Anal. Method Environ. Chem. J. 4 (1) (2021) 26-35  
Research Article, Issue 1  
Analytical Methods in Environmental Chemistry Journal  
AMECJ  
Novel graphite rod electrode modied with iron-  
functionalized nanozeolite for efcient wastewater treatment  
by microbial fuel cells  
Mostafa Hassania, Mohsen Zeeba*, Amirhossein Monzavib, Zahra Khodadadia and Mohammad Reza Kalaeec,d  
aDepartment of Applied Chemistry, Faculty of Science, Islamic Azad University, South Tehran Branch, Tehran, Iran  
bDepartment of Polymer and Textile Engineering, Islamic Azad University, South Tehran Branch, Tehran, Iran  
cDepartment of Polymer Engineering, Islamic Azad University, South Tehran Branch, Tehran, Iran  
dNanothecnology Research Center, Islamic Azad University,South Tehran Branch,Tehran, Iran  
A R T I C L E I N F O :  
Received 10 Nov 2020  
Revised form 14 Jan 2021  
Accepted 23 Feb 2021  
A B S T R A C T  
Microbial fuel cells (MFCs) are a green and efcient approach to treat  
wastewater and generate energy. According to the present research,  
a novel MFC fabricate based on graphite rod electrodes (GRE). The  
surface of this cathode was modied with iron-functionalized ZSM-  
5 nanozeolite. The characterization of Iron doping in nanozeolite  
structure and electrode surface modication were obtained by XRD  
and EDX analyzes, respectively. Chemical analysis of square wave  
(Sqw)andcyclicvoltammetry(CV)determinedforallofthreegraphite  
electrodes (G, G-Z and G-Z/Fe) with higher efciency. Morover, the  
comparison of experimental results from 72-hour fuel cell steering  
was evaluated and showed that the G-Z/Fe graphite electrodes has  
maximum efciency and effectiveness. Thus, the efciency of fuel  
cell output current and residual chemical oxygen demand removal  
with this electrode increased up to 21.8% and 36.9%, respectively.  
The efucient recovery for the modication of the graphite electrode  
surface was achieved due to increasing of the specic surface area,  
the active sites of functionalized nanozeolite and the elevation in the  
electrical conductivity through the presence of iron particles doped in  
the ZSM-5/Fe nanocatalyst structure. Therefore, the G-Z/Fe cathode  
can be used as a favorite electrode for the construction of MFCs based  
on GRE with high efciency and economic.  
Available online 29 Mar 2021  
------------------------  
Keywords:  
Microbial Fuel Cells (MFCs),  
Graphite electrodes,  
Iron-functionalized ZSM-5 nanozeolit,  
Wastewater treatment  
methodforwastewatertreatment.MFCscandivided  
1. Introduction  
into two main categories, mediated and unmediated  
groups. The MFCs separated the compartments of  
the anode (oxidation) and the cathode (reduction).  
Most of MFCs use an organic electron donor that  
is oxidized to produce CO2, protons, and  
electrons. The cathode acts by different electron  
acceptors such as oxygen (O2). Other electron  
acceptors studied for metal treatment by reduction,  
nitrate reduction, and sulfate reduction in 25 °C  
and pH of 7 [2-4]. Microorganisms within an  
Microbial fuel cell (MFC) has different approach  
for wastewater treatment because the wastewater  
treatment process generates electricity or hydrogen  
gas instead of consuming electricity [1]. The  
MFC technology is depended on generating bio-  
electricity from bacterial biomass as the latest  
*Corresponding Author: Mohsen Zeeb  
Treatment of wastewater by G-Z/Fe electrode in MFCs  
Mostafa Hassani et al  
27  
MFC, can be decomposed the organic matter by  
oxidizing, produce electrons that pass through a  
series of respiratory enzymes inside the cell and  
produce energy for the cell in the form of ATP.  
Then. the electrons are released towards a nal  
electron acceptor. This receptor captures and  
reduces the electrons. For example, oxygen can  
be converted to water by the catalytic reaction  
of electrons with proton [5]. Previous research  
on electrodes used catalytic adhesives, carbon  
with non-platinum catalysts, at carbon, carbon-  
coated tube and bio electrodes in the fabrication  
of carbon-based cathodes. Therefore, this study  
employed a carbon rod electrode coated with ZSM-  
5/Fe nanocatalyst [6-8]. Zeolites are tetrahedral  
crystalline aluminosilicates bonded with oxygen  
bridges. Due to their SSA, the specic channel  
structure, high thermal and hydrothermal stability,  
they are widely used in industries such as chemistry  
and petrochemicals, and water and wastewater  
treatment [9-11]. As mentioned, extensive research  
has been performed throughout the world to make  
fuel cells exploiting new electrodes.The researchers  
developed a cathode made of nickel-doped reduced  
nanographene as well as acid-hydroionized  
reduced nanographene to determine and evaluate  
the efciency of the power output density with  
each of these electrodes. According to the results,  
the acid-hydroionized reduced nanographene  
showed the higher power output density (37%)  
than the nickel-doped reduced nanographene [12].  
In another study, the researchers were developed a  
triple nanocomposite cathode containing graphene  
oxide, polyethylene dioxythiophene and iron oxide  
nanorods to increase the current efciency of  
MFCs. Due to the large specic surface area of the  
electrode, high electrical conductivity as well as  
large sites for oxygen uptake in this electrode, the  
oxidation-reduction reaction occurs very quickly;  
as far as the power output density of the cell could  
be maintained for more than 600 hours [13]. By  
previous studies, a cathode was made of carbon  
nanotubes doped with titanium oxide nanoparticles  
aimed at enhancing the current output density and  
increasing the elimination of residual chemical  
oxygen demand (COD). The results of this study  
revealed an increase in the specic surface area  
and the active sites for oxygen uptake, so that the  
maximum current output density produced was  
15.16 mW m-2 and the COD removal efciency  
was reported between 54-71% (after 10 days),  
which was related to the presence of active reaction  
sites on the electrode [14]. The results showed us,  
the specic surface area is a very effective factor in  
increasing the efciency of MFCs.  
In this study, the graphite rod as a high stability and  
electrical conductivity was used for wastewater  
treatment. So, the surface modication of graphite  
rod by zeolite nanocatalyst will increase the  
specic surface area of the electrode. On the other  
hand, the modication of graphite rods with zeolite  
nanocatalyst were compared to simple graphite  
rod with the low price and poor efciency [15,  
16]. Metal nanoparticles can greatly inuence the  
oxygen reduction [17-22]. Hence, in this study the  
graphite rod electrodes were modied with iron  
particles (Fe) as a doping agent on ZSM-5 nano-  
zeolite (G-Z/Fe/ ZSM-5) for increasing of MFC  
efciency for wastewater treatment.  
2. Experimental  
2.1. Material  
The ZSM-5 nanocatalyst powder (from the Zeolites  
family) was purchased from Sigma Aldrich with  
a crystal size of 0.5 μm and a pore size of 5.5A0.  
Ferric chloride (FeCl3), the potassium chloride  
(KCl), the sodium di-hydrogen phosphate dihydrate  
(NaH2PO4.2H2O), di-sodium hydrogen phosphate  
dihydrate (Na2HPO4.2H2O), the ammonium  
chloride (NH4Cl) and sulfuric acid (H2SO4,  
%98) were also purchased from Merck Germany.  
Naon117 membrane (DuPont, the USA) was used  
to Preparation the cell.  
2.2. Preparation of ZSM-5/Fe Nanocatalyst  
To Preparation the functionalized ZSM-5  
nanocatalyst, rst 2.5 g of ZSM-5 nanozeolite  
powder was placed in the furnace at a temperature  
of 500°C for 4 hours and calcined. Then, 0.5 g of  
ferric chloride (FeCl3) powder was dissolved in  
Anal. Method Environ. Chem. J. 4 (1) (2021) 26-35  
28  
Fig.1. Schematic of the preparation process and calcination of ZSM-5/Fe nanocatalyst  
distilled water twice for one hour, added to the  
calcined ZSM-5 nanozeolite powder and mixed  
for another 30 minutes, and ltered with a lter  
paper. The resulting powder was rinsed three times  
with distilled water and placed in an oven at a  
temperature of 80°C for 2 hours. Next, the powder  
was separated from the lter paper and re-calcined  
at a temperature of 500°C for 4 hours. The method  
of preparation above nanocatalyst is schematically  
illustrated in Figure1.  
metal. Brunauer-Emmett-Teller (BET) surface  
area analysis (Belsorb apparatus, Japan) was used  
to determine the SSA of nanocatalyst particles,  
and energy-dispersive X-ray spectroscopy (EDX,  
MIRA III SAMX, Czech Republic) were applied to  
investigate the surface modication of the graphite  
electrode by each of the nanocatalysts.  
2.4. Electrode Modication  
To modify the graphite surface and to impregnate  
with the synthesized nanocatalyst powders, 0.5 g  
of each of the produced nanocatalysts (ZSM-5,  
ZSM-5/Fe) was poured into a test tube and 10 ml  
of ethanol was added and the graphite electrode  
was inserted into the test tube and placed in an  
2.3. Characterization  
X-ray diffraction (XRD, STADI-P, the USA)  
was used to investigate ferrous (Fe) metal in the  
nanocatalyst structure functionalized with these  
Fig. 2. Schematic of electrode surface modication by ZSM-5/Fe nanocatalyst  
Treatment of wastewater by G-Z/Fe electrode in MFCs  
Mostafa Hassani et al  
29  
ultrasonic bath for 20 minutes. Then, the resulting  
electrode was rinsed twice with deionized water  
and placed in a furnace at a temperature of 300°C  
for 2 hours (Fig.2).  
this purpose, in order to maintain the acid strength  
in the cell, 50 mM of phosphate buffered solution  
(PBS) (0.13 g L-1 of potassium chloride, 3.32 g L-1  
of sodium di-hydrogen phosphate dihydrate, 5.13 g  
L-1 of di-sodium hydrogen phosphate dihydrate, and  
0.31 g L-1 of ammonium chloride) was prepared in  
the cathode chamber and 375 mL was poured into  
the cathode chamber [23].  
2.5. MFC construction and operation  
This study applied with a separate two-part cell  
consisting of anaerobic anode and aerobic cathode.  
The chambers were made based on 500 mL pyrex  
glass with 75% of the volume as a working volume  
(375 mL). The two chambers were separated by a  
pyrex tube with an inner diameter of 0.8 cm and a  
length of 13.4 cm embedded in the middle portion  
with the proton exchange Naon 117 membrane.  
The electrodes were made with rod graphite and  
heated at 3000°C with an area of 22.62 cm2. In order  
to remove any impurities and improve membrane  
performance, the membrane was rst boiled  
for an hour in 3% H2O2 and then washed in 1 M  
sulfuric acid for 1 hour. Oxygen gas was injected  
into the cathode with a sparger at a ow rate of 20  
ml min-1, and nitrogen gas was injected into the  
anode chamber to provide anaerobic conditions. A  
magnetic stirrer was used to stir the solutions inside  
the anode and cathode chambers, and a copper  
wire was used to bond the anode and the cathode  
electrodes. Acidication of the medium inhibits  
the optimal growth of the bacteria in the anode  
chamber, so it is necessary to use a buffer with  
appropriate pH in the bacterial growth medium. For  
2.6. Microorganisms  
In the anodic chamber of the fuel cell, the anaerobic  
wastewater prepared from the industrial town  
treatment plant was used as inoculum. The samples  
from the treatment plant were stored in stainless  
steel containers at 4°C, and transferred to the  
laboratory. The combined inoculum was inoculated  
into the pre-prepared culture medium containing  
1 g L-1 of glucose, 3 g L-1 of yeast extract, 11 g  
L-1 of peptone, 0.5 g L-1 of ammonium chloride  
[24]. During the experiments, the cells were kept  
at room temperature and stirred at 50 rpm for 72  
hours (Table 1).  
2.7. Analytical method  
A multimeter (MASTECH MS8360G, China) was  
used to measure the output voltage of the cell. The  
residual COD of the samples was measured with  
COD meter (Model 76133, Aqua Litik, Germany).  
Three-electrode systems including, anode electrode  
Table.1. Anaerobic wastewater prole for anode chamber  
of fabricated fuel cell in the present study  
Parametrs  
T
Scale  
22/81  
7/13  
1159  
2076  
1216  
505  
Unit  
oC  
pH  
----  
SV1  
mg L-1  
mg L-1  
mg L-1  
mg L-1  
mg L-1  
(MPN/100 mL)  
MLSS  
COD  
BODs  
DO  
0.6  
Total Coliform  
9000  
Anal. Method Environ. Chem. J. 4 (1) (2021) 26-35  
30  
(modied electrodes), platinum wire electrode, and  
silver/silver chloride electrode (as the working  
electrode) were used to electrochemically measure  
the made electrodes. Cyclic voltammetry (CV) and  
square wave voltammetry (Sqw) with scanning rate  
of 5mV•s1 in 50 mM phosphate buffered solution  
(PBS) (Palmsense 3, the Netherlands) were used  
to investigate the electrochemical behaviors of the  
electrodes.  
calibration curve was drawn. It was measured by  
placing the absorbance of the unknown sample in  
the residual COD calibration equation.  
3. Results and Discussion  
3.1. BET characterization  
By comparing the as, BET parameter as in Figure  
3 and the results in Table 2, in each of the four BET  
analysis curves of the nanocatalysts, the highest  
SSA was related to the catalyst functionalized with  
Fe metal (ZSM-5/Fe, which was determined to be  
408.41 m2 g-1).  
Spectrophotometric method was used to examine  
the treated wastewater. Initially, standard  
solutions with concentrations of 100-800 with 3  
ml of digestion solution (containing potassium  
dichromate, sulfuric acid and silver sulfate) and  
7 ml of stock solution (potassium hydrogen  
phethalate) are prepared and placed in an oven at  
150 ° C for 1.5 hours was placed. After cooling, it  
was placed in a spectrophotometer (600nm) and the  
3.2. X-Ray Diffraction (XRD) analysis  
The XRD spectrum for the ZSM-5 and the ZSM-5/  
Fe nanocatalyst was shown in Figure 4. The ZSM-  
5/Fe nanocatalyst conrms the presence of iron  
particles doped with silicate particles (Fig. 4).  
Fig.3. BET curves of prepared nanocatalysts  
Table 2. specic surface area of prepared nanocatalysts  
Row  
Nanocatalysts  
BET  
Unit  
1
2
ZSM-5  
ZSM-5/Fe  
374.66  
408.41  
m2 g-1  
m2 g-1  
Treatment of wastewater by G-Z/Fe electrode in MFCs  
Mostafa Hassani et al  
31  
Fig. 4. X-ray diffraction (XRD) analysis of nanocatalysts, ZSM-5 and ZSM-5/Fe.  
3.3. Energy dispersive X-ray spectroscopy (EDX)  
analysis  
presence of doped iron particles (in 1Kev area  
in the second curve). The presence of alumina  
and silicate peaks in both curves conrms that  
the surface of the electrodes has been covered by  
nanocatalysts.  
The curves of EDX analyzes for the surface of  
G-Z and G-Z/Fe electrodes compared as Figure  
5a and 5b. The EDX analyzes showed the  
a
b
Fig.5. Energy-dispersive X-ray spectroscopy (EDX) analysis  
of the surface modied electrodes (a) G-Z; (b) G-Z/Fe