Browsing by Author "Linkov, V"

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    The application of high capacity ion exchange absorbent material, synthesized from fly ash and acid mine drainage, for the removal of heavy and trace metals from secondary co-disposed process waters
    (University of the Western Cape, 2005) Hendricks, Nicolette Rebecca; Linkov, V; Dept. of Chemistry; Faculty of Science
    The objective of this study was to investigate the feasibility of the application of low cost high capacity inorganic ion exchange material, synthesized form collected fly ash and acid mine drainage solid residues, for the decontamination of secondary co-disposal process waters, with emphasis on investigating the processes governing the solid/solution interface.
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    A comparative study for the removal of humic acids from power plants make-up waters
    (University of the Western Cape, 2002-06) Linkov, V
    Water treatment forms an integral part of thermal electric power generation (coal fired as well as nuclear power stations). There are generally two main water cycles associated with thermal power generation, namely the steam/water cycle that uses demin water for the production of steam and the cooling water circuit, which is used for condensing the steam back to water. The two cycles are isolated from each other and exchange heat via a condenser. Power station make up water treatment plants have traclltionally been designed to produce water of a very high quality (free from inorganic salts) by synthetic ion exchange resins. Raw water quality (mainly TDS, OA and silica) is the key factor in the design of the plant. Any deterioration of raw water quality during the life cycle of the plant, which is currently a South African and worldwide phenomenon, will inevitably have a negative impact on treatment plant performance and plant integrity. ln order to meet the specifications of the water quality required for proper plant operation, an extra burden, as well as associated treatment costs, will therefore have to be placed on existing treatment processes to compensate for change in feed water quality.
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    Electrochemical performance of zinc carbodiimides based porous nanocomposites as supercapacitors
    (Elsevier, 2021) Linkov, V; Shen, J; Chen, X
    The low energy densities of supercapacitors are generally limited by the used anodes. To develop supercapacitors with high energy densities, metal–organic framework (TRD-ZIF-8) derived honeycomb-like porous zinc carbodiimide (ZnNCN) based nanocomposites (HPZC) surface loaded with graphitized carbon nitride (g-C3N4) are synthesized. After their detailed characterization by means of electron microscopy, spectroscopy and electrochemical techniques, the materials are used to prepare asymmetric supercapacitor cells (HPZC-4//AC ASCs) with HPZC-4 and active carbon as electrodes, which demonstrate power and energy densities as high as 7839 W Kg−1 and 213 Wh Kg−1, respectively. The unique honeycomb-like porous structure of HPZC loaded with a 2D material (g-C3N4) improves charge/mass transport efficiency and reduces ion diffusion resistance, contributing to a specific capacitance of 779 F g−1 at a current density of 3 A g−1.
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    Lanthanum modified Fe3N/carbon foam as highly efficient electrode for zinc-air batteries
    (Journal of Alloys and Compounds, 2023) Wang, M; Linkov, V; Ji, S
    Efficient electrocatalysts for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) are of great importance for large-scale application of rechargeable zinc-air batteries. Iron-nitrogen-carbon materials are known for their excellent ORR catalytic activity, but it is their low OER performance that is responsible for poor charging operation causing slow market adoption of these energy storage devices. Herein, lanthanum (La) is applied to enhance OER electrocatalytic properties of iron-nitrogen-carbon materials used as zinc-air battery electrodes. According to X-ray diffractometry, the presence of La alters the electronic structure of surrounding N and Fe elements, resulting in more negative N and positive Fe ions to appear on the surface and form Fe3N active species. Electrochemical analysis demonstrated enhanced bi-functional electrocatalytic performance of La-modified Fe3N carbon foam (La-Fe0.1:1/NFC) which total overpotential was among the lowest of previously reported metal-nitrogen-carbon materials. La-Fe0.1:1/NFC exhibited high power density and charge-discharge cycling stability in a real zinc-air battery cell.
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    Three-dimensional N-doped super-hydrophilic carbon electrodes with porosity tailored by Cu2O template-assisted electrochemical oxidation to improve the performance of electrical double-layer capacitors
    (Royal Society of Chemistry, 2021) Linkov, V; Lv, X; Ji, S
    Three-dimensional (3D), binder-free, porous carbon-based electrodes exhibit high charge storage ability in electrical double-layer capacitors owing to their well-developed porous structures enhancing mass transfer and achieving relatively high electroconductivity. A 3D N-doped carbon electrode with abundant oxygen-containing functional groups was prepared by depositing a PDA-derived N-doped carbon layer and electrochemical oxidation using a porosity-regulatingin situgenerated Cu2O sacrificial template. The optimized electrode demonstrated a high specific capacitance of 2852 mF cm−2at a current density of 1 mA cm−2and good rate capability. The material was used as an electrode in a symmetric capacitor, exhibiting an energy density of 16.4 mW h cm−3at a power density of 180 mW cm−3, which maintained 89% of its value after 15 000 cycles. This study describes a new method of manufacturing high-performance porous electrodes suitable for practical application in electric double-layer capacitors.