Biomedical Engineering Reference
In-Depth Information
9.87 W/m 3 . By replacing the canvas cloth with a highly waterproof and durable
Gore-Tex cloth, Zhuang and his colleagues further raised the power density to
11 W/m 3 [ 63 ]. A comparison of the manufacturing cost of different SCAs showed
that only 198.1 USD/m 3 is needed to construct such a cloth-based SCA, which is
only a half the cost of membrane cathode assemblies. Zhang et al. [ 64 ] designed a
SCA using non-biodegradable glass fiber as the separator material; the MFC gen-
erated a power density of 70 W/m 3 at a 2-cm electrode spacing. The employment of
a double SCA further increased the power density to 150 W/m 3 at 2-cm electrode
spacing and dramatically to 696 W/m 3 at 0.3-cm spacing. This enhancement was
mainly attributed to the extremely low ohmic resistance of 2.2 X in such a SCA
configuration. Recently, Zhang et al. [ 37 ] also applied glass fiber separators in a
scalable MFC configuration to produce a maximum power density of 154 W/m 3 ,
implying a high suitability of such materials for practical use in MFCs.
It is worthwhile to note that poor contact between the separator and the cathode
in a SCA could significantly impair the system performance [ 6 ]. Therefore, an
appropriate application of hydrogel [ 10 ] or a supporter [ 64 ] is essential to bind the
separator and cathode together and to avoid possible deformation of separator in
practical application.
2.4 Microbiology
In the past few years, there has been a dramatic increase in the reported number
of microorganisms that can generate electricity in MFCs. Apart from several
frequently-reported bacterial families such as Shewanella, Geobacter and
Proteobactor, some new strains have also been recently discovered to effectively
catalyze electrochemical reactions. Nevertheless, the categories of exoelectrogens
are still relatively small compared to the vast diversity of microorganisms, and
many of the known exoelectrogen strains show low electricity-producing ability.
From the point of view of the biocathode, the community structure, metabolism
pathways, and interactions of many biocathode bacteria remain unclear, which
limits the biocathode capability and application. Therefore, to further promote
power generation, highly efficient microorganisms need to be further explored, and
the metabolic and catalytic activities of bacteria need to be enhanced. These all
require a more fundamental understanding of the intracellular and extracellular
electron transfer processes.
2.4.1 Bacteria Screening/Enrichment
The power generation performance of an MFC depends heavily on the enrichment
degree and activity of exoelectrogenic bacteria. Thus, screening or enrichment of
competitive exoelectrogens that can rapidly oxidize organic matter and transfer
electrons to the anode is of vital importance for the establishment of an efficient
Search WWH ::




Custom Search