Hydrodechlorination of Aroclor 1260 in Aqueous Two-phase Mixture Catalyzed by Biogenerated Bimetallic Catalysts
Franco Baldi
Dipartimento di Scienze Molecolari e Nanosistemi, Università Ca’ Foscari Venezia, via Torino 155, 30170 Venezia, Mestre, Italy
Michele Gallo
Dipartimento di Scienze Molecolari e Nanosistemi, Università Ca’ Foscari Venezia, via Torino 155, 30170 Venezia, Mestre, Italy
Stefano Paganelli
Dipartimento di Scienze Molecolari e Nanosistemi, Università Ca’ Foscari Venezia, via Torino 155, 30170 Venezia, Mestre, Italy
Riccardo Tassini
Dipartimento di Scienze Molecolari e Nanosistemi, Università Ca’ Foscari Venezia, via Torino 155, 30170 Venezia, Mestre, Italy
Laura Sperni
Dipartimento di Scienze Molecolari e Nanosistemi, Università Ca’ Foscari Venezia, via Torino 155, 30170 Venezia, Mestre, Italy
Oreste Piccolo *
SCSOP, Via Bornò 5, 23896 Sirtori (LC), Italy
Stefano Zambon
Dipartimento di Scienze Ambientali, Informatica e Statistica, Università Ca’ Foscari Venezia, via Torino 155, 30170 Venezia, Mestre, Italy and Lab-Control Srl, via Cà Donà 545, 45030 San Martino di Venezze (RO), Italy
Rossano Piazza
Dipartimento di Scienze Ambientali, Informatica e Statistica, Università Ca’ Foscari Venezia, via Torino 155, 30170 Venezia, Mestre, Italy
Marta Maria Natile
Dipartimento di Scienze Chimiche, IENI – CNR and INSTM, Università di Padova, Via F. Marzolo 1, 35131 Padova, Italy
Lidia Armelao
Dipartimento di Scienze Chimiche, IENI – CNR and INSTM, Università di Padova, Via F. Marzolo 1, 35131 Padova, Italy
*Author to whom correspondence should be addressed.
Abstract
The PCBs are known recalcitrant and toxic pollutants and significant values of contamination could be found in water. PCBs can be hydrodechlorinated using Pd-based catalysts and hydrogen, but the research to identify more efficient heterogeneous catalysts, able to work in an aqueous phase, less sensible to deactivation and easily removable at the end of the treatment, remains a considerable interesting goal. A strain of Klebsiella oxytoca, DSM 29614, known to produce a specific exopolysaccaride (EPS), was grown in different media with sodium citrate or with sodium citrate plus ferric citrate, as sole energy and carbon sources under anaerobic conditions. The cultures were amended with 50 mg of palladium as Pd(NO3)2 to generate Pd-EPS (Pd content 13%) or FePd-EPS (Pd content 8.4%; Fe 7.4%) species which were secreted from the cells, isolated by treatment with a cold ethanol solution (70%) and dried under vacuum as powders. The catalytic ability of these mono- and bi-metallic species was tested in the hydrodechlorination reaction of the Aroclor 1260 PCBs mixture under aqueous biphasic conditions. Here we demonstrate that the degree of PCBs hydrodechlorination is dependent by the nature of catalyst and of base used to neutralize HCl produced, the bimetallic species being more active and an organic base resulting more effective. Working with a substrate/catalyst 8/1 molar ratio, at 3 MPa H2 and 60°C in 20 h a significant removal of highly chlorinated PCBs was obtained under the best conditions. The result seems promising for remediation of groundwater contaminated with PCBs.
Keywords: PCBs, Klebsiella oxytoca, biogenerated catalyst, bi-metallic polysaccharide, FePd-EPS, aqueous hydrodechlorination