Reduction Of Permanganate Research Articles

STUDY ON THE PREPARATION OF MANGANESE DIOXIDE VIA CATHODIC ELECTROLYSIS

A novel synthesis method was developed to prepare manganese dioxide via cathodic electrolysis in potassium permanganate solution. The morphology and the composition of the synthesized products were analyzed by scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction spectroscopy (XRD). The electrolyzed products include two kinds of materials: amorphous and crystalline manganese dioxide. The manganese dioxides were formed by cathodic reduction via two reaction mechanisms: direct and indirect electrochemical reactions. The electrolysis current performance strongly depends on the electrolyte solution temperature, applied voltage and not clearly depends on electrolyte solution concentration. With high current performance and uniformity products, the cathodic reduction of potassium permanganate is promising method for manganese dioxide fabrication.

Multicommuted Flow Injection Analysis Using Chemiluminescence Detection (MCFIA-CL) for Olive Oil Analysis

This article describes the applicability of multicommuted chemiluminescence flow injection analysis (MCFIA-CL) to the determination of olive oil quality parameters. Two automated MCFIA methods were developed and validated for the determination of peroxide value (PV) and phenolic compounds in commercial extra virgin olive oil samples. The PV method proposed is based on the chemiluminescent (CL) signal produced from luminol oxidation by the olive oil hydroperoxides in basic conditions using Co(II) as catalyst, while the determination of phenolic compounds is based on CL emission generated from permanganate reduction in acidic media by hydroalcoholic extracts of olive oil. The flow assemblies for automated liquid handling consisted, respectively, of 2 and 3 three-way solenoid valves, which were controlled by a homemade electronic interface and Java-written software together with a CL detector. The signals obtained correlated well against the PV and total phenolic contents measured by the official and the Folin-Ciocalteu methods, respectively. The linear response range observed for PV allows checking whether the samples are in compliance with European Union regulations. On the other hand, the phenolic compounds content also correlated well with data reported by the well-known FC method across the entire typical concentration range of these compounds in virgin olive oils. The proposed methods are faster, safer, and more environmentally friendly than the respective official or classical ones involving lower consumption of solvents, reagents, and sample, as well as less waste generation together with a high sample throughput. Moreover, they are straightforward and cost-effective to implement in routine analysis, and can be regarded as a feasible alternative to the official or classic methods.

Nafion particles doped with methyl viologen: electrochemistry.

Nafion sub-micro particles doped with methyl viologen (MV2+) are synthesized using the re-precipitation method and characterized by scanning electron microscopy and UV-Vis spectroscopy. The electrochemical behavior of MV2+ incorporated into Nafion particles was investigated at both the ensemble and single particle levels. The charge transferred to single MV-Nafion particles was observed using the nano-impact method and shown to be quantitative. Finally, the charge transferred via individual MV-Nafion particle was substantially enhanced in the presence of permanganate. The mechanism of the catalytic nano-impact reaction of mediated permanganate reduction by single MV-Nafion particle is revealed as proceeding via MV+˙ reduced from MV2+ incorporated in Nafion particles through one electron transfer followed by the reduction of permanganate.

Hierarchical manganese dioxide nanoflowers enable accurate ratiometric fluorescence enzyme-linked immunosorbent assay.

We first developed a green, mild and rapid method for the preparation of hierarchical manganese dioxide nanoflowers (MnO2 NFs) as nanozymes with intrinsic oxidase-like activity using citric acid for the reduction of potassium permanganate. The open structure of MnO2 NFs can lead to a larger specific surface area for improving the antibody loading amount and oxidase mimicking activity. In addition, carboxyl groups from the residual citric acid on the surface of MnO2 NFs afford a good affinity with the antibody through an amidation coupling reaction, which does not need complex surface modification anymore. Then, a reliable ratiometric fluorescence nanozyme-linked immunosorbent assay towards C-reactive protein (CRP) was designed successfully based on the MnO2 NFs. The high sensitivity and clinical feasibility of the presented methodology were demonstrated, which hold great promise in biomedical fields. Moreover, the mild and simple process for the synthesis of MnO2 NFs will make good contributions to many other applications.

Improved electrochemical properties of highly porous amorphous manganese oxide nanoparticles with crystalline edges for superior supercapacitors

An electrochemical electrode, based on dual-morphology manganese-oxide nanoparticles, is fabricated via acidic reduction of potassium permanganate, which consists of amorphous, porous surface, terminated by crystalline edges. The higher surface-to-volume ratio into the pores promotes the surface redox reaction via higher utilization of active materials, whereas the crystalline edges enhance bulk insertion/de-insertion of cations/protons to promote bulk redox reactions. This combinatorial effect increases the charge storage performance of the manganese-oxide-based supercapacitor electrode considerably, with a specific capacitance ∼1000 F g−1. Additionally, removal of K+-ions within manganese-oxide matrix, via repeated rinsing steps during synthesis, enhances the charge transport properties for improved supercapacitive activity.

Colorimetric detection of pyrethroid metabolite by using surface molecularly imprinted polymer

A simple colorimetric method was developed for the detection of 3-Phenoxybenzaldehyde (3-PBD), the metabolite of pyrethroid pesticides, based on surface molecularly imprinted polymer (MIP). In this method, MIP layer was coated on the surface of monodispersed silica nanoparticles via sol-gel process with 3-Aminopropyltriethoxysilane (APTES) and phenyltrimethoxysilane (PTES) as monomers. Compare with single functional monomer, APTES and PTES can interact with 3-PBD mainly by hydrogen bonding and π-π staking interaction, which makes the synthetic MIPs show better affinity and absorption capacity towards target than that of signal functional monomer. After eluted from MIP nanoparticles, the 3- PBD resulted in a distinctive color fading by potassium permanganate reduction. Taking advantage of this phenomenon, the 3- PBD could be detected by recording the absorption of potassium permanganate solution with MIPs as the recognition element. The MIPs, synthesized under various conditions, were characterized by fourier transform infrared spectrometry and scanning electro microscopy. Meanwhile, their absorption performance were also investigated. Under the optimum condition, the proposed method exhibited a linear concentration range of 3-PBD from 0.1μgmL−1 to 1μgmL−1 with a lower detection limit of 0.052μgmL−1 (S/N=3). Moreover, this method was further used to detect 3-PBD in real samples form river water, fruit juice, and beverage. Satisfactory recovery was achieved in the range of 90.0∼98.9%, which clearly demonstrating the potential value of this strategy in the detection of total pyrethroid pesticides.

Physicochemical properties of manganese oxides obtained via the sol–gel method: The reduction of potassium permanganate by polyvinyl alcohol

Experimental data on the sol–gel synthesis of manganese oxides formed during the reduction of potassium permanganate by polyvinyl alcohol in an aqueous medium are presented. The physicochemical properties of the obtained manganese oxide systems that depend on the conditions of the synthesis are studied by means of DTA, XRD, SEM, and the low temperature adsorption–desorption of nitrogen. It is found that the obtained samples have a mesoporous structure and predominantly consist of double potassium–manganese oxide K2Mn4O8 with a tunnel structure and impurities of oxides such as α-MnO2, MnO, α-Mn2O3, and Mn5O8. It is shown that the proposed method of synthesis allows us to regulate the size and volume of mesopores and, to a lesser extent, the texture of the obtained oxides, which can be considered promising sorbents for the selective extraction of strontium and cesium ions from multicomponent aqueous solutions.

A simple method to produce birnessite‐coated quartz sand

AbstractBirnessite is a highly reactive manganese oxide and common in soil. We checked the attachment of birnessite, synthesized by the reduction of permanganate by lactate, on sand‐sized quartz to produce birnessite‐coated sand (BCS). Attachment and aggregation of birnessite increased with pH and reaction time. The extent of Cu and Zn adsorption to BCS was similar to that of birnessites in previous studies. Based on these results and the stability of this BCS, it may be used in water treatment.

Advanced supercapacitor prototype using nanostructured double-sided MnO2/CNT electrodes on flexible graphite foil

Development of advanced supercapacitors which provide greater energy density while retaining high power density can revolutionize energy storage solutions for both civilian and military applications. Herein, we present fabrication and characterization of nanostructured supercapacitor electrodes using manganese dioxide and carbon nanotubes (MnO2/CNTs) on flexible graphite foil substrate for integration into a supercapacitor prototype cell, without any additives or binders. Low-cost, thermal chemical vapor deposition process in a tube furnace was used to synthesize CNTs, acting as the current conductors, directly on both sides of the flexible, conducting graphite foil current collector. Thin-film MnO2 deposition on the CNTs was achieved by electrochemical technique using in situ reduction of potassium permanganate (KMnO4), without any supporting electrolyte, which provides excellent bonding between the two for enhanced stability. Eight electrodes were assembled in a stack with polypropylene separators and packaged in a pouch cell with organic electrolyte (1 M tetraethylammonium tetrafluoroborate in acetonitrile) yielding a total capacitance of nearly 2.8 F at 2.5 V and a corresponding specific capacitance of 388 F g−1 was calculated for MnO2. High cell capacitance and a low DC resistance yield a maximum specific power value of 36.1 kW kg−1 and a maximum specific energy of 48.5 Wh kg−1 at 2.5 V when considering the total mass including that of CNTs and MnO2. Cycling data showed nearly 100% capacitance retention over 3000 charge discharge cycles. To the best of our knowledge, a supercapacitor prototype cell in this configuration has not been fabricated and/or reported previously. Schematic representation of the prototype supercapacitor cell consisting of a stack of eight electrodes with polypropylene separators. On the right is a blow-up representation of a double side electrode with MnO2/CNT on both sides of the graphite foil substrate. The equivalent circuit diagram can be seen on the left, consisting of seven capacitors in parallel

Nanoscaled Platforms Based on SiO2 and Al2O3 Impregnated with Potassium Permanganate Use Color Changes to Indicate Ethylene Removal

The development of novel tools/devices to monitor and oxidize ethylene (C2H4), a volatile compound responsible for the ripening and senescence in plants, can be a potential approach to maintain and provide information on the postharvest quality of fruits and vegetables. Here, we propose nanoscaled platforms based on silica (SiO2) and alumina (Al2O3) nanoparticles impregnated with potassium permanganate (KMnO4) that use color changes to indicate ethylene removal. SiO2 and Al2O3 in the microscale and nanoscale were impregnated with varied concentrations of KMnO4 through a simple mixture route, which systems were capable of oxidizing the ethylene in a closed atmosphere under relative humidity of 45, 60, 75, and 90%. Ethylene removal and color changes were monitored using gas chromatography and colorimetry, respectively. The nanoscaled platforms impregnated with KMnO4 were capable of scavenging ethylene more efficiently for 1-h exposure. Additionally, the color changes experienced by the nanoscaled platforms, arising from the chemical reduction of potassium permanganate, function as an indicator of ethylene removal, which is particularly suitable for postharvest application.

Sorption of strontium ions onto mesoporous manganese oxide of OMS-2 type

Sorption of stable and radioactive strontium ions onto mesoporous manganese oxide of OMS-2 type, prepared by the sol–gel method via reduction of potassium permanganate with polyvinyl alcohol in aqueous medium, was studied. The influence exerted by the pore structure parameters and by the phase and chemical composition of manganese oxide on its sorption properties and selectivity to Sr ions was examined. Manganese oxide samples prepared using a 0.1 wt % KMnO4 solution exhibit the highest values of the sorption capacity for Sr, about 100–150 mg g–1, and of the Sr distribution coefficient, K d = (11.5–19.5) × 103 cm3 g–1. Introduction of 0.1 M NaCl into this solution considerably decreases the sorption of stable Sr ions, and for all the samples the sorption capacity is 25–35 mg g–1. On the other hand, for the most active sorbents the distribution coefficient in the presence of 0.1 M NaCl increases by a factor of approximately 8–10 relative to distilled water and reaches (91–208) × 103 cm3 g–1. Introduction of 0.05 M CaCl2 also decreases the Sr uptake, and the sorption capacity of the most active sorbents for stable Sr ions is 25–35 mg g–1 at K d (85Sr) equal to (0.14–0.35) × 103 cm3 g–1.

Adsorption Properties of Nano-MnO2–Biochar Composites for Copper in Aqueous Solution

There is a continuing need to develop effective materials for the environmental remediation of copper-contaminated sites. Nano-MnO2–biochar composites (NMBCs) were successfully synthesized through the reduction of potassium permanganate by ethanol in a biochar suspension. The physicochemical properties and morphology of NMBCs were examined, and the Cu(II) adsorption properties of this material were determined using various adsorption isotherms and kinetic models. The adsorption capacity of NMBCs for Cu(II), which was enhanced by increasing the pH from 3 to 6, was much larger than that of biochar or nano-MnO2. The maximum adsorption capacity of NMBCs for Cu(II) was 142.02 mg/g, which was considerably greater than the maximum adsorption capacities of biochar (26.88 mg/g) and nano-MnO2 (93.91 mg/g). The sorption process for Cu(II) on NMBCs fitted very well to a pseudo-second-order model (R2 > 0.99). Moreover, this process was endothermic, spontaneous, and hardly influenced by ionic strength. The mechanism of Cu(II) adsorption on NMBCs mainly involves the formation of complexes between Cu(II) and O-containing groups (e.g., COO–Cu and Mn–O–Cu). Thus, NMBCs may serve as effective adsorbents for various environmental applications, such as wastewater treatment or the remediation of copper-contaminated soils.

Birnessite-Type Manganese Oxide on Granular Activated Carbon for Formaldehyde Removal at Room Temperature

Formaldehyde (HCHO) is a priority indoor air pollutant due to its adverse impact to human health. A layer of birnessite-type manganese oxide (MnOx) was facilely coated on the granular activated carbon (AC) via in situ reduction of permanganate with AC at room temperature. The properties and growing process of MnOx were characterized by scanning electron microscopy, energy-dispersive spectrometry, high-resolution transmission electron microscopy, X-ray diffraction, and Raman. As-prepared MnOx/AC exhibited high activity in removing HCHO at room temperature. Gas chromatography analysis indicates that removed HCHO can be finally transformed into CO2 for a much longer time. Accumulation of carbonate on the surface of MnOx and partial hydroxylation of MnOx lead to the deactivation of MnOx/AC. However, the deactivated sample can be regenerated at 60 °C for 2 h. These results indicate that as-prepared MnOx/AC can be applied for indoor air purification due to its easy preparation and regeneration and high activity...

Natural hydroxyapatite‐supported MnO2: a green heterogeneous catalyst for selective aerobic oxidation of alkylarenes and alcohols

Natural hydroxyapatite‐supported MnO2 (MnO2@NHAp) was easily prepared in situ from reduction of potassium permanganate with natural hydroxyapatite derived from cow bones in water at room temperature, and its structure was characterized using flame atomic absorption spectroscopy, X‐ray diffraction, thermogravimetric analysis, scanning electron microscopy and energy dispersive spectroscopy. The catalytic activity of the synthesized catalyst was investigated for the aerobic oxidation of alkylarenes and alcohols. MnO2@NHAp shows excellent catalytic performance for the oxidation of alkylarenes and alcohols to their corresponding carbonyl compounds without using any other oxidizing agent. This catalyst can be readily recycled and reused for several runs without any significant loss of efficiency. Copyright © 2016 John Wiley & Sons, Ltd.

Hydrothermal express synthesis of CNT/MnO2 composite for asymmetric supercapacitor

A hydrothermal technique for the express synthesis of a composite based on carbon nanotubes (CNTs) and manganese dioxide by means of the direct reduction of potassium permanganate from an aqueous isopropanol solution is proposed in this work. The synthesis conditions (time, temperature, ratios between reagents) are optimized; the primary and secondary processes taking place in the system are considered in detail. The synthesized CNT/MnO2 composite is studied with the help of a wide range of physicochemical and electrochemical methods to assess the possibility of its use as a positively charged electrode of an asymmetric supercapacitor (SC). The assembled SC cell based on this composite and an activated carbon (AC) electrode has fairly high power typical of conventional electric double-layer capacitors (0.82 kW/kg) with a twofold increase in the energy density (12.14 W h/kg).

Kinetic and Mechanistic Aspects of the Reactions of Iodide and Hypoiodous Acid with Permanganate: Oxidation and Disproportionation.

Oxidation kinetics of iodide and HOI/OI(-) by permanganate were studied in the pH range of 5.0-10.0. Iodide oxidation and iodate formation were faster at lower pH. The apparent second-order rate constants (k(obs)) for iodide oxidation by permanganate decrease with increasing pH from 29 M(-1) s(-1) at pH 5.0 and 6.9 M(-1) s(-1) at pH 7.0 to 2.7 M(-1) s(-1) at pH 10.0. k(obs) for HOI abatement are 56 M(-1) s(-1) at pH 5.0, 2.5 M(-1) s(-1) at pH 7.0, and 173 M(-1) s(-1) at pH 10.0. Iodate yields over HOI abatement decrease from 98% at pH 6.0 to 33% for pH ≥ 9.5, demonstrating that HOI disproportionation dominates HOI transformation by permanganate at pH ≥ 8.0. MnO2 formed as a product from permanganate reduction, oxidizes HOI to iodate for pH < 8.0, and promotes HOI disproportionation for pH ≥ 8.0. The rate of HOI oxidation or disproportionation induced by MnO2 is much lower than for permanganate. During treatment of iodide-containing waters, the potential for iodinated disinfection byproducts (I-DBPs) formation is highest at pH 7.0-8.0 due to the long lifetime of HOI. For pH < 6.0, HOI/I2 is quickly oxidized by permanganate to iodate, whereas for pH ≥ 8.0, HOI/OI(-) undergoes a fast permanganate-mediated disproportionation.

Mechanism of sonochemical reduction of permanganate to manganese dioxide in aqueous alcohol solutions: Reactivities of reducing species formed by alcohol sonolysis

The sonochemical reduction of MnO4− to MnO2 in aqueous solutions was investigated as a function of alcohol concentration under Ar. The rate of MnO4− reduction initially decreased with increasing alcohol concentration, and then increased when the alcohol concentration was increased further. The concentrations at which the reduction rates were minimum depended on the hydrophobic properties of the added alcohols under ultrasonic irradiation. At low concentrations, the alcohols acted as OH radical scavengers; at high concentrations, they acted as reductant precursors: Rab, formed by abstraction reactions of the alcohols with sonochemically formed OH radicals or H atoms, and Rpy, formed by alcohol pyrolysis under ultrasonic irradiation. The results suggest that the reactivity order of the sonochemically formed reducing species with MnO4− at pH 7–9 is the sum of H2O2 and H>Rpy>Rab. The peak wavelengths of MnO2 colloidal solutions formed at high 1-butanol concentrations shifted to shorter wavelengths, suggesting the formation of small particles at high 1-butanol concentrations. The rates of sonochemical reduction of MnO2 to Mn2+ in the presence of 1-butanol were slower than that in the absence of 1-butanol, because the sonochemical formation of H2O2 and H, which act as reductants, was suppressed by 1-butanol in aqueous solutions.

Biological synthesis of manganese dioxide nanoparticles by Kalopanax pictus plant extract.

Manganese dioxide (MnO₂) nanoparticles were synthesised by the reduction of potassium permanganate (KMnO₄) using Kalopanax pictus leaf extract at room temperature. A transparent dark-brown colour appeared after the addition of K. pictus leaf extract to the solution of permanganate. The time course of the reduction of KMnO₄and synthesis of MnO₂ nanoparticles was monitored by means of UV-Vis spectra. The reduction of KMnO₄occurred after addition of plant extract with disappearance of KMnO₄specific peaks and emergence of peak specific for MnO₂nanoparticles. MnO₂nanoparticles showed absorption maxima at 404 nm. The electron dispersive X-ray spectroscopy analyses confirmed the presence of Mn and O in the sample. X-ray photoelectron spectroscopy revealed characteristic binding energies for MnO₂nanoparticles. Transmission electron microscopy micrographs revealed presence of uniformly dispersed spherical shaped particles with average size of 19.2 nm. The selected area electron diffraction patterns revealed the crystalline nature of MnO₂nanoparticles. Fourier transform-infrared spectroscopy spectra of pure MnO₂show the occurrence of O-Mn-O vibrational mode at around 518 cm⁻¹. The phyto-synthesised MnO₂nanoparticles showed degradation ability of dyes (congo red and safranin O) similar to chemically synthesised MnO₂nanoparticles. This study shows simple and eco-friendly synthesis of MnO₂nanoparticles by plant extract and their utilisation for dye degradation for the first time.

The Use of C-MnO2 as Hybrid Precursor Support for a Pt/C-MnxO1+x Catalyst with Enhanced Activity for the Methanol Oxidation Reaction (MOR)

Platinum (Pt) nanoparticles are deposited on a hybrid support (C-MnO2) according to a polyol method. The home-made catalyst, resulted as Pt/C-MnxO1+x, is compared with two different commercial platinum based materials (Pt/C and PtRu/C). The synthesized catalyst is characterized by means of FESEM, XRD, ICP-MS, XPS and μRS analyses. MnO2 is synthesized and deposited over a commercial grade of carbon (Vulcan XC72) by facile reduction of potassium permanganate in acidic solution. Pt nanoparticles are synthesized on the hybrid support by a polyol thermal assisted method (microwave irradiation), followed by an annealing at 600 °C. The obtained catalyst displays a support constituted by a mixture of manganese oxides (Mn2O3 and Mn3O4) with a Pt loading of 19 wt. %. The electro-catalytic activity towards MOR is assessed by RDE in acid conditions (0.5 M H2SO4), evaluating the ability to oxidize methanol in 1 M concentration. The synthesized Pt/C-MnxO1+x catalyst shows good activity as well as good stability compared to the commercial Pt/C based catalyst.

Direct chemiluminescence of fluorescent gold nanoclusters with classic oxidants for hydrogen peroxide sensing

Direct chemiluminescence (CL) of fluorescent gold nanoclusters was observed for the first time upon oxidation with classic oxidants. The CL mechanism was investigated by the studies of CL spectrum, UV–vis absorption spectra and X-ray photoelectron spectra before and after the reaction. The excited state Mn(II)∗, originating from the reduction of permanganate with gold nanoclusters, was suggested as the possible luminophor for the reaction. The potential analytical application was demonstrated by using hydrogen peroxide as an example, based upon the fact that hydrogen peroxide decreased the CL signal significantly. The decreased CL intensity was proportional to the concentration of hydrogen peroxide in the range 1.0×10−6–1.0×10−4molL−1. The detection limit was 5×10−7molL−1 and the relative standard deviation was 1.4% for 1.0×10−5molL−1 hydrogen peroxide in 11 replicated measurements. This method was applied to the determination of hydrogen peroxide in water samples with satisfactory results.