INVESTIGADORES
FLEXER Victoria
congresos y reuniones científicas
Título:
New materials and pre-activation techniques enhance the current density of microbial bioelectrochemical systems
Autor/es:
VICTORIA FLEXER; CHEN, J.; DONOSE, B.C.; SHERRELL, P.; WALLACE, G.G.; KELLER, J
Lugar:
Harbin
Reunión:
Conferencia; 1st Asia-Pacific ISMET meeting (International Society for Microbial Electrochemistry and Technologies); 2013
Institución organizadora:
International Society for Microbial Electrochemistry and Technologies
Resumen:
In microbial
bioelectrochemical systems, whole cells are used as biocatalysts to catalyse
oxidation and reduction reactions. Microbial fuel cells are the classical and
more widely studied example of bioelectrochemical systems, performing the
double task of wastewater treatment and electricity generation. More recently,
the concept has been extended to the possibility of generating higher value
products than electricity. In a typical microbial system, the anode is used to
harvest electrons from wastewater, while oxidising organic pollutants, with the
electrons being used as reducing power in the cathode to create valuable
products.
The viability of prospective
applications of microbial bioelectrochemical systems is highly dependent on
performance improvement, i.e. in current
increase. Current production is dependent, among other factors, on the
microbial consortia, bioelectrochemical reactor design, and electrode
materials. While the first two key characteristics have been widely researched
for more than a decade, until very recently, most of the work on
bioelectrochemical systems used only commercially available carbonaceous
materials.
We will present results on a new prospective microbial
electrode material bearing a hierarchical porous structure. A new method was
recently developed to directly grow carbon nanotube (CNT) networks on any type
of substrate. This is achieved by modifying the generally employed route of
chemical vapour deposition (CVD) synthesis. The so called CNT NanoWeb,
comprises entangled multi-wall carbon nanotubes integrated onto an underlying
conductive carbon layer.[1,
2] CNT NanoWeb was directly grown on reticulated
vitreous carbon (RVC) scaffold. The results show that the new electrode
material combines the advantages of both CNT nanoWeb and an open
three-dimensional scaffold. The biofilm is formed on top of CNT texture
structure.
A very high current density of
6.8 mA cm-2 (10.6 mA cm-3) was recorded at room
temperature with only mild stirring, i.e.
in the absence of forced flow through the electrode. This high current was the
product of the combined effect of the carefully chosen hierarchical porosity.
The macroporous structure hosts a large microbial loading, and at the same time
allows good mass transport that supplies the high substrate needs and removes
the undesirable products, mostly H+ in the current situation.
The improved bioanode performance suggests that carbon
nanotube nanostructure not only improves the bacterial attachment to the
electrode surface but also enhances the extracellular electron transfer, and
therefore boosts the current production.
Finally, we will also present results on new pre-activation
techniques for carbonaceous electrode materials. We aim at changing the
inherited hydrophobicity of carbonaceous materials, in order to increase
microorganisms adhesion and enhance the electron transfer rate to the electrode
surface. Pre-activation techniques are of outmost importance when working with
three dimensional porous structures. Highly porous carbonaceous materials are
usually quite hydrophobic. Increasing the wettability of these surfaces is
neccesary in order to ensure good bacterial development all over the interior
of the electrode volume. We are currently testing different physical techniques
that would allow for the scalability of the proccess with possible industrial
applications.