Reduction Of Permanganate Research Articles

Structure, cation valence states and electrochemical properties of nanostructured Mn3O4

Nanostructured Mn3O4 with an average crystallite of ~10nm is synthesized by the controlled reduction of potassium permanganate using hydrazine. The phase purity, average crystallite/particle size, morphology and state of agglomeration were studied using X-ray diffraction (XRD), Transmission Electron microscopy (TEM) and Scanning Electron Microscopy (SEM) analyses. Nitrogen sorption studies give a specific surface area of 62m2/g and also reveal the mesoporous nature. The presence of Mn4+ ions is inferred from the Fourier Transform Infra-Red (FTIR) spectroscopy and X-ray Photoelectron Spectroscopy (XPS) studies. The decrease in the c/a ratio obtained from XRD analysis also indicates the presence of Mn4+ ions. Electrochemical analysis was done on a symmetric capacitor with nanostructured Mn3O4 as the active material and 6M KOH solution as the electrolyte. Cyclic voltammograms revealed pseudocapcitive behavior with specific capacitance values falling sharply with scan rate. The power density and energy density values obtained from chornopotentiograms are fairly large and indicate the potential application in the field of supercapacitors.

Role of chemiexcited particles in permanganate reduction by citric acid: Investigation with spectrophotometric and chemiluminescence methods

Potassium permanganate reduction by citric acid in the presence of sulfuric acid includes stages of chemigeneration of electronically excited Mn(II) and emission of photons by it. The electronic absorption, reactant concentration, and chemiluminescence kinetics have been investigated. It has been shown that the chemiexcited species Mn(II) (chemiluminescence emitter) acts as a permanganate reduction catalyst.

Optical, electrical and magnetic properties of nanostructured Mn3O4 synthesized through a facile chemical route

Nanostructured Mn3O4 sample with an average crystallite size of ∼15nm is synthesized via the reduction of potassium permanganate using hydrazine. The average particle size obtained from the Transmission Electron Microscopy analysis is in good agreement with the average crystallite size estimated from X-ray diffraction analysis. The presence of Mn4+ ions at the octahedral sites is inferred from the results of Raman, UV–visible absorption and X-ray photoelectron spectroscopy analyzes. DC electrical conductivity of the sample in the temperature range 313–423K, is about five orders of magnitude larger than that reported for single crystalline Mn3O4 sample. The dominant conduction mechanism is identified to be of the polaronic hopping of holes between cations in the octahedral sites. The zero field cooled and field cooled magnetization of the sample is studied in the range 20–300K. The Curie temperature for the sample is about 45K, below which the sample is ferrimagnetic. A blocking temperature of 35K is observed in the field cooled curve. It is observed that the sample shows hysteresis at temperatures below the Curie temperature with no saturation, even at an applied field (20kOe). The presence of an ordered core and disordered surface of spin arrangements is observed from the magnetization studies. Above the Curie temperature, the sample shows linear dependence of magnetization on applied field with no hysteresis characteristic of paramagnetic phase.

Polyol-mediated syntheses of crystalline nanosized manganese oxides

Potassium-type birnessite and lithium-containing manganese oxides were prepared by the polyol process. The Mn(III)/Mn(IV) mixed-valencies compounds are obtained through the controlled reduction of potassium permanganate in a basic water–diethylene glycol mixture at moderate temperature and very short reaction time, 70 °C and 10 min, respectively. Both solids are quite well crystallized and display high specific surface areas, 137 and 329 m2 g−1, respectively. Several polyols with variable chain lengths have been used and it is shown that the nature of the polyol has a marked influence on the textural properties of the birnessite-type solid.

Chemiluminescence quantum yield in permanganate reduction reactions in acid medium

Chemiluminescence quantum yields for the reactions of permanganate with oxalic, tartaric, and citric acids; hydrazine; KBr; and FeSO4 in aqueous solutions of sulfuric acid have been measured. The maximum quantum yield reaches 1.2 × 10−5 einstein/mol with the chemiexcitation yield being 2%. Hence, the relatively low chemiluminescence quantum yield is due to a low yield of light emission by chemiexcited particles, rather than the low chemiexcitation yield.

Permanganate diffusion and reaction in sedimentary rocks

In situ chemical oxidation using permanganate has frequently been used to treat chlorinated solvents in fractured bedrock aquifers. However, in systems where matrix back-diffusion is an important process, the ability of the oxidant to migrate and treat target contaminants within the rock matrix will likely determine the overall effectiveness of this remedial approach. In this study, a series of diffusion experiments were performed to measure the permanganate diffusion and reaction in four different types of sedimentary rocks (dark gray mudstone, light gray mudstone, red sandstone, and tan sandstone). Results showed that, within the experimental time frame (~2 months), oxidant migration into the rock was limited to distances less than 500 μm. The observed diffusivities for permanganate into the rock matrices ranged from 5.3 × 10(-13) to 1.3 × 10(-11) cm(2)/s. These values were reasonably predicted by accounting for both the rock oxidant demand and the effective diffusivity of the rock. Various Mn minerals formed as surface coatings from reduction of permanganate coupled with oxidation of total organic carbon (TOC), and the nature of the formed Mn minerals was dependent upon the rock type. Post-treatment tracer testing showed that these Mn mineral coatings had a negligible impact on diffusion through the rock. Overall, our results showed that the extent of permanganate diffusion and reaction depended on rock properties, including porosity, mineralogy, and organic carbon. These results have important implications for our understanding of long-term organic contaminant remediation in sedimentary rocks using permanganate.

Morphology-controlled synthesis and growth mechanisms of branched α-MnO2 nanorods via facile microwave-assisted hydrothermal method

Multiple branched manganese oxide nanorods were obtained through the rapid one-step microwave-assisted hydrothermal synthesis by the reduction of potassium permanganate in hydrochloric acid solution without using any catalysts or surfactants. The formation mechanism of the branched α-MnO2 was studied by systematically varying the reaction time, which were “oriented attachment” and rolling-cum-phase process. The electrochemical performance of the samples was examined by cyclic voltammetry. The specific surface area of the branched α-MnO2 and the electrolyte in the solution were found to remarkably affect the specific capacitance. This microwave-assisted technique enables the quick and simple preparation of branched MnO2 nanorods under mild conditions and maybe readily extended to the preparation of many other branched nanoparticles.

Synthesis of MnO2/short multi-walled carbon nanotube nanocomposite for supercapacitors

Multi-walled carbon nanotubes (MWNTs) were selectively etched in molten nitrate to produce short MWNTs (s-MWNTs). MnO2/s-MWNT nanocomposite was synthesized by a reduction of potassium permanganate under microwave irradiation. For comparative purpose, MnO2/MWNT nanocomposite was also synthesized and investigated for its physical and electrochemical performance. Uniform and conformal MnO2 coatings were more easily formed on the surfaces of individual s-MWNTs. MnO2/s-MWNT nanocomposite estimated by cyclic voltammetry (CV) in 0.5 M Na2SO4 aqueous solution had the specific capacitance as high as 392.1 F g−1 at 2 mV s−1. This value was more than 48.9% larger than MnO2/s-MWNT nanocomposite. In addition, MnO2/s-MWNT nanocomposite was also examined by repeating the CV test at a scan rate of 50 mV s−1, exhibiting an excellent cycling stability along with 99.2% specific capacitance retained after 1000 cycles. Therefore, MnO2/s-MWNT nanocomposite is a promising electrode material in the supercapacitors.

Effect of Potassium Ions on the Formation of Crystalline Manganese Oxide Nanorods via Acidic Reduction of Potassium Permanganate

Uniformly grown manganese oxides nanorods are synthesized via a simple and rapid process through an acidic reduction of potassium permanganate followed by heat treatment. The as-produced manganese oxides nanorods are characterized with X-ray diffraction, energy dispersive X-ray analysis, scanning electron microscopy, and transmission electron microscopy. The crystallinity of the nanostructure is found to have a dominant Mn2O3 phase. The compositional and microstructural analyses reveal that the potassium concentration within the as-prepared material has a profound effect on the morphological conversion of manganese oxide nanoparticles to nanorods. Potassium ions are believed to act as a template for the formation of nanorods and the conversion efficiency increases with the increasing content of potassium. Also the morphology of products is found to depend strongly on the annealing time. The mechanism of nanorod growth with respect to different potassium contents and annealing times is discussed.

Enhanced Supercapacitor Performance of Mn3O4 Nanocrystals by Doping Transition-Metal Ions

Pristine and transition-metal-doped Mn3O4 nanocrystals shaped in octahedrons have been synthesized by hydrothermal reduction of potassium permanganate and characterized by SEM/TEM, X-ray diffraction, X-ray photoelectron spectroscopy, and electrochemical experiments. The results reveal that a multistep reduction process is taking place, and the introduction of doping ions causes a direct synthesis of single-phase Mn3O4 nanocrystals. To assess the properties of Mn3O4 nanocrystals for their use in supercapacitors, cyclic voltammetry and galvanostatic charging-discharging measurements are performed. The phase stability during cycling and charge-transfer behavior are greatly improved by doping with transition metal, and Cr-doped Mn3O4 nanocrystals exhibit a maximum specific capacitance of 272 F g(-1) at a current density of 0.5 A g(-1). These doped Mn3O4 nanocrystals could be a promising candidate material for high-capacity, low-cost, and environmentally friendly electrodes for supercapacitors. In addition, these results have verified the ability of doping to improve capacitive performances of spinel-structured transition-metal oxides.

Influence of permanganate reduction on CaCO3 crystals' growth on a rotating metal surface

CaCO3 growth on a stainless steel rotating electrode surface has been carried out in optimised conditions. Without permanganate ions in the solution, the formed scale appears compact and sticky as it is confirmed by microscopic observations and the low residual current density observed at cathodic polarisations.In this work we were interested by the behaviour of permanganate on CaCO3 growth because it is generally considered as a corrosion inhibitor. Permanganate ions injected in the solution are readily reduced at cathodic potentials, provided that the ions reach the surface of the polarised electrode. Permanganate reduction leads, through several steps, to the formation of MnO2. This semi-conductor specie has the particularity to be solid and develops on the metal surface. CaCO3 growth on a surface electrode covered by MnO2 remains possible. But the deposit formed appears to be porous and much less adherent than without manganese species. Our observations obtained at 25°C have been verified at higher temperatures.

Facile Synthesis of Activated Carbon-Supported Porous Manganese Oxide via in situ Reduction of Permanganate for Ozone Decomposition

Lichen-like porous manganese oxides (MnOx) with birnessite-type structure, which were assembled with curled nanosheets (less than 10 nm in thickness), were deposited in situ on the surface of activated carbon (AC) via facile reduction of permanganate by AC, and were tested for the decomposition of ozone, a common air pollutant. Despite the low Mn loading (typically 0.04%–0.14%), the as-synthesized MnOx/AC catalysts exhibited high catalytic activity and stability for ozone decomposition at room temperature and high relative humidity, which can be attributed to the enrichment of the Mn element on the catalyst surface and a well-organized porous surface morphology of MnOx.

Synthesis of highly flexible and light-weight manganese oxide/carbon fiber cloth electrode for electrochemical capacitor

A free-standing, totally flexible and light-weight manganese dioxide/carbon fiber cloth electrode has been simply and cost-effectively fabricated by direct reduction of permanganate. The nano-scaled MnO2 film, being in physical contact with the carbon fiber substrate, provides an enhancement of the kinetics and mechanical flexibility. The electrochemical stability is improved due to the efficient release of bending stress by inter-cluster gap adjustment of nano-scaled MnO2 film and adsorption of carbon fibers. The maximum capacitance loss is only of 0.05% during operating shape change. By short transport/diffusion path lengths and large specific surface areas, the nano-scaled MnO2 film presents superior rate capability. The specific capacitance still retains about 53% when the scan rate increases as much as 50 times.

High-throughput sequential injection assay method for chlorpromazine

This manuscript reports the optimization and validation of a new, rapid, reagent-saving and environmentally-safe method for chlorpromazine assay in pharmaceutical formulations utilizing sequential injection analysis (SIA) technique. Despite its benefits over univariate approach, chemometrics has been rarely exploited for optimizing SIA methods. Moreover, in those methods, some conditions have not been considered in optimization process. In the current study, more conditions, namely volumes and concentrations of reagents, have been optimized by chemometrics for the first time. A developing oxidation reaction of chlorpromazine by permanganate in acidic media was adopted. A spectrophotometric detection of the reduction of permanganate was applied at 526 nm using miniaturized fiber optic devices. The 24 full-factorial design and response surface approaches were exploited for method optimization. The method was validated and realized by a British Pharmacopoeia method. Experimental conditions and analytical aspects of the current SIA method were compared with those of a previous SIA method. Some analytical aspects were comparable while other aspects demonstrated better results from the current method than those from the previous one. The current method is rapid with a sample frequency of 51.4 samples/h. It is also reagent-saving with a total volume of consumed reagents and sample of 260 μL as well as environmental-safety with a total volume of waste production of 1260 μL. The method is therefore efficient for industrial-scale pharmaceutical analysis.

Facile synthesis of manganese oxide/aligned carbon nanotubes over aluminium foil as 3D binder free cathodes for lithium ion batteries

Lithium ion batteries have attracted a lot of attention due to their high energy density, but they have relatively lower power density and poorer cyclic stability compared with supercapacitors. Manganese oxide is a promising electrode material for lithium ion batteries due to its low cost, low toxicity, high theoretical capacity, and wide availability. However, it suffers from serious capacity fading which impedes its commercial application. In this work, aligned carbon nanotubes (ACNTs) were grown directly over Al foil as 3D current collectors and then manganese oxide thin film was coated over ACNTs through a spontaneous reduction of potassium permanganate. The obtained 3D manganese oxide/ACNT coaxial nanotube arrays on Al foils provide remarkable advantages such as the large surface area of the 3D thin manganese oxide layer, the very low electric resistance of the electrode, excellent lithium ion diffusion in the manganese oxide layer and in the channel between the tubes, and excellent elastic properties to tolerate the large volume changes during charge and discharge. As a result, a remarkable improvement of rate capability and stability of the lithium ion batteries was achieved. The 3D thin film electrodes can deliver a capacity of 308 mA h g−1 at 0.1 C which is identical to the theoretical capacity of 95 mA h g−1 at 20 C and maintain a capacity of 133 mA h g−1 after 100 cycles at 1 C. The continuous growth of a solid electrolyte interface (SEI) layer due to trace amounts of water remaining in the manganese oxide layers has been identified as the main cause of the capacity fading. The stability was improved but the initial capacity decreased with increasing annealing temperature in the inert gas.

Synthesis of carbon nanofibers@MnO2 3D structures over copper foil as binder free anodes for lithium ion batteries

A 3D structured composite of carbon nanofibers@MnO2 on copper foil is reported here as a binder free anode of lithium ion batteries, with high capacity, fast charge/discharge rate and good stability. Carbon nanofiber yarns were synthesized directly over copper foil through a floating catalyst method. The growth of carbon nanofiber yarns was significantly enhanced by mechanical polishing of the copper foils, which can be attributed to the increased surface roughness and surface area of the copper foils. MnO2 was then grown over carbon nanofibers through spontaneous reduction of potassium permanganate by the carbon nanofibers. The obtained composites of carbon nanofibers@MnO2 over copper foil were tested as an anode in lithium ion batteries and they show superior electrochemical performance. The initial reversible capacity of carbon nanofibers@MnO2 reaches up to around 998 mAh·g−1 at a rate of 60 mmA·g−1 based on the mass of carbon nanofibers and MnO2. The carbon nanofibers@MnO2 electrodes could deliver a capacity of 630 mAh·g−1 at the beginning and maintain a capacity of 440 mmAh·g−1 after 105 cycles at a rate of 600 mA·g−1. The high initial capacity can be attributed to the presence of porous carbon nanofiber yarns which have good electrical conductivity and the MnO2 thin film which makes the entire materials electrochemically active. The high cyclic stability of carbon nanofibers@MnO2 can be ascribed to the MnO2 thin film which can accommodate the volume expansion and shrinking during charge and discharge and the good contact of carbon nanofibers with MnO2 and copper foil.

Gamma radiation induced formation and characterization of the nano-oxides of manganese

Nano-crystalline oxide powders of manganese were formed by the radiolytic reduction of permanganate (MnO4−) at ambient temperature and pressure in (i) acid (ii) neutral and (iii) alkali mediums. Gamma radiolysis generated brown/black precipitates of manganese oxides were analyzed by X-ray powder diffraction, Raman spectroscopy, XPS, AFM and SEM. The influence of oxygen on the nature of oxides formed was studied. Permanganic acid (HMnO4), at low concentrations (2.5mM) and irradiated to 123kGy, produced λ-MnO2 with an average crystallite size of 30nm whereas at high concentrations (8mM) and absorbed dose of 300kGy, MnOOH was formed. The XRD pattern of the oxide powder obtained in all other cases showed broad peaks indicating nano-crystalline nature. The results of nitrogen adsorption–desorption experiments showed high specific surface area of ∼53m2/g corresponding to ∼5nm average pore size for the oxide obtained from 8mM HMnO4 irradiated to 300kGy. Atomic force microscopy (AFM) indicated a minimum particle size of ∼13nm for the same oxide whereas the SEM images showed presence of nano-rods.

Synthesis and characterization of whisker-shaped MnO2 nanostructure at room temperature

Manganese dioxide nanoparticles have been synthesized, via a facile one-step solution phase approach, by the reduction of potassium permanganate with sodium thiosulphate at room temperature. Upon addition of thiosulphate to the solution of permanganate, a transparent dark-brown color species appeared which was stable for several months. The obtained MnO2 solution was characterized by means of UV–vis spectra, Transmission electron microscopy (TEM), and Fourier transforms infrared spectroscopy. Fourier transforms infrared spectroscopy spectra of pure MnO2 show the occurrence of O–Mn–O vibrational mode at around 600 and 475 cm−1. The chemical composition was obtained by EDX analysis and confirmed the presence of Mn and O in the sample. From the TEM image, the surface morphology of the sample shows uniformly dispersed particles, which are spherical in shape. The selected area electron diffraction patterns revealed that the MnO2 are crystalline in nature.

Mn2O3 decorated graphene nanosheet: An advanced material for the photocatalytic degradation of organic dyes

Abstract A one step sonochemical route has been developed to prepare graphene–Mn 2 O 3 nanocomposite with uniform distribution of Mn 2 O 3 nanoparticles throughout the surface of graphene nanosheet. Growth of such nanoparticles over this two dimensional carbon network is simply accelerated by the simultaneous reduction of potassium permanganate along with graphene oxide, in which metal ions are first anchored through binding with oxy-functional groups of graphene oxide and finally reduced by hydrazine. The final product ensure a new platform for the photodegradation of organic dyes, as it can store electrons and circulate them towards dye molecules through the formation of hydroxyl radical under the exposure of UV-light. Almost 80% photocatalytic degradation of eosin, methylene blue and rhodamine B have been observed within few minutes, which has not been obtained by using bare manganese oxide itself.

Reduction and Immobilization of Potassium Permanganate on Iron Oxide Catalyst by Fluidized-Bed Crystallization Technology

A manganese immobilization technology in a fluidized-bed reactor (FBR) was developed by using a waste iron oxide (i.e., BT-3) as catalyst which is a by-product from the fluidized-bed Fenton reaction (FBR-Fenton). It was found that BT-3 could easily reduce potassium permanganate (KMnO4) to MnO2. Furthermore, MnO2 could accumulate on the surface of BT-3 catalyst to form a new Fe-Mn oxide. Laboratory experiments were carried out to investigate the KMnO4-reduction mechanism, including the effect of KMnO4 concentration, BT-3 dosage, and operational solution pH. The results showed that the pH solution was a significant factor in the reduction of KMnO4. At the optimum level, pHf 6, KMnO4 was virtually reduced in 10 min. A pseudo-first order reaction was employed to describe the reduction rate of KMnO4.