studied Mn deposits: (1) Mn(II)-oxidizing bacteria effectively catalyzed the deposition of considerable Mn oxides under oxygenated bottom water columns, a process that was simultaneously sustained by oxygenic microbial mats such as cyanobacteria; (2) Buried Mn oxides were reduced by highly reactive organic matter sourced from dead biomats of Mn(II)-oxidizing bacteria and benthic phototrophs, a process mediated by Mn(IV)-reducing bacteria which not only promoted the reaction rate but also served as nucleation sites for Mn carbonate minerals. This model can also help to explain the occurrence of diverse authigenic accessory minerals (e.g., quartz, apatite, and talc) and remarkable enrichments of several specific elements (e.g., Co, Ce, and Mo) in the studied Mn ores, which were closely linked to the decomposed cells and extracellular polymeric substance (EPS). By comparing with previous microbial investigations on Mn deposits over geological history, we further highlight the fundamental role of microorganisms in regulating the formation of economic Mn carbonate deposits.

A distinct manganese deposit on a Middle Permian carbonate platform in South China

During the Middle Permian, Earth experienced a period of profound environmental changes, including the final stages of the Late Paleozoic Ice Age (LPIA), global seawater regression, the Guadalupian mass extinction event, and the eruption of the Emeishan Large Igneous Province (ELIP) in South China. These events collectively induced significant shifts in both the environment and biosphere, yielding several geochemical anomalies, including deposition of manganese (Mn) deposits. The link between Middle Permian Mn deposits and the prevailing environmental conditions, however, remains unclear. Here, four sections spanning the Middle Permian Maokou Formation to the Late Permian Longtan Formation in the Zunyi area of northern Guizhou, South China are investigated. Through sedimentological and geochemical analyses, this work aims to elucidate the evolution of sedimentary environments over the Middle to Late Permian. During this period, a transition from a shallow-water carbonate platform in the 1st Member of the Maokou Formation to a deeper, siliceous deposit in its 2nd Member was recorded. This shift results in a pronounced paleogeographic differentiation in the 3rd Member, juxtaposing the shallow-water carbonate platform against a deeper Mn-enriched basin. A number of geochemical proxies indicate a strong hydrothermal signal in the Mn deposits. Combined with positive Eu anomalies and low Sr isotopes, the data underscore the profound influence of hydrothermal input linked with early subaqueous eruptions from the ELIP on the nearby marine environment. A detailed examination of carbon isotope profiles from the Maokou Formation indicates that volcanic influences, shifts in marine ecosystems, and changes in primary production caused the fluctuations of δ13Ccarb and δ13Corg. Moreover, the formation of Mn carbonate in deeper waters effectively sequestered organic C. Collectively, our new data demonstrate that the essential conditions for the development of the carbonate-hosted Mn deposits include drowning of the carbonate platform through an increase in sea level, the availability of a sufficient Mn source, and the presence of a redox-stratified water column.

Discovery of Late Carboniferous high-grade carbonate-hosted manganese mineralization in the Maerkansu area of the Western Kunlun Orogen, Northwest China

The Aoertuokanashi deposit located in the Western Kunlun Orogen is the first known Late Carboniferous large high-grade carbonate-hosted Mn deposit in the world and it has been mined since 2018. The deposit is considered to have formed in a back-arc basin developed during the northward subduction of the Paleo-Tethys Ocean beneath the Tarim Block. The Re-Os isotope isochron age of Mn ore at the Aoertuokanashi deposit is 302 ± 9 Ma. The minimum initial 187Os/188Os values obtained from the deposit is 0.28, which indicates the presence of a mantle source for the mineralization. The Aoertuokanashi deposit is similar in age to the 301 ± 5 Ma Wajilitag kimberlite in the Tarim Block, which is considered to be the initial magmatic pulse triggered by the Tarim mantle plume. The Late Carboniferous Aoertuokanashi Mn deposit was likely promoted by igneous activity from the Tarim mantle plume.The Aoertuokanashi deposit shows geochemical characteristics of hot water activity in a back-arc basin. The Mn mineralization is hosted in the restricted platform facies. Framboidal pyrite, typical biomat, and authigenic quartz are observed in the Mn deposit, indicating the influence of microbial processes. The sedimentary facies show a starving basin feature that can enhance microbial mediation. The δ13CV-PDB values of mineralized rocks (from −19.5 to −8.2 ‰) are more negative than those of wall rocks (from −5.3 to + 4.2 ‰), whereas the δ13CV-PDB values (around −29 ‰) of kerogen for the Mn ore are significantly lower than those of the whole rock. These compositions indicate that the reducing function of organic matter played an important role in Mn mineralization. In the inferred extensional tectonic environment, under the influence of a mantle plume, the stratum with strong hot water activities and a large amount of organic matter becomes the focal point for the formation of carbonate type manganese ore deposit.

Boron isotopes of Manganese ores from the northern part of the Kalahari Manganese Deposit, South Africa

Abstract 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 metal-grade 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.

Late Mesoproterozoic iron and manganese deposition on a deep-water carbonate platform (Penganga Group), Adilabad, India: Constraints from C, O and Sr isotopes

Abstract The Penganga Group in the Pranhita-Godavari Rift Valley of central India includes a rather unique example of Late Mesoproterozoic iron and manganese formations deposited in a deep-water below storm wave base distal carbonate platform environment. The carbonate rocks of the Penganga Group are mostly lime-mudstones that have been classified into a number of sedimentary cycles with intervals mostly distinguished by color, ranging from brown/pink and siliceous gray to steel-gray and black. At least two about one-meter-thick Mn-Fe formations occur in siliceous gray limestone of the distally steepened part of the Penganga carbonate platform. A number of northwest-southeast striking thrust faults repeat the succession in down dip sections bringing up distal profiles of the Penganga Group against proximal counterparts at the present exposure level. This contribution provides the first comprehensive record of stable C and O and radiogenic Sr isotopes for proximal and distal profiles, allowing for direct comparison and thus, providing context for the environmental conditions of Fe and Mn deposition in a Mesoproterozoic platform environment. Carbon and oxygen isotope compositions determined from the proximal and distal profiles of the platform yield trends that are attributed to variations in circulation pattern and cycles of warm and cold climatic stages across the platform. Secular trends of Sr-isotope compositions suggest a variation in continental input between cold (0.7065) and warm climatic stages (0.7149), similar to that observed for modern marine sediments. The sedimentation of siliceous deposits and ferromanganese deposits in the distal platform environment was likely favored by the onset of upwelling circulation during cold climatic stages. The moderately negative δ13CPDB values (-5.34‰ to -6.34‰) of the Mn-carbonates and variation in δ13Corg values 31.7‰ to -21.7‰ obtained for early diagenetic Mn-carbonate ovoids indicate oxidation of organic matter in the ferromanganese deposits by Mn-oxides during early diagenesis. We conclude that upwelling and platform-wide deposition of ferromanganese deposits on the Penganga carbonate platform may mark the transition from the stagnant Mid-Proterozoic ‘sulphidic’ ocean to a ‘respiring’ open ocean during the Late Mesoproterozoic Era.

Hydrological dynamics and manganese mineralization in the wake of the Sturtian glaciation

The Cryogenian Sturtian and Marinoan glaciations stand as the most extreme climate events in Earth history. Intriguingly, large-scale Mn carbonates characterize the nonglacial interlude of this period in South China. The formation mechanism of Mn carbonates and the potential correlation underlying this temporal association remain elusive. Here, we present an integrated petrographic and geochemical study of drill core materials intercepting the Mn-bearing Datangpo Formation. Rare earth element patterns of these Mn carbonates exhibit positive Ce anomalies and a lack of Y anomalies, which differ from those of modern seawater but resemble marine Mn-Fe oxides. These features, combined with negative carbonate carbon isotope compositions (δ13Ccarb as light as −9.9 ‰ VPDB), indicate the presence of oxide precursors and the incorporation of light carbon during Mn-carbonate precipitation. Phosphate oxygen isotope ratios (δ18Op) of HCl-extractable apatite reveal a ∼4 ‰ difference in the average δ18Op between Mn-rich and Mn-poor rocks. We propose that the more positive δ18Op of Mn-rich samples may result from the dominance of phosphate released by reductive dissolution of metal oxides or a heavier oxygen isotope signal of surrounding waters with which isotopic equilibrium has been reached. We further illustrate how marine invasions into coastal anoxic basins could have triggered the formation of Mn oxides and highlight the role of glaciation–deglaciation in the development of giant Mn deposits.

A method for studying the influence of Mn oxyhydroxides on the trace element content of aquatic bryophytes

The main objective of this study was to develop and test a method of separating externally deposited Mn oxyhydroxides and co-precipitated elements from samples of aquatic moss (the moss Fontinalis antipyretica). The method, which uses 0.1 M hydroxylamine to dissolve the oxyhydroxides, was tested with samples collected in rivers with slightly acidic, well‑oxygenated waters, where high rates of Mn precipitation occur. The method was effective (it extracted up to 84 % of the Mn) and selective (Fe oxyhydroxides were not extracted). The elements Ba, Cd, Zn and Ni were associated with the Mn oxyhydroxides, while Al, As, Cr, Cu, Fe, Hg and Pb were not. Deposition of Mn therefore increased the concentration of some elements in the moss samples. However, as Mn precipitation depends on Eh and pH, which are independent of the concentrations of the elements in water, the relationship between water and moss element concentrations is not clear (i.e. the data are noisy). This is a problem in biomonitoring studies, which assume a close relationship between element concentrations in moss and water. The value of the proposed extraction method is that it can be used to correct the effect of Mn deposition. We present an example of this correction applied to the Cd concentrations in the test data. We found that the noise introduced by the Mn, including age-related effects (observed by comparing concentrations in 0–2.5 and 2.2–5.0 cm sections from the shoot apex), can be reduced. Additionally, the correction revealed recent increases in Cd concentrations in one site that were not observed in the uncorrected data. Another finding of interest was the low content of total Mn and different extractability (of most elements) observed in moss samples collected in alkaline waters. Finally, we discuss how future studies designed for different environmental scenarios can benefit from application of the proposed method.

Surface water oxygenation and low bioproductivity during deposition of iron formation of the Jacadigo Group (Brazil): Insights from combined cadmium – Chromium isotopes

The Banda Alta Formation (Urucum district, Mato Grosso do Sul, Brazil) comprises ∼600 Ma Fe and Mn deposits, which are among the world's youngest and largest Neoproterozoic sedimentary Fe and Mn formations (IF; MnF). These have been deposited in a redox-stratified, marine sub-basin (Jacadigo Basin), which was strongly influenced by glacial advance/retraction cycles with temporary influx of continental freshwater and upwelling of metal-enriched deep anoxic seawater. Cr and Cd isotopes measured on meticulously separated hematite mesobands from drill core samples are relatively homogenous throughout the ca. 325 m thick sequence sampled in the Banda Alta Fm., with average authigenic δ53Cr values of +0.93 ± 0.24 ‰ (2σ; n = 23) and δ114Cd values of −0.14 ± 0.14 ‰ (2σ; n = 15). The significant enrichment of Cr, in parallel with the strong enrichments of other redox sensitive elements (U, Mo), attests for effective and efficient reduction removal processes in the surface waters during cycles where upwelling Fe2+-rich waters reached the oxygenated surface layer exposed to the atmosphere during episodic glacier retreat stages. Assuming a similar quantitative and efficient removal pathway of dissolved Cd by iron oxyhydroxides, the so-inferred average δ114Cd signature of −0.14 ± 0.14 ‰ in the Jacadigo Basin surface water is significantly lower than signatures of modern ocean surface waters with a range of δ114Cd of ca. ∼0.4 to ∼1 ‰ and even lower than the signature of modern ocean deep waters with δ114Cd of ∼0.3 ‰. It possibly attests to reduced primary production levels and lower nutrient utilization rates during deposition of the Late Neoproterozoic Jacadigo Group, compared to today. This despite the inferred oxidized surface water layer that must have prevailed during this time, as implied by the strongly positively fractionated Cr isotope signatures and pronouncedly negative Ce-anomalies recorded in the seawater-like, shale-normalized Rare Earth Element and Yttrium (REY) patterns exhibited by the hematite mesobands. Data presented herein speak for: (1) a stable, isotopically heavy Cr input to the Jacadigo Basin at the time of deposition, implying high atmospheric O2 levels in the Late Neoproterozoic (2) likely quantitative, reductive incorporation / adsorption processes of dissolved Cr and Cd, respectively, into/onto precipitating iron oxyhydroxides, and (3) the prevalence of low nutrient concentrations and utilization rates in the Jacadigo Basin during glacier retreat cycles. Banded iron formations are considered suitable archives for reconstructing redox and bioproductivity levels in past marine depositional basin, including those prevalent in Neoproterozoic glacial conditions, via employing the CrCd isotope double tracer to iron-rich mesobands.

Bifunctional low molecular weight polyacrylic acid as aqueous binder and coating agent enables high performance LiMn2O4 cathode for lithium-ion batteries

LiMn2O4 is considered to be a promising cathode material for lithium-ion batteries due to its decent energy density, low price and environmental benignity. However, the problems of Mn dissolution, migration and deposition during the cycle, seriously affect its lifespan, especially at high temperature. In this study, we developed a strategy by which we killed two birds with one stone. A low molecular weight polyacrylic acid (PAA) mixed with sodium carboxymethyl cellulose (CMC) is applied as binder and coating agent for cathode particles at the same time. The conventional and environmental unfriendly polyvinylidene difluoride (PVDF)-N-methylpyrrolidone (NMP) system is replaced by the cheap and green aqueous binder with improved adhesive effect. Furthermore, the binder-based surface coating layer not only alleviates the side reaction between the electrolyte and the cathode particles, but also chelates the dissolved Mn2+ by the large amount of carboxyl groups in PAA molecules and so prevents the following migration and deposition of Mn2+. In the button half-cell with low molecular weight PAA based binder, the capacity retention reaches 94.1 % after 1000 cycles at room temperature and 92.0 % after 200 cycles at 60 degrees centigrade. Meanwhile, 18650-type cylindrical cells were prepared with this binder, which shows a great high temperature storage performance. After the cell was held at 60 degrees centigrade for 25 days at full charged state, the internal resistance increased by only 1.25mΩ, the voltage decreased by only 0.1 V, the residual capacity retention and recovery capacity retention reaches 85.6 % and 92.2 %. This work shows the great potential of the aqueous binder in dealing with the problem of Mn dissolution during the cycling of manganese-based cathode materials for lithium-ion batteries.

Correlating Mn Dissolution and Capacity Fade in LiMn0.8Fe0.2PO4/Graphite Cells During Cycling and Storage at Elevated Temperature

LiMnxFe1−xPO4 is a promising positive electrode material for Li-ion batteries. In order to understand the failure mechanisms of this material, LiMn0.8Fe0.2PO4/graphite pouch cells were cycled at 40 or 55 °C over three voltage ranges: 2.5–3.6 V (Fe plateau), 3.6–4.2 V (Mn plateau), and 2.5–4.2 V (full voltage range). Cells cycled at higher temperature and over the full voltage range had the highest capacity fade. Differential voltage analysis showed that cells cycled over the Mn plateau and full voltage range had the highest Li inventory loss, and there was no active mass loss in any of the cells. Micro X-ray fluorescence spectroscopy showed that cells with higher levels of Mn deposition on the negative electrode had higher Li inventory loss. Constant voltage storage experiments at 55 °C showed rapid capacity loss for cells held at top of charge. Despite having similar Li inventory loss trends to the cycled cells, there was less Mn deposition on the negative electrodes. Thus, the capacity fade mechanisms are different for cells that undergo cycling and storage.