Preparation of Manganese Oxide and Its Adsorption Properties

The in-situ oxidation of manganese sulfate solution with H2O_(2),sodium hypochlorite,potassium permanganate and oxygen as oxidants was investigated by means of SEM,EDS,XRD,BET and infrared analysis,and the effects of different oxidants on the morphology,phase composition,surface properties and specific surface area of manganese oxides were investigated.The experimental results show that the diameter of manganese oxide particles prepared with H_(2)O_(2)is the smallest,about 50 nm,and the specific surface area is the largest,63.8764 m^(2)/g.It has the advantages of abundant surface hydroxyl groups,no introduction of other impurities and large adsorption potential.It is most suitable to be used as an oxidant for oxidizing manganese sulfate solution to prepare manganese oxide by in-situ oxidation.Nano manganese oxide prepard by H_(2)O_(2)in-situ oxidation method is used as adsorbent to adsorb cobalt and nickel impurities in manganese sulfate.When the reaction pH is 6,the reaction time is 30min and the amount of adsorbent is 1.0 g,the adsorption rates of cobalt and nickel impurities in 100ml manganese sulfate solution are 97.59%and 97.67%,respectively.The residual amounts of cobalt and nickel meet the industrial process standard of first-class products(Co,Ni w/%≤0.005)of high-purity manganese sulfate(Hg/t4823-2015)for batteries.The study plays a guiding role in the preparation and regulation of manganese oxide,and provides a new method with high efficiency,purity and adsorbent availability for the preparation of high-purity manganese sulfate solution.

Advances of manganese-oxides-based catalysts for indoor formaldehyde removal

Formaldehyde(HCHO)has been identified as one of the most common indoor pollutions nowadays.Manganese oxides(MnO_(x))are considered to be a promising catalytic material used in indoor HCHO oxidation removal due to their high catalytic activity,low-cost,and environmentally friendly.In this paper,the progress in developing MnO_(x)-based catalysts for HCHO removal is comprehensively reviewed for exploring the mechanisms of catalytic oxidation and catalytic deactivation.The catalytic oxidation mechanisms based on three typical theory models(Mars-van-Krevelen,Eley-Rideal and Langmuir-Hinshelwood)are discussed and summarized.Furthermore,the research status of catalytic deactivation,catalysts’regeneration and integrated application of MnO_(x)-based catalysts for indoor HCHO removal are detailed in the review.Finally,the technical challenges in developing MnO_(x)-based catalysts for indoor HCHO removal are analyzed and the possible research direction is also proposed for overcoming the challenges toward practical application of such catalysts.

MnO Stabilized in Carbon-Veiled Multivariate Manganese Oxides as High-Performance Cathode Material for Aqueous Zn-Ion Batteries

Aqueous Zn-ion battery has emerged as one of the most prospective energy storage devices due to its low cost,high safety,and eco-friendliness.However,Zn-ion batteries are bottlenecked by significant capacity fading during long-term cycling and poor performance at high current rates.Here,we report an available cooperation of multivariate manganese oxides@carbon hybrids(MnO_(2)/MnO@C and MnO_(2)/Mn_(3)O_(4)@C)via a plasma-assisted design as an attractive Zn-ion cathode.Among them,the MnO_(2)/MnO@C cathode exhibits a reversible specific capacity of 165 m Ah g^(-1)over 200 cycles at a high rate of 0.5 A g^(-1),and possesses great rate performance with high capacities of 110 and 100 m Ah g^(-1)at a high rate of 0.8 and 1 A g^(-1),respectively.The good cathode performance significantly results from the facile charge transfer and ions(Zn^(2+)and H^(+))insertion in the manganese oxides/carbon hybrids featuring phase stability behavior in the available cooperation of multivalence and carbon conductive substrates.This work will promote the Zn-manganese dioxide system for the design of low-cost and high-performance aqueous rechargeable Zn-ion batteries.

Comparative structural and electrochemical properties of mixed P2/O′3-layered sodium nickel manganese oxide prepared by sol-gel and electrospinning methods:Effect of Na-excess content

The effect of Na-excess content in the precursor on the structural and electrochemical performances of sodium nickel manganese oxide(NNMO)prepared by sol-gel and electrospinning methods is investigated in this paper.X-ray diffraction results of the prepared NNMO without adding Na-excess content indicate sodium loss,while the mixed phase of P2/O′3-type layered NNMO presented after adding Na-excess content.Compared with the sol-gel method,the secondary phase of NiO is more suppressed by using the electrospinning method,which is further confirmed by field emission scanning electron microscope images.N_(2) adsorption-desorption isotherms show no remarkably difference in specific surface areas between different preparation methods and Na-excess contents.The analysis of X-ray absorption near edge structure indicates that the oxidation states of Ni and Mn are+2 and+4,respectively.For the electrochemical properties,superior electrochemical performance is observed in the NNMO electrode with a low Na-excess content of 5wt%.The highest specific capacitance is 36.07 F·g^(-1)at0.1 A·g^(-1)in the NNMO electrode prepared by using the sol-gel method.By contrast,the NNMO electrode prepared using the electrospinning method with decreased Na-excess content shows excellent cycling stability of 100%after charge-discharge measurements for 300 cycles.Therefore,controlling the Na excess in the precursor together with the preparation method is important for improving the electrochemical performance of Na-based electrode materials in supercapacitors.

An amorphous manganese iron oxide hollow nanocube cathode for aqueous zinc ion batteries

Aqueous zinc ion batteries(ZIBs) are attracting considerable attentions for practical energy storage because of their low cost and high safety.Nevertheless,the traditional manganese oxide cathode materials suffer from the low intrinsic electronic conductivity,sluggish ions diffusion kinetics,and structural collapse,hindering their large-scale application.Herein,we successfully developed a latent amorphous Mn_(1.8)Fe_(1.2)O_(4) hollow nanocube(a-H-MnFeO) cathode material derived from Prussian blue analogue precursor.The amorphous nature endows the cathode with lower diffusion barrier and narrower band gap compared with crystalline counterpart,resulting in the superior Zn^(2+) ions and electrons transport kinetics.Hollow structure can furnish abundant surface sites and suppress the structural collapse during the repeated charge/discharge processes.By virtue of the multiple advantageous features,the a-H-MnFeO cathode exhibits exceptional electrochemical performance,in terms of high capacity,excellent rate capability,and prolonged cycle life.This strategy will pave the way for the structural design of emerging cathode materials.

Selective catalytic oxidation of NO over iron and manganese oxides supported on mesoporous silica

The selective catalytic oxidation （SCO） of NO was studied on a catalyst consisting of iron-manganese oxide supported on mesoporous silica （MPS） with different Mn/Fe ratios. Effects of the amount of manganese and iron, oxygen, and calcination temperature on NO conversion were also investigated. It was found that the Mn-Fe/MPS catalyst with a Mn/Fe molar ratio of 1 showed the highest activity at the calcination temperature of 400 °C. The results showed that over this catalyst, NO conversion reached 70% under the condition of 280 °C and a space velocity of 5000 h-1. SO2 and H2O had no adverse impact on the reaction activity when the SCO reaction temperature was above 240 °C. In addition, the SCO activity was suppressed gradually in the presence of SO2 and H2O below 240 °C, and such an effect was reversible after heating treatment.

Morphology and Crystallinity-controlled Synthesis of Manganese Cobalt Oxide/Manganese Dioxides Hierarchical Nanostructures for High-Performance Supercapacitors

We demonstrate a novel preparative strategy for the well-controlled MnCo_2O_(4.5)@MnO_2 hierarchical nanostructures.Bothδ-MnO_2 nanosheets andα-MnO_2 nanorods can uniformly decorate the surface of MnCo_2O_(4.5)nanowires to form core-shell heterostructures.Detailed electrochemical characterization reveals that MnCo_2O_(4.5)@δ-MnO_2 pattern exhibits not only high specific capacitance of 357.5 F g^(-1)at a scan rate of 0.5 A g^(-1),but also good cycle stability(97%capacitance retention after 1000 cycles at a scan rate of 5 A g^(-1)),which make it have a promising application as a supercapacitor electrode material.

Flexible Zn-ion batteries based on manganese oxides: Progress and prospect

The ever-growing market of wearable electronic devices has greatly stimulated the rapid development of flexible Zn-ion batteries(ZIBs).Manganese oxides are one of the most commonly used hosts for zinc ion accommodation and thus receive particular research interest for high-performance flexible ZIB constructions.In this review,a comprehensive summary of the recent development of flexible ZIBs with manganese oxides as cathode materials is presented.Apart from the brief introduction of flexible electronic devices and ZIBs,the charge storage mechanisms and crystal structures of various manganese oxides are summarized.Modifications of the cathode materials in terms of morphology,conductivity,structures,and flexibilities are illustrated in detail,together with the demonstration of structure-performance relationships and applications in flexible ZIBs.Finally,limitations to be overcome are indicated and the future work directions are proposed.

Roles of Ceria on Copper and Manganese Oxides Catalyst——Adsorption of NO and CO

A microreactor system and TPD techniques were used to study the reaction kinetics of the CO+ NO reaction and the adsorption of CO,NO,CO_2 and N_2O over Cu-Mn-O(Ⅰ)and Cu-Mn-Ce-O(Ⅱ) catalysts.The results show that the catalytic activity of(Ⅱ)is higher than that of(Ⅰ)for the CO+NO reac- tion,and the higher the conversion of NO,the larger was the activity difference between(Ⅰ)and(Ⅱ).For (Ⅰ)the rate of NO elimination is dependent on the partial pressures of NO,CO,CO_2 with the kinetics or- ders of 0.48,0.56,0.08,respectively.The TPD study shows that the presence of Ce in(Ⅱ)may promote the adsorption of NO,CO on the surface,i.e.an increase of the coverage θ_(NO),θ_(CO),which result in a decrease of the hindrance of the reaction products.For CO_2 and N_2O the situation is in the opposite,the presence of Ce makes the θ_(CO)_2)and θ_(NO)on(Ⅱ)decrease,which weakens the inhibition of CO_2 for the reaction.

Critical role of corrosion inhibitors modified by silyl ether functional groups on electrochemical performances of lithium manganese oxides

Lithium manganese oxides(Li Mn2 O4, LMO) have attracted significant attention as important cathode materials for lithium-ion batteries(LIBs), which require fast charging based on their intrinsic electrochemical properties. However, these properties are limited by the rapid fading of cycling retention, particularly at high temperatures, because of the severe Mn corrosion triggered by the chemical reaction with fluoride(F-) species existing in the cell. To alleviate this issue, three types of silyl ether(Si–O)-functionalized task-specific additives are proposed, namely methoxytrimethylsilane, dimethoxydimethylsilane, and trimethoxymethylsilane. Ex-situ NMR analyses demonstrated that the Si-additives selectively scavenged the F-species as Si forms new chemical bonds with F via a nucleophilic substitution reaction due to the high binding affinity of Si with F-, thereby leading to a decrease in the F concentration in the cell. Furthermore, the addition of Si-additives in the electrolyte did not significantly affect the ionic conductivity or electrochemical stability of the electrolyte, indicating that these additives are compatible with conventional electrolytes. In addition, the cells cycled with Si-additives exhibited improved cycling retention at room temperature and 45 °C. Among these candidates, a combination of MTSi and the LMO cathode was found to be the most suitable choice in terms of cycling retention(71.0%), whereas the cell cycled with the standard electrolyte suffered from the fading of cycling retention triggered by Mn dissolution(64.4%). Additional ex-situ analyses of the cycled electrodes using SEM, TEM, EIS, XPS, and ICP-MS demonstrated that the use of Si-additives not only improved the surface stability of the LMO cathode but also that of the graphite anode, as the Si-additives prevent Mn corrosion. This inhibits the formation of cracks on the surface of the LMO cathode, facilitating the formation of a stable solid electrolyte interphase layer on the surface of the graphite anode. Therefore, Si-additives modified by Si–O functional groups can be effectively used to increase the overall electrochemical performance of the LMO cathode material.

Location and size regulation of manganese oxides within mesoporous silica for enhanced antibiotic degradation

Refractory antibiotics in domestic wastewater are hard to be completely eliminated by conventional methods,and then lead to severe environmental contamination and adverse effects on public health.In present work,advanced oxidation processes(AOPs)are adopted to remove the antibiotic of sul-fachloropyridazine(SCP).Nanosized Mn_(2)O_(3) was fabricated on the SBA-15 material to catalytically acti-vate potassium peroxydisulfate(PDS)to generate reactive oxygen radicals of.OH and SO_(4).for SCP degradation.The effects of location and size of Mn_(2)O_(3) were explored through choosing either the as-made or template free SBA-15 as the precursor of substrate.Great influences from the site and size of Mn_(2)O_(3) on the oxidation activity were discovered.It was found that Mn_(2)O_(3) with a large size at the exterior of SBA-15(Mn-tfSBA)was slightly easier to degrade SCP at a low manganese loading of 1.0-2.0 mmol.g;however,complete SCP removal could only be achieved on the catalyst of Mn_(2)O_(3) with a refined size at the interior of SBA-15(Mn-asSBA).Moreover,the SO_(4).species were revealed to be the decisive radicals in the SCP degradation processes.Exploring the as-made mesoporous silica as a support provides a new idea for the further development of environmentally friendly catalysts.

Lead and Cadmium Adsorption onto Iron Oxides and Manganese Oxides in the Natural Surface Coatings Collected on Natural Substances in the Songhua River of China

Natural surface coatings collected from natural substances （NSCsNS） were employed to study the roles of the main chemical components （iron oxides, manganese oxides, and other components） in controlling the adsorption of lead（Pb） and cadmium（Cd） in aquatic environments. The selective chemical extraction followed by the adsorption of Pb and Cd experiments and statistical analysis, were used to investigate the adsorption property of each component. Hydroxylamine hydrochloride was used to remove manganese oxides selectively, and sodium dithionite was used to extract iron oxides and manganese oxides. The result indicated that iron oxides and manganese oxides played an important role in the adsorption of Pb and Cd on NSCsNS, and the relative contribution was about two-thirds. The contribution of manganese oxides was the greatest, with a lesser role indicated for other components. The adsorption ability of manganese oxides for Pb and Cd was greater than that of iron oxides or other components for Pb and Cd. The Pb adsorption observed in each component was greater than Cd adsorption.

Factors Affecting Cr(Ⅲ) Oxidation by Manganese Oxides

The high oxidation ability of manganese oxides or soils was used to study effects of pH and coatingon Cr(Ⅲ) oxidation. The results indicated that Cr(Ⅲ) oxidation peaked in pH 4.0-6.5. The amount andrate of Cr(Ⅲ) being oxidized by uncoated δ-MnO2 were larger than those by Fe oxide- or CaCO3-coatedone. Inorganic Cr(Ⅲ) was more easi1y oxidized by MnO2 than organic complex Cr(Ⅲ) due to differentsurface affinities. Precipitated Cr(Ⅲ) and adsorbed Cr(Ⅲ) might be transferred onto MnO2 surface andthen oxidized to Cr(VI).

Kinetics of Manganese Oxides Dissolution in Sulphuric Acid Solutions Containing Oxalic Acid

The kinetics of the interaction of MnO2, Mn2O3, and Mn3O4, with sulphuric acid solutions and the effect of oxalic acid on this process are studied. As the sulphuric acid concentration is increased from 0.1 to 5 N, the dissolution rate of Mn2O3, Mn3O4 to MnO2 and Mn2+ ions decreases, whereas it increases with the concentration of Mn2+ ions. Upon the addition of H2Ox, the complete dissolution of Mn3O4 occurs more quickly. The reaction order with respect to the H+ and O x2- ions is +0.5 ± 0.1. A mechanism of MnO2 dissolution promotion by?O x2- is proposed. The dissolution rate was found to depend on the concentrations of?MnHOx - ions and was highest at pH 1.6 ± 0.2. A rate law and mechanism are suggested for manganese oxides dissolution.

Geochemistry of Major Oxides in Host Rocks in Vizianagarm Manganese Ores Belt (A.P.), India

The abundance, distribution trends and significance of the major oxides in the host rocks in Vizianagarm Manganese Ores Belt (A.P.) (between N latitude 18°12' and 18°30' and E longitudes 83°20' and 83°45'), 15 samples of host rocks from different localities of the area under study were collected and analyzed for major oxides. We describe here in major oxides geochemistry of host rocks and manganese ore deposits associated with Precambrian Khondalite and Charnockite in Vizianagarm Manganese Ores Belt (A.P.): 1) Preponderance of SiO2 over Al2O3;2) Dominance of K2O and CaO over Na2O;3) Abnormally high concentration of phosphorus and a positive relationship of P2O5 with CaO and Ti contents;4) Manganese increases with increases of iron, lime and soda and vice versa, 5) CaO increases with the increases of Al2O3, Ti, K2O and vice versa.?High P2O5content in these manganese ores appears to be the result of precipitation from secondary manganese rich solutions containing dissolved phosphorus from the P2O5 enriched host rocks.?Another source of P2O5 may be the associated granitic and pegmatitic intrusions. Elements like K, Na, Ca, Mg, Co, Ni, Pb and Zn etc. appear to be mostly concentrated in the Mn-minerals viz. psilomelane, cryptomelane, hollandite and pyrolusite and related secondary phases [1] and [2]. Stratigraphically, the study area includes within a thick succession of Precambrian Group belonging to the Khondalite and Charnockite Groups of Dharwar Supergroup, that form a part of Eastern Ghat Complex of India. The manganiferous rocks that have been encountered in the Vizianagarm Manganese Ores Belt (A.P.) India are known as Kodurites.

Mechanism of Capacity Fading Caused by Mn(Ⅱ)Deposition on Anodes for Spinel Lithium Manganese Oxide Cell

The capacity fade of spinel lithium manganese oxide in lithium-ion batteries is a bottleneck challenge for the large-scale application.The traditional opinion is that Mn（Ⅱ） ions in the anode are reduced to the metallic manganese that helps for catalyzing electrolyte decomposition.This could poison and damage the solid electrolyte interface（SEI） film,leading to the the capacity fade in Li-ion batteries.We propose a new mechanism that Mn（Ⅱ） deposites at the anode hinders and/or blocks the intercalation/de-intercalation of lithium ions,which leads to the capacity fade in Li-ion batteries.Based on the new mechanism assumption,a kind of new structure with core-shell characteristic is designed to inhabit manganese ion dissolution,thus improving electrochemical cycle performance of the cell.By the way,this mechanism hypothesis is also supported by the results of these experiments.The LiMn2-xTixO4 shell layer enhances cathode resistance to corrosion attack and effectively suppresses dissolution of Mn,then improves battery cycle performance with LiMn_2O_4 cathode,even at high rate and elevated temperature.

Sulfur resource recovery based on electrolytic manganese residue calcination and manganese oxide ore desulfurization for the clean production of electrolytic manganese

An environmentally friendly and resource-conserving route to the clean production of electrolytic manganese was developed,in which the electrolytic manganese residue(EMR)was initially calcined for cement buffering;then the generated SO2-containing flue gas was managed using manganese oxide ore and anolyte(MOOA)desulfurization;at last,the desulfurized slurry was introduced to the electrolytic manganese production(EMP).Results showed that 4.0 wt%coke addition reduced the sulfur of calcined EMR to 0.9%,thereby satisfying the cement-buffer requirement.Pilot-scale desulfurization showed that about 7.5 vol%of high SO2 containing flue gas can be cleaned to less than 0.1 vol%through a five-stage countercurrent MOOA desulfurization.The desulfurized slurry had 42.44 g·L-Mn2+and 1.92 g·L-1 S2 O62-,which was suitable for electrowinning after purification,and the purity of manganese product was 99.93%,satisfy the National Standard of China YB/T051-2015.This new integrated technology fulfilled 99.7%of sulfur reutilization from the EMR and 94.1%was effectively used to the EMP.The MOOA desulfurization linked the EMP a closed cycle without any pollutant discharge,which promoted the cleaner production of EMP industry.

Enhanced removal of organics by permanganate preoxidation using tannic acid as a model compound-Role of in situ formed manganese dioxide

The effect of permanganate preoxidation on organic matter removal during the coagulation with aluminum chloride was investigated using tannic acid as a model compound. Results showed that a small amount of KMnO4 （0.75 mg/L） increased the removal efficiency of tannic acid up to 20%, as compared to the process of coagulation by aluminum chloride alone. The key factor enhancing the removal efficiency of tannic acid in preoxidation process was the in situ formation of a reductant manganese dioxide. The complexation model was used to describe the reaction between MnO2 and tannic acid. Under weak pH condition, tannic acid was difficult to be adsorbed by MnO2 due to the static electrical repulsive forces. The presence of Ca2＋ served as a bridge to hold the negative charged MnO2 and tannic acid together, which could be a crucial factor influencing tannic acid adsorption by in-situ manganese dioxide.

Mechanism of Boron Oxide as a Phase Regulator for Modification of Manganese Slag

The current research focused on adjusting the low hydration activity of the metallurgical slag by phase reconstruction technique. Boron oxide was used as a phase regulator to improve the amorphous phase composition of the manganese slag, consequently enhancing its hydraulic activity. The effects of boron oxide dosage and calcination temperature on the manganese slag amorphous phase content were investigated. XRD and DTG were performed to analyze the hydration mechanism of the manganese slag powder and cement. Results show that, when boron oxide dosage is 15%, calcination temperature is 1 300℃, and holding time for 1 hour, the amorphous content of the modified manganese slag reaches 95% and its 28-day activity index reaches 8 1.7%. The manganese slag powder can then be used as cement or concrete admixtures for the building materials industry.

Effects of carrier and Mn loading on supported manganese oxide catalysts for catalytic combustion of methane

Supported manganese oxide catalysts were prepared by incipient wetness impregnation method for methane catalytic combustion, and effects of the support （Al2O3, SiO2 and TiO2） and Mn loading were investigated. These catalysts were characterized with N2 adsorption, X-ray diffraction, X-ray photoelectron spectroscopy and temperature-programmed reduction techniques. Methane conversion varied in a large range depending on supports or Mn loading. Al2O3 supported 15% Mn catalyst exhibited better activity toward methane catalytic oxidation. The manganese state and oxygen species played an important role in the catalytic performance,