MINISTRY OF
EDUCATION AND TRAINING

VIETNAM ACADEMY OF SCIENCE AND
TECHNOLOGY

GRADATE UNIVERSITY OF SCIENCE AND TECHNOLOGY

------------------

NGUYEN THANH TUAN

RESEARCH ON EFFECTIVE TREATMENT OF DDT BY
PHOTOCATALYTIC METHOD USING Fe-CuOx/GO;
SBA – 15 NANOCOMPOSITE MATERIALS

Major: Theoretical Chemistry and Physical Chemistry
Code : 62.44.01.19

SUMMARY OF DOCTOR THESIS

Hanoi - 2019


The thesis was completed at Institute of Chemistry, Vietnam
Academy of Science and Technology.
Supervisors:
1. Prof. PhD. Vu Anh Tuan

2. PhD. Trịnh Khac Sau


Convention, up to 8 types of POPs-pesticides include Aldrin,
chlordane, DDT, Dieldrin, Endrin, Hetachlor, Mirex and Toxaphene.
Then, at the sixth meeting (May 2013), the convention added a list of
POPs up to the total 28 of persistent organic pollutants.
In Vietnam, persistent organic pollutants such as Dioxin (due to
war consequences, the burning of hazardous wastes, PVC,...),
pesticides such as Chlordane, DDT, 2,4-D; 2,4,5-T as well as PCBs
(from waste oil in transformers) cause serious pollution affecting
human health, the environment and sustainable development.
To remove these pollutants in water environment, many methods
have been used such as: adsorption, biodegradation, chemical
decomposition, advanced oxidation ... In which the adsorption
method causes secondary pollution, biodegradation method requires
1


long time and low efficiency. Therefore, the advanced oxidation
processes

(AOPs)

improved

the

removal

efficiency

using

functional groups like hydroxyl, carbonyl, epoxi, carboxylic on the
surface, so it is easy to form covalent bonds, strong chemical bonds
with transition metal ions. Therefore, GO is an ideal carrier in the
synthesis of new composite nanomaterials. Meanwhile, SBA-15 is a
material with well-ordered hexagonal mesoporous silica structure
which has a very large surface area (600 - 1000m2/g). However, the
purely siliceous SBA-15 has a lack of functionality due to its
electrically neutral framework, it can be used as adsorbent but not as
acidic or redox catalysts. In order to use as catalysts, SBA-15 can be
modified by incorporation of transition metals into framework by
direct synthesis and post-synthesis. In this thesis, we focus on
2


studying how to incorporate of Fe and Cu atoms into GO and SBA15 frameworks by atomic implantation method to create new,
advanced and highly efficient nanocomposite catalysts for DDT
treatment. From the above arguments, we choose the thesis topic:
"Research on effective treatment of DDT by photocatalyst method
using Fe - CuOx /GO; SBA – 15 nanocomposite materials" to
research and evaluate the catalytic activity of these new catalytic
systems for DDT degradation.
* Objectives of the study
Focusing on studying how to incorporate of Fe and Cu atoms into
GO and SBA-15 frameworks by atomic implantation method to
create new, advanced and highly efficient nanocomposite catalysts
for DDT treatment.
* Main research contents of the thesis
- Synthesize some new and advanced nanocomposite materials
based on metalic oxide combination with GO and SBA-15 as highefficiency photocatalysts for toxic and persistent organic pollutants
treatment by various methods such as co-precipitation, hydrothermal

mentioned in this chapter includes the theoretical basis and
classification of the AOP, the theoretical basis of Fenton processes
(Fenton homogeneous process, Fenton heterogeneous process,
Fenton photo process). Chapter 1 also introduces some highly
effective nanocomposite catalysts based on graphene, GO and SBA15 in the treatment of persistent organic pollutants in water
environment. Overview of synthetic methods, research and
application of nanocomposite catalysts for advanced oxidation
4


processes to treat persistent organic substances in water environment
was introduced. Evaluation and analysis of the applicability of these
catalysts in environmental treatment: dye treatment; toxic organic
substances and DDT.
Chapter 2. Experimental
Chapter 2 is presented in 20 pages including:
2.1. Process of synthesizing materials
- Synthesis of Fe3O4, Fe3O4/GO nanocomposite materials by coprecipitation method.
- Synthesis of TiO2/GO and Fe-TiO2/GO nanocomposite materials by
hydrothermal method.
- Synthesis of Fe-Cu/SBA-15 and Fe-Cu/GO nanocomposite
materials by atomic implantation method. The equipment for
synthesis of Fe-Cu/GO nanocomposite by atomic implantation
method is illustrated in Figure 2.6.

Figure 2.6. Schematic illustrating the equipment for synthesis of
Cu/Fe/GO nanocomposite by atomic implantation method.
- Study on photocatalytic process in the decomposition reaction of
DDT by these synthesized catalysts.
- Analysis and evaluation of intermediate products formed in the

6


57.5 ° (018), 62.3 ° (214) and 64 ° (300) which fit the standard data
for the structure of Fe2O3.

Figure 3.3. XRD patterns of Fe3O4
và Fe3O4/GO nanocomposite
material

Figure 3.5. XRD patterns of GO,
Fe/GO và Fe-Cu/GO
nanocomposite material

Figure 3.6. Small-angle X-ray scattering patterns (a) and wide-angle X-ray
scattering patterns (b) of SBA-15, 5Fe-2Cu/SBA-15, 10Fe-2Cu/SBA-15 and
15Fe-2Cu/SBA-15 samples.

In figure 3.6, small-angle X-ray scattering patterns showed
that all samples has three peaks, in which the peak intensity is
sharp and strong at 2  0.8o and two peaks are smaller at 2
1.5o và 2 1.7o that can be indexed as the (100), (110), and
(200) diffractions of 2D hexagonal p6mm symmetry of SBA15, respectively [20,28,32]. The peak intensity of these samples

7


was slightly changed according to the different Cu-Fe loading
amounts into SBA-15 framework.
3.1.2 Scanning electron microscopy (SEM) and Transmission

Figure 3.14. SEM and HR-TEM images of SBA-15(a); 5Fe-2Cu/SBA-15(b);
10Fe-2Cu/SBA-15(c) and 15Fe-2Cu/SBA-15(d).

9


3.1.3. Energy-dispersive X-ray spectroscopy (EDX)
EDX mapping images and EDX analysis for the elemental
composition (Figure 3.18 and 3.19) of nanocomposite Fe-Cu/GO
showed that Fe content accounted for 17.87% by weight and Cu
content only accounted for 1.84% by weight.

Figure 3.18. EDX mapping images and Figure 3.19. EDX analysis
for the elemental composition of nanocomposite Fe-Cu/GO
EDX analysis of Fe-Cu/SBA-15 nanocomposite materials with
different Fe/Cu ratios showed that when Fe, Cu with content

-CH2

Si-O-Si

Cu2O

4000

3500

3000

2500

2000

1500

1000

500

4000

-1
Wavenumber (cm )

Figure 3.23. FTIR spectra of
GO, Fe/GO and Cu-Fe/GO

1000

500

Wavenumber (cm-1)

Figure 3.24. FTIR spectra of
SBA-15, Fe-Cu/SBA-15 samples
with different Fe/Cu ratio

The FTIR spectra of SBA-15 and Fe-Cu/SBA-15 nanocomposite
materials in Figure 3.24 are shown the stretching vibrations of the
associated silanol groups (Si-OH) at 3,437 cm-1 and 1632 cm-1. The
vibration bands centered at 1080 cm-1; 815 cm-1; 459 cm-1 were
corresponded to Si-O-Si bending vibration of the silica frameworks
[48,49,136]. Observation of the FTIR spectra of Fe-Cu/SBA-15
nanocomposite samples revealed that the large peak at 660 cm-1 also
attributed to the presence of Fe2O3 and CuO bound into SBA-15
frameworks [128].

11


3.1.5. N2 adsorption–desorption isotherms (BET)
It can be seen from the nitrogen adsorption–desorption isotherms
in figure 3.28, the graphs displayed type IV (according to IUPAC
classification) which are featured of mesoporous structured materials.
Table 3.7 shows the structural parameters of the synthesized
materials based on GO samples. Table 3.11 shows the structural
parameters of Fe-Cu/SBA-15 nanocomposite materials with different

331

105

173

180

161

130

0.0015

0.005

0.003

0.004

0.0075

0.0034

12


Vpore
(cm3/g)


SBET

Smeso

Smicro

2

(m /g)

2

(m /g)

2

(m /g)

SBA-15

668

485

5Fe-2Cu/SBA-15

667

10Fe-2Cu/SBA-15
15Fe-2Cu/SBA-15


623

427

195

0.78

7.36

4.84

571

457

113

0.94

7.23

4.94

3

3.1.6. X-ray Photoelectron Spectroscopy (XPS)
As seen in Figure 3.31, XPS spectra showed that the occurrence
of peaks at binding energy of 931 eV; 943 eV and 951 eV ascribed to

on synthesized catalysts

Figure 3.36. Comparison of
photocatalytic activity of
synthesized catalysts

Figure 3.37. TOC measurements and
DDT removal efficiency of Cu-Fe/GO
and Fe-Cu/SBA-15 catalysts

Evaluation of photocatalytic activity of synthesized catalysts
includes: Fe3O4, Fe3O4/GO, Fe-TiO2/GO, Fe/GO, Fe-Cu/GO and FeCu/SBA-15. The DDT degradation process is carried out under the
same conditions: initial DDT concentration is 10 mg/L; The catalytic
concentration is 0,2 g/L; H2O2 concentration is 15 mg/L; pH = 5;
temperature T = 30oC and reaction time of 3 hours. The comparison
result of DDT removal efficiency is shown in Figure 3.36. The
catalysts reached the removal efficiency after 3 hours of reaction time
in the order of Fe3O4 < Fe-TiO2/GO < Fe-Cu/SBA-15 < Fe3O4/GO

 O2  H 

2
3
FeSurface
 H 2O2  Fesurface
 OH   OH 
2
3
FeSurface
 OH   Fesurface
 OH 

GO + hv→ GO (h+ + e-)

 Fe3+ →  Fe2+ + GO
GO(h+) +  Fe3+ →  Fe4+ + GO
Fe4+ + OH- →  Fe3+ + OH
GO(e-) +



OH + DDT → Intermediate decomposition products → CO2+H2O

16


Figure 3.45. Intermediate products of

Figure 3.46. DDT

degradation of DDT using Fe-

nanocomposite catalyst

Cu/GO nanocomposite catalyst

The investigation of the effect of pH, H2O2 dosage, catalyst dosage
and the initial DDT concentration on DDT photo-Fenton degradation
process using Fe-Cu/GO catalyst is shown on Figure 3.47, Figure
3.48, Figure 3.49 and Figure 3.50. To study the stability of Fe-Cu/GO
catalyst, we re-use Fe-Cu/GO catalyst after each reaction by recovery
using magnet, then filter and dry at 60oC for 12 hours. The amount of
catalyst was weighed and used for the next experiments. The catalytic
loss is negligible (
40

50

60

70

2 degree

Figure 3.51. DDT removal
efficiency on Fe-Cu/GO catalyst
after different reaction times

Figure 3.52. XRD patterns of
Fe-Cu/GO photocatalyst after 1st
and 4th reaction time

Figure 3.53. FE-SEM images of Fe-Cu/GO photocatalyst after 1st and 4th
reaction time

3.2.4. Effects of parameters on the degradation of DDT using FeCu/SBA-15 nanocomposite catalyst
The influencing factors such as pH, Fe/Cu ratio, H2O2 dosage,
catalyst dosage and the initial DDT concentration in DDT photoFenton degradation process using Fe-Cu/SBA-15 catalyst were
studied. Figure 3.54 shows that the 10Fe-Cu/SBA-15 catalyst has the
most efficient photocatalytic activity. DDT removal efficiency
increased from 2Cu/SBA-15 < 5Fe-2Cu/SBA-15 < 10Fe-2Cu/SBA15. Figure 3.55 shows that DDT removal efficiency increases from
67.8 to 92.3% when catalyst dosage increases from 10 mg/L - 40
mg/L with an initial concentration of DDT of 10 mg/L. However,
19


the degradation of DDT using 10Fe-

2Cu/SBA-15 nanocomposite catalyst

2Cu/SBA-15 nanocomposite catalyst

20


3.2.5. Comparison of photocatalytic activity of our synthesized
materials with other published catalysts
In our synthesized and investigated catalysts in the degradation of
DDT, Fe-Cu/GO nanocomposite catalyst is the highest photocatalytic
activity which achieves DDT removal efficiency upto 99.2% after 3 h
under illumination conditions. The best conditions were found to be:
initial DDT concentration is 10 mg/L; the catalyst dosage is 0.2 g/L;
H2O2 dosage is 15 mg/L; pH = 5; temperature T=30oC. The high
photocatalytic activity of the Fe-Cu/GO sample can be explained by
the formation of nanoparticles with very small particle size (5 - 10
nm), uniformly distributed on GO carrier which acts as the active
site. Therefore, they increase the formation of free radicals •OH
which is the main contribution of catalytic activity in Photo-Fenton
reaction. The Fe-Cu/GO catalyst (layer structure) has a higher
removal efficiency than Fe-Cu/SBA-15 catalyst (tube structure). It
can be explained that the diffusion of DDT to the surface of FeCu/GO catalyst is more favorable than that of Fe-Cu/SBA-15
catalyst. The comparison of photocatalytic activity of our synthesized
materials with other published catalysts is given in Table 3.13.
However, the results are hardly comparable because the conditions
for the catalytic reaction are not quite the same. The results of our

graphene oxide (GO) is highly effective. Among our synthesized
materials, Fe-Cu/GO reached the highest photocatalytic activity of
the DDT removal efficiency upto 99.2% after 3 h under
illumination conditions. The best conditions were found to be:
initial DDT concentration is 10 mg/L; the catalyst dosage is 0.2
22


g/L; H2O2 dosage is 15 mg/L; pH = 5; temperature T=30oC. The
rapid decomposition rate is due to the interaction between GO and
Fe3+ together with Cu2+, which has created active centers to
accelerate the decomposition process of DDT. The presence of Cu
plays a very important role in increasing the formation of free
radicals •OH in the Fenton reaction. Moreover, CuO itself is also
a highly active photocatalyst contributing to enhance the activity
of Fe-Cu/GO composite catalytic system.
3. In the synthetic catalytic systems, the Fe-Cu/GO catalyst (layer
structure) has a higher photocatalytic activity than Fe-Cu/SBA-15
catalyst (tube structure). It can be explained that the diffusion of
DDT to the surface of Fe-Cu/GO catalyst is more favorable than
that of Fe-Cu/SBA-15 catalyst.
4. Investigation of the influencing factors such as pH, H2O2 dosage,
catalyst dosage and the initial DDT concentration showed that pH
has little effect on DDT removal efficiency while H2O2 dosage
has a great influence. The catalyst concentration plays an
important role in DDT removal efficiency especially when the
initial DDT concentration is high.
5. The mechanism of decomposing DDT pesticides on Fe-Cu/GO
catalyst has been proposed through dechlorination, breaking the
carbon chains and followed by decyclization. Intermediate