Bamboo-like MnO2⋠Co3O4: High-performance catalysts for the oxidative removal of toluene.

The manganese-cobalt mixed oxide nanorods were fabricated using a hydrothermal method with different metal precursors (KMnO4 and MnSO4·H2O for MnOx and Co(NO3)2⋅6H2O and CoCl2⋅6H2O for Co3O4). Bamboo-like MnO2⋅Co3O4 (B-MnO2⋅Co3O4 (S)) was derived from repeated hydrothermal treatments with Co3O4@MnO2 and MnSO4⋅H2O, whereas Co3O4@MnO2 nanorods were derived from hydrothermal treatment with Co3O4 nanorods and KMnO4. The study shows that manganese oxide was tetragonal, while the cobalt oxide was found to be cubic in the crystalline arrangement. Mn surface ions were present in multiple oxidation states (e.g., Mn4+ and Mn3+) and surface oxygen deficiencies. The content of adsorbed oxygen species and reducibility at low temperature declined in the sequence of B-MnO2⋅Co3O4 (S) > Co3O4@MnO2 > MnO2 > Co3O4, matching the changing trend in activity. Among all the samples, B-MnO2⋅Co3O4 (S) showed the preeminent catalytic performance for the oxidation of toluene (T10% = 187°C, T50% = 276°C, and T90% = 339°C). In addition, the B-MnO2⋅Co3O4 (S) sample also exhibited good H2O-, CO2-, and SO2-resistant performance. The good catalytic performance of B-MnO2⋅Co3O4 (S) is due to the high concentration of adsorbed oxygen species and good reducibility at low temperature. Toluene oxidation over B-MnO2⋅Co3O4 (S) proceeds through the adsorption of O2 and toluene to form O*, OH*, and H2C(C6H5)* species, which then react to produce benzyl alcohol, benzoic acid, and benzaldehyde, ultimately converting to CO2 and H2O. The findings suggest that B-MnO2⋅Co3O4 (S) has promising potential for use as an effective catalyst in practical applications.

Co-doped cryptomelane-type manganese oxide in situ grown on a nickel foam substrate for high humidity ozone decomposition.

Monolithic catalysts with excellent O3 catalytic decomposition performance were prepared by in situ loading of Co-doped KMn8O16 on the surface of nickel foam. The triple-layer structure with Co-doped KMn8O16/Ni6MnO8/Ni foam was grown spontaneously on the surface of nickel foam by tuning the molar ratio of KMnO4 to Co(NO3)2·6H2O precursors. Importantly, the formed Ni6MnO8 structure between KMn8O16 and nickel foam during in situ synthesis process effectively protected nickel foam from further etching, which significantly enhanced the reaction stability of catalyst. The optimum amount of Co doping in KMn8O16 was available when the molar ratio of Mn to Co species in the precursor solution was 2:1. And the Mn2Co1 catalyst had abundant oxygen vacancies and excellent hydrophobicity, thus creating outstanding O3 decomposition activity. The O3 conversion under dry conditions and relative humidity of 65%, 90% over a period of 5 hr was 100%, 94% and 80% with the space velocity of 28,000 hr-1, respectively. The in situ constructed Co-doped KMn8O16/Ni foam catalyst showed the advantages of low price and gradual applicability of the preparation process, which provided an opportunity for the design of monolithic catalyst for O3 catalytic decomposition.

Protection of cultured vascular endothelial cells against cadmium cytotoxicity by simultaneous treatment or pretreatment with manganese.

Cadmium is a heavy metal that pollutes the environment and foods and is a risk factor for vascular disorders. We have previously demonstrated that pretreatment of vascular endothelial cells with zinc and copper protects the cells against cadmium cytotoxicity. In contrast, cadmium cytotoxicity was potentiated in cells following exposure to lead, thereby indicating that in vascular endothelial cells, cadmium cytotoxicity can be differentially modified by the co-occurrence of other heavy metals. In this study, we revealed that simultaneous treatment or pretreatment with manganese protects vascular endothelial cells against cadmium cytotoxicity. Intracellular accumulation of cadmium was observed to be reduced by simultaneous treatment with manganese, although not by pretreatment. The mRNA expression of metal transporters that regulate the uptake of both cadmium and manganese (ZIP8, ZIP14, and DMT1) remained unaffected by either simultaneous treatment or pretreatment with manganese, and simultaneous treatment with manganese suppressed the cadmium-induced expression of metallothionein but pretreatment with manganese did not exhibit such suppressive effect. Thus, the protection of vascular endothelial cells against cadmium cytotoxicity conferred by simultaneous treatment with manganese is assumed to be partially attributed to a reduction in the intracellular accumulation of cadmium, whereas the effects of pretreatment with manganese are independent of both the reduced intracellular accumulation of cadmium and the induction of metallothionein. These observations accordingly indicate that the protective effects of manganese are mediated via alternative (as yet unidentified) mechanisms.

Trivalent manganese in dissolved forms: Occurrence, speciation, reactivity and environmental geochemical impact.

The cycling processes of elemental manganese (Mn), including the redox reactions of dissolved Mn(III) (dMn(III)), directly and indirectly influences the biogeochemical processes of many elements. Though increasing evidence indicates the widespread presence of dMn(III) mediates the fate of many elements, its role may be currently underestimated. There is both a lack of clear understanding of the historical research framework of dMn(III) and a systematic overview of its geochemical properties and detection methods. Therefore, the primary aim of this review is to outline the understanding of dMn(III) in multiple fields, including soil science, analytical chemistry, biochemistry, geochemistry, and water treatment, and summarize the formation pathways, species forms, and detection methods of dMn(III) in aquatic systems. This review considers how the characteristics of dMn(III), the intermediate formed in the single-electron reaction processes of Mn(II) oxidation and Mn(IV) reduction, determines its participation in environmental geochemical processes. Its widespread presence in diverse water systems and active redox properties coupling with various elements confirm its significant role in natural elemental geochemistry cycle and artificial water treatment processes. Therefore, further investigation into the role of dissolved Mn(III) in aquatic systems is warranted to unravel unexplored coupled elemental redox reaction processes mediated by dissolved Mn(III), filling in the gaps in our understanding of manganese environmental geochemistry, and providing a theoretical basis for recognizing the role of dMn(III) role in water treatment technologies.

Unlocking the Potential of Organic-Inorganic Hybrid Manganese Halides for Advanced Optoelectronic Applications.

Organic-inorganic hybrid manganese(II) halides (OIMnHs) have garnered tremendous interest across a wide array of research fields owing to their outstanding optical properties, abundant structural diversity, low-cost solution processibility, and low toxicity, which make them extremely suitable for use as a new class of luminescent materials for various optoelectronic applications. Over the past years, a plethora of OIMnHs with different structural dimensionalities and multifunctionalities such as efficient photoluminescence (PL), radioluminescence, circularly polarized luminescence, and mechanoluminescence have been newly created by judicious screening of the organic cations and inorganic Mn(II) polyhedra. Specifically, through precise molecular and structural engineering, a series of OIMnHs with near-unity PL quantum yields, high anti-thermal quenching properties, and excellent stability in harsh conditions have been devised and explored for applications in light-emitting diodes (LEDs), X-ray scintillators, multimodal anti-counterfeiting, and fluorescent sensing. In this review, the latest advancements in the development of OIMnHs as efficient light-emitting materials are summarized, which covers from their fundamental physicochemical properties to advanced optoelectronic applications, with an emphasis on the structural and functionality design especially for LEDs and X-ray detection and imaging. Current challenges and future efforts to unlock the potentials of these promising materials are also envisioned.

Cyclotron production of manganese-52: a promising avenue for multimodal PET/MRI imaging.

BACKGROUND: The integration of positron emission tomography (PET) and magnetic resonance imaging (MRI) holds promise for advancing diagnostic imaging capabilities. The METRICS project aims to develop cyclotron-driven production of 52Mn for PET/MRI imaging. RESULTS: Using the 52Cr(p,n)52Mn reaction, we designed chromium metal targets via Spark Plasma Sintering and developed a separation procedure for isolating 52Mn. Labeling tests were conducted with traditional chelators (i.e. S-2-(4-Isothiocyanatobenzyl)-1,4,7,10-tetraazacyclododecane tetraacetic acid) and the 1.4-dioxa-8-azaspiro[4.5]decane-8- carbodithioate ligand to produce radioactive complexes suitable for PET/MRI applications. Our methodology yielded high-quality 52Mn suitable for PET radiopharmaceuticals and PET/MRI imaging. Preliminary studies on phantom imaging using microPET and clinical MRI demonstrated the efficacy of our approach. CONCLUSIONS: The developed technology offers a promising avenue for producing 52Mn and enhancing PET/MRI imaging capabilities. Further in vivo investigations are warranted to evaluate the potential advantages of this hybrid imaging technique.

Monoclinic Silver Vanadate (Ag0.33V2O5) as a High-Capacity Stable Cathode Material for Aqueous Manganese Batteries.

Aqueous rechargeable metal batteries have recently garnered considerable attention owing to their low cost, sufficient capacity, and the use of non-flammable water-based electrolytes. Among them, manganese batteries are particularly favored because of their stability, abundance, affordability, and high energy density. Despite their advantages, Mn storage host structures remain underexplored. Therefore, developing innovative host materials is crucial for advancing this field. In this paper, the study reports for the first time, the use of Ag0.33V2O5 as a cathode material in aqueous manganese batteries. The study explains the displacement/intercalation behavior of manganese and silver using electrochemical, structural, and spectroscopic analyses. Additionally, it is shown that cation (Ag+, Mn2+, H+) diffusion pathways can be simulated using diffusion-barrier calculations. Finally, the study demonstrates high-performance manganese batteries that exhibit a remarkable reversible capacity of ≈261.9 mAh g-1 at a current of 0.1 A g-1 and an excellent cycle retention of 69.1% after 2000 cycles at a current density of 1.5 A/g. The findings of this study contribute to the advancement of aqueous manganese battery technology, offering a promising pathway for developing safer, more cost-effective, and high-performance energy storage systems.

The Bioactive Interface of Titanium Implant with Both Anti-Oxidative Stress and Immunomodulatory Properties for Enhancing Osseointegration under Diabetic Condition.

The poor implant-osseointegration under diabetic condition remains a challenge to be addressed urgently. Studies have confirmed that the diabetic pathological microenvironment is accompanied by excessive oxidative stress, imbalanced immune homeostasis, and persistent chronic inflammation, which seriously impairs the osteogenic process. Herein, a multifunctional bioactive interface with both anti-oxidative stress and immunomodulatory properties is constructed on titanium implants. Briefly, manganese dioxide nanosheets are coated onto mesoporous polydopamine nanoparticles loaded with carbon monoxide gas precursor, namely MnO2-CO@MPDA NPs, and then they are integrated on the titanium implant to obtain MCM-Ti. In the simulated diabetic microenvironment, under the action of MnO2 nanoenzymes, MCM-Ti can effectively eliminate intracellular reactive oxygen species while alleviating hypoxic state. Interestingly, the microenvironment mediates the responsive release of CO gas, which effectively drives macrophages toward M2 polarization, thereby ameliorating inflammatory response. The potential mechanism is that CO gas up-regulates the expression of heme oxygenase-1, further activating the Notch/Hes1/Stat3 signaling pathway. Furthermore, the conditioned medium derived from macrophages on MCM-Ti surface significantly enhances the osteogenic differentiation of BMSCs. In a type 2 diabetic rat model, MCM-Ti implant effectively alleviates the accompanying inflammation and enhances the osseointegration through the synergistic effects of resisting oxidative stress and remodeling immune homeostasis.

Unraveling the Anionic Redox Chemistry in Aqueous Zinc-MnO2 Batteries.

Activating anionic redox reaction (ARR) has attracted a great interest in Li/Na-ion batteries owing to the fascinating extra-capacity at high operating voltages. However, ARR has rarely been reported in aqueous zinc-ion batteries (AZIBs) and its possibility in the popular MnO2-based cathodes has not been explored. Herein, the novel manganese deficient MnO2 micro-nano spheres with interlayer "Ca2+-pillars" (CaMnO-140) are prepared via a low-temperature (140 °C) hydrothermal method, where the Mn vacancies can trigger ARR by creating non-bonding O 2p states, the pre-intercalated Ca2+ can reinforce the layered structure and suppress the lattice oxygen release by forming Ca-O configurations. The tailored CaMnO-140 cathode demonstrates an unprecedentedly high rate capability (485.4 mAh g-1 at 0.1 A g-1 with 154.5 mAh g-1 at 10 A g-1) and a marvelous long-term cycling durability (90.6% capacity retention over 5000 cycles) in AZIBs. The reversible oxygen redox chemistry accompanied by CF3SO3- (from the electrolyte) uptake/release, and the manganese redox accompanied by H+/Zn2+ co-insertion/extraction, are elucidated by advanced synchrotron characterizations and theoretical computations. Finally, pouch-type CaMnO-140//Zn batteries manifest bright application prospects with high energy, long life, wide-temperature adaptability, and high operating safety. This study provides new perspectives for developing high-energy cathodes for AZIBs by initiating anionic redox chemistry.

Morphological Enrichment and Environmental Factors Correlation of Heavy Metals in Dominant Plants in Typical Manganese Ore Areas in Guizhou, China.

Bioavailable heavy metal and their efficient phytoremediation in mining areas have major implications for environmental and human health. In this study, we investigated 12 dominant plants in a typical Mn ore area of Zunyi, Guizhou Province, China, to determine the heavy metal contents, morphologies, and environmental factors affecting Mn, Cd, Pb, Cu, Zn, and Cr in the plant parts and rhizosphere soil. The bioavailabilities and degrees of metals were evaluated using the ratios of the secondary to primary phase distributions and potential ecological risk indices. Principal component analysis, cluster analysis, positive matrix factorisation modelling, and redundancy analysis were used to trace the origins and correlations among the metals. The results indicate that the bioavailabilities were the highest for Mn and Cd in the study area, and all of the target heavy metals had bioavailabilities above the moderate ecological harm level. Statistical modelling indicates that there are four main pollution sources: mining, smelting, processing operations, and atmospheric deposition. The dominant plants had high heavy metal enrichments, bioconcentration factors, and translocation factors for Mn, Cu, Cr, Cd, and Zn. The redundancy analysis indicates that soil total N, total P, and pH affect metal absorption and distributions in Compositae and non-Compositae plants in low-N, low-P, and slightly alkaline mining environments. This study provides a feasible basis for the screening of heavy metal enrichment plants and the improvement of remediation technology in manganese ore area under the extreme environment of poor nutrition.

A multifunctional scaffold that promotes the scaffold-tissue interface integration and rescues the ROS microenvironment for repair of annulus fibrosus defects.

Due to the limited self-repair ability of the annulus fibrosus (AF), current tissue engineering strategies tend to use structurally biomimetic scaffolds for AF defect repair. However, the poor integration between implanted scaffolds and tissue severely affects their therapeutic effects. To solve this issue, we prepared a multifunctional scaffold containing loaded lysyl oxidase (LOX) plasmid DNA exosomes and manganese dioxide nanoparticles (MnO2 NPs). LOX facilitates extracellular matrix (ECM) cross-linking, while MnO2 NPs inhibit excessive reactive oxygen species (ROS)-induced ECM degradation at the injury site, enhancing the crosslinking effect of LOX. Our results revealed that this multifunctional scaffold significantly facilitated the integration between the scaffold and AF tissue. Cells were able to migrate into the scaffold, indicating that the scaffold was not encapsulated as a foreign body by fibrous tissue. The functional scaffold was closely integrated with the tissue, effectively enhancing the mechanical properties, and preventing vascular invasion, which emphasized the importance of scaffold-tissue integration in AF repair.

Ca2+-controlled Mn(II) removal process in Aurantimonas sp. HBX-1: Microbially-induced carbonate precipitation (MICP) versus Mn(II) oxidation.

The application of manganese-oxidizing bacteria (MnOB) to produce manganese oxides (MnOx) has been widely studied, but often overlooking the concurrent formation of MnCO3. In this study, we found Ca2+ plays a crucial role in controlling Mn(II) removal in the bacterium Aurantimonas sp. HBX-1. Under conditions with 6.8 mM Ca2+ and without adding Ca2+, 100 µM Mn(II) was removed by 96.96 % and 38.28 % within 8 days, respectively. X-ray photoelectron spectroscopy (XPS) showed that adding Ca2+ increased the average oxidation state (AOS) of the solid products from 2.05 to 2.37. X-ray absorption fine structure (XAFS) analysis revealed the product proportions as follows: under Ca2+-supplemented condition, the ratio of MnOx (1 < x ≤ 2) to MnCO3 was 52 % to 28.1 %, while under Ca2+-free condition, the ratio shifted to 4.6 % for MnOx (1 < x ≤ 2) and 55.2 % for MnCO3. Urease activity assay and proteomic analysis confirmed the expression of urease and carbonic anhydrase, leading to the formation of MnCO3. Additionally, animal heme peroxidase (AHP) in strain HBX-1 was found to be responsible for Mn(II) oxidation through superoxide production, with Ca2+ addition promoting its expression level. Given the widespread presence of Ca2+ in wastewater, its potential impact on the biogeochemical Mn(II) cycle driven by bacteria should be reconsidered.

ZnMn2(PO4)2·nH2O: An H2O-Imbedding-Activated Cathode for Robust Aqueous Zinc-Ion Batteries.

Component modulation endows Mn-based electrodes with prominent energy storage properties due to their adjustable crystal structure characteristics. Herein, ZnMn2(PO4)2·nH2O (ZMP·nH2O) was obtained by a hydration reaction from ZnMn2(PO4)2 (ZMP) during an electrode-aging evolution. Benefiting from the introduction of lattice H2O molecules into the ZMP structure, the ion transmission path has been expanded along with the extended d-spacing, which will further facilitate the ZMP → ZMP·nH2O phase evolution and electrochemical reaction kinetics. Meanwhile, the hydrogen bond can be generated between H2O and O in PO43-, which strengthens the structure stability of ZMP·nH2O and lowers the conversion barrier from ZMP to ZMP·4H2O during the Zn2+ uptake/removal process. Thereof, ZMP·nH2O delivers enhanced electrochemical reaction kinetics with robust structure tolerance (106.52 mA h g-1 at 100 mA g-1 over 620 cycles). This high-energy aqueous Zn||ZMP·nH2O battery provides a facile strategy for engineering and exploration of high-performance ZIBs to realize the practical application of Mn-based cathodes.

Studying the Structure and Viscosity of MnO-SiO2-CaO-Al2O3-MgO Slag System.

The relationship between slag structure and viscosity is studied, employing Raman spectroscopy for the five-component slag system of MnO-SiO2-CaO-Al2O3-MgO and its subsystems. This study aims to investigate the influence of variations in slag composition on viscosity, which is crucial for optimizing industrial processes. Based on industrial slag compositions produced in a silicomanganese submerged arc furnace, 17 slags with a fixed content of MnO of 10 wt% are synthesized with varying contents of SiO2 of 33 to 65 wt%; CaO within the range of 14 to 40 wt%; and fixed contents of Al2O3 and MgO of 17 and 6 wt%, respectively. The slag compositions are divided into four groups, ranging from low basicity (0.38) to high basicity (0.80), with each group containing the four slag systems of MnO-SiO2-CaO, MnO-SiO2-CaO-Al2O3, MnO-SiO2-CaO-MgO, and MnO-SiO2-CaO-Al2O3-MgO, with fixed basicity. Additionally, a five-component composition with the lowest basicity of 0.28 is considered. Raman spectroscopy measurements are performed in the wavenumber range of 200 to 1200 cm-1 using a green source laser with a 532 nm wavelength. The high-wavenumber region of the Raman spectra (800 to 1200 cm-1) is deconvoluted to quantitatively investigate the effect of each oxide on the slag structure and the degree of polymerization (DOP) of the silicate network. Results indicate that measured NBO/T increases with increasing basicity, demonstrating a reduction in DOP of the silicate structure. This depolymerization effect is more pronounced in slags containing Al2O3 compared to those without it. In a group of slags with similar basicity, the substitution of SiO2 with Al2O3 leads to further depolymerization. In contrast, substituting CaO with MgO has little effect on the silicate structure in slags without Al2O3 but causes depolymerization in slags containing Al2O3. To study the relationship between structure and viscosity, viscosity data obtained from FactSage are used as reference values. The predictions of slag viscosity using the Raman-structure model and the NBO/T viscosity model are then compared to the FactSage results. The adjustable parameters of the Raman-structure model are re-determined using the FactSage data for the studied slag compositions. The NBO/T viscosity model employs both calculated NBO/T values from the slag compositions and measured NBO/T values from the deconvolution results. The findings of this study reveal good agreement between the predictions of the Raman-structure model and the FactSage viscosity data.

Evolution of river-aquifer disconnections and the migration and transformation of iron and manganese under non-time-varying/time-varying riverbed permeability.

Changes in the composition, structure, and thickness of riverbed sediments caused by riverbed clogging strongly affect the hydraulic connection, migration and transformation of nutrients between river water and groundwater in groundwater source areas. However, previous studies have not extensively investigated the mechanisms of river-aquifer disconnection and the migration and transformation processes of iron and manganese under non-time-varying and time-varying conditions of riverbed permeability. This study developed a model using the COMSOL Multiphysics platform to characterize the riverbed clogging-groundwater exploitation-disconnection process, considering microbial growth and related biogeochemical processes, and investigated feedbacks between the reactive migration of iron and manganese and physical clogging-groundwater exploitation processes or bioclogging processes. The research findings showed that under non-time-varying conditions of riverbed permeability, the evolution of river-aquifer disconnection was strongly affected by the thickness and permeability coefficient of riverbed sediments. The dissolved oxygen attenuation rate in the disconnection zone decreased by up to 88.8 %. Additionally, the Mn2+ and Fe2+ generation rates in sediment pore water decreased by 65.8 % and 62.7 %, respectively. In contrast, during the riverbed bioclogging process, as the biofilms on the surface of the riverbed sediments developed, the sediment pores gradually clogged, leading to a significant reduction in the porosity and permeability coefficient. Consequently, the hydraulic connection between the river and aquifer transitioned from a saturated connection to a disconnection. However, reduced permeability due to riverbed bioclogging primarily controlled the release of Fe and Mn. When the river-aquifer was in complete disconnection, compared to the saturated connection state, the Mn2+ and Fe2+ generation rates increased by up to 5.8 and 3.8 times, respectively. This study deepens our understanding of the biogeochemical cycling mechanisms of Fe and Mn under riverbed clogging conditions in groundwater source areas and contributes to ensuring a secure and stable water supply in these areas.

Dietary manganese supplementation decreases hepatic lipid deposition by regulating gene expression and enzyme activity involved in lipid metabolism in the liver of broilers.

This study aimed to characterize the effects of different dietary forms of supplemental manganese (Mn) on hepatic lipid deposition, gene expression, and enzyme activity in liver fat metabolism in 42-day-old broiler chickens. In total 420 one day-old Arbor Acres (AA) broilers (rooster: hen = 1:1) were assigned randomly based on body weight and sex to one of six treatments (ten replicate cages per treatment and seven broilers per replicate cage) in a completely randomized design using a 2 (sex) × 3 (diet) factorial arrangement. The three diets were basal control diets without Mn supplementation and basal diets supplemented with either Mn sulfate or Mn proteinate. No sex × diet interactions were observed in any of the measured indexes; thus, the effect of diet alone was presented in this study. Dietary Mn supplementation increased Mn content in the plasma and liver, adipose triglyceride lipase (ATGL) activity, and ATGL mRNA and its protein expression in the liver by 5.3%-24.0% (P < 0.05), but reduced plasma triglyceride (TG), total cholesterol (TC), and low-density lipoprotein (LDL-C) levels, liver TG content, fatty acid synthase (FAS) and malic enzyme (ME) activities, mRNA expression of sterol regulatory element-binding protein 1 (SREBP1), FAS, stearoyl-coA desaturase (SCD), and ME, as well as the protein expression of SREBP1 and SCD in the liver by 5.5%-22.8% (P < 0.05). No differences were observed between the two Mn sources in all of the determined parameters. Therefore, it was concluded that dietary Mn supplementation, regardless of Mn source, decreased hepatic lipid accumulation in broilers by inhibiting SREBP1 and SCD expression, FAS and ME activities, and enhancing ATGL expression and activity.

A critical review of Mnammox coupled with the NDMO for innovative nitrogen removal.

In the context of increasing global nitrogen pollution, traditional biological nitrogen removal technologies like nitrification and denitrification are hindered by high energy consumption. Additionally, the deployment of anaerobic ammonium oxidation (Anammox) technology is constrained due to the slow growth rate of Anammox bacteria and there is a bottleneck in nitrogen removal efficiency. To overcome these technical bottlenecks, researchers have discovered a revolutionary nitrogen removal technology that cleverly combines the redox cycling of manganese with nitrification and denitrification reactions. In this new process, manganese dependent anaerobic ammonium oxidation (Mnammox) bacteria can convert NH4+ to N2 under anaerobic conditions, while nitrate/nitrite dependent manganese oxidation (NDMO) bacteria use NO3-/NO2- as electron acceptors to oxidize Mn2+ to Mn4+. Mn4+ acts as an electron acceptor in Mnammox reaction, thereby realizing the autotrophic nitrogen removal process. This innovative method not only simplifies the steps of biological denitrification, but also significantly reduces the consumption of oxygen and organic carbon, providing a more efficient and environmentally friendly solution to the problem of nitrogen pollution. The article initially provides a concise overview of prevalent nitrogen removal technologies and the application of manganese in these processes, and discusses the role of manganese in biogeochemical cycles, including its discovery, mechanism of action, microbial communities involved, and its impact on these key factors in the process. Subsequently, metabolic principles, benefits, advantages, and environmental considerations of Mnammox coupled with the NDMO process are analyzed in detail. Finally, this article summarizes the shortcomings of current research and looks forward to future research directions. The goal of this article is to provide a valuable reference for researchers to fully understand the application of manganese in nitrogen removal processes.

Electro-Chemo-Mechanical Evolution at the Garnet Solid Electrolyte-Cathode Interface.

Solid-state batteries promise higher energy density and improved safety compared with lithium-ion batteries. However, electro-chemomechanical instabilities at the solid electrolyte interface with the cathode and the anode hinder their large scale implementation. Here, we focus on resolving electro-chemo-mechanical instability mechanisms and their onset conditions between a state-of-the-art cathode, LiNi0.6Mn0.2Co0.2O2 (NMC622), and the garnet Li7La3Zr2O12 (LLZO) solid electrolyte. We used thin-film NMC622 on LLZO pellets to place the interfacial region within the detection depth of the X-ray characterization techniques. The experimental probes of the near-interface region included in operando X-ray absorption spectroscopy and ex situ focused ion beam scanning electron microscopy. Electrochemical degradation was not observable during cycling at room temperature with 4.3 V versus Li/Li+ charge voltage cutoff, or with stepwise potentiostatic hold up to 4.1 V versus Li/Li+. In contrast, secondary phases including reduced transition metal species (Ni2+, Co2+) were found after cycling up to 4.3 V versus Li/Li+ at 80 °C and during potentiostatic hold at 4.3 V versus Li/Li+ (Ni2+). Intergranular cracks between NMC622 grains and delamination at the NMC622|LLZO interface occurred readily after the first charge. These interface reaction products and mechanical failure lowered the capacity and cell efficiency due to partial loss of the NMC622 phase, partial loss of contact at the interface, and a higher polarization resistance. Electrochemical instability between delithiated NMC622 and LLZO could be mitigated by using a low charge voltage cutoff or cycling at lower temperature. Ways to engineer the mechanical properties to avoid crack deflection and delamination at the interface are also discussed for enhancing mechanical stability.

Redox-Driven Formation of Mn(III) in Ice.

Redox-driven reactions involving Mn(II) species adsorbed at Mn(IV) oxide surfaces can release Mn(III) in the form of dissolved Mn(III)-ligand species in natural waters. Using pyrophosphate (PP) as a model ligand, we show that freezing accelerates and enhances Mn(III) formation in the form of Mn(III)-PP complexes. This freeze-promoted reaction is explained by the concentration of Mn(IV) oxides and solutes (Mn(II), Na+, and Cl-) into the minute fractions of liquid water locked between ice (micro)crystals - the Liquid Intergrain Boundary (LIB). Time-resolved freezing experiments at -20 °C showed that Mn(III) yields were greatest at low salt (NaCl) content. In contrast, high salt content promoted Mn(III) formation through chloride complexation, although yields became lower as the cryosalt mineral hydrohalite (NaCl·2H2O) dehydrated the LIB by drawing water into its structure. Consecutive freeze-thaw cycles also showed that dissolved Mn(III) concentrations increased within the very first few minutes of each freezing event. Because each thaw event released unreacted PP previously locked in ice, each sequential freeze-thaw cycle increased Mn(III) yields, until ∼80% of the Mn was converted to Mn(III). This was achieved after only seven cycles. Finally, temperature-resolved freezing experiments down to -50 °C showed that the LIB produced the greatest quantities of Mn(III) at -10 °C, where the volumes were greater. Reactivity was however sustained in ice formed below the eutectic (-21.3 °C), down to -50 °C. We suspect that this sustained reactivity was driven by persistent forms of supercooled water, such as Mn(IV) oxide-bound thin water films. By demonstrating the freeze-driven production of Mn(III) by comproportionation of dissolved Mn(II) and Mn(IV) oxide, this study highlights the potentially important roles these reactions could play in the production of pools of Mn(III) in natural water and sediments of mid- and high-latitudes environments exposed to freeze-thaw episodes.