• Title/Summary/Keyword: Co(II)

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Mediated Electrochemical Oxidation of High Molecular Weight PEGs by Co(III)/Co(II) and Fe(III)/Fe(II) Redox Systems (Co(III)/Co(II) 및 Fe(III)/Fe(II) 산화환원계에 의한 고분자량 폴리에텔렌글리콜류의 매개전해산화)

  • Park, Seung-Cho;Kim, Ik-Seong
    • Applied Chemistry for Engineering
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    • v.16 no.2
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    • pp.206-211
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    • 2005
  • Mediated electrochemical oxidation (MEO) of polyethylene glycols (PEGs) of molecular weight of 1000, 4000 and 20000, was carried out on both platinum (Pt) and titanium-iridium electrodes in 8.0 M nitric acid solution containing 0.5 M Fe(II) and Co(II) ion. The electrochemical parameters such as current densities, kinds of electrode, electrolyte concentration and removal efficiency were investigated in both Fe(III)/Fe(II) and Co(III)/Co(II) redox systems. The PEGs was decomposed into carbon dioxide by MEO in Fe(III)/Fe(II) and Co(III)/Co(II) redox system during 180 min and 210 min at the current density of $0.67A/cm^2$ on the Pt electrode. Removal efficiency of PEGs by MEO was better in Co(III)/Co(II) redox system than Fe(III)/Fe(II) redox system, indicating mediated electrochemical removal efficiency was 100%.

Studies on Electroanalytical Chemistry for the Oxygen Adducted Tetradentate Schiff base Cobalt(III) Complexes in Pyridine Solution (Pyridine 용액에서 산소 첨가된 네자리 Schiff base Cobalt(III) 착물들의 전기 분석화학적 연구)

  • Rim, Chae-Pyeong;Chae, Hee-Nam;Chjo, Ki-Hyung;Choi, Yong-Kook
    • Analytical Science and Technology
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    • v.8 no.1
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    • pp.55-62
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    • 1995
  • Tetradentate Schiff base cobalt(II) complexes such as $Co(II)_2-N$, N-bis(salicylidene)-m-phenylendiimine; [$Co(II)_2(SMPD)_2(H_2O)_4$] and $Co(II)_2-N$, N-bis(salicylidene)-p-phenylendiimine: [$Co(II)_2(SPPD)_2(H_2O)_4$], and oxygen adducted cobalt (III) complexes such as [$Co(III)_2O_2(SMPD)_2(Py)_2$] and [$Co(III)_2O_2(SPPD)_2(Py)_2$] in pyridine solutions were synthesized. It was identified that the oxygen adducted cobalt(III) complexes have hexacoordinated octahedral configuration with pyridine and oxygen from the measurement of elemental analysis, AA, IR spectra, and TGA. The redox processes were investigated for the oxygen adducted complexes in 0.1M TEAP-pyridine solution, using cyclic voltammetry on the glassy carbon electrode. The redox processes of oxygen adducted Co(III) complexes result in $$[Co(III)_2-O_2-CO(III)]\rightarrow^{e^-}[Co(III)-O_2-Co(II)]\rightarrow^{e^-}[Co(II)-O_2-Co(II)]\rightleftarrows^{e^-}[Co(II)+Co(II)+O_2{\cdot}^-]\rightleftarrows^{e^-}[Co(II)+Co(I)+O_2{\cdot}^-]\rightleftarrows^{e^-}[Co(I)+Co(I)+O_2{\cdot}^-]$$.

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Electrochemical Properties of Binuclear Cobalt (II) Complexes with Tetradentate Schiff Base in Aprotic Solvents (III) (비수용매에서 이핵성 네자리 Schiff Base Cobalt(II) 착물들의 전기화학적 성질 (제 3 보))

  • Chjo Ki-Hyung;Choi Yong-Kook;Seo Seong-Seob;Lee Song-Ju
    • Journal of the Korean Chemical Society
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    • v.35 no.4
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    • pp.379-388
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    • 1991
  • We synthesized the binuclear Tetradentate Schiff base cobalt (II) complexes; [Co(II)$_2$(SMPD)$_2$(L)$_2$] and [Co(II)$_2$(SPPD)$_2$(L)$_2$] (where, SMPD: N,N'-bis(salicylaldehyde)-m-phenylenediimine, SPPD: N,N'-bis(salicylaldehyde)-p-phenylenediimine, L: Py, DMSO and DMF). We identified the binuclear structure of these complexes by elemental analysis, IR-spectrum, and T. G. A. According to the results of cyclic voltammetry and DPP measurements in aprotic solvents containing 0.1M TEAP as supporting electrolyte, it was found that diffusionally controlled redox process of two step for one electron was reversible or quasi reversible process in 0.1M TEAP-pyridine and 0.1M TEAP-DMSO solution at mononuclear complexes; [Co(II)(SOPD)(L)$_2$]. But, we knew that diffusionally controlled reduction processes of four steps with one electron for binuclear [Co(II)$_2$(SMPD)$_2$(L)$_2$] and [Co(II)$_2$(SPPD)$_2$(L)$_2$] complexes was Co(III)$_2\;{\longrightarrow^e}$ Co(III)Co(II) ${\longrightarrow^e}$ Co(II)$_2\;{\longrightarrow^e}$ Co(II)Co(I) ${\longrightarrow^e}$ Co(I)$_2$ in aprotic solvents.

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A Separation of manganese (II) and cobalt (II) ions by D2EHPA/TBP-immobilized PolyHIPE membrane

  • Chen, Jyh-Herng;Mai, Le Thi Tuyet
    • Membrane and Water Treatment
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    • v.10 no.2
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    • pp.127-137
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    • 2019
  • The D2EHPA/TBP co-extractants immobilized PolyHIPE membrane can be used for the selective separation of Mn (II) from Co (II). By solvent-nonsolvent method, D2EHPA/TBP co-extractants can be effectively immobilized into PolyHIPE membrane. The pore structure of PolyHIPE membrane and the presence of TBP enhance the stability of immobilized co-extractants. The optimal operating conditions for the separation of Mn (II) and Co (II) are feeding phase at pH 5.5, sulfuric acid concentration in the stripping phase of about 50 g/L and stirring speed at 400 rpm. The D2EHPA/TBP co-extractants ratio of 5:1 shows synergetic effect on Mn/Co separation factor about 22.74. The removal rate and recovery rate of Mn (II) is about 98.4 and 97.1%, respectively, while for Co (II) the transport efficiency is insignificant. The kinetic study of Mn (II) transport shows that high initial flux, $J_f^o=80.1({\mu}mol/m^2s)$, and maxima stripping flux, $J_s^{max}=20.8({\mu}mol/m^2s)$, can be achieved with D2EHPA/TBP co-extractants immobilized PolyHIPE membrane. The stability and reusability study shows that the membrane can maintain a long term performance with high efficiency. High purity of Co (II) and Mn (II) can be recovered from the feeding phase and stripping phase, respectively.

Studies on The Electrochemical Properties of Oxygen adducts Tetradentate Schiff Base Cobalt(II) Complexes in DMSO (I) (DMSO용액에서 네자리 Schiff Base Cobalt(II) 착물들의 산소 첨가 생성물에 대한 전기화학적 성질에 관한 연구 (제 1 보))

  • Chjo Ki-Hyung;Jin-Soon Chung;Heui-Suk Ham;Seoing-Seob Seo
    • Journal of the Korean Chemical Society
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    • v.31 no.6
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    • pp.542-554
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    • 1987
  • Tetradentate schiff base cobalt(II) complexes; Co(SED), Co(SND) and Co(SOPD) have been prepared, these complexes have react with dry oxygen in DMSO to form oxygen adducts cobalt(III) complexes; $[Co(SED)(DMSO)]_2O_2,\;[Co(SND)(DMSO)]_2O_2$ and $[Co(SOPD)(DMSO)]_2O_2$. It seems to be that the oxygen adducts cobalt(Ⅲ) complexes have heexa coordinated octahedral configration with tetradentate schiff base cobalt (III), DMSO and oxygen, and the mole ratio of oxygen to cobalt(II) complexes are 1 : 2, these complexes have been identified by IR-Spectra, T.G.A., magnetic susceptibilitis and elemental analysis of C.H.N. and Cobalt. The redox reaction process of Co(SED), Co(SND) and Co(SOPD) complexes was investigated by cyclic voltammetry with glassy carbon electrode in 0.1M TEAP-DMSO. The results of redox reaction process of Co(II) / Co(III) and Co(II) / Co(I) for cobalt(SED) and cobalt(SOPD) complexes and Co(II) / Co(III) process for cobalt(SND) complex are reversible process but Co(II) / Co(I) process of Cobalt(SND) complex is irreversible, and oxygen adduct complexes to quasi reversibly with oxygen should be very closed related to the redox potentials of range, $E_{pc}$ = -0.80~-0.89V and $E_{pa}$ = -0.70~-0.76V.

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Electrocatalytic Effect of Dioxygen Reduction at Glassy Carbon Electrode Modified with Schiff Base Co(II) Complexes (Schiff Base Co(II) 착물이 변성된 유리질 탄소전극에서 산소 환원의 전기촉매 효과)

  • Seong, Jeong-Sub;Chae, Hee-Nam;Choi, Yong-Kook
    • Analytical Science and Technology
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    • v.11 no.6
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    • pp.460-468
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    • 1998
  • Schiff base ligands such as $SOPDH_2$, $SNDH_2$, $EBNH_2$, and $PBNH_2$ and their Co(II) complexes such as [$Co(II)(SND)(H_2O)_2$], [$Co(II)(SOPD)(H_2O)_2$], [$Co(II)(EBN)(H_2O)$], and [$Co(II)(PBN)(H_2O)$] have been synthesized. The mole ratio of Shiff base ligand to cobalt(II) for the Co(II) complexes was found to be 1:1. Also these complexes have been configurated with hexa-coordination. Reduction of dioxygen was investigated by cyclic voltammetry at glassy carbon electrodes modified with Schiff base Co(II) complexes in 1 M KOH aqueous solution. At modified glassy carbon electrode with Schiff base Co(II) complexes, reduction peak current of oxygen was increased and peak potential was shifted to more positive direction compared to bare glassy carbon electrode. The electrokinetic parameters such as number of electron and exchange rate constant were calculated from the results of cyclic voltammogrms. The reduction of dioxygen at glassy carbon electrode has been $2e^-$ reaction pathway. Exchange rate constant at glassy carbon electrode modified with Co(II) complexes was increased 2~10 times compared to bare electrode.

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Electrochemical Properties of Binuclear Tetradentate Schiff Base Cobalt(II), Nickel(II) and Copper(II) Complexes in Nonaqueous Solvents. (V) (비수용매에서 이핵성 네자리 Schiff Base Cobalt(II), Nickel(II) 및 Copper(II) 착물들의 전기화학적 성질 (제 5 보))

  • Chjo Ki-Hyung;Choi Yong-Kook;Lee Song-Ju;Kim Chan-Young;Rim Chae-Pyeong
    • Journal of the Korean Chemical Society
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    • v.36 no.5
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    • pp.709-719
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    • 1992
  • We synthesized the binuclear tetradentate Schiff base cobalt(II), nickel(II) and copper(II) complexes such as [Co(II)_2(TSBP)(L)_4], [Ni(II)_2(TSBP)(II)_4] and [Cu(II)_2(TSBP)] (TSBP: 3,3',4,4'-tetra(salicylideneimino)-1,1'-biphenyl, L: Py, DMSO and DMF). We identified the binucleated structure of these complexes by elemental analysis, IR-spectrum, UV-visible spectrum, T.G.A. and D.S.C. According to the results for cyclic voltammogram and differential pulse polarogram of 1 mM complexes in nonaqueous solvents included 0.1M TEAP-L (L; Py, DMSO and DMF) as supporting electrolyte, it was found that diffusionally controlled redox processes of four steps through with one electron for binucleated Schiff base Cobalt(II) complex was Co(III)_2 {^\longrightarrow \\_\longleftarrow^e^-}Co(III)Co(II)_2{^\longrightarrow \\_\longleftarrow^e^-}Co(II){^\longrightarrow \\_\longleftarrow^e^-}Co(I){^\longrightarrow \\_\longleftarrow^e^-}Co(I)_2 and two steps with one electron for Nickel(II) and Copper(II) complexes were M(II)_2 {^\longrightarrow \\_\longleftarrow^e^-}M(I)M(I){^\longrightarrow \\_\longleftarrow^e^-}M(I)_2 (M; Ni and Cu) in nonaqueous solvents.

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Electrochemical Properties of Cobalt(II) Schiff Base Complexes in Nonaqueous Solvent (비수용매에서 Schiff Base를 가진 Cobalt(II) 착물들의 전기화학적 성질)

  • Oh, Jeong-Geun;Choi, Yong-Kook
    • Analytical Science and Technology
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    • v.15 no.2
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    • pp.97-101
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    • 2002
  • Co(II) complexes with tridentate Schiff base-NOIPH and tetradentate Schiff base-$NOTDH_2$ and $TNBPH_4$ were synthesized. The redox process of the complexes in DMF solution containing 0.1M TBAP was investigated at glassy carbon electrode by cyclic voltammetry and differential pulse voltammetry techniques. Reduction step of [Co(II)$(NOIP)_2$] and [Co(II)$(H_2O)_2$] complexes were observed in two step as one electron process of irreversible or quasi-reversible and diffusion-controlled reaction. [$Co(II)_2$(TNBP)] complex was observed in one step as one electron process of quasi-reversible and diffusion-controlled reaction.

Electrochemical Properties of Oxygen Adducts Pentadentate Schiff Base Cobalt (Ⅱ) Complexes in Aprotic Solvents (비수용매에서 다섯 자리 Schiff Base Cobalt (Ⅱ) 착물들의 산소 첨가 생성물에 대한 전기화학적 성질)

  • Choe, Ju Hyeong;Jeong, Jin Sun;Choe, Yong Guk;Seo, Seong Seop
    • Journal of the Korean Chemical Society
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    • v.34 no.1
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    • pp.51-62
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    • 1990
  • Pentadentate Schiff base cobalt(II) complexes; Co(II)(Sal-DET) and Co(II)(Sal-DPT) were synthesized and these complexes were allowed to react with dry to form oxygen adducts of cobalt(II) complexes such as [Co(III)(Sal-DET)]$_2O_2$ and [Co(III)(DPT)]$_2O_2$ in aprotic solvents. These complexes have been identified by IR spectra, TGA, DSC, magnetic susceptibility measurements, and elemental analysis. It has been found that the oxygen adadduct complexes of $\mu$-peroxo type have hexaccordinated octahedral configuration with pentadentate schiff base cobalt(II) and oxygen, but the mole ratio of oxygen to cobalt(III) complexes of first step for oxygen adduct formation reaction of cobalt(II) complexes in aprotic solvents are 1:1. The redox reaction processes of Co(II)(Sal-DET), Co(II)(Sal-DPT), and oxygen adduct of cobalt(II) complexes were investigated by cyclic voltammetry and DPP method with glassy carbon electrode in 0.1M TEAP-DMSO and 0.1M TEAP-pyridine. As a result the reduction reaction processes of Co(III)/Co(II) and Co(II)/Co(I) for cobalt(II) complexes and oxygen adducts of cobalt(II) complexes are two irreversible steps of one eletron process, and reaction processes of oxygen for oxygen adducts complexes were quasireversible and redox range of potential was $E_{pc}$ = -0.97V∼-0.86V and $E_{pa}$ = -0.87V ∼ 0.64V.

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Continuous Mediated Electrochemical Oxidation of Ethylene Glycol by Co(III)/Co(II) and Fe(III)/Fe(II) Redox Systems (Co(III)/Co(II) 및 Fe(III)/Fe(II) 산화환원계에 의한 에텔렌글리콜의 연속 매개전해 산화)

  • Kim, Ik-Seong;Park, Seung-Cho
    • Applied Chemistry for Engineering
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    • v.16 no.5
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    • pp.635-640
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    • 2005
  • Mediated electrochemical oxidation (MEO) is an aqueous process which oxidizes organics electrochemicallly at low temperatures and pressures. The useful process can be used to treat mixed wastes containing hazardous organics. This paper have studied MEO of ethylene glycol (EG) in nitric acids by Fe(III)/Fe(II) and Co(III)/Co(II) system. It investigated current density, supporting electrolyte concentration, hydraulic retention time, removal efficiency of EG by MEO. Removal efficiency of EG by MEO was superior in Co(III)/Co(II) redox system than Fe(III)/Fe(II) redox system, where MEO removal efficiency was 100 percent. In case of EG, the reactions were fast and good yields of carbon dioxide formation was observed.