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1.
XAS and micro-XRF analysis of mono and bi-metallic exopolysaccharide (FePd-EPS) bio-generated by K. oxytoca
Franco Baldi, Katarina Vogel-Mikuš, Michele Gallo, Oreste Piccolo, Stefano Paganelli, Iztok Arčon, 2016, objavljeni povzetek znanstvenega prispevka na konferenci

Opis: Bacteria Klebsiella oxytoca (DSM 29614) secret a specific exopolysaccharide (EPS) in the presence of Fe(III)-citrate, as sole carbon and energy source, and produces after 7 days an iron gel precipitate (Fe-EPS) [1]. In the presence of palladium or other metal species, the culture of K. oxytoca can produce other mono or bimetal species (Pd-EPS, FePd-EPS) [2]. These bio-materials may be used as green biogenerated catalysts or for other biotechnological purposes. In this work we present the analysis of the morphology and the chemical state of the metals in mono and bi-metallic (Fe-EPS, Pd-EPS, FePd-EPS) complexes, by a combination of micro X-ray fluorescence, X-ray absorption spectroscopy methods (XANES and EXAFS), and transmission electron microscopy. The results show that iron in monometallic Fe-EPS and bimetalic FePd-EPS is in the mineralized form of iron oxides/hydroxides, predominantly in the form of Fe3+, with a small amount of Fe2+ in the structure, as a mixture of different nano-crystalline iron oxides and hydroxides. Palladium on the other hand is found as Pd(0) in the form of metallic nanoparticles with fcc structure in both, bi-metallic (FePd-EPS) and mono-metallic (Pd-EPS) species. In bi-metallic species Pd and Fe nanoparticles agglomerate in larger clusters, but they remain spatially separated. Access to the SR facilities at ESRF (beamline ID21, project LS-2225), DESY (beamline C) Hamburg (project I-20110511 EC) and ELETTRA (beamline XAFS, project 20115112) is acknowledged.
Najdeno v: osebi
Ključne besede: Klebsiella oxytoca, Fe, Pd, XANES, EXAFS, exopolysaccharide, FePd-EPS
Objavljeno: 28.06.2016; Ogledov: 2289; Prenosov: 0
.pdf Polno besedilo (388,27 KB)

2.
Alternative Recovery and Valorization of Metals from Exhausted Catalytic Converters in a New Smart Polymetallic Catalyst
Oreste Piccolo, Laura Sperni, Michele Gallo, Katarina Vogel-Mikuš, Iztok Arčon, Franco Baldi, Sebastiano Tieuli, Stefano Paganelli, 2019, izvirni znanstveni članek

Opis: A new metals-polymeric composite, Metx-EPS (I), was prepared to be used as catalyst in water or in two-phase aqueous conditions. The metals source was an exhausted catalytic converter that was grinded and treated with an acidic solution at room temperature. After filtration, the solution was concentrated, neutralized and added to a broth of Klebsiella oxytoca DSM 29614 to produce (I) where metals are embedded in a peculiar polysaccharide structure (EPS). The composite was easily recovered from the fermentation broth and purified. The process protocol was verified many times and was shown to be reproducible satisfactorily. The % recovery of metals, originally present in the converter, was good as determined by atomic absorption. The morphology and the chemical state of main metals in (I) were investigated by X-ray absorption spectroscopy methods (XANES and EXAFS). No metallic alloy seems to be evident. The catalytic activity and a possible synergic effect due to the presence of the different metals was valuated in the hydrogenation of some substrates, valuable precursors for theproduction of fine chemicals.
Najdeno v: osebi
Ključne besede: Biogenerated polymetallic exopolysaccharide, biphasic catalysis, hydrogenation, metals-polymeric composite, new catalyst from metallic wastes, EXAFS, XANES
Objavljeno: 06.05.2019; Ogledov: 206; Prenosov: 0
.pdf Polno besedilo (2,87 MB)

3.
A Biogenerated Polymetallic Catalyst from Society's Wastes
Oreste Piccolo, Stefano Paganelli, Petro Zanatta, Sebastiano Tieuli, Laura Sperni, Franco Baldi, Iztok Arčon, Michele Gallo, Katarina Vogel-Mikuš, 2019, izvirni znanstveni članek

Opis: Aims:Preparation of the new metals - polymeric composite, Met x-EPS (I), to be used as a green catalyst in water or in two-phase aqueous conditions. Study Design: Recovery and valorization of polymetallic wastes to obtain directly new catalysts using a microorganism to explore their application in removal of difficult and dangerous chemical pollutants present in aqueous environment
Najdeno v: osebi
Ključne besede: Metals - polymeric composite, biogenerated polymetallic exopolysaccharide, new catalyst from metallic wastes, hydrodechlorination of PCBs in water
Objavljeno: 06.05.2019; Ogledov: 276; Prenosov: 0
.pdf Polno besedilo (373,55 KB)

4.
An extracellular polymeric substance quickly chelates mercury(II) with N-heterocyclic groups
Claudia Faleri, Dario Battistel, Salvatore Daniale, Michele Gallo, Franco Baldi, Alojz Kodre, Iztok Arčon, 2017, izvirni znanstveni članek

Opis: A strain of Klebsiella oxytoca DSM 29614 is grown on sodium citrate in the presence of 50 mg l−1 of Hg as Hg(NO3)2. During growth, the strain produces an extracellular polymeric substance (EPS), constituted by a mixture of proteins and a specific exopolysaccharide. The protein components, derived from the outer membrane of cells, are co-extracted with the extracellular exopolysaccharide using ethanol. The extracted EPS contains 7.5% of Hg (total amount). This indicates that EPS is an excellent material for the biosorption of Hg2+, through chemical complexation with the EPS components. The binding capacity of these species towards Hg2+ is studied by cyclic voltammetry, and Hg L3-edge XANES and EXAFS spectroscopy. The results found indicate that Hg2+ is mainly bound to the nitrogen of the imidazole ring or other N-heterocycle compounds. The hydroxyl moities of sugars and/or the carboxyl groups of two glucuronic acids in the polysaccharide can also play an important role in sequestring Hg2+ ions. However, N-heterocyclic groups of proteins bind Hg2+ faster than hydroxyl and carboxyl groups of the polysaccharide.
Najdeno v: osebi
Ključne besede: Klebsiella oxytoca, Biosorption, Proteins, Polysaccharide, Cyclic voltammetry, EXAFS analysis
Objavljeno: 03.03.2017; Ogledov: 1460; Prenosov: 0
.pdf Polno besedilo (1,66 MB)

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