• Analytical Science and Technology
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• v.8 no.4
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• pp.569-574
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• 1995

In-situ spectroelectrochemical studies have been carried out on the oxidation of Mn(II) at platinum, gold, lead dioxide, and bismuth doped lead dioxide electrodes. The Mn(III), $MnO_2$, and/or ${MnO_4}^-$ species are produced depending on experimental conditions employed during electrolysis. Mn(III) is shown to be produced from a very early stage during the anodic potential scan and undergo disproportionation-conproportionation reactions depending on the relative concentration of each species near the electrode surface. An oxidation mechanism consistent with these observations is proposed.

• Journal of the Korean Chemical Society
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• v.36 no.3
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• pp.428-441
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• 1992

We synthesized a series of binuclear pentadentate Schiff base complexes such as $Co(Ⅱ)_2$ (BSPP)($H_2O)_2$, $Co(Ⅱ)_2$ (BSPD)($H_2O)_2$, $Mn(Ⅱ)_2$ (BSPP)($H_2O)_2$ and $Mn(Ⅱ)_2$ (BSPD)($H_2O)_2$, mononuclear pentadentate Schiff base complexes such as Co(Ⅱ)(BSP)($H_2O)$ and Mn(Ⅱ)(BSP)($H_2O)$. The composition of these complexes identified by IR, UV-visible spectrum, T.G.A., DSC, and elemental analysis. The electrochemical redox processes have been examined by cyclic voltammetry and differential pulse polarography with glassy carbon electrode in 0.1M TEAP-Py(-DMSO and -DMF) as a supporting electrolyte solution. As a result of electrochemical measurements, the reduction processes for pentadentate binuclear Schiff base cobalt(Ⅱ) and manganese(Ⅱ) complexes occurred to four steps in $M(Ⅲ)_2$ / $Mn(Ⅱ)_2$ and $Mn(Ⅱ)_2$ / $M(Ⅰ)_2$ (M; Co, Mn) two processes through each two reduction steps with one electron, by contrast, the mononuclear pentadentate Schiff base cobalt(Ⅱ) and manganese(Ⅱ) complexes occurred to two steps in M(Ⅲ) / M(Ⅱ) and M(Ⅱ) / M(Ⅰ) (M; Co, Mn) two processes with one electron reduction steps.

• Journal of the Korean Magnetic Resonance Society
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• v.14 no.2
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• pp.55-75
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• 2010

An ion-exchanged reaction of $MnCl_2$ with Al-incorporated solid core/mesoporous shell silica (AlSCMS) followed by calcinations generated manganese species, where average oxidation state of manganese ion is 3+, in the mesoporous materials. Dehydration results in the formation of $Mn^{2+}$ ion species, which can be characterized by electron spin resonance (ESR). The chemical environments of the manganese centers in Mn-AlSCMS were investigated by diffuse reflectance, UV-VIS and ESR spectroscopic methods. Upon drying at 323 K, part of manganese is oxidized to higher oxidation state ($Mn^{3+}$ and $Mn^{4+}$) and further increase in (average) oxidation state takes place upon calcinations at 823 K. It was found that the manganese species on the wall of the Mn-AlSCMS were transformed to tetrahedral $Mn^{3+}$ or $Mn^{4+}$ and further changed to square pyramid by additional coordination to water molecules upon hydration. The oxidized $Mn^{3+}$ or $Mn^{4+}$ species on the surfaces were reversibly reduced to $Mn^{2+}$ or $Mn^{3+}$ species or lower valances by thermal process. Mn(II) species I with a well resolved sextet was observed in calcined, hydrated Mn-AlSCMS, while Mn (II) species II with g = 5.1 and 3.2 observed in dehydrated Mn-AlSCMS. Both species I and II are considered to be non-framework Mn(II).

• Journal of the Korean Magnetic Resonance Society
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• v.6 no.2
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• pp.118-131
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• 2002

Manganese-doped H-SAPO-34 samples were prepared by an ion-exchanged reaction between H-SAPO-34 and paramagnetic Mn(II) species in methanol media and characterized by ESR and Electron Spin-Echo Modulation(ESEM) studies. In the hydrated (W)MnH-SAPO-34 measured in water, the Mn(II) ion was octahedrally coordinated with four framework oxygens and two water molecules at a displaced site IV of the eight membered ring window in the ellipsoidal cavity, while the Mn(II) ion was octahedrally coordinated to three framework oxygens and three water molecules at a displaced site I' of the six membered ring window in the ellipsoidal cavity in hydrated(M)MnH-SAPO-34 measured in methanol. The similar result was found in the experiments with methanol adsorbents except ethanol.

• Proceedings of the IEEK Conference
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• 2001.10a
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• pp.275-280
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• 2001

Typically, manganese (II) ions are incompletely removed from water as $MnO_2$ on increasing the pH of the water to 10. The water then has to be neutralized before it can be used. We propose a new and effective method for removing Mn (II) from water using a new combination of symbiotic microbes consisting of manganese-oxidizing bacteria and filamentous algae. The microbes rapidly oxidize Mn(II) to Mn (IV) at a neutral pH with no organic matter required as a nutrient and $MnO_2$is precipitated immediately. This differs from the use of heterotrophic manganese-oxidizing bacteria where organic nutrients are required. Our results suggest that this method will be useful in developing new systems for removal of manganese(II) ions from industrial and mining wastewater and drinking water. In addition, there are other possibilities such as recycling of dry batteries which are presently discarded without treatment

• Economic and Environmental Geology
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• v.40 no.1 s.182
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• pp.29-45
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• 2007

Biogeochemical characteristics involving redox processes in groundwater from a riverine alluvial aquifer was investigated using multi-level monitoring wells (up to 30m in depth). Anaerobic conditions were predominant and high Fe ($14{\sim}37mg/L$) and Mn ($1{\sim}4mg/L$) concentrations were observed at 10 to 20 m in depth. Below 20 m depth, dissolved sulfide was detected. Presumably, these high Fe and Mn concentrations were derived from the reduction of Fe- and Mn-oxides because dissolved oxygen and nitrate were nearly absent and Fe and Mn contents were considerable in the sediments. The depth range of high Mn concentration is wider than that of high Fe concentration. Dissolved organics may be derived from the upper layers. Sulfate reduction is more active than Fe and Mn reduction below 20 m in depth. Disparity of calculated redox potential from the various redox couples indicates that redox states are in disequilibrium condition in groundwater. Carbonate minerals such as siderite and rhodochrosite may control the dissolved concentrations of Fe(II) and Mn(II), and iron sulfide minerals control for Fe(II) where sulfide is detected because these minerals are near saturation from the calculation of solubility equilibria.

• Bulletin of the Korean Chemical Society
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• v.31 no.11
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• pp.3173-3179
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• 2010

New complex $[Mn(II)H_{1.5}L]_2[Mn(II)H_3L]_2(ClO_4)_5{\cdot}3H_2O$ (1), where $H_3L$ is tris {2-(4-imidazolyl)methyliminoethyl} amine (imtren), has been prepared by reacting manganese(II) perchlorate hexahydrate with the imtren ligand in methanol. X-ray crystallographic study revealed that the imtren ligand hexadentately binds to Mn(II) ion through the three Schiff-base imine N atoms and three imidazole N atoms with a distorted octahedral geometry, and the apical tertiary amine N atom of the ligand pseudo-coordinates to Mn(II), forming overall a pseudo-seven coordination environment. The hydrogen-bonds between imidazole and imidazolate of $[Mn(II)H_{1.5}L]^{0.5+}$ complex ions are extended to build a 2D puckered network with trigonal voids. $[Mn(II)H_3L]^{2+}$ complex ions constitutes another extended 2D puckered layer without hydrogen bonds. Two layers are wedged each other to constitute overall stack of the crystal. Peroxidase activity of complex 1 was examined by observing the oxidation of 2,2'-azinobis(3-ethylbenzothiazoline)-6-sulfonic acid (ABTS) with hydrogen peroxide in the presence of complex 1. Generation of $ABTS^{+{\cdot}}$ was observed by UV-vis and EPR spectroscopies, indicating that the complex 1, a fully-coordinated mononuclear Mn(II) complex with nitrogen-only ligand, has a heme-independent peroxidase activity.

• Bulletin of the Korean Chemical Society
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• v.33 no.7
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• pp.2299-2304
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• 2012

Two new metal(II) complexes, $[Mn(dpa)(phen)(H_2O)_2]_n$ (1) ($H_2dpa$ = dephenic acid, phen = 1,10-phenanthroline) and $[Ni_2(nda)(phen)_2(H_2O)_6](nda)(H_2O)$ (2) ($H_2nda$ = 2,6-naphthalenedicarboxylic acid) have been synthesized and characterized by elemental analysis, infrared spectroscopy, thermogravimetric analysis, and single crystal X-ray diffraction. In complex 1, Mn(II) ion is six-coordinated, and Mn(II) ions are bridged by dpa ligands into 1D chains. While, the complex 2 is dimer and two Ni(II) ions are bridged by one nda ligand cooperated with the terminal ligand phen. In each complex, the dicarboxylate ligand is coordinated to metal(II) ions as a bis-monodentate.

• Bulletin of the Korean Chemical Society
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• v.32 no.5
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• pp.1729-1732
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• 2011

• Journal of Korean Society of Water and Wastewater
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• v.32 no.2
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• pp.145-152
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• 2018

This study is focused on manganese (Mn(II)) removal by ozonation in surface water. Instant ozone demand for the water was 0.5 mg/L in the study. When 0.5 mg/L of Mn(II) is existed in water, the optimum ozone concentration was 1.25 mg/L with reaction time 10 minutes to meet the drinking water regulation. The ozone concentration to meet the drinking water regulation was much higher than the stoichiometric concentration. The reaction of soluble manganese removal was so fast that the reaction time does not affect the removal dramatically. When Mn(II) is existed with Fe, the removal of Mn(II) was not affected by Fe ion. However As(V) is existed as co-ion the removal of Mn(II) was decreased by 10%. Adding ozone to surface water has limited effect to remove dissolved organic matter. When ozone is used as oxidant to remove Mn(II) in the water, the existing co-ion should be evaluated to determine optimum concentration.