XAS analysis of iron and palladium bonded to a polysaccharide produced anaerobically by a strain of Klebsiella oxytoca.
Klebsiella oxytoca BAS-10 ferments citrate to acetic acid and CO2, and secretes a specific exopolysaccharide (EPS), which is able to bind different metallic species. These biomaterials may be used for different biotechnological purposes, including applications as innovative green biogenerated catalysts. In production of biogenerated Pd species, the Fe(III) as ferric citrate is added to anaerobic culture of K. oxytoca BAS-10, in the presence of palladium species, to increase the EPS secretion and improve Pd-EPS yield. In this process, bi-metallic (FePd-EPS) biomaterials were produced for the first time. The morphology of bi-metallic EPS, and the chemical state of the two metals in the FePd-EPS, are investigated by transmission electron microscopy, Fourier transform infra-red spectroscopy, micro-X-ray fluorescence, and X-ray absorption spectroscopy methods (XANES and EXAFS), and compared with mono-metallic Pd-EPS and Fe-EPS complexes. Iron in FePd-EPS is in the mineralized form of iron oxides/hydroxides, predominantly in the form of Fe(3+), with a small amount of Fe(2+) in the structure, most probably a mixture of different nano-crystalline iron oxides and hydroxides, as in mono-metallic Fe-EPS. Palladium is found as Pd(0) in the form of metallic nanoparticles with face-centred cubic 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. The catalytic ability of bi-metallic species (FePd-EPS) in a hydrodechlorination reaction is improved in comparison with mono-metallic Pd-EPS.
University of Nova Gorica, Vipavska 13, Nova Gorica 5000, Slovenia.
Iztok
I
Arčon
Dipartimento di Scienze Molecolari e Nanosistemi, Università Cà Foscari, Via Torino 155, 30170 Venezia-Mestre, Italy.
Stefano
S
Paganelli
Dipartimento di Scienze Molecolari e Nanosistemi, Università Cà Foscari, Via Torino 155, 30170 Venezia-Mestre, Italy.
Oreste
O
Piccolo
Dipartimento di Scienze Molecolari e Nanosistemi, Università Cà Foscari, Via Torino 155, 30170 Venezia-Mestre, Italy.
Michele
M
Gallo
Department of Biology, Biotechnical Faculty, University of Ljubljana, Večna pot 111, Ljubljana 1000, Slovenia.
Katarina
K
Vogel-Mikuš
Dipartimento di Scienze Molecolari e Nanosistemi, Università Cà Foscari, Via Torino 155, 30170 Venezia-Mestre, Italy.
Franco
F
Baldi
D000693:Anaerobiosis; D005285:Fermentation; D005290:Ferric Compounds / Q000737:chemistry; D007501:Iron / Q000032:analysis*; D041121:Klebsiella oxytoca / Q000378:metabolism*; D008854:Microscopy, Electron; D053758:Nanoparticles; D010165:Palladium / Q000032:analysis*; D011135:Polysaccharides, Bacterial / Q000737:chemistry*; D013052:Spectrometry, X-Ray Emission; D017550:Spectroscopy, Fourier Transform Infrared; D017356:Synchrotrons; D056928:X-Ray Absorption Spectroscopy
D005290:Ferric Compounds; D011135:Polysaccharides, Bacterial; C000499:ferric oxide; D010165:Palladium; C025314:ferric citrate; D007501:Iron
EXAFS; Fe K-edge; Pd K-edge; XANES; bi-metallic exopolysaccharide; citrate fermentation; µ-XRF