EN
Sustainable production methods for catalytic palladium (Pd) nanoparticles
are currently being investigated due to their increasing use, limited
availability and price volatility. The bio-palladium (bio-Pd) method uses
bacteria as a producer and carrier of Pd nanoparticles. In this method,
Pd leaching results in economical loss and environmental risk. In this
study we therefore investigate the influence of different parameters on the
leaching process: temperature (4-21°C), medium (H2O or mineral medium),
pH (1–12), atmosphere (air, O2, N2, H2) and bacterial carrier. We show
leaching is an important phenomenon for biosupported Pd: 20% of the Pd
was released at 21°C in water after 100 days. Minimal leaching occurred at
lower temperatures, low pH and in an isotonic medium. Up to 5 times more
leaching was observed under anaerobic conditions (H2 or N2 atmosphere)
than under aerobic conditions (O2 or air atmosphere). The producer/carrier
Cupriavidus metallidurans leached up to 5% zerovalent Pd compared with
20% in Shewanella oneidensis. No loss of catalytic activity due to leaching
was observed when the leachate remained in the reaction medium. This
paper shows for the first time that release of Pd nanoparticles from the
bacterial carrier of bio-Pd can be significant particularly under anaerobic
conditions, at high temperature or high pH.