• Title/Summary/Keyword: Electrochemical catalysis

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Electrochemical degradation of Orange G in K2SO4 and KCl medium

  • Hamous, Hanene;Khenifi, Aicha;Bouberka, Zohra;Derriche, Zoubir
    • Environmental Engineering Research
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    • v.25 no.4
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    • pp.571-578
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    • 2020
  • In this work, a detailed study on the electrochemical degradation of an azo dye, Orange G is performed using a platinum electrode. Indeed, the influence of the dye concentration (50-150 mg/L), the pH of the medium and the density of the electric current is studied on the rate of discoloration, the rate of mineralization, the efficiency of the electric current and the energy consumption. The UV-visible spectra of OG plotted against the degradation time show the decrease of the intensity of the characteristic dye peaks. In an environment rich in chlorides, all peaks disappear after 15 min of degradation. However, the peaks at wavelengths of 200 and 290 nm appeared after one hour of treatment. In K2SO4, the eliminated percentages are respectively 46, 54 and 61% for wavelengths of 245, 330 and 480 nm. This suggests that the degradation mechanisms in K2SO4 and KCl environments are not the same. In the middle rich in chlorides, the eliminated percentage of OG did not seem to be affected by the concentrations increase. These results confirm the hypothesis that electrochemical oxidation process is very favorable for concentrated pollutants discharge.

Methyl Viologen Mediated Oxygen Reduction in Ethanol Solvent: the Electrocatalytic Reactivity of the Radical Cation

  • Lin, Qianqi;Li, Qian;Batchelor-McAuley, Christopher;Compton, Richard G.
    • Journal of Electrochemical Science and Technology
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    • v.4 no.2
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    • pp.71-80
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    • 2013
  • The study of methyl viologen ($MV^{2+}$) mediated oxygen reduction in electrolytic ethanol media possesses potential application in the electrochemical synthesis of hydrogen peroxide mainly due to the advantages of the much increased solubility of molecular oxygen ($O_2$) and high degree of reversibility of $MV^{2+/{\bullet}+}$ redox couple. The diffusion coefficients of both $MV^{2+}$ and $O_2$ were investigated via electrochemical techniques. For the first time, $MV^{2+}$ mediated $O_2$ reduction in electrolytic ethanol solution has been proved to be feasible on both boron-doped diamond and micro-carbon disc electrodes. The electrocatalytic response is demonstrated to be due to the radical cation, $MV^{{\bullet}+}$. The homogeneous electron transfer step is suggested to be the rate determining step with a rate constant of $(1{\pm}0.1){\times}10^5M^{-1}s^{-1}$. With the aid of a simulation program describing the EC' mechanism, by increasing the concentration ratio of $MV^{2+}$ to $O_2$ electrochemical catalysis can be switched from a partial to a 'total catalysis' regime.

Electrochemical Technologies : Water Treatment (전기화학공학 기술 : 수처리 공정)

  • Lee, Jaeyoung;Lee, Jae Kwang;Uhm, Sunghyun;Lee, Hye Jin
    • Applied Chemistry for Engineering
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    • v.22 no.3
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    • pp.235-242
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    • 2011
  • This perspective describes recent advances made in the development of various electrochemical technologies to treat waste water containing organic pollutants, reducible/oxidizable and non-reducible/non-oxidizable anions and cations using redox reactions on the solid surface as well as at the interface between solid electrode and liquid electrolyte. Some of representative multiplexing and hybrid electrochemical treatment technologies are discussed, which have great advantages of high efficiency, stability and cost-effective instrumentation without the need of considering non-specific conditions such as high-temperature and high-pressure; however, choices and usages of electrode materials are absolutely critical issues.

Bioelectrochemical Mn(II) Leaching from Manganese Ore by Lactococcus lactis SK071115

  • Jeon, Bo-Young;Park, Doo-Hyun
    • Journal of Microbiology and Biotechnology
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    • v.21 no.2
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    • pp.154-161
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    • 2011
  • L. lactis sk071115 has been shown to grow more actively and generate lower levels of lactate in glucose-defined medium with nitrate than in medium with Mn(IV). By adding Mn(IV) to a L. lactis culture, lactate production was relatively reduced in combination with Mn(II) production, but cell mass production levels did not increase. Both cell-free extract and intact L. lactis cells reacted electrochemically with Mn(IV) but did not react with Mn(II) upon cyclic voltammetry using neutral red (NR) as an electron mediator. A modified graphite felt cathode with NR (NR-cathode) was employed to induce electrochemical reducing equivalence for bacterial metabolism. Cell-free L. lactis extract catalyzed the reduction of Mn(IV) to Mn(II) under both control and electrochemical reduction conditions; however, the levels of Mn(II) generated under electrochemical reduction conditions were approximately 4 times those generated under control conditions. The levels of Mn(II) generated by the catalysis of L. lactis immobilized in the NR-cathode (L-NR-cathode) under electrochemical reduction conditions were more than 4 times that generated under control conditions. Mn(II) production levels were increased by approximately 2.5 and 4.5 times by the addition of citrate to the reactant under control and electrochemical reduction conditions, respectively. The cumulative Mn(II) produced from manganese ore by catalysis of the L-NR-cathode for 30 days reached levels of approximately 3,800 and 16,000 mg/l under control and electrochemical reduction conditions, respectively. In conclusion, the electrochemical reduction reaction generated by the NR-cathode activated the biochemical reduction of Mn(IV) to Mn(II) by L. lactis.

Ionic Recognition with Quinone-Derivatized Calixarenes in Solution and at Self-Assembled Monlayers

  • Kim Hasuck;Kang Sun Kil;Chung Taek Dong
    • Journal of the Korean Electrochemical Society
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    • v.3 no.2
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    • pp.69-71
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    • 2000
  • Redox-active calix[4]arenes with carboxylic acid and disulfide groups were prepared and spontaneous deposition on silver and gold surfaces was observed. Owing to their unusual structure, the calix[4]arenes exhibit selective affinity fur alkaline earth metal ions in aqueous media. When annular ionophores are immobilized on the surface, voltammetric and spectroscopic studies show the entrapment of metal ions. Furthermore, it was possible to reversibly capture and remove the ions using strong chelating agents such as ethylenediaminetetraacetic acid (EDTA).

Electrocatalytic Oxidation of HCOOH on an Electrodeposited AuPt Electrode: its Possible Application in Fuel Cells

  • Uhm, Sung-Hyun;Jeon, Hong-Rae;Lee, Jae-Young
    • Journal of Electrochemical Science and Technology
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    • v.1 no.1
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    • pp.10-18
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    • 2010
  • Controlled electrodeposition of dendritic nano-structured gold-platinum (AuPt) alloy onto an electrochemically pretreated carbon paper substrate was conducted in an attempt to improve catalyst utilization and to secure an electronic percolation network toward formic acid (FA) fuel cell application. The AuPt catalysts were obtained by potentiostatic deposition. AuPt catalysts synthesized as bimetallic alloys with 60% Au content exhibited the highest catalytic activity towards formic acid electro-oxidation. The origin of this high activity and the role of Au were evaluated, in particular, by XPS analysis. Polarization and stability measurements with 1 mg $cm^{-2}$ AuPt catalyst (only 0.4 mg $cm^{-2}$ Pt) showed 52 mW $cm^{-2}$ and sustainable performance using 3M formic acid and dry air at $40^{\circ}C$.

Lessons from Korean Innovation Model for ASEAN Countries Towards a Knowledge Economy

  • Ocon, Joey D.;Phihusut, Doungkamon;del Rosario, Julie Anne D.;Tuan, Trinh Ngoc;Lee, Jaeyoung
    • STI Policy Review
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    • v.4 no.2
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    • pp.19-40
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    • 2013
  • The Association of Southeast Asian Nations (ASEAN) achieved relatively rapid economic growth over the past decade. Sustainable growth among member states, however, is put into question due to macroeconomic challenges, political risk, and vulnerability to external shocks. Developed countries, in contrast, have turned into less labor-intensive technologies to further expand their economies. In this paper, we review the science, technology, and innovation (STI) policies and statuses of the scientific and technological capabilities of the ASEAN member countries. Empirical results based on STI indicators (R&D spending, publications, patents, and knowledge economy indices) reveal considerable variation between the science and technology (S&T) competence and effectiveness of STI policies of ASEAN members. We have categorized nations into clusters according their situations in their S&T productivity. Under the Korean Innovation Model, Cambodia, Laos, Myanmar, and Brunei are classified as being in the institutional-building stage, while Malaysia, Thailand, Indonesia, the Philippines, and Vietnam in the catch up stage, and Singapore in the post-catch up stage. Finally, policy prescriptions on how to enhance the S&T capabilities of the developing ASEAN countries, based on the South Korea development experience, are presented.

Voltammetric Studies of Guanine and Its Derivatives by (TEX)$Ru(bpy)^{2+/3+}$(/TEX) Mediator on Indium Tin Oxide Electrode

  • Kim, Jin Hyeong
    • Bulletin of the Korean Chemical Society
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    • v.21 no.7
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    • pp.709-711
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    • 2000
  • Oxidizing metal complex mediates the electrochemical oxidation of guanine nucleotides. This catalysis results in an enhancement in cyclic voltammograms that yield the rate constant for the oxidation of guanine by the metal complex via digital simulation. The rate constant of oxidation of guanine by Ru(bpy)3(3+) is 6.4 x 10(5)M(-1)s(-l). The rate constant and the enhanced current depend on the number of phosphate groups on the sugar of nucleotidc. Also the modified guanine bases show different oxidation rate constants following the trend guanine-5'- monophosphatc (GMP) > 8-bromo-guanine-5'-monophosphate (8-Br-GMP) > xanthosine -5'-monophosphate (XMP) > inosinc-5'-monophosphate (IMP). The guanine bases derivatized differently are all distinguishable from one another, providing a basis for studying electrochemistry of DNA and RNA and developing electrochemical biosensors.

Electrochemical and Spectroelectrochemical Studies of Cobalt Salen and Salophen as Oxygen Reduction Catalysts

  • Bertha Ortiz;Park, Su Mun
    • Bulletin of the Korean Chemical Society
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    • v.21 no.4
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    • pp.405-411
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    • 2000
  • Electrochemical and spectroelectrochemical studies of cobalt-Schiff (Co-SB) base complexes, Co(salen) [N-N'-bis(salicylaldehyde)-ethylenediimino cobalt(II)] and Co(salophen) [N-N'-bis(salicylaldehyde)-1,2-pheny-lenediimino cobalt(II)], have been c arried out to test them as oxygen reduction catalysts. Both compounds were found to form an adduct with oxygen and exhibit catalytic activities for oxygen reduction. Comparison of spec-tra obtained from electrooxidized complexes with those from Co-SB complexes equilibrated with oxygen in-dicates that the latter are consistent with the postulated complex formed with oxygen occupying the coaxial ligand position, namely, Co(III)-SB·O2 - .The catalysis of oxygen reduction is thus achieved by reducing Co(III) in the oxygen-Co-SB adduct, releasing the oxygen reduction product, e.g., O2 - ., from the Co(II)-SB complex.