CARBON | Academic Articles

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Posts Tagged ‘CARBON’

Effect of effluent organic matter on the adsorption of perfluorinated compounds onto activated carbon

Abstract: Effect of effluent organic matter (EfOM) on the adsorption of perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) onto powdered activated carbon (PAC) was quantitatively investigated at environmentally relevant concentration levels. The adsorption of both perfluorinated compounds (PFCs) onto PAC followed pseudo-second order kinetics and fitted the Freundlich model well under the given conditions. Intraparticle diffusion was found to be the rate-controlling step in the PFC adsorption process onto PAC in the absence and presence of EfOM. The presence of EfOM, either in PFC–EfOM simultaneous adsorption onto fresh PAC or in PFC adsorption onto EfOM-preloaded PAC, significantly reduced the adsorption capacities and sorption rates of PFCs. The pH of zero point of charge was found to be 7.5 for fresh PAC and 4.2 for EfOM-preloaded PAC, suggesting that the adsorbed EfOM imparted a negative charge on PAC surface. The effect of molecular weight distribution of EfOM on the adsorption of PFCs was investigated with two EfOM fractions obtained by ultrafiltration. The low-molecular-weight compounds (<1kDa) were found to be the major contributors to the significant reduction in PFC adsorption capacity, while large-molecular-weight compounds (>30kDa) had much less effect on PFC adsorption capacity. [Copyright &y& Elsevier]

July 19, 2012 Tags: Activated, ADSORPTION, CARBON, CHEMICAL kinetics, FLUORINATION, MOLECULAR weights, ORGANIC compounds, PERFLUOROOCTANE sulfonate, POWDERS
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Voltammetric study and electrodeposition of copper in 1-butyl-3-methylimidazolium salicylate ionic liquid

Abstract: The voltammetric behavior of cuprous ions has been studied at disk electrodes of glassy carbon and polycrystalline platinum in a new hydrophilic 1-butyl-3-methylimidazolium salicylate ionic liquid (BMI-SAL IL). Cuprous ions Cu(I) were introduced into the IL by the anodic dissolution of a Cu wire electrode or by the addition of CuCl. This air- and water-stable hydrophilic IL is very similar to dicyanamide (DCA)-based ILs because both DCA anions and salicylate (SAL) anions have very strong ligand properties; therefore, many metal salts, such as metal halides, are very soluble in this IL. However, the source of SAL anions, sodium salicylate, is considerably cheaper than sodium dicyanamide salt. The potentiostatic electrodeposition of copper onto iron substrates has also been investigated in this study. The surface morphologies of the copper deposits were significantly altered by the electrodeposition potential; granular, mirror-like, and porous copper deposits could be obtained at different negative potentials. The activity of the copper deposit-modified iron electrodes toward the electrochemical nitrate reduction in alkaline solutions was found to significantly depend on the surface morphologies. The granular and the porous surfaces showed better activities. The mirror-like surface, however, had no activity on the electrochemical nitrate reduction. [Copyright &y& Elsevier]

July 7, 2012 Tags: CARBON, COPPER, ELECTRODES, ELECTROFORMING, IONIC liquids, METHYL groups, SALICYLATES, VOLTAMMETRY
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Theoretical and experimental study of anode process at the carbon in kf–alf3–al2o3 melts

Abstract: The influence of the [KF]/[AlF3] ratio (1.1–1.5molmol−1), the Al2O3 concentration (1–5wt.%) and the temperature (973–1073K) on the overpotential of the anode process for a glassy carbon electrode in a KF–AlF3–Al2O3 melt under stationary and non-stationary conditions was studied by galvanostatic polarisation and chronopotentiometry. A theoretical (mathematical) description of the two-step electrode process at the carbon anode in KF–AlF3–Al2O3 melts under stationary and non-stationary conditions is suggested. The charge of the electric double-layer, the formation of an intermediate COads adsorption product at the anode surface, the limitations of the current transfer, which include the charge transfer through the electrode/electrolyte interface, and the diffusion and chemical interaction of the electroactive ions in the melt near the anode surface were taken onto account. Alterations of the basic parameters of the process were monitored and analysed. Estimates of anode process kinetics parameters (e.g., exchange current densities and the degree of the anode surface coverage by the intermediate product COads) for different experimental conditions were made by a comparison of the modelled and experimental polarisation curves. The electrochemical desorption of the intermediate product COads from the anode surface (the second step) was shown to be relatively slower than the charge transfer process (the first step). In addition, slow chemical reactions at current densities of 0.1–1Acm−2 can occur prior to the electrode process. [Copyright &y& Elsevier]

July 7, 2012 Tags: ADSORPTION, ANODES, CARBON, CHEMISTRY, ELECTRODES, Physical & theoretical, SURFACE chemistry, TEMPERATURE effect
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Increasing the electrochemically available active sites for heat-treated hemin catalysts supported on carbon black

Abstract: A nano-sized non-noble metal catalyst containing hemin supported on carbon black was synthesized for the oxygen reduction reaction (ORR). The hemin supported on carbon black was heat-treated (HT), and subjected to additional ultrasound treatments to increase the BET surface area and available active sites for the ORR. The HT hemin supported on carbon black was characterized with thermogravimetric analysis (TGA), elemental analysis, transmission electron microscopy (TEM), and BET surface area analysis. The catalytic activity of the synthesized electrocatalysts was analyzed with cyclic voltammetry (CV), rotating disk electrode (RDE), and rotating ring disk electrode (RRDE). The effect of BET surface area on formal potential, anodic and cathodic peak currents, limiting currents, half wave potentials, and kinetic rate constant for ORR were studied. We found an apparent correlation between catalytic activity and BET surface area for this particular catalyst. Increasing BET surface area, the ORR catalytic activity increases significantly. Our research on HT hemin indicates that the catalytic activity for ORR significantly improves by reducing the particle size and increasing the surface area. [Copyright &y& Elsevier]

June 22, 2012 Tags: CARBON, CATALYST supports, CATALYSTS -- Synthesis, ELECTROCHEMICAL analysis, HEMIN, METAL catalysts, OXIDATION-reduction reaction
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Functionalization of glassy carbon surface by means of aliphatic and aromatic amino acids. an experimental and theoretical integrated approach

Abstract: Glassy carbon (GC) electrode surfaces are functionalized through electrochemical assisted grafting, in oxidation regime, of six amino acids (AA): β-alanine (β-Ala), l-aspartic acid (Asp), 11-aminoundecanoic acid (UA), 4-aminobenzoic acid (PABA), 4-(4-amino-phenyl)-butyric acid (PFB), 3-(4-amino-phenyl)-propionic acid (PFP). Thus, a GC/AA interface is produced featuring carboxylic groups facing the solution. Electrochemical (cyclic voltammetry and electrochemical impedance spectroscopy) and XPS techniques are used to experimentally characterize the grafting process and the surface state. The theoretical results are compared with the experimental evidence to determine, at a molecular level, the overall grafting mechanism. Ionization potentials, standard oxidation potentials, HOMO and electron spin distributions are calculated at the CCD/6-31G* level of the theory. The comparison of experimental and theoretical data suggests that the main electroactive species is the “zwitterionic” form for the three aliphatic amino acids, while the amino acids featuring the amino group bound to the phenyl aromatic moiety show a different behaviour. The comparison between experimental and theoretical results suggests that both the neutral and the zwitterionic forms are present in the acetonitrile solution in the case of 4-(4-amino-phenyl)-butyric acid (PFB) and 3-(4-amino-phenyl)-propionic acid. [Copyright &y& Elsevier]

June 21, 2012 Tags: ALIPHATIC compounds, AMINO acids, CARBON, CHEMISTRY, ELECTROCHEMICAL analysis, ELECTRODES, OXIDATION, Physical & theoretical, SURFACE chemistry
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Electrochemistry of horseradish peroxidase entrapped in graphene and dsdna composite modified carbon ionic liquid electrode

Abstract: In this paper, a graphene (GR) and double-stranded DNA (dsDNA) composite material was prepared and used for the immobilization of horseradish peroxidase (HRP) on the surface of a carbon ionic liquid electrode (CILE). Direct electrochemistry and bioelectrocatalysis of HRP incorporated in the composite film were carefully investigated. The presence of the dsDNA–GR biocomposite film on the electrode surface could provide a specific microenvironment for HRP with its direct electron transfer rate greatly enhanced on the electrode, which could be attributed to the synergistic contributions of the materials used. Cyclic voltammetric results exhibited that a pair of well-defined quasi-reversible redox peaks was observed on Nafion/HRP–dsDNA–GR/CILE in 0.1mol/L pH 3.0 phosphate buffer solution with the formal potential () as −0.193 V (vs. SCE), which was the typical characteristics of the heme Fe(III)/Fe(II) redox couple. The electrochemical parameters, such as the electron transfer coefficient (α) and the electron transfer rate constant (k s ) of HRP in the dsDNA–GR composite modified electrode were calculated with the results as 0.46 and 0.495s−1, respectively. The fabricated HRP modified electrode showed excellent electrocatalytic activity to the reduction of trichloroacetic acid over the concentration range of 1.0–21.0mmol/L with the detection limit of 0.133mmol/L (3σ). So the modified electrode provided a potential platform for the third-generation electrochemical biosensor. [Copyright &y& Elsevier]

June 19, 2012 Tags: CARBON, COMPOSITE materials, ELECTROCHEMISTRY, ELECTRODES, GRAPHENE, HORSERADISH peroxidase, IONIC liquids, SURFACE chemistry
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Dopamine molecularly imprinted electrochemical sensor based on graphene–chitosan composite

Abstract: A molecularly imprinted polymers (MIPs) electrochemical sensor based on graphene (GR)–chitosan (CS) composite was constructed, finally used in dopamine (DA) measurement. The MIPs-GR sensor was prepared through electrodepositing DA–GR–CS composited film on the glass carbon electrode (GCE) and then removing DA from the film via electrochemical induced elution. X-ray diffraction (XRD), attenuated total reflection infrared spectroscopy (ATR-IR), electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and differential pulse voltammetry (DPV) characterizations indicated that MIPs-GR/GCE formed an affinity film. Owing to excellent electronic properties, unique two-dimensional structure and large surface area of GR, the prepared sensor exhibited highly sensitive response to the oxidation of DA with enhanced current signal and short response time. The oxidation peak current of DPV was well-proportional to the concentration of DA in the range from 1.0×10−9 to 8.0×10−8 and 1.0×10−7 to 1.0×10−4 M. The developed sensor obtained a recovery of 96.7–105.0% in the DA determination of blood serum, resulted from the specific recognition to DA against the structural analog and coexisting interferences. [Copyright &y& Elsevier]

June 18, 2012 Tags: CARBON, COMPOSITE materials, DOPAMINE, ELECTROCHEMICAL analysis, ELECTRODES, GRAPHENE, IMPRINTED polymers, X-rays -- Diffraction
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Carbon–nb0.07ti0.93o2 composite supported pt–pd electrocatalysts for pem fuel cell oxygen reduction reaction

Abstract: Carbon–Nb0.07Ti0.93O2 (C67wt%–(Nb0.07Ti0.93O2)33wt%) composite support for Pt0.55Pd0.45 alloy catalysts was prepared by hydrolysis of metal alkoxides in the presence of carbon. Physical characterization by XRD, EDX, BET, TEM and TGA showed that the Nb0.07Ti0.93O2 was well distributed on the carbon particle surface with an average particle size of 15nm, and this support has a high surface area of 176m2/g and a similar porosity to that of carbon used to prepare this composite support. Pt0.55Pd0.45 alloy nanoparticles were deposited on the composite support to form a Pt0.55Pd0.45/C67wt%–(Nb0.07Ti0.93O2)33wt% catalyst, which shows a higher catalytic activity toward ORR than those of monometallic counterpart Pt/C67wt%–(Nb0.07Ti0.93O2)33wt%, Pt0.55Pd0.45/C, and Pt0.55Pd0.45/Nb0.07Ti0.93O2. Pt0.55Pd0.45/C67wt%–(Nb0.07Ti0.93O2)33wt% showed higher stability than Pt0.55Pd0.45/C, and similar to the commercially available Pt/C catalyst. [Copyright &y& Elsevier]

June 17, 2012 Tags: CARBON, COMPOSITE materials, ELECTROCATALYSIS, NIOBIUM compounds, OXIDATION-reduction reaction, PHOTOELECTROMAGNETIC effects, PLATINUM catalysts
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Wood gas wizard!

The article focuses on use of scrap wood as fuel. The Alabama native farmer Wayne Keith uses scrap wood to fuel his truck since 2004 instead of gasoline. He has saved nearly 40,000 dollars by using wood chunks. He also burns scrap wood for his sawmill. Using wood as fuel is not new and there were more than one million wood gas civilian vehicles operating in Asia and Europe by the end of World War II. Wood is biomass and does not contain carbon.

May 1, 2012 Tags: BIOMASS, CARBON, FUEL, GASOLINE
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Credible commitment in carbon policy

In this article the problem of credible commitment in carbon policy is discussed. Investors favour long-term predictability of the policy, but without any external enforcement mechanisms a commitment made by a government can be withdrawn, leading to scepticism and lack of credibility. This results in increased market risks and investment hold-up. Regulatory uncertainty stems from (i) strategic interactions between government and firms, (ii) potential learning about climate damage and abatement cost and (iii) political volatility. Although commitment to future policy encourages private investment, it also imposes costs in the form of reduced flexibility to accommodate new information or preferences. The article reviews devices that may help policy makers raise the level of commitment while also leaving some room for flexible adjustments. In particular, legislation of a long-term governance framework, delegation to an independent carbon agency and securitization of investors’ stakes in emission markets offer palliative approaches. [ABSTRACT FROM AUTHOR]

March 10, 2012 Tags: ASSET-backed financing, BUSINESS enterprises, CAPITALISTS & financiers, CARBON, ENVIRONMENTAL policy, INCENTIVE awards, INVESTMENTS, SKEPTICISM
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