Non-enzymatic palladium recovery on microbial and synthetic surfaces

Authors

  • Amelia-Elena Rotaru,

    1. Department of Bioscience, Aarhus University, Ny Munkegade 116, 8000 Aarhus C, Denmark; telephone: +4560202794; fax: +4589422722
    2. Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Ny Munkegade 120, 8000 Aarhus C, Denmark; telephone :+4589423932; fax: + 4586196199
    Current affiliation:
    1. Department of Microbiology, University of Massachusetts, Amherst, Massachusetts 01003, USA.
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  • Wei Jiang,

    1. Department of Plant, Soil, and Insect Sciences, University of Massachusetts, Amherst, Massachusetts
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  • Kai Finster,

    1. Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Ny Munkegade 120, 8000 Aarhus C, Denmark; telephone :+4589423932; fax: + 4586196199
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  • Troels Skrydstrup,

    Corresponding author
    1. Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Ny Munkegade 120, 8000 Aarhus C, Denmark; telephone :+4589423932; fax: + 4586196199
    2. Institute of Chemistry, Aarhus University, Langelandsgade 140, 8000 Aarhus C, Denmark
    • Department of Bioscience, Aarhus University, Ny Munkegade 116, 8000 Aarhus C, Denmark; telephone: +4560202794; fax: +4589422722.
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  • Rikke Louise Meyer

    Corresponding author
    1. Department of Bioscience, Aarhus University, Ny Munkegade 116, 8000 Aarhus C, Denmark; telephone: +4560202794; fax: +4589422722
    2. Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Ny Munkegade 120, 8000 Aarhus C, Denmark; telephone :+4589423932; fax: + 4586196199
    • Department of Bioscience, Aarhus University, Ny Munkegade 116, 8000 Aarhus C, Denmark; telephone: +4560202794; fax: +4589422722.
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Abstract

The use of microorganisms as support for reduction of dissolved Pd(II) to immobilized Pd(0) nanoparticles is an environmentally friendly approach for Pd recovery from waste. To better understand and engineer Pd(0) nanoparticle synthesis, one has to consider the mechanisms by which Pd(II) is reduced on microbial surfaces. Escherichia coli, Shewanella oneidensis, and Pseudomonas putida were used as model organisms in order to elucidate the role of microbial cells in Pd(II) reduction under acidic conditions. Pd(II) was reduced by formate under acidic conditions, and the process occurred substantially faster in the presence of cells as compared to cell-free controls. We found no difference between native (untreated) and autoclaved cells, and could demonstrate that even a non-enzymatic protein (bovine serum albumin) stimulated Pd(II) reduction as efficiently as bacterial cells. Amine groups readily interact with Pd(II), and to specifically test their role in surface-assisted Pd(II) reduction by formate, we replaced bacterial cells with polystyrene microparticles functionalized with amine or carboxyl groups. Amine-functionalized microparticles had the same effect on Pd(II) reduction as bacterial cells, and the effect could be hampered if the amine groups were blocked by acetylation. The interaction with amine groups was confirmed by infrared spectroscopy on whole cells and amine-functionalized microparticles. In conclusion, bio-supported Pd(II) reduction on microbial surfaces is possibly mediated by a non-enzymatic mechanism. We therefore suggest the use of amine-rich biomaterials rather than intact cells for Pd bio-recovery from waste. Biotechnol. Bioeng. 2012; 109:1889–1897. © 2012 Wiley Periodicals, Inc.

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