Reduction Of Manganese Dioxide Research Articles

Hydrometallurgical processing of non-concentrated manganese - containing raw material with receiving high-quality products

The production of ferroalloys occupies a leading position in the economy of the Republic of Kazakhstan. With the depletion of rich in the content of the initial manganese raw materials, a problem arose that it was necessary to involve technogenic products, i.e. poor sub-standard ores and wastes produced by ferroalloys. From the point of view of environmental protection of regions producing manganese alloys, the current tasks are: the introduction of new efficient dust collection processes; issues of cleaning of waste gases and sludges; neutralization and utilization of waste. The creation of rational technological schemes for the utilization of dispersed materials that contain the target element of the ferroalloy to be melted is an economically viable and environmentally sound measure for increasing the profitability of production. Sulfuric acid leaching is the main operation of most schemes of hydrometallurgical processing of manganese-containing raw materials. Hydrogen peroxide, metallic iron, pyrite concentrate, sulfur dioxide, sulfite-bisulphite solutions used as the reducing agent. The article presents the results of hydrometallurgical processing of manganese dusts produced by the silicomanganese of the Aksu Ferroalloy Plant. To convert the solution of psilomelane (MnOMnO2) – an oxide compound, in which manganese is represented in silicomanganese dust, the presence of a reducing agent in the sulfuric acid solution, which is used as a pyrite concentrate, is necessary. The effect of pyrite on the reduction of manganese dioxide during leaching with sulfuric acid studied by mathematical planning of the experiment by a probabilistic-deterministic method. The determining factors of the leaching process are: temperature, duration of the process, amount of pyrite added, concentration of sulfuric acid. On the basis of significant equations of partial dependence, a mathematical model for the leaching of manganese dust by sulfuric acid in the presence of pyrite is compiled in the form of a generalized equation: Yрасч = 3,7•10-6(0,9399х1+5,1847)(-13,761х22+62,507х2+23,402)(-0,7429х32+14,143х3+23,4)(-00071х42+1,466х4+18,323). On the basis of the obtained equation, the optimal conditions for manganese leaching into a sulfuric acid solution are selected: temperature 700 °C, duration 3 hours, sulfuric acid concentration 5 %, additive of pyritic concentrate 90 % of the dust weight. The degree of manganese extraction was 95.8 %.

The mechanism on reducing manganese oxide ore with elemental sulfur

Extraction of Mn from manganese oxide ore via sulfur-based reduction followed by acid leaching has received much attention. In this study, the mechanism on reducing manganese oxide ore with elemental sulfur was investigated. The reduction of manganese dioxide by sulfur is feasible thermodynamically, and the experimental validation proved that manganese dioxide was reduced stepwise to low-valence state in the order of MnO2 → Mn2O3 → Mn3O4 (together with MnSO4 or SO2). Subsequently, Mn3O4 would be reduced to form MnS or MnO, and the tendency of forming MnO was enhanced with increase in the temperature. Manganese oxide (MnO) will further react with excessive sulfur forming MnS and MnSO4. However, the formed MnS on the surface of the particles would inhibit further reduction or sulfidation. During the reductive roasting process, MnSO4 as well as gaseous SO2 were simultaneously generated. The reaction between MnS and Mn3O4 occurred at temperatures over 500 °C, which facilitated producing MnO and SO2. The roasted product contained MnS, MnSO4, MnO and unreacted Mn3O4 at lower temperature (<500 °C), whereas the main products were MnO and MnSO4 at higher temperature (≥500 °C). The content of MnO increased gradually while that of MnS was decreased by increasing the roasting temperature.

Equilibrium kinetics of manganese-ore carbon-reduction between molten steel and slag

ABSTRACTThe equilibrium condition between molten steel and slag during manganese-ore carbon-reduction was studied using both resistance furnaces and induction furnaces. The resistance furnace experiment shows that it is difficult to further increase the yield of manganese (maintained at around 37%) without stirring. The bottom blowing and top slag stirring were strengthened in the induction furnace test, where white slag was continuously produced to promote the carbon reduction of manganese dioxide in slag between molten steel and slag. Under these conditions, the yield of manganese between molten steel and slag can reach greater than 90%. The main factors affecting the manganate capacity are the carbon and silicon content in molten steel. The limiting process of manganese mass transfer is mainly the mass transfer of manganese in molten steel. Under carbon reduction in molten steel the limiting factor affecting the mass transfer of manganese is the mass transfer of manganese in slag.

ChemInform Abstract: Reduction of Manganese Dioxide by Dissolved Lithium in Liquid Ammonia for Li‐Mn‐O Spinels.

AbstractLi1.12Mn1.88O4 spinel is synthesized by reduction of MnO2 by lithium dissolved in liquid ammonia (‐33 °C) and subsequent heat treatment (600—700 °C, 5—10 h).

Practice of Mass Transport Model Application for Biogeochemical Redox Process in Aquifer

Biogeochemical reduction processes are active in alluvial aquifers, because organic carbon which is indispensable for bacteria growth is abundant. As a result of reduction process, significant changes of groundwater quality take place; denitrification, reduction of manganese dioxide, iron-hydroxide, sulfate, arsenate, and methane are well known as reduction processes in an anaerobic groundwater condition. Therefore, the prediction of redox environment in an aquifer is a key subject in order to understand how the groundwater quality is affected. If the mechanism of groundwater quality formation in aquifer scale is systematically understood, impacts caused by accidents or illegal dumping can be predicted, and subsequently, an appropriate management of aquifer will be established. In the present paper, quantitative discussions are made by the numerical simulations applied for the one-dimensional column experiment and two-dimensional fresh-salt water mixing zone. Recommendation and the future subject are presented through the results of two numerical simulations.

Reduction of manganese dioxide in the sediment and its negative impact on the physiology of clams on two sandy tidal flats, Midori River Tidal Flat and Arao Tidal Flat, in Ariake Bay

On Midori River Tidal Flat and Arao Tidal Flat, which are major sandy tidal flats in Ariake Bay, Kyushu, Japan, I examined various heavy metal contents of the surface sediment to reconfirm that, among the heavy metals, only manganese deposited on the sediment at extremely high levels. On these two tidal flats, 790 to 2,230 mg kg−1 dry sediment of total manganese was detected in the surface sediment. The manganese deposited (mainly as manganese dioxide) in the sediment tends to be reduced by bacterial activities, released as manganese ion to the interstitial water of the sediment, and weakly bound electronically in an exchangeable form with organic or inorganic matter in the sediment. I also examined the manganese ion concentration of the interstitial water and the content of the exchangeable form of manganese of the sediment. High concentrations of manganese ions, as affect the physiology of the aquatic organisms, were detected from the interstitial water of the sediment on Midori River Tidal Flat (5.8 to 9.9 mg L−1), while high contents of the exchangeable form of manganese (approximately 28 mg kg−1 dry sediment) were found from the sediment on Arao Tidal Flat. It seems probable that the manganese ions reduced from the manganese in the sediment acts as one of the major limiting factors on the occurrence of the clam on these two tidal flats.

Atomic Absorption Spectrometry for the Automatic Indirect Determination of Ascorbic Acid Based on the Reduction of Manganese Dioxide

A new and simple flow injection method followed by atomic absorption spectrometry has been developed for the indirect determination of ascorbic acid. The proposed method is based on oxidation of ascorbic acid to dehydroascorbic acid using a solid-phase manganese dioxide (30% m/m suspended on silica gel beads) reactor. The flow of the sample through the column reduces the MnO2 to Mn(II) in an acidic carrier stream of 6.3 mM HNO3 (pH 2.2) with flow rate of 4.0 ml/min at room temperature; Mn(II) is measured by atomic absorption spectrometry. The absorbance of Mn(II) is proportional to the concentration of ascorbic acid in the sample. The calibration curve was linear up to 30 mg/L, with a detection limit of 0.2 mg/L for a 220 microL injected sample volume. The developed procedure was found to be suitable for the determination of AsA in pharmaceuticals and foods with a relative standard deviation better than 1.09% and a sampling rate of about 95 h(-1). The results exhibit no interference from the presence of large amounts of organic compounds. The reliability of the method was established by parallel determination against the 2,6-dichlorophenol-indophenol methods.

RECENT DEVELOPMENTS IN PROCESSING OCEAN MANGANESE NODULES—A CRITICAL REVIEW

This article reviews the state of the art in processing and extracting ocean manganese nodules. It briefly reviews the mining sites where abundant rich nodules occur and also describes the metal distribution in nodules. The physicochemical characteristics of the nodules, touching upon different facets such as mineralogy, geochemistry, moisture content, and textural properties of the nodules, are discussed in detail. In the extraction aspects of the nodules, is article reviews two different extraction routes often mentioned in the literature during the last two decades, namely hydrometallurgical and biohydrometallurgical treatments. The hydrometallurgical techniques include leaching by mineral acids, ammoniacal leaching, leaching at high temperature, and pressure and leaching with reducing agents. Reduction of manganese dioxide by organics and its probable application in leaching of nodules is described in a detailed manner. The biohydrometallurgy section extensively reviews the bioreduction phenomenon for manganese dioxide and suggests possible application in leaching of nodules. Projected future developments in the field, with an eye on commercialization, are also discussed.

In vitro reduction of manganese dioxide by a ferrireductase system from the white-rot fungus Phanerochaete sordida YK-624

Reduction of manganese dioxide is demonstrated for an in vitro ferrireductase system that includes NADPH-dependent ferrireductase and the iron-binding compound (IBC) isolated from the white-rot fungus Phanerochaete sordida YK-624. The Fe(II)–IBC complex was more effective in reducing manganese dioxide to Mn(II) than were complexes of Fe(II) and organic acids of low molecular weight such as nitrilotriacetate, although IBC also reduced manganese dioxide to Mn(II) in the absence of Fe(II). The generated Fe(III)–IBC complex was a better substrate for NADPH-dependent ferrireductase than were other ferric chelates, suggesting that the Fe(III)–IBC complex is reduced to an Fe(II) complex by NADPH-dependent ferrireductase. Moreover, production of the Fe(III)–IBC complex by the reduction of manganese dioxide in a reaction system containing Fe(II) and IBC was observed to be coupled to reduction of the Fe(III)–IBC complex by NADPH-dependent ferrireductase. These results indicate that the ferrireductase system of P. sordida YK-624 plays an important role in the reduction of manganese dioxide, which is necessary for the production and function of manganese peroxidase.

Intracellular ferrireductase involved in Mn(IV)-reducing enzyme system to supply Mn(II) for lignin biodegradation by white-rot fungus Phanerochaete sordida YK-624

In the biobleaching of kraft pulp with white-rot fungus Phanerochaete sordida YK-624, it was confirmed that manganese dioxide (Mn(IV)) in kraft pulp was reduced to Mn(II) by ESR analysis. By this reaction, the production of manganese peroxidase (MnP) by P. sordida YK-624 was triggered and then the kraft pulp was bleached with MnP. In the liquid culture, the reduction of manganese dioxide was observed by the washed mycelia of P. sordida YK-624 although smaller amount of Mn(II) was produced by the extracellular culture fluid. The reduction by the washed mycelia was dependent on Fe(II), a metal chelator, and NAD(P)H. Moreover, the cell-free extract from P. sordida YK-624 catalyzed the reduction of ferric chelate to ferrous chelate in the presence of NAD(P)H. It is likely, therefore, that ferrous chelate reduces manganese dioxide and that the produced ferric chelate is reduced by intracellular NAD(P)H-dependent reductase to regenerate ferrous chelate. An intracellular NADPH-dependent reductase, namely NADPH-dependent ferrireductase (molecular weight 35 kDa, pI 5.1), was purified from P. sordida YK-624. Moreover, there was a good correlation between the production of intracellular ferrireductase and that of extracellular MnP in a liquid culture containing manganese dioxide. These results suggest that the ferrireductase is involved in the production of MnP by the reduction of manganese dioxide to Mn(II).

Role for Outer Membrane Cytochromes OmcA and OmcB of Shewanella putrefaciens MR-1 in Reduction of Manganese Dioxide

Shewanella putrefaciens MR-1 can use a wide variety of terminal electron acceptors for anaerobic respiration, including certain insoluble manganese and iron oxides. To examine whether the outer membrane (OM) cytochromes of MR-1 play a role in Mn(IV) and Fe(III) reduction, mutants lacking the OM cytochrome OmcA or OmcB were isolated by gene replacement. Southern blotting and PCR confirmed replacement of the omcA and omcB genes, respectively, and reverse transcription-PCR analysis demonstrated loss of the respective mRNAs, whereas mRNAs for upstream and downstream genes were retained. The omcA mutant (OMCA1) resembled MR-1 in its growth on trimethylamine N-oxide (TMAO), dimethyl sulfoxide, nitrate, fumarate, thiosulfate, and tetrathionate and its reduction of nitrate, nitrite, ferric citrate, FeOOH, and anthraquinone-2,6-disulfonic acid. Similarly, the omcB mutant (OMCB1) grew on fumarate, nitrate, TMAO, and thiosulfate and reduced ferric citrate and FeOOH. However, OMCA1 and OMCB1 were 45 and 75% slower than MR-1, respectively, at reducing MnO(2). OMCA1 lacked only OmcA. While OMCB1 lacked OmcB, other OM cytochromes were also missing or markedly depressed. The total cytochrome content of the OM of OMCB1 was less than 15% of that of MR-1. Western blots demonstrated that OMCB1 still synthesized OmcA, but most of it was localized in the cytoplasmic membrane and soluble fractions rather than in the OM. OMCB1 had therefore lost the ability to properly localize multiple OM cytochromes to the OM. Together, the results suggest that the OM cytochromes of MR-1 participate in the reduction of Mn(IV) but are not required for the reduction of Fe(III) or other electron acceptors.

Oxidation of manganese(II) and reduction of manganese dioxide in sulphuric acid

Oxidation of Mn 2+ to MnO 2 and reduction of MnO 2 on Pt electrode in sulphuric acid was investigated by cyclic voltammetry as a function of the Mn 2+ concentration, acid concentration, scan rate, temperature and convection. It was observed that oxidation of Mn(II) to Mn(IV) was mass transfer controlled. High temperature and stirring enhanced the oxidation rate of Mn(II) to Mn(IV). Decreasing acid concentration favours MnO 2 deposition while high acid concentrations inhibit the formation of MnO 2. The mechanism of MnO 2 deposition from Mn(II) is suggested to be an ECE sequence with the formation of an insulating intermediate (MnOOH). Small amounts of deposited MnO 2 may be reduced electrochemically at the electrode surface.

Change in oxidation state of manganese atoms in kraft pulp during biological bleaching with white-rot fungusPhanerochaete sordida YK-624

Change in the oxidation state of manganese atoms in unbleached hardwood kraft pulp (UKP) during the biological bleaching of UKP withPhanerochaete sordida YK-624 was determined by the electron spin resonance (ESR) method. The spectrum of Mn(II), which reveals hyperfine splitting, was not observed in the ESR analysis of UKP, but the spectrum for manganese dioxide was observed. After fungal treatment of UKP withP. sordida YK-624, the spectrum of Mn(II) was detected. The reduction of manganese dioxide was triggered by the increase in NADPH-dependent ferrireductase activity. It is concluded that the manganese dioxide dominant in UKP was reduced byP. sordida YK-624 to Mn(II), which stimulates the production and function of manganese peroxidase.

Reduction of Mn(IV) oxide by (NH 4) 2SO 3 in the presence of metal ions in ammoniacal medium

The reduction of manganese dioxide with ammonium sulphite in the presence of Cu(II), Ni(II) and Co(II) has been studied. It was observed that the catalytic activity is in the order Cu(II)>Co(II)>Ni(II). The activation energies were estimated to be approximately 41, 70 and 74 kJ mol −1 in the presence of Cu(II), Co(II) and Ni(II), respectively. The catalytic reduction follows the shrinking core model. The interactive effects of metal ions were studied using 2 3 full factorial design of experiments. The linear coefficients for the three metals were positive whereas Cu(II)–Co(II) showed a negative correlation and Ni(II) did not have any synergistic effect.

NADPH-dependent ferrireductase produced by white-rot fungusPhanerochaete sordida YK-624

An intracellular, soluble ferrireductase thought to be involved in the reduction of manganese dioxide by white-rot fungusPhanerochaete sordida YK-624 was purified for the first time. Two isoenzymes, NAD(P)H-dependent and NADPH-dependent, respectively, were detected by hydrophobic chromatography. The NADPH-dependent ferrireductase was purified to homogeneity by ammonium sulfate fractionation, hydrophobic interaction, gel permeation, and anion-exchange chromatography. The purified protein, which is monomeric, has a molecular mass of 35 kDa (determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis) and pl 5.1 (determined by isoelectric focusing). The purified protein did not use cellobiose as an electron donor. The purified protein reduced Fe(III)-nitrilotriacetate complex, Mn(III)-malonate complex, methoxy-p-benzoquinone, and cytochrome c; veratraldehyde, 2-hydroxy-1,4-naphthoquinone, phenazine methosulfate, and plumbagin could not be reduced. Particularly, the protein showed the highest reducing rate for Fe(III)-organic acid complexes, such as Fe(III)-nitrilotriacetate, among these electron acceptors.

Studies on reduction of manganese dioxide by (NH 4) 2SO 3 in ammoniacal medium

The reduction of MnO 2 by (NH 4)SO 3 has been studied. The reaction path has been described by the model 1−(1− α) 1/3= kt. The reaction was found to be first order with respect to sulfite concentration and 0.5 order with respect to MnO 2. Ammonia and ammonium sulphate concentrations did not affect the kinetics of reduction of MnO 2 in the studied range. The activation energy was estimated to be 62 kJ mol −1. The reduced products were mixtures of Mn 2+, Mn 3+ and Mn 4+. With the increase in the reaction temperature from 353 to 383 K, the ratio of Mn 2+/Mn 3+ increased from 1.10 to 5.12 indicating preference of formation of lower valency states of manganese at higher temperatures. The obeyance of the shrinking core model in spite of formation of a variety of reduced products clearly indicates that none of the products form a protective layer on the manganese dioxide particles. Since the overall reduction kinetics of MnO 2 are governed by a shrinking core model, it is implied that the reduction of any intermediate Mn 3+ species to Mn 2+ during the course of reaction follows a similar path. Depending on the experimental conditions, the dithionate content varied between 1.0 and 2.33 g l −1, indicating predominant formation of sulphate over dithionate.

Oscillatory oxidation of Mn(II) ions by hexacyanoferrates(III) and bistability in the reductions of MnO 2 by hexacyanoferrates(II) in a CSTR

A new transition metal oscillator based on the oxidation of Mn 2+ ions by Fe(CN) 3− 6 ions in a CSTR has been found. As well as the oscillations of the absorbance of the Mn(IV) species, pH-oscillations have been observed. In the reduction of manganese dioxide by Fe(CN) 4− 6 ions a kinetic bistability has been described. A skeleton mechanism described recently for Mn(II)H 2O 2 and Mn(II)Br 2 oscillators has been applied here and further developed by the idea of the catalytic activity of colloidal particles and of the assistance of the pH-value change of both main processes, i.e. of the Mn(II) oxidation by Fe(CN) 3− 6 ions and of the Mn(IV) reduction by Fe(CN) 4− 6 ions. This appears to be the first case where both sides of a reversible reaction are autocatalytic.

Measuring variation in EMD reduction with location in primary alkaline batteries

Reduction of manganese dioxide is not uniform throughout alkaline cells with thick cathodes. Quantification of the degree of reduction of MnO2 as a function of location in the cathode by determining the degree of EMD reduction in discharged alkaline cathodes is described, using a new experimental technique which allows collection and analysis of regionally defined electrolytic manganese dioxide (EMD) samples from commercial primary alkaline batteries of different sizes. This method has been developed for 1.5V D-size and C-size alkaline batteries. The information gained can be used to better explain the behaviour of real cells with thick cathodes.

Creation of metal-complexing agents, reduction of manganese dioxide, and promotion of manganese peroxidase-mediated Mn(III) production by cellobiose:quinone oxidoreductase from Trametes versicolor.

Culture supernatants of the white-rot fungus Trametes versicolor were found to contain Mn(III)-complexing agents able to effectively promote manganese-dependent peroxidase (MnP)-mediated oxidation of phenol red. The high molecular weight fractions of these supernatants contained carbohydrate polymers that functioned as effective Mn(III)-complexing agents. Gluconic and glucuronic acids were also found to be effective Mn(III)-complexing ligands capable of supporting MnP-mediated phenol red oxidation, as was the cellobionic acid formed from cellobiose by cellobiose:quinone oxidoreductase (CBQase) (EC 1.1.5.1). The formation of cellulose-derived sugar acid manganese-complexing agents by CBQase increased in the presence of wood pulp and cellulolytic enzymes. CBQase, while oxidizing cellobiose, reduced insoluble Mn(IV)O2 to Mn(II) or Mn(III) by a reaction whose rate is determined by the nature of the manganese-complexing agents present. A model is proposed to explain how oxidation of carbohydrate and reduction of MnO2 and quinones by CBQase may complement oxidation by MnP, thus promoting lignin biodegradation.

The electrochemical reduction of manganese dioxide in acidic solutions Part III. Voltammetric peak 3

The electrochemical reduction of manganese dioxide in acidic solutions Part III. Voltammetric peak 3