Biomedical Engineering Reference
In-Depth Information
Contaminants often persist in the environment due to a lack of suitable electron
acceptors, whereas the electrodes of MFCs could be a highly attractive option,
because they can provide a sustainable clean electron sink for the degradation or
conversion of harmful environmental contaminants [
78
]. Thus, it is widely
believed that MFCs could be a practical viable technology for treatment of toxic
and complex matters that are not readily treated by conventional methods [
79
].
Mu et al. [
80
] used a dual-chamber MFC to decolorize Acid Orange 7, achieving a
maximum decolorization rate of 2.64 mol/m
3
/d at the cathode and even more when
external power was supplied. Liu et al. [
32
] also achieved efficient methyl orange
reduction at a pseudo-first-order decolorization rate kinetic constant of 0.05 h
-1
and a 20% further improvement after modifying the cathode with thionine.
Zhu and Ni [
81
] managed to construct an MFC-Fenton system for enhanced azo
dye degradation by incorporating an electro-Fenton process into MFC design. In
this system, the electrons produced from a microbial reaction were utilized to drive
electro-Fenton reactions for p-nitrophenol degradation in the MFC cathode, which
enabled a continuous hydrogen peroxide (H
2
O
2
) generation and a high oxidation
efficiency. However, an acid environment is required in that case, which limited its
application. In a more recent study, Feng et al. [
82
] further improved this process
to make it adaptable to neutral pH conditions. A PPy/AQDS-modified anode was
used to lower electron transfer resistance. Moreover, a mineral iron oxide instead
of Fe
2+
was used as the iron source, so that the iron reagent could be easily
recycled. With these improvements, the H
2
O
2
production at the cathode was
significantly enhanced, leading to rapid mineralization of Orange II at a rate of
0.145 h
-1
. Antibiotics are another group of bio-refractory compounds that are
widely present in water. Wen et al. [
83
] studied the possibility of degrading
penicillin by an MFC. It was interesting to find that the glucose-penicillin mix-
tures played an active role in the production of electricity, which might have
resulted from an enhanced permeability of microbial cell membranes in the
presence of penicillin and thus an accelerated electron transfer.
In addition to the organic compounds, the biomass is also an important
refractory substance that is proposed to fuel MFCs. Anaerobic sludge has been
demonstrated to be a feasible substrate for MFCs [
14
]. Significant sewage sludge
degradation accompanied by power generation was reported by Jiang et al. [
84
]in
a two-chamber MFC using potassium ferricyanide as the electron acceptor. After
250 h operation, the total COD (TCOD) of sludge was reduced by 46.4% from an
initial TCOD of 10,850 mg/L. Recently, blue-green algae was also tested as the
feedstock for a tubular MFC [
85
]. Over 78.9% of the TCOD and 80.0% of soluble
COD (SCOD), and 91.0% of total nitrogen (TN) were removed within 12 days.
Moreover, more than 90% of microcystins released from blue-green algae were
removed, exhibiting a potential means of power generation from blue-green algae
coupled with removal of algal toxins. This capability of removing toxicants can be
very valuable in biological processes. For example, experiments have shown that
MFCs are able to remove fermentation inhibitors that accumulate during cellulosic
biomass pretreatment [
86
]. This removal of the inhibitors would undoubtedly
allow for more efficient subsequent fermentation processes.
Search WWH ::
Custom Search