Manganese Sulfate Solution Research Articles

Efeito da densidade de corrente e temperatura na área superficial do dióxido de manganês eletrolítico

Neste artigo foi estudado o efeito da densidade de corrente e da temperatura na produção de dióxido de manganês eletrolítico (DME) a partir de soluções ácidas de sulfato de manganês por meio de voltametria de varredura linear, microscopia eletrônica de varredura e medidas de área superficial (BET). Foi observado que na temperatura de 65º C a produção de DME foi limitada pelo fenômeno de passivação dos anodos de titânio e que, a 90º C este efeito era substancialmente reduzido. Foi também verificado que o aumento da densidade de corrente e a diminuição da temperatura proporcionaram um aumento significativo na área superficial específica do depósito de DME. A maior área superficial, de 168 m²/g, foi obtida com uma densidade de corrente de 8mA/cm², em solução 0,34M de H2SO4 a 65ºC, enquanto que a menor, de 52 m²/g, foi obtida com uma densidade de corrente de 4mA/cm², na mesma solução, a 90ºC.

Synthesis of Size-Controlled Monodisperse Manganese Carbonate Microparticles as Templates for Uniform Polyelectrolyte Microcapsule Formation

Inorganic colloids are usually prepared via precipitation reactions, which involve two sequential steps: nucleation and growth of the nuclei. On the basis of this theory, preformed manganese carbonate nanoseeds were prepared by mixing diluted ammonium hydrogen carbonate with manganese sulfate solution to serve as nuclei for production of monodisperse manganese carbonate microparticles. It was found that the average particle diameter can be finely tuned from 1 to 10 μm by adding a different volume of nanoseed solution. It was further verified that the manganese carbonate microparticles can be used as templates for efficient formation of uniform, smooth multilayer polyelectrolyte microcapsules, which are promising systems for biomedical and other applications, such as biosensors, bioreactors, and drug-delivery devices.

Experimental measurements of neutron fluxes produced by proton beams (23–80 MeV) on Be and Pb targets

The “manganese bath” technique has been perfected to measure the total number of neutrons emitted when 23–80 MeV proton beams bombard a beryllium target. It consists in surrounding the neutron source with a large metallic cylinder filled with a manganese sulphate (MnSO 4) solution. The neutrons are slowed down by water and partly captured by manganese (production of 56Mn; T 1 / 2 = 2.6 h ). The absolute calibration has been performed with a Ra–Be neutron source. Corrections have been applied for escaping neutrons in both cases. Our experimental results show that the total number of neutrons produced ( S 0) by the p+Be reaction, per second and per microampere of beam, can be approximated (for proton energy E p between 23 and 80 MeV) by: S 0 = 5.58 × 1 0 8 ( E p[MeV]) 1.69. Some measurements have also been done with a lead target.

電解析出法によるマンガン‐イリジウム複合酸化物薄膜の生成とエレクトロクロミック特性

Manganese and iridium oxides composite films were obtained by anodic codeposition using a mixture solution of manganese (ll) sulfate and iridium (lll) sulfate, and their electrochromic properties were investigated.To prepare the electrolyte, 0.2wt% manganese (ll) sulfate aqueous solution and 0.2wt% Iridium (lll) sulfate solution were mixed in various proportions. The anodic codeposition was carried out using a pulse wave of 1350mV and −200mV (vs Ag/AgCl), with hold time for 6 sec at room temperature.From XPS analysis, it was confirmed that the manganese-iridium oxide composite films of different oxide ratios can be obtained by anodic codeposition. The electrochemical and electrochromic properties of composite films of different metal oxide ratios have been characterized by cyclic voltammogram in 0.05 M NaOH aqueous solution. The composite Mn-Ir (9 : 1) oxide film shows higher charge densities and a broad and stable C. V. curve compared to that of pure manganese oxide film. The composite Mn-Ir (9 : 1) oxide film exhibited maximum optical density (ΔOD) at 400nm.The morphology of the composite film anodically deposited from MnSO4 : Ir2(SO4)3=9 : 1 electrolyte consisted of nanoparticles of 20-30nm in diameter, while the pure manganese oxide film was fiber, and the pure iridium oxide film consisted of particles of 100-200nm. It seems that enhancement of electrochromic characteristics are due to the nanostructure of the Mn-Ir (9 : 1) composite thin film.

Improved performance of rechargeable alkaline batteries via surfactant-mediated electrosynthesis of MnO 2

An innovative application of surfactant-mediated modifications of electrolytic MnO 2 (EMD), proved to be a major step toward enhancement of the rechargeability in alkaline batteries. Presence of different surfactants in boiling acidic solutions of manganese sulfate, under atmospheric pressure, enhanced a variety of EMD products, with various structural and electrochemical properties. Surfactants employed consisted of: anionic sodium n-dodecylbenzenesulfonate (SDBS), cationic cetyltrimethylammonium bromide (CTAB) and non-ionic t-octyl phenoxy polyethoxyethanol (Triton X-100). Among them, EMDs produced in the presence of CTAB has a slight positive effect on the cycle performances, while SDBS inhibits it. Interestingly, the EMD powders prepared from the micellar solution, in the range of 0.3 wt.% of Triton X-100, exhibited much higher discharge capacities, as well as better cyclabilities in comparison with the commercial EMD sample known as TOSOH™. The superiority of the former EMD was further confirmed through electrochemical cyclic voltammetry and also electrochemical impedance spectroscopy (EIS). Modifications of electrolytic MnO 2, via mediations of different surfactants were perceived through changes in their compositions, crystal structures and morphologies. The characteristics of the produced materials were determined by thermogravimetric analysis (TGA), powder X-ray diffraction (XRD) and scanning electron microscopy (SEM). Enhancements of electrochemical properties, observed for Triton X-100 modified EMD, could be attributed to a homogeneous current distribution with unique crystalline structure, based on the modified electrode/solution interface, through adsorbed surfactant layers. Moreover, the observed improvements appear connected to the enhanced film growth, with different degrees of mesoscopic organizations. Higher cycle performances, mechanical stabilities and the ease of production make this method excellent for being employed in a number of industrial applications.

Gypsum–anhydrite transformation in hot acidic manganese sulfate solution. A comparative kinetic study employing several analytical methods

Transformation of calcium sulfate dihydrate (gypsum) into anhydrous calcium sulfate (anhydrite) proceeds slowly in a manganese sulfate/sulfuric acid medium (36 g Mn 2+/kg of solution and 36 g H 2SO 4/kg of solution) at 95 °C, conditions pertinent to some industrial processes, without any apparent intermediate species. The kinetics of the transformation have been probed by following the change in mole fraction of gypsum and/or anhydrite versus time in both solution (dissolved [Ca], by ICP-AES) and solid-state (XRD and TGA). The kinetics fit an autocatalytic process, with a very small initial [product] o (typically ∼10 −4 M, consistent with a high purity gypsum starting material) and a rate constant k∼0.12 h −1 at 95 °C. Variations in the observed half-life for transformation found between the solid-state (∼65 h) and the solution (∼77 h) measurements may reflect non-equilibrium solution behaviour associated with slow crystallization of anhydrite, consistent with a dissolution–precipitation mechanism. Addition of an anhydrite seed at commencement of the reaction diminishes the induction period and accelerates the transformation, as expected for an autocatalytic process.

Simultaneous solvent extraction of cobalt and nickel in the presence of manganese and magnesium from sulfate solutions by Cyanex 301

The simultaneous extraction and separation of Co(II) and Ni(II) from manganese and mgnesium sulfate solutions have been carried out using the thio-organophosphinic extractant Cyanex 301, diluted in Exxsol D-80. Statistical design and analysis of experiments were used in order to determine the main effects and interactions of the solvent extraction factors, which were the extraction pH at equilibrium, temperature, extractant concentration and organic to aqueous phase ratio. A statistically designed experiment was also carried out in order to study the stripping of the cobalt- and nickel-loaded Cyanex 301 organic phase by hydrochloric acid solution. The Slope analysis method was used to determine the nature of the cobalt and nickel complexes extracted. The number of stages required for both extraction and stripping processes of cobalt and nickel was also evaluated. The results of the continuous counter current, mini plant tests demonstrated the simultaneous recovery of cobalt and nickel from manganese and magnesium sulfate solution.

Effect of bath temperature on electrochemical properties of the anodically deposited manganese dioxide

The effect of bath temperature on the electrochemical properties of electrolytic manganese dioxide (EMD) was studied. EMD was produced by anodic deposition from acidic aqueous solution of manganese sulfate at different bath temperatures in the range of 60–120°C. At temperatures above the boiling point of water, the electrolysis was carried out in an autoclave. The EMD produced at 120°C was of gamma type, identified by X-ray diffraction (XRD). Furthermore, the materials produced at 115 and 120°C were quality-controlled by cycling a sample as cathode mix in small size RAM-cells and by scanning electron microscopy. The results indicated an increase in cyclic charge/discharge performance and an improvement of crystallization conditions of EMD produced at elevated temperature when compared to data of commercially available γ-MnO 2.

Sorption of Zn(II), Cu(II), Fe(III) on carbon adsorbents from manganese sulfate solutions

Sorption of Zn 2+, Cu 2+, Fe 3+/Fe 2+ on carbon adsorbents under static (batch) and dynamic (columns) conditions from model and industrial MnSO 4 solutions has been studied. The industrial solutions were obtained by reducing acidic leaching of manganese and pyrite concentrates. The initial manganese concentration was ∼35 mmol/l and concentration of Zn 2+, Cu 2+, Fe 3+ ions was ∼0.2 mmol/l. It was found out that a complete separation of Mn 2+ and Me 2+(Fe 3+) ions is possible under dynamic conditions. As a result purified MnSO 4 solutions are obtained which can be applied in MnO 2 electroevolution processes.

Synthesis, characterization and application of doped electrolytic manganese dioxides

Abstract Electrolytic manganese dioxides (EMDs) were prepared on the 100 g scale by anodic deposition from acidic aqueous solutions of manganese sulfate. In situ doping with titanium ions was achieved by addition of tetra- n -butoxytitanium to the electrolytic bath. Samples were also doped ex situ by washing the products with aqueous barium hydroxide solution. The EMDs were characterized by electron microscopy studies and BET surface area determinations. Cyclic abrasive stripping voltammetry was successfully applied to evaluate the rechargeability of the newly synthesized undoped and doped EMDs in 9 M KOH. Relative discharge capacities at different depths of discharge (DOD) with respect to the first one-electron reduction of γ-MnO 2 are compared for different EMDs. At about 30% DOD, resulting relative discharge capacities show essentially the same trend as those measured in AA cells from about 10 to 20 discharge/charge cycles onwards. Accordingly, titanium-doped EMD was shown to exhibit superior charge retention and rechargeability when compared to the titanium-free samples.

Cobalt-manganese separation: the extraction of cobalt(II) from manganese sulphate solutions by cyanex 301

The extraction and stripping reactions of cobalt(II) by Cyanex 301 in Iberfluid diluent from aqueous manganese sulphate solutions has been investigated. The effect of different variables which should influence the extraction-stripping of cobalt was evaluated, including equilibration time, temperature, organic diluent, extractant concentration, aqueous pH, cobalt loading, strip solution concentration, etc. The number of stages required for the extraction and stripping of cobalt was also evaluated. The results were used to define the conditions for the purification of manganese sulphate solutions. © 1998 Society of Chemical Industry

Characterization and leaching of ferromanganese slag

Ferromanganese slag, a product of the manganese industry, was characterized mineralogically. The slag, which contains high Mn values, was characterized using optical microscopy, XRD analysis and electron microscopy. No separate Mn-bearing oxide mineral phase was found. The slag is amorphous, and no crystalline phase was identified in the bulk sample by XRD. However, in fine fractions, quartz was identified. Scanning electron microscopy (SEM) revealed the presence of Mn, Si, Al and Ca in the matrix without the development of a mineral phase. Leaching experiments using H2SO4 were carried out to determine if Mn could be extracted from the slag. At room temperature, almost 100% of the manganese could be dissolved at a solid-liquid ratio of 1:10 by leaching with dilute sulfuric acid. The impurities could be precipitated by pH adjustment to produce a manganese sulfate solution suitable for the production of MnO2 or electrolytic Mn metal. Based on the laboratory-scale experiments, a suitable process is proposed to recover manganese values from the ferromanganese slag.

Preparation and Properties of Uniform Coated Inorganic Colloidal Particles. 11. Nickel and Its Compounds on Manganese Compounds

Uniform cubic manganese carbonate, MnCO3, particles of two modal sizes (∼0.8 and 8 μm) were produced by homogeneous precipitation from aqueous solutions of manganese sulfate and urea at elevated temperatures under limited experimental conditions. The larger particles were converted into Mn2O3 and MnO on calcination at 700 °C either in the flow of air and or in nitrogen. The MnCO3 particles were also coated with NiCO3.Ni(OH)2·H2O by aging dispersions of the cores in aqueous solutions of nickel sulfate and urea at 80 °C, yielding a molar ratio [Ni]/[Mn] = 0.45 in the final solid. On calcination at 700 °C in air, the shell and core materials of the coated particles transformed independently into NiO and Mn2O3, which on further heating at 350 °C in hydrogen were reduced to Ni and Mn, respectively. The coating solutions aged at the same temperature in the absence of cores resulted in nearly spherical of NiCO3·Ni(OH)2·H2O particles of narrow size distribution. The latter solids transformed into NiO on calcinati...

Ion exchange purification of manganese sulphate solutions from cobalt

The recovery and separation of cobalt and manganese were investigated according to ion exchanger properties and pH of solutions. It was determined that cobalt sorption increases with pH increase to 5.5. The cobalt and manganese separation is performed using manganese substitution by cobalt ions at pH more than 3.5 on chelating resins ANKB-35 and AMF-2M. The cobalt content of manganese sulphate solutions does not exceed 0.6 mg/l.

Microstructural characteristics of chemically processed manganese oxide nanofibres

Nanostructured fibrous manganese oxide cryptomelane-type hollandite powders were prepared via a chemical route. Powders were obtained by the chemical reaction of the aqueous solutions of potassium permanganate and manganese sulfate in the presence of a strong acid, followed by crystalline growth at elevated temperatures. These powders were characterized by powder X-ray diffraction (XRD), Rietveld refinement, analytical scanning electron microscopy (SEM), transmission electron microscopy (TEM) combined with micro-micro diffraction (μμd), and high resolution transmission electron microscopy (HRTEM). The crystalline structure, morphology, crystallite size, fibre growth direction, and structural defects are discussed.

Sulphation of Carajás manganese ore

This paper presents the results of laboratory scale experiments carried out at CVRD Centre of Technology on the sulphation of Carajás manganese ore using the classical method of pyrometallurgical reduction/ leaching with sulphuric acid. In addition, the removal from impurities of the resulting manganese sulphate solutions was studied by means of jarosite and sulphide precipitation. The results obtained provide preliminary data for the utilization of Carajás ore by the chemical industry, and indicate that this ore is a suitable raw material for the manufacture of manganous sulphate and other manganese containing compounds.

ESR Spectra of VO2+ and Mn2+ in Aqueous Solution at L-Band

Abstract L-Band (1.2 GHz) electron spin resonance (ESR) spectra of aqueous solution of vanadyl and manganese sulfate are reported with a comparison to those at X-band (9.4 GHz). ESR spectra of 0.5 mol dm−3 VO2+ and Mn2+ aqueous solution consisted of 3 and 2 resonance lines at L-band, respectively, while those gave 8 and 6 lines at X-band, respectively. The origin of the characteristic ESR spectra will be discussed in terms of frequency dependence of hyperfine coupling constant and line-broadening.

Kinetic study on the precipitation of alunite from manganese sulphate solutions

The kinetics of precipitating alunite (KAl 3 (SO 4) 2(OH) 6) from manganese sulphate solutions containing 0.2 g/l potassium was evaluated at different temperatures (80–95°C), controlled solution pH's (2.5–3.5) and aluminium/potassium (Al/K) molar ratios ( 3 1 6 1 and 9 1 ). The experimental data fit a second-order kinetic model which shows two regions of precipitation with rate constant dependent on the precipitation parameters. At the stoichiometric Al/K ratio of 3, the variation of rate constants with temperatures from 80–95°C yields activation energies of 58.5 and 43.2 kj/mol for the initial induction stage and the subsequent crystal growth respectively. At Al/K molar ratios of 6 and 9, the activation energies are 110 and 132 kJ/mol for the two stages of precipitation. Seeding the solutions with alunite crystals before the precipitation (at 5 and 10 g/l) decreases the induction period and improves the kinetics significantly. An increase of sulphate concentration also improves the crystal growth rate.

Preparation of manganese ferrite from ?-Mn2O3 and its characterization

Samples of γ-Mn 2 O 3 with different iron concentrations were prepared by coprecipitating appropriate amounts of manganese sulphate and ferric nitrate solution in boiling solution of sodium hydroxide. The precipitates were then washed with distilled water to keep them free from adsorbed impurities, and were finally dried in air. The absence of any appreciable sodium content in the precipitate was tested by using a digital flame photometer

オゾン酸化によって酸性硫酸マンガン溶液から析出した二酸化マンガン粒子

Manganese dioxide was precipitated from slightly and strongly acidic solution of manganese sulfate by ozone oxidation at temperatures up to 80°C. The particles were characterized by SEM observation and X-ray diffraction.Ozone was found to be very effective to produce manganese dioxide even at acid concentration as high as 5.0mol/l.The size and surface morphology of the particle were strongly affected by acidity and temperature. At pH 2 or 3, the particles were as small as about 0.2μm and had rugged surface. Particles consisted of nearly spherical grains of a size of 1-2μm with smooth surface at 1 or 2mol/l H2SO4. The particle surface turned rougher and finally was covered almost uniformly with thin needle-like crystals as the acid concentration increased up to 5.0mol/l. It was observed that the particle had rougher surface as the reaction temperature was raised.X-ray diffraction analysis showed that γ-MnO2 was a main reaction product under the conditions excluding pH 3.0 and 5.0mol/l H2SO4 at 80°C where α-MnO2 was detected.Also, use of ozone was proved to enable us to produce very fine particles of manganese dioxide with discharge behavior comparable to commercial electrolytic manganese dioxide for a battery-active material.