Anal. Method Environ. Chem. J. 4 (1) (2021) 26-35

Research Article, Issue 1

Analytical Methods in Environmental Chemistry Journal

Journal home page: www.amecj.com/ir

AMECJ

Novel graphite rod electrode modiﬁed with iron-

functionalized nanozeolite for efﬁcient wastewater treatment

by microbial fuel cells

Mostafa Hassani^a, Mohsen Zeeb^a*, Amirhossein Monzavi^b, Zahra Khodadadi^aand Mohammad Reza Kalaee^c,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 efﬁcient 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 modiﬁed with iron-functionalized ZSM-

5 nanozeolite. The characterization of Iron doping in nanozeolite

structure and electrode surface modiﬁcation 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 efﬁciency. 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 efﬁciency and effectiveness. Thus, the efﬁciency of fuel

cell output current and residual chemical oxygen demand removal

with this electrode increased up to 21.8% and 36.9%, respectively.

The efﬁucient recovery for the modiﬁcation of the graphite electrode

surface was achieved due to increasing of the speciﬁc 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 efﬁciency 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

Email: zeeb.mohsen@gmail.com

https://doi.org/10.24200/amecj.v4.i01.133

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 ﬁnal

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, ﬂat 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 speciﬁc 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 efﬁciency 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 efﬁciency of

MFCs. Due to the large speciﬁc 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 speciﬁc surface area

and the active sites for oxygen uptake, so that the

maximum current output density produced was

15.16 mW m^-2and the COD removal efﬁciency

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 speciﬁc surface area is a very effective factor in

increasing the efﬁciency of MFCs.

In this study, the graphite rod as a high stability and

electrical conductivity was used for wastewater

treatment. So, the surface modiﬁcation of graphite

rod by zeolite nanocatalyst will increase the

speciﬁc surface area of the electrode. On the other

hand, the modiﬁcation of graphite rods with zeolite

nanocatalyst were compared to simple graphite

rod with the low price and poor efﬁciency [15,

16]. Metal nanoparticles can greatly inﬂuence the

oxygen reduction [17-22]. Hence, in this study the

graphite rod electrodes were modiﬁed with iron

particles (Fe) as a doping agent on ZSM-5 nano-

zeolite (G-Z/Fe/ ZSM-5) for increasing of MFC

efﬁciency 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.

Naﬁon117 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, ﬁrst 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 ﬁltered with a ﬁlter

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 ﬁlter 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 modiﬁcation of the graphite

electrode by each of the nanocatalysts.

2.4. Electrode Modiﬁcation

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 modiﬁcation 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^-1of potassium chloride, 3.32 g L^-1

of sodium di-hydrogen phosphate dihydrate, 5.13 g

L^-1of di-sodium hydrogen phosphate dihydrate, and

0.31 g L^-1of 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 Naﬁon 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 ﬁrst boiled

for an hour in 3% H₂O₂and then washed in 1 M

sulfuric acid for 1 hour. Oxygen gas was injected

into the cathode with a sparger at a ﬂow 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. Acidiﬁcation 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^-1of glucose, 3 g L^-1of yeast extract, 11 g

L^-1of peptone, 0.5 g L^-1of 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 proﬁle 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

(MPN/100 mL)

MLSS

COD

BODs

DO

0.6

Total Coliform

9000

Anal. Method Environ. Chem. J. 4 (1) (2021) 26-35

30

(modiﬁed 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•s⁻¹in 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 m²g^-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 conﬁrms the presence of iron

particles doped with silicate particles (Fig. 4).

Fig.3. BET curves of prepared nanocatalysts

Table 2. speciﬁc surface area of prepared nanocatalysts

Row

Nanocatalysts

BET

Unit

1

2

ZSM-5

ZSM-5/Fe

374.66

408.41

m²g^-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 conﬁrms 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 modiﬁed electrodes (a) G-Z; (b) G-Z/Fe

Anal. Method Environ. Chem. J. 4 (1) (2021) 26-35

32

of 5mV•s⁻¹in 50 mM phosphate-buffered saline

(PBS) at an ambient temperature and in the potential

range of 1 to 90 volts were compared. Comparing

the electrode peaks, the G-Z/Fe electrode peak has

the highest current (3500 μA cm^-2) relative to other

electrodes. The graphite electrode peak has the

lowest current (2000 μA cm^-2), which indicates that

the ZSM-5 nanocatalyst doped with iron caused to

increase the current of analysis.

3.4. Electrochemical characterization

Comparing the cyclic voltammetry (CV) cerves for

G, G-Z and G-Z/Fe was shown in Figure 6a, 6b

and 6c. The peak of the graphite electrode modiﬁed

with iron-doped nanocatalyst (ZSM-5/Fe), which

has a higher speciﬁc surface area, has the maximum

current compared to other electrodes. Due to Figure

7, the square wave (Sqw) voltammetric peaks of the

G, GZ-5 and GZ-5/Fe electrodes, with the scan rate

Fig. 6. Cyclic voltammetry (CV) analysis of electrodes prepared in 50 mM phosphate

buffered solution (PBS) in room temperature. (a)G, (b)G-Z, (c)G-Z/Fe

Treatment of wastewater by G-Z/Fe electrode in MFCs

Mostafa Hassani et al

33

Fig.7. Square wave voltammetry (Sqw) analysis of electrodes prepared

in 50 mM phosphate buffered solution (PBS) in room temperature.

According to Figure 7 and 8, the peak related to

the output current and removal of COD during 72-

hour fuel cell steering, it can be concluded that the

produced G-Z/Fe cathode electrode has a higher

output efﬁciency (21/8%) and COD removal

efﬁciency (36/9%) than G-Z electrode and simple

graphite. The electrochemical analyzes (CV and

Sqw) show higher efﬁciency of this electrode and

Figure 9 showed the chemical oxygen demand

(COD) for graphen, G-Z and G-Z/Fe electrods..

Fig.8. Cell current output per time for G, GZSM-5 and GZSM-5/Fe

Fig..9. The efﬁcient removal of COD for G,G-Z and G-Z/Fe electrods

Anal. Method Environ. Chem. J. 4 (1) (2021) 26-35

34

production, Sci. Total Energy Prod., 754

4. Conclusions

(2021) 142429.

Byprocedure, anewmicrobialfuelcellwasmadeby

graphite rod electrodes. The surface of the cathode

was modiﬁed by ZSM-5 and ZSM-5 functionalized

with iron nanocatalyst. All three electrodes (G,

G-ZSM and G-ZSM/Fe) were analyzed by square

wave and cyclic voltammetry. Both analyses

were introduced that the G-Z/Fe electrode had the

higher efﬁciency as compared to others (Fig. 6-7).

Experimental results of fuel cell steering was also

studied as the Figure 8 and 9 by the G, G-Z and G-Z/

Fe electrode, the results showed that the efﬁciency

of fuel cell output current (I) and residual chemical

oxygen demand (%COD) based on this electrode

increased up to 21.8% and 36.9%, respectively as

compared to other graphite electrode. The high

efﬁciency of G-ZSM/Fe nanocatalyst electrode is

due to high speciﬁc surface area and the presence

of iron particles with high electrical conductivity.

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