1. Removal of copper from aqueous solutions with zeolites and possible treatment of exhaust materialsNataša Zabukovec Logar, Iztok Arčon, Janez Kovač, Margarita Popova, 2021, original scientific article Abstract: The mechanism of Cu2+ loading into commercially available natural HEU-type and synthetic LTA-type zeolites for their
possible use in environmental processes, such as water and air treatment applications, was studied. Elemental analysis,
SEM/EDXS, XRD, XAS and XPS analyses revealed 4-fold coordination of Cu2+ cations with oxygen atoms in the pores, a
predominant location of copper atoms on the surface of crystallites and retained crystallinity of zeolites throughout the
processes. The post-treatment of Cu2+-loaded samples with HCl and/or NaCl solutions confirmed the predominantly
reversible sorption of copper on zeolites from aqueous solutions by ion-exchange mechanism and, therefore, excellent
regeneration possibilities for both types of zeolites. Furthermore, with the calcination of exhaust metal-loaded zeolites,
catalysts for total toluene oxidation reaction, as a model VOC pollutant, were obtained. Keywords: Cu2+ ion exchange, Total toluene oxidation, X-ray absorption spectroscopy, X-ray photoelectron spectroscopy, Zeolite Published in RUNG: 03.06.2021; Views: 1484; Downloads: 151
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2. Effect of the Morphology of the High-Surface-Area Support on the Performance of the Oxygen-Evolution Reaction for Iridium NanoparticlesLeonard Moriau, Marjan Bele, Živa Marinko, Francisco Ruiz-Zepeda, Gorazd Koderman, Martin Šala, Angelija Kjara Šurca, Janez Kovač, Iztok Arčon, Primož Jovanovič, Nejc Hodnik, Luka Suhadolnik, 2021, original scientific article Abstract: The development of affordable, low-iridium-loading,
scalable, active, and stable catalysts for the oxygen-evolution
reaction (OER) is a requirement for the commercialization of
proton-exchange membrane water electrolyzers (PEMWEs).
However, the synthesis of high-performance OER catalysts with
minimal use of the rare and expensive element Ir is very challenging
and requires the identification of electrically conductive and stable
high-surface-area support materials. We developed a synthesis
procedure for the production of large quantities of a nanocomposite
powder containing titanium oxynitride (TiONx) and Ir.
The catalysts were synthesized with an anodic oxidation process
followed by detachment, milling, thermal treatment, and the
deposition of Ir nanoparticles. The anodization time was varied to grow three different types of nanotubular structures exhibiting different lengths and wall thicknesses and thus a variety of properties. A comparison of milled samples with different degrees of nanotubular clustering and morphology retention, but with identical
chemical compositions and Ir nanoparticle size distributions and dispersions, revealed that the nanotubular support morphology is
the determining factor governing the catalyst’s OER activity and stability. Our study is supported by various state-of-the-art
materials’ characterization techniques, like X-ray photoelectron spectroscopy, scanning and transmission electron microscopies, Xray powder diffraction and absorption spectroscopy, and electrochemical cyclic voltammetry. Anodic oxidation proved to be a very suitable way to produce high-surface-area powder-type catalysts as the produced material greatly outperformed the IrO2 benchmarks
as well as the Ir-supported samples on morphologically different TiONx from previous studies. The highest activity was achieved for the sample prepared with 3 h of anodization, which had the most appropriate morphology for the effective removal of oxygen
bubbles. Keywords: electrocatalysis, oxygen-evolution reaction, TiONx-Ir powder catalyst, iridium nanoparticles, anodic oxidation, morphology−activity correlation Published in RUNG: 04.01.2021; Views: 2051; Downloads: 0 This document has many files! More... |
3. Structural and CO [sub] 2 capture properties of ethylenediamine-modified HKUST-1 metal-organic frameworkNika Vrtovec, Matjaž Mazaj, Gianpiero Buscarino, Angela Terracina, S. Agnello, Iztok Arčon, Janez Kovač, Nataša Zabukovec Logar, 5, original scientific article Keywords: functionalization, modification, adsorption, extended X-ray absorption fine structure, materials Published in RUNG: 17.10.2020; Views: 2143; Downloads: 0 |
4. Removal of manganese in batch and fluidized bed systems using beads of zeolite a as adsorbentMina Jovanovic, Iztok Arčon, Janez Kovač, Nataša Novak Tušar, Bojana Obradovic, Nevenka Rajić, 2016, original scientific article Abstract: In this study the uptake capacity of Mn(II) ions by zeolite A beads was investigated for different initial Mn concentration (100e400 mg Mn dm^-3) in batch mode at 25e55 C. The obtained adsorption capacity varying from 30 to 50 mg Mn g^-1 demonstrated a high affinity of zeolite A towards Mn(II) present in solutions. Kinetic studies indicated the intra-particle diffusion as the rate limiting step up to 45 C with apparent diffusivities in the range (1.2e2.0) x 10^-13 m2 s^-1 and the activation energy of 21.9 kJ mol^-1, which implies strong interactions between the zeolite A and Mn ions. At 55 C ion-exchange became the rate limiting step. The adsorption isotherms were studied at 25 C showing that the Mn adsorption is the best described by the Langmuir model suggesting a homogenous zeolite surface. XPS analysis of the Mnloaded beads showed that there is no surface accumulation of Mn but an almost uniform Mn distribution inside zeolite A, whereas XANES and EXAFS suggested that the adsorption of Mn(II) was followed by the Mn(II) oxidation and oxide formation. Regeneration of the spent zeolite was examined in 8 adsorption/desorption cycles by a chelating Na2EDTA in a fluidized column. It has been found that zeolite A beads could be reused for at least 4 cycles with satisfactory Mn(II) adsorption efficiencies of about 70%. Keywords: Zeolite A
Manganese
Adsorption kinetics
EXAFS/XANES
XPS Published in RUNG: 01.04.2016; Views: 4717; Downloads: 0 This document has many files! More... |