Synthesis of Fe₂O₃/TiO₂/graphene aerogel composite as an efficient Fenton-Photocatalyst for removal of methylene blue from aqueous solution

Cite this paper: Vietnam J. Chem., 2020, 58(5), 697-704 Article 
DOI: 10.1002/vjch.202000109 
697 Wiley Online Library © 2020 Vietnam Academy of Science and Technology, Hanoi & Wiley-VCH GmbH 
Synthesis of Fe2O3/TiO2/graphene aerogel composite as 
an efficient Fenton-photocatalyst for removal of methylene blue 
from aqueous solution 
Tran Hoang Tu1,3, Le Tan Tai1,3, Nguyen Tan Tien1, Le Minh Huong2,3, Doan Thi Yen Oanh4, 
Hoang Minh Nam1,2,3, Mai Thanh Phong2,3, Nguyen Huu Hieu1,2,3* 
1VNU-HCM Key Laboratory of Chemical Engineering and Petroleum Processing (CEPP Lab), Ho Chi Minh 
City University of Technology, 268 Ly Thuong Kiet Street, district 10, Ho Chi Minh City 70000, Viet Nam 
2Faculty of Chemical Engineering, Ho Chi Minh City University of Technology, 
268 Ly Thuong Kiet street, district 10, Ho Chi Minh City 70000, Viet Nam 
3Vietnam National University Ho Chi Minh City, 
6,Linh Trung ward, Thu Duc district, Ho Chi Minh City 70000, Viet Nam 
4Publishing House for Science and Technology, Vietnam Academy of Science and Technology, 
18 Hoang Quoc Viet, Cau Giay district, Hanoi 10000, Viet Nam 
Submitted July 6, 2020; Accepted September 4, 2020 
Abstract 
In the present study, the composites including Fe2O3/TiO2/graphene aerogel (Fe2O3/TiO2/GA) and TiO2/graphene 
aerogel (TiO2/GA), and graphene aerogel (GA) were synthesized by hydrothermal method. The as-prepared materials 
were characterized using X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, 
energy dispersive X-ray, Raman spectroscopy. The characterization results showed that the Fe2O3 and TiO2 particles 
were uniformly attached in GA structure, increasing number of active sites of materials and extending the light 
absorption range. The removal performance of Fe2O3/TiO2/GA is 97.38 % which is higher than of TiO2/GA and TiO2. 
The degradation data were well consisted with pseudo-first-order kinetic model. Accordingly, Fe2O3/TiO2/GA is 
potential to be used as an efficient photocatalysis for treatment of MB from water. 
Keywords. Fe2O3, TiO2, Graphene aerogel, nanocomposite, photocatalysis, methylene blue. 
1. INTRODUCTION 
Recently, water pollution is an increasing global 
problem. The industrialization in developing 
countries has led to a mass discharge of organic dyes 
into water. These agents are important source used 
in various industries comprising textile, 
pharmaceuticals, food, paper, and cosmetic. The 
molecular structure of organic dyes is highly 
stability, persistent for a long time, and resistant to 
biodegradation in aqueous solution.[1] Organic 
matter can cause oxygen depletion, 
immunosuppression, reproductive failure and acute 
poisoning in aquatic organisms. The presence of 
dyes has significant impact on the human health 
because even the smallest amount of these agents is 
toxic or even carcinogenic.[2] Consequently, the 
developing effective handling methods are urgently 
necessitated. To date, various techniques have been 
utilized to separate these organic dyes such as 
advanced oxidation processes (AOPs), 
photocatalysis, adsorption, membranes, and 
biological degradation.[3] 
AOPs have developed based on the performance 
of highly reactive and nonselective hydroxyl radicals 
(OH•), which have the oxidizing capability to 
remove non-biodegradable organic compounds in 
water. Among a variety of AOPs, Fenton process 
based the catalysis effect of Fe3+/Fe2+ with H2O2 
agents to generate the OH• radical, reacting with 
organic compounds to decompose into CO and H2O. 
However, the Fenton process has a few drawbacks: 
(i) low utilization efficiency of the generated active 
species, (ii) incomplete removal of dye pollutants, 
(iii) applicable at low pH (pH 2-4), (iv) difficult to 
separate and reuse catalysts.[4,5] 
To increase the efficiency of AOPs, the recent 
studies have pay attention to the development of 
Vietnam Journal of Chemistry Nguyen Huu Hieu et al. 
 © 2020 Vietnam Academy of Science and Technology, Hanoi & Wiley-VCH GmbH www.vjc.wiley-vch.de 698 
heterogeneous Fenton-like catalysts in removing 
organic pollutants from wastewater. Titanium oxide 
(TiO2) is the most common semiconductor 
photocatalyst used due to its potential benefits such 
as low cost, non-toxicity, and high stablity. The 
agglomeration of particles phenomenon and the 
recombination of photo generated electron-hole pairs 
decreased the degradation efficiency of TiO2. 
Additionally, the TiO2 has a large band gap (Eg = 3.2 
eV) which absorbed in the ultraviolet light region. 
To tackle the mentioned above, TiO2 has been doped 
and coupled with various materials such as Fe2O3, 
ZnO, WO3, etc. to extent the light absorption and 
improve the degradation activity of organic 
pollutant.[3] 
Hematite (α-Fe2O3), is an iron(III) oxide form, 
has attracted countless attention due to its diversity 
in characteristics including low cost, low toxicity, 
high stability, excellent optical properties, 
environmental friendly, narrow band gap (2.0-2.2 
eV), and oxidative nature.[3] The combination of 
TiO2 with Fe2O3 to form the heterostructure was 
considered as an effective way to lower the band gap 
energy level and improve the absorption light 
efficiency of the catalyst. Simultaneously, the 
attaching Fe2O3 and TiO2 particles to the substrate to 
increase surface area and promote removal 
efficiency. Graphene aerogel (GA), is a three-
dimensional (3D) graphene-based structure, contains 
many outstanding properties including low density, 
high porosity and surface area, low thermal 
conductivity, and high electric conductivity. The GA 
substrate enabes to create the small size 
nanoparticles and elevate the production of free 
radical and advancing the catalytic efficiency of 
material. Besides, GA substrate promotes the 
transfer of electrons to prevent the recombination 
rate of electrons-holes.[ ... erized by the crystalline 
defects and G-band is assigned to the sp2-hybridized 
carbon atoms in the carbon network. The intensity 
ratio of these peaks (ID/IG) reflected the degree of 
functional and disordered sites in graphene-based 
materials.[15] The ID/IG value of Fe2O3-TiO2/GA is 
1.25, which is higher comparing to that of TiO2/GA 
(ID/IG = 1.18) and GA (ID/IG = 1.14). The number of 
bonds between Fe2O3, TiO2 particles and GA were 
higher than GA, indicating the good incorporation of 
the particles with the GA.[16] 
(a) (b) 
Figure 5: (a) Raman spectra of GA, TiO2/GA, and Fe2O3-TiO2/GA; 
(b) UV-Vis spectra of TiO2/GA and Fe2O3-TiO2/GA 
Besides, the absorption bands of TiO2/GA and 
Fe2O3-TiO2/GA were shifted to the visible region, 
expanding to a longer wavelength than of TiO2 as 
shown in figure 5b. The band-gap energies of the 
composites were calculated from Kubelka-Munk 
equation were found to be 2.63 (TiO2/GA) and 2.08 
eV (Fe2O3-TiO2/GA) which are smaller than of TiO2 
(3.2 eV). The band gap of composites decreased 
which shows the formation of bonds between the 
particles and carbon network of GA.[17] This result 
confirmed the effect of GA on the distribution of 
particles increase number of nuclating sites, leading 
to the formation of smaller particles size and 
expensing in the efficiency of light absorption.[3] The 
presence of Fe2O3 acts as a co-sensitizer to enhance 
the number of photo-generated electrons and holes 
in the Fenton reaction.[18] The Fe2O3 and TiO2 
particles were successfully formed and evenly 
distributed on GA substrate to form Fe2O3-TiO2/GA, 
enhancing the absorption of light irradiation and 
improving the photo-activity for the removal of 
organic dyes.[17] 
3.2. Photocatalytic performance 
Figure 6 shows the Fenton-photocatalytic of TiO2, 
TiO2/GA, and Fe2O3-TiO2/GA at different 
irradiation times. It is clear that the residual 
concentration of MB in solution obviously decreases 
with enhancing the time. The removal efficiencies of 
TiO2/GA and Fe2O3-TiO2/GA are about 76.52 and 
97.38 %, respectively, which are higher than that of 
TiO2 (H = 55.69 %) after 60 min of UV-light 
irradiation. For the Fe2O3-TiO2/GA, the degradation 
rate rapidly accelerated within 10 min and the MB 
dye almost vanished after 40 min in the present of 
Fe2O3-TiO2/GA.
Vietnam Journal of Chemistry Nguyen Huu Hieu et al. 
 © 2020 Vietnam Academy of Science and Technology, Hanoi & Wiley-VCH GmbH www.vjc.wiley-vch.de 702 
Figure 6: Effect of irradiation time on the MB 
degradation performance of TiO2, TiO2/GA, and 
Fe2O3-TiO2/GA 
Figure 7: Pseudo-first-order kinetic plots 
of the MB degradation 
The pseudo-first-order model applied to 
examine the degradation kinetic of materials and the 
linear plots were presented in figure 7. The plots are 
in straight line with the negative slope value. The 
parameters of linear pilots are showed in table 3. 
The degradation process is highly suitable the 
pseudo-first-order model for high correlation 
coefficients (R2 > 0.90). The values of rate constant 
of photocatalytic samples are 0.0558, 0.0228, and 
0.0131 min-1 corresponding to the Fe2O3-TiO2/GA, 
TiO2/GA, and TiO2, respectively. The phenomenon 
could be ascribed to the synthesized composites with 
the distribution of particles in GA, preventing the 
agglomeration particles and increasing more number 
of active sites in the composite. The role of electron 
conduction in GA network promotes the migration 
efficiency of photo-generated electrons-hole pairs, 
thus the degradation activities of composites are 
higher than that of TiO2.[19] 
The removal performances of synthesized 
materials are compared with other materials from 
other studies which are presented in Table 4. The 
superior characteristics of Fe2O3-TiO2/GA indicated 
that the photo-generated electron-hole pairs 
separation between the band gap of Fe2O3 and TiO2, 
expanding the solar light absorption region of 
material. Under light irradiation, the electron placing 
in the valence band of TiO2 is stimulated and shifted 
to conduction band with ease, which leads to the fact 
that the interfacial electron hole is separated. The 
holes reacted with water molecules to generate O2−• 
radical. The photo-excited electron transferred to the 
conduction band of Fe2O3 is converted to Fe2+ from 
Fe3+ through the reduction reaction. Then, the 
Fe2+/Fe3+ pair reacted with H2O2 to produce the 
•OOH and via Fenton. The reactive oxidation 
radicals interacted and degraded MB dye.[6,7] 
Table 3: The parameters for pseudo-first-order 
degradation kinetic model 
Materials k (min-1) R2 
Fe2O3-TiO2/GA 0.0558 0.9608 
TiO2/GA 0.0228 0.9273 
TiO2 0.0131 0.9819 
On the other hand, GA substrate plays a crucial 
role in the photocatalytic degradation of Fe2O3-
TiO2/GA by cooperation effects between adsorption 
and Fenton reaction.[14] The interconnected network 
and functional groups of GA was favorable for the 
formation of electrostatic and π-π interactions with 
MB, leading to the enrichment of MB molecular in 
the composite. Thus, the MB concentration in the 
composite increased and the contact abilities of 
particles with MB adsorbed were also advanced, 
accelerating the Fenton oxidation reaction to 
degrade the pollutants. Besides, the evenly 
distribution of particles in GA provides the more 
active sites and generate photo-excited electron–hole 
pairs.[22] Moreover, GA transferred the charge 
carriers between TiO2 and Fe2O3 particles, reducing 
the electron-hole recombination, resulting in the 
prolong life time electron-hole pair and advancing 
the removal performance.[3] 
The reusability of Fe2O3-TiO2/GA was also 
tested to evaluate the heterogeneous Fenton catalysts 
as shown in figure 8. The degradation performance 
still remained over 80 % after 5 cycles. This result 
proved the catalysis has an excellent reusability in 
photodegradation activity. 
Vietnam Journal of Chemistry Synthesis of Fe2O3/TiO2/graphene 
© 2020 Vietnam Academy of Science and Technology, Hanoi & Wiley-VCH GmbH www.vjc.wiley-vch.de 703 
Table 4: The removal performance of graphene-based materials 
Materials Conditions Removal efficiency (%) References 
Fe2O3-TiO2/GA 20 mg of photocatalyst, 20 mL of MB 
(50 mg/L), 2 mL of H2O2, irradiation 
time of 60 min, 25 W UV lamp 
97.38 This work 
TiO2/GA 20 mg of photocatalyst, 20 mL of MB 
(50 mg/L), 2 mL of H2O2, irradiation 
time of 60 min, 25 W UV lamp 
76.52 This work 
TiO2 20 mg of photocatalyst, 20 mL of MB 
(50 mg/L), 2 mL of H2O2, irradiation 
time of 60 min, 25 W UV lamp 
55.69 This work 
α-Fe2O3/rGO 50 mg of photocatalyst, 100 mL of MB 
(10 mg/L), irradiation time of 90 min, 
100 W tungsten lamp 
97.00 [20] 
α-Fe2O3/GO 100 mg of photocatalyst, 400 mL of MB 
(40 mg/L), H2O2 (1.10 mM), irradiation 
time of 70 min, 100W high-pressure 
mercury lamp 
96.0 [21] 
ZnO-
Fe3O4/rGO 
20 mg of photocatalyst, 50 mL of MB 
(10 mg/L), 30 µM of H2O2, irradiation 
time of 150 min, 300 W UV Xe lamp 
97.0 [22] 
Figure 8: Stability of the Fe2O3-TiO2/GA composite 
in the removal of MB 
4. CONCLUSION 
In this work, the fabrication of Fe2O3-TiO2/GA 
composite succeeded in using hydrothermal method 
and applying to degradation MB from the aqueous 
solution. The as-synthesized composite has uniform 
distribution of Fe2O3 and TiO2 particles on GA with 
size ranges of 0.5-3.5 nm. XRD, FTIR, and Raman 
results indicated the good incorporation of the 
particles with the GA through electrostatic force. 
The removal performance of Fe2O3-TiO2/GA is 
higher than that of TiO2/GA and TiO2 with value of 
97.38 % under UV irradiation after 60 min. The 
combination of particles and GA helps to expand the 
region of light absorption and prevent electron-hole 
recombination, leading to the elevation of 
photocatalysis activity. The degradation data were 
well fitted to pseudo-first-order kinetic model. 
Accordingly, Fe2O3/TiO2/GA could be concerned as 
an efficient Fenton-photocatalysis for the 
degradation of dye from water. 
Conflict of interest. The authors declare that they 
have no competing interests. 
Acknowledgments. This research is funded by Ho 
Chi Minh City University of Technology, VNU-
HCM, under grant number T-PTN-2019-46. We 
acknowledge the support of time and facilities from 
Ho Chi Minh City University of Technology 
(HCMUT), VNU-HCM for this study. 
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Corresponding author: Nguyen Huu Hieu 
VNU-HCM Key Laboratory of Chemical Engineering 
and Petroleum Processing (CEPP Lab) 
Ho Chi Minh City University of Technology 
268, Ly Thuong Kiet street, district 10, Ho Chi Minh City 70000, Viet Nam 
E-mail: nhhieubk@hcmut.edu.vn.