Effect of porosity on ocv and westwater treatment efficiency of a clay partitioned ion exchange double-chamber microbial fuel cell

Effect of Porosity on Ocv And Westwater Treatment Efficiency of A Clay Partitioned Ion-Exchange Double-
Chamber Microbial Fuel Cell , R. Y. Tamakloe, M. Commey, Agoe Obed Nai, Turkson Samuel Kwamena,
K. Singh, Journal Impact Factor (2015): 8.5041 (Calculated By Gisi) www.jifactor.com
www.iaeme.com/ijaret.asp 6 editor@iaeme.com
1
Department of Physics – College of Science,
Kwame Nkrumah University of Science and Technology, KNUST
2
Technology Consultancy Centre
Kwame Nkrumah University of Science and Technology, KNUST
ABSTRACT
A microbial fuel cell (MFC) is a device that converts biochemical energy to electrical energy by
the catalytic reaction of microorganisms. Two membraneless clay partitions were fabricated using local
materials (Mfensi clay and alumina). Two double chambered MFCs were constructed using the clay
partitions and operated under the same conditions (ambient temperature and pressure, pH, electrode size,
substrate type and COD of 7200 mg/L) for 18 days. The performances of the cells were then compared in
terms of wastewater treatment, power generation and coulombic efficiency. The maximum open circuit
voltage (OCV) obtained for cell 1 and 2 were 1173.0 mV and 1333.0 mV respectively. The maximum
power densities of cell 1 and 2 were 116.377 Wm-2
and 134.709 Wm-2
respectively. After operation, the
cells showed decrease in the COD (Chemical oxygen demand) values of the wastewater of 3720 mg/L
and 2610 mg/L respectively. The coulombic efficiency of cell 1 and 2 were 56.96 % and 46.37 %
respectively. The wastewater treatment efficiency for cell 1 and 2 were 48.3 % and 63.8 % respectively.
Cell 1 was found to be the best for MFC setup focused on power generation whiles Cell 2 was found to
be the best for MFC setup focused on wastewater treatment.
Keywords: Microbial Fuel Cell; DC-MFC = Double Chambered MFC; Open Circuit Voltage
INTRODUCTION
Due to the seemingly unceasing energy crisis and global warming, eco-friendly sources of energy
have been looked into over the years. Solar, biomass, nuclear energy and wind are to a considerable
length being explored and exploited. These sources which come as non-conventional sources are the key
to solving our energy crisis. We cannot afford to release stored carbon into the atmosphere at this time
when the atmosphere is heavily loaded with greenhouse gases (AltEnergy, 2010). Other sources of
energy having minimal or no net CO2 emission was required; that was the birth of fuel cells and the
microbial fuel cell also described as the bioreactor. Microbial fuel cell technology symbolizes a
fascinating approach to the quest for other sources of energy. As part of basic and applied research,
MFCs work on the principles of microbial physiology combined with electrochemistry. The nuances of
EFFECT OF POROSITY ON OCV AND WASTEWATER TREATMENT
EFFICIENCY OF A CLAY PARTITIONED ION-EXCHANGE
DOUBLE-CHAMBER MICROBIAL FUEL CELL
R. Y. Tamakloe1
, M. Commey2
, Agoe Obed Nai1
, Turkson Samuel Kwamena1
, K. Singh1
Volume 6, Issue 6, June (2015), Pp. 06-11
Article ID: 20120150606002
International Journal of Advanced Research in Engineering and
Technology (IJARET)
© IAEME: www.iaeme.com/ ijaret.asp
ISSN 0976 - 6480 (Print)
ISSN 0976 - 6499 (Online)
IJARET
© I A E M E

electrical and materials engineering are made apparent from the structural designs of MFCs
(Vishwanathan and Sai, 2010).
The idea of using microbial fuel cells in an attempt to produce electricity was first conceived in
the early twentieth century. Potter in 1911(Potter, 1911) showed that electricity can be produced directly
from the degradation of organic matter in a microbial fuel cell. Like a normal fuel cell, an MFC has both
an anode and a cathode chamber. The anoxic anode chamber is connected internally to the cathode
chamber via an ion exchange membrane with the circuit completed by an external wire.
Fuel cells use some clever chemistry, based on the idea that hydrogen gas and oxygen gas always come
together to make water by the equation:
2H2 + O2 → 2H2O (1)
As shown in Fig. 1, the microbial fuel cell is divided into two halves: aerobic and anaerobic. The
aerobic half (cathode) has a positively charged electrode and is abundant in oxygen. The anaerobic half
(anode) does not have oxygen, allowing a negatively charged electrode to act as the electron receptor for
the bacterial processes. The chambers are separated by a semi-permeable membrane to keep oxygen out
of the anaerobic chamber while still allowing hydrogen ions (H+
) pass through (illumin, 2015).
In this research, a number of clay mixtures were used as separator (proton exchange membrane)
in designing the MFC and observations made on the effects of these materials on the MFCs
characteristics; electricity generation and wastewater treatment. The focus is to build an efficient MFC
using local material. Mfensi and alumina are the materials under study.
METHODOLOGY
Fabrication of the Local Clay as Ion-Exchange Clay Partition
Mfensi clay and alumina were used in the fabrication of the partition. The mass per mixture of the
alumina was kept constant as that of Mfensi clay was varied as shown in Table 1.The mixtures were then
moulded using 10 cm x 10 cm x 0.8 cm slabs, dried and fired in a gas kiln at a maximum temperature of
982 ᵒC. The slabs were then left to cool down in the kiln for 48 hours.
Table 1 Composition of slab samples
Materials Mass of Powdered Sample 1/ G Mass of powdered sample 2/g
Mfensi clay 50 100
Alumina 50 50
TOTAL 100 150
Apparent Porosity 22 % 19 %
The porosities of the slabs were found using the boiling water method.
Four (4) plastic containers with a volume of 800 mL each were paired making two different DC-
MFC setups. The clay slabs were then shaped to dimensions of 7.3 cm x 7.3 cm with four holes drilled at
the corners of the slabs. Square exchange gateways of dimensions 4 cm x 4 cm were made on the faces of
the containers. That is, each DC-MFC has an exchange partition of 4 cm x 4 cm. shown in Fig. 1. Zinc
and copper rods were used as anode and cathode respectively.

Fig. 1 DC-MFC Setup
Wastewater from Guinness Ghana Breweries Limited was used in the anode chamber. This
substrate of COD 7200 mg/L at a pH of 6.75 contains the microorganism. The cathode chamber was then
filled with hydrogen peroxide (H2O2) and water in a 4: 1 ratio. The containers were covered and sealed
with masking tape to prevent air from entering.
The composition of Mfensi clay is as follows:
Table 2: Mfensi Clay: Geological Survey Department X-Ray Fluorescence Laboratory Results
Element % Element %
Na2O 6.15 K2O 1.66
MgO 1.28 CaO 0.54
Al2O3 13.82 TiO2 0.04
SiO2 65.26 MnO 0.07
P2O5 0.23 Fe2O3 0.83
SO3 0.10 LOI 10.00
Cl 0.02 Total 100
DATA COLLECTION
The anode and cathode wires were connected to a variable resistor board with resistances ranging
from 100 Ω to 15 KΩ to determine the polarization, and their corresponding voltages were recorded
using a 2010DMM digital multimeter.
The anode and cathode wires were later connected to the low and high ports of a Campbell
(CRX10) datalogger for 16 hours. The open-circuit-voltage (OCV) was then recorded through the
datalogger. Finally, the anode and cathode wires were connected in parallel to a 1 KΩ resistor and to the
datalogger, and the MFCs were left to operate for 18 days with readings stored every minute. All two
cells were operated and observed under the same conditions (ambient temperature and pressure, pH,
electrode size, substrate type and COD of 7200 mg/L). The corresponding voltages plotted against time
(average of hour’s readings) as shown in Fig 2.
H
L
CR10X Datalogger
H2O2 Substrate
Copper Cathode
Electrode
Clay
Slab
Zinc Anode
Electrode
Wastewater
Substrate -Anode

Fig. 2 Variation of voltage with time (average of hour’s readings)
As observed from the graph, OCV for the various cells increased gradually with the time of 16
hours operation and the maximum open circuit voltages for cell 1 and 2 were 1173.0 mV and 1333.0 mV
respectively. There was a sharp decrease in operating voltage with time for 10 hours, when a load of 1
KΩ was connected to the circuit, then a further decrease between 26 hours and 163 hours. Between the
hours of 233 and 385, distinct relationship between cells 1 and 2 were observed (voltage of cell 2 >
voltage of cell 1). The decrease in voltage can be caused by a number of factors; losses due to resistances
to the flow of electrons through the circuit and to the flow of ions through clay partition, losses due to the
energy needed for oxidation as more dilution H2O2 continued.
POLARIZATION AND INTERNAL RESISTANCE
Fig. 3 Variation of voltage with resistance

The voltage increases with external resistance. The corresponding currents for the various voltage
points were calculated using Ohm’s law; Voltage (V) = Current (I) x Resistance of conductor (R). The
coulombic efficiency (Logan, 2008) of cell 1 and 2 were 56.96 and 46.37 respectively.
Fig. 4 Variation of Pd, Power density with current density (polarization curve for all two cells)
As shown in Fig 4, the polarization curve obtained by connecting each of the two cells to a
variable resistor board. The maximum power densities (normalized to the anode surface area = 0.0039
m2
) of cell 1 and 2 were 116.377 Wm-2
and 134.709 Wm-2
respectively. Internal resistances
corresponding to the peaks of power density curves of cell 1 and 2 was 300 Ω.
The voltage falls more slowly and is fairly linear with the current in the ohmic losses zone.
Voltage keeps decreasing as the current density increases; in this zone the concentration losses dominate.
WASTEWATER TREATMENT
The wastewater treatment performances of all two cells were observed under the same
conditions i.e. ph and temperature of wastewater, the initial value of the COD was the same for all two
cells (COD = 7200mg/L) so the observation was based on final values of the individual cells after
operation. The final COD values observed for cell 1 and 2 was 3720 mg/L and 2610 mg/L respectively,
Cell 2 was the highest in terms of COD removal. The wastewater treatment efficiency of cell 1 and 2
were 48.3 % and 63.8 %. This parameter indicates how much fuel has been converted in the cells either
into power or microorganism growth.
CONCLUSION
The clay partition for a typical double chamber microbial fuel cell was fabricated using local
materials; Mfensi clay and alumina. Cell 1 gave the highest coulomb efficiency of 56.96 % and cell 2
gave the highest wastewater treatment efficiency of 63.8 %. Cell 1 was found to be best for MFC setups
focused on power generation whiles Cell 2 was found to be the best for MFC setups focused on
wastewater treatment. The use of H2O2 is also recommended as a good oxidizing agent.

ACKNOWLEDGEMENTS
Authors would like to thank GGBL, Kumasi, Ghana for using its wastewater and also for COD
measurements. We would also like to thank the Head of Physics Department for providing all necessary
support for this work.
REFERENCES
1. AltEnergy., 2010. Microbial Fuel Cells - Principles and Applications _ AltEnergyMag. [Online]
Available at: http://www.altenergymag.com/emagazine.php?art_id=1424, 14-12-2015
2. illumin, 2015. [Online] Available at: http://illumin.usc.edu/134/microbial-fuel-cells-generating-
power-from-waste/8-2-2015
Logan, B. E. (2008) Microbial Fuel Cells, John Wiley & Sons, Inc, pp 49.
3. Potter, M.C. Potter (1911). Electrical effects accompanying the decomposition of organic
compounds. Royal Society (Formerly Proceedings of the Royal Society) B, 84, p260-276
4. Vishwanathan, A. S. & Sai, S. S. S., 2010. Microbial Fuel Cells - Principles and Applications _
AltEnergyMag. [Online] Available at: www.altenergymag.com 14-12-2015
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Effect of porosity on ocv and westwater treatment efficiency of a clay partitioned ion exchange double-chamber microbial fuel cell

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