Study on 2-diazo-4,6-dinitrophenol in waste water using UV-H2O2/TiO2

Chemistry & Environment 
N.V. Huong, L.Q. Minh, N.M. Khai, “Study on 2-Diazo-4,6-Dinitrophenol  UV-H2O2/TiO2.” 52 
STUDY ON 2-DIAZO-4,6-DINITROPHENOL IN WASTE WATER 
USING UV-H2O2/TiO2 
Nguyen Van Huong1*, Luu Quang Minh2, Nguyen Manh Khai
2
Abstract: This article focuses on researching the possibility of applying Nano 
TiO2 photocatalyst in an advanced UV-H2O2 oxidation process to decompose 2-
Diazo-4,6-dinitrophenol (DDNP) in wastewater of propellant and explosives 
production facilities. Effects of reaction time (0-120 minutes), pH, UV light, molar 
ratio of H2O2/TiO2, reaction temperature and initial DDNP concentration on DDNP 
treatment efficiency were evaluated. The results showed that at CoDDNP = 370.9 
mg/L, the molar ratio of H2O2/TiO2 = 20, pH = 3,  = 185 nm, 99.41% of DDNP 
was treated after 120 minutes of reaction. Temperature does not significantly affect 
DDNP processing speed and efficiency. 
Keywords: DDNP; UV- H2O2; Nano TiO2. 
1. INTRODUCTION 
2-Diazo-4,6-dinitrophenol (DDNP) has a molecular formula C6H2N4O5; 
Molecular weight: 210.104 g/mole, with nitro (-NO2) and diazo (-N=N) groups 
connect to benzene ring. DDNP exists in the form of yellow crystals but the 
technical product’s color can range from dark yellow, green to dark brown, its 
density is 1.63 g/cm3. DDNP is a poison, causes eye, skin or respiratory irritation, 
leading to headaches, dizziness, nausea, vomiting, diarrhea, and decreased vision. 
Long-term exposure to nitro compounds of aromatic hydrocarbons causes damage 
to the liver, kidneys, toxic hepatitis and kidney fat degradation [1]. 
Every year, explosive manufacturers produce a large amount of waste water 
contains DDNP. This type of waste usually contains elements that are highly toxic 
to the environment and difficult to decompose. Therefore, the detoxification 
technology for water sources contaminated with these compounds is an issue of 
interest to study. In order to treat DDNP in waste water, there are many research 
and application works. Methods have been studied and applied are advanced 
oxidation methods (fenton, UV fenton), electrochemical methods; ozonation 
method; method of using plants [2,3,4]. However, most of these technologies when 
applied are inconvenient and do not have high efficiency due to unstable operation 
or high processing costs. In order to treat DDNP in waste water, the technique of 
using photocatalyst oxidation process is widely applicable and highly effective, low 
cost and easy to implement [6]. 
The use of Nano TiO2 a catalyst in advanced oxidation processes to treat DDNP 
is one of the interested research directions. Moreover, TiO2 is a typical, non-toxic, 
non-polluting nano material, chemically stable and reusable, less affected by other 
inorganic salts. Especially, it opened a new prospect in the catalytic photochemical 
processes by taking advantage of the available infinite radiation source from the 
sun using UV-A radiation [4,5,7,8]. Photocatalytic oxidation is a newly developed 
technology. UV radiation is used as an energy source to stimulate the creation of 
photon-optical holes pairs. These two agents are very flexible, they can combine 
with H2O and O2 in the atmosphere to produce 
OH and O2
 free radicals. These 
Research 
Journal of 
free radicals react with other organic substances (RH) to form highly reactive 
organic bases, these products contin
result is forming of CO
this method produces strong oxidants, which is promising for the treatment of 
persistent pollutants.
H2
concentration of DDNP to the efficiency of treatment in waste water.
2.1
2.1.1
- Ana
- PH meter HI 2211, Hanna Instrument (USA).
- Heating Magnetic Stirrer 03403
- Quartz tubes, UV lamps, aerator.
- High performance liquid chromatography s
chain detector (DAD) manufactured by Agilent (USA), placed at the 
Environmental Technology Department, Institute for New Technology, Academy 
of Military Science and Technology.
2.1.2
- 
(Merck 
- H
- High purity Nano TiO
- Solvents: Acetonitrile, ethanol, methanol, n
analys
2.1.3 Experimental models
This study introduces the re
O2
. Experimental preparation
2-diazo
2O
/TiO
. Equipment
lytical balance PA214, Ohaus (USA), accuracy of ± 0,0002 g.
. Chemicals
2 with analytical purity, concentration of 30% (Merck 
Figure 1.
Military 
2
-
- Germany).
is (Merck 
 molar ratio, pH, temperature, wavelength of UV light, initial 
4,6-trinitrophenol
Science and
-
 Experimental device model of DDNP/UV
 Germany).
2
2
, H
 (Japan).
 Technology, Special Issue, No.
2O, N
2. BACKGROUND
(DDNP) in crystal form with analytical purity 
2 
search results on the effects of factors such as 
-15, Cole
ue to participate in secondary reactions. The 
molecules and NO
-Parmer Instrument Company (USA).
ystem (HPLC) HP Model 1100, using 
-
hexane have high purity for HPLC 
60
3
A, 
- radical [7,8,9]. Therefore, 
-
05 
-
H2
- 201
 Germany).
O2
9
/TiO
2
 system
. 
53
Chemistry & Environment 
N.V. Huong, L.Q. Minh, N.M. Khai, “Study on 2-Diazo-4,6-Dinitrophenol  UV-H2O2/TiO2.” 54 
The advanced oxidation reactions were conducted in the batch test model, 
shown in Figure 1. Reaction system consists of a glass bottle (2) with a capacity of 
1 liter, it can control temperature and monitor pH changes during reaction. The 
reaction solution container (2) is left open to saturate oxygen in the air. 15W UV 
lamps with wavelengths 185, 254 and 313 nm were protected by quartz tube and 
placed inside the reaction system. The experimental system was aerated by aerator 
(3) to enhance the oxidation processes. 
2.2. Sample preparation method 
Experiments to study the effect of H2O2/TiO2 ratio on the decomposition of 
DDNP in UV-H2O2/TiO2 systems were conducted at the same conditions C
o
DDNP = 
370.9 mg/L, pH= 3, CTiO2 = 8.75x10
-4M,  = 185 nm, change the ratio of 
H2O2/TiO2 by 5; 10; 15; 20. 
Experiments to study the effect of pH on the decomposition of DDNP in UV-
H2O2/TiO2 systems were conducted under the same conditions C
o
DDNP = 370.9 mg/L, 
CTiO2 = 8.75x10
-4M,  = 185 nm, H2O2/ TiO2 ratio = 20, change pH by 3; 7; 9. 
Experiments to study the effect of wavelength on the decomposition of DDNP 
in UV-H2O2/TiO2 systems were conducted at the same conditions C
o
DDNP = 370.9 
mg/L, pH = 3, CTiO2 = 8.75x10
-4M, H2O2/TiO2 ratio = 20, changing wavelength by 
185; 254; 313 nm. 
Experiments to study the effect of temperature on the decomposition of DDNP 
in UV-H2O2/ TiO2 systems were conducted at the same conditions C
o
DDNP = 370.9 
mg/L, pH = 3, CTiO2= 8.75x10
-4M,  = 185 nm, H2O2/TiO2 ratio = 20, changes the 
temperature by 30oC, 40oC and 50oC. 
Experiments to study the effect of the initial concentration on the decomposition of 
DDNP in UV-H2O2/TiO2 systems were conducted at the same condition pH = 3, = 
185 nm, CTiO2 = 8.75x10
-4 M, H2O2/ TiO2 ratio = 20, changing DDNP concentration 
with values of 222.5 mg/L; 370.9 mg/L; 450.8 mg/L; 550.5 mg/L; 722 mg/L. 
2.3. Research methods 
Determining the concentration of DDNP in the experiment using UV-Vis 
measurement method. The formulas for calculating the efficiency and reaction 
speed are as follows [1,5]: 
% =	
	

		100	(%); 
In which: H is the processing efficiency, Co and Ct are the concentration of 
DDNP at the initial time and reaction time t, mg/L. 
3. RESULTS AND DISCUSSION 
3.1. The effect of H2O2/TiO2 ratio on DDNP decomposition efficiency 
Research results of the effect of H2O2/TiO2 ratio on DDNP decomposition 
efficiency are presented in Figure 2. The results in Figure 2 show that when the 
TiO2 concentration is fixed, increasing H2O2 concentration from 4.375x10
-3M to 
17.5x10-3M (CH2O2/CTiO2 ratio = 20), the efficiency of DDNP decomposition 
Research 
Journal of Military Science and Technology, Special Issue, No.60A, 05 - 2019 55
process also increases. When increasing the concentration of H2O2 to 21.875x10
-
3M (the ratio of CH2O2/CTiO2 = 25), the treatment efficiency of DDNP changed 
insignificantly compared with the concentration of H2O2 = 17.5x10
-3M 
(CH2O2/CTiO2 = 20). 
Figure 2. Effect of H2O2/TiO2 ratio on DDNP decomposition efficiency in 
UV-H2O2/TiO2 system. 
From the above results, with the ratio of CH2O2/CTiO2 = 20 and 25, the efficiency 
and decomposition rate of DDNP after 60 minutes of reaction are the same and 
both higher among the others. 
The mechanism of DDNP reaction rate raises as H2O2 concentration increases 
can be explained as follows: When increasing the H2O2 (CH2O2/CTiO2 ratio 
increases), the number of free OH radicals are formed more. On the other hand, 
TiO2 under the effect of UV light also produces a significant amount of OH, 
contributing to improve the reaction efficiency. However, when the concentration 
of H2O2 is too high, the amount of residual H2O2 reacts with OH radicals reduces 
the reaction agents: 
H2O2 + 
OH HO2
 + H2O 
HO2 + OH H2O + O2 
The nature of the photocatalytic process is indirect photochemical process, TiO2 
catalyst receives UV radiation energy forming photogenic electrons and bio-optical 
holes. These two agents are very flexible, they can participate with water and air 
oxygen to produce hydroxyl free radicals •OH and O2
•: 
TiO2 e
- + h+ 
h+ + H2O 
•OH + H+ 
0
10
20
30
40
50
60
70
80
90
100
0 20 40 60 80 100 120
E
ff
ic
ie
n
cy
 (
%
) 
Time (minutes)
Effect of H2O2/TiO2 ratio 
H2O2/TiO2 ratio = 5
H2O2/TiO2 ratio = 10
H2O2/TiO2 ratio = 15
H2O2/TiO2 ratio = 20
H2O2/TiO2 ratio = 25
Chemistry & Environment 
N.V. Huong, L.Q. Minh, N.M. Khai, “Study on 2-Diazo-4,6-Dinitrophenol  UV-H2O2/TiO2.” 56 
h+ + OH- •OH + H+ 
H2O2 is also affected by photochemical process of UV radiation, producing 
•OH 
radicals: 
H2O2 2
•OH 
These free radicals react with other organic substances (RH) to form highly 
reactive organic bases, these products continue to participate in secondary 
reactions. The result is forming of CO2, H2O, N2 molecules and NO3
- radical [5]. 
From the results obtained, we see that at the ratio of CH2O2/CTiO2 = 20 and 25, 
the decomposition efficiency of DDNP is almost equivalent. If the ratio of 
CH2O2/CTiO2 = 25 is applied, even though the reaction efficiency is slightly higher in 
the early stages, the amount of H2O2 residual in the solution might reduce the 
reaction agents. Therefore, we choose the molar ratio of H2O2/TiO2 = 20 to be 
optimal for next experiments. 
3.2. The effect of pH on DDNP decomposition efficiency 
Research results of the effect of pH on DDNP decomposition efficiency are 
shown in Figure 3. 
Figure 3. Effect of pH on DDNP decomposition efficiency in UV-H2O2/TiO2 system. 
The results show that at the condition of pH = 3, the decomposition rate of 
DDNP is fast and the processing efficiency reaches 99.41% at 120 minutes with 
DDNP concentration = 370.9 mg/L. With pH = 2 and pH = 5, the reaction speed is 
slower, the reaction efficiency is 72.89% and 55.94% after 120 minutes, 
respectively. 
The increase of DDNP metabolism in acidic environment (pH = 3) can be 
explained as follows: O2 in water receive electrons from TiO2 surface to form O2
-, 
O2
- continue to reacts with one proton H+ and one electron creating H2O2. Then 
0.00
10.00
20.00
30.00
40.00
50.00
60.00
70.00
80.00
90.00
100.00
0 20 40 60 80 100 120
E
ff
ic
ie
n
cy
 (
%
) 
Time (minutes)
Effect of pH
pH = 3
pH = 2
pH = 5
Research 
Journal of Military Science and Technology, Special Issue, No.60A, 05 - 2019 57
H2O2 reduces one electron to produce free OH
 radical. These free OH radicals 
react with DDNP molecules to form highly reactive organic bases, these bases 
continue to participate in secondary reactions to form CO2, H2O, N2 molecules and 
NO3
- radical. At pH below 2, hydroxyl free radicals can be consumed by H+ ions 
themselves: 
H2O2 + H
+ → H3O2
+ 
OH. + H+ + e - → H2O 
At pH above 4, hydrogen peroxide is degraded quite quickly and this is the 
main reason for reducing the efficiency of the decomposition process. 
3.3. The effect of temperature on DDNP decomposition efficiency 
Research results of the effect of temperature on DDNP decomposition 
efficiency are shown in Figure 4. 
Figure 4. Effect of temperature on DDNP decomposition efficiency in 
UV-H2O2/TiO2 system. 
Although the thermal energy is not sufficient to activate TiO2 surface, most 
studies suggest that the increase in temperature promotes the recombination and 
adsorption of organic compounds to the surface of TiO2. Because of that, when the 
temperature increases, the decomposition process of DDNP is also more effective. 
Figure 4 shows that the decomposition efficiency of DDNP is maximum at the 
temperature of 50oC, when the temperature drops to 40oC and 30oC, the DDNP 
decomposition speed and efficiency decrease. However, the increase of 
temperature does not significantly affect DDNP decomposition efficiency. 
3.4. The effect of UV wavelength on DDNP decomposition efficiency 
Research results of the effect of UV wavelength on DDNP decomposition 
efficiency are presented in Figure 5. After 120 minutes, the decomposition 
efficiency of DDNP at  = 185 nm, 254 nm and 313 nm was 99.41%, 48.95% and 
47.35% respectively. From this result, we can conclude that the system reached its 
highest efficiency at wavelength  = 185 nm. It can be explained that the shorter 
Chemistry & Environment 
N.V. Huong, L.Q. Minh, N.M. Khai, “Study on 2-Diazo-4,6-Dinitrophenol  UV-H2O2/TiO2.” 58 
wavelengths produced more OH radicals, therefore increases the efficiency of the 
decomposition process. 
Figure 5. Effect of UV wavelength on DDNP decomposition efficiency in 
UV-H2O2/TiO2 system. 
3.5. The effect of initial DDNP concentration 
Research results of the effect of initial DDNP concentration on DDNP 
decomposition efficiency are shown in Figure 6. 
Figure 6. Effect of initial DDNP concentration on DDNP decomposition efficiency 
in UV-H2O2/TiO2 system. 
0
10
20
30
40
50
60
70
80
90
100
0 20 40 60 80 100 120
E
ff
ic
ie
n
cy
 (
%
) 
Time (minutes)
Effect of UV wavelength 
UV wavelength = 185 nm
UV wavelength = 254 nm
UV wavelength = 313 nm
0
10
20
30
40
50
60
70
80
90
100
0 20 40 60 80 100 120
E
ff
ic
ie
n
cy
 (
%
) 
Time (minutes)
Effect of initial DDNP concentration 
Co = 222.5 mg/L
Co = 370.9 mg/L
Co = 450.8 mg/L
Co = 550.5 mg/L
Co = 722.0 mg/L
Research 
Journal of Military Science and Technology, Special Issue, No.60A, 05 - 2019 59
Figure 6 shows that at an initial concentration of 222.5 mg/L, DDNP 
decomposes the most quickly and takes the least time. When the initial 
concentration increased, the efficiency and decomposition rate decreased. At 
CoDDNP = 722 mg/L, in the first 30 minutes, DDNP decomposition efficiency was 
55.47%, while 99.02% DDNP was decomposed (nearly doubled) with an initial 
concentration of 222.5 mg/L. 
With the fixed ratio of H2O2/TiO2, pH, wavelength and temperature, DDNP 
decomposition efficiency also depends on the initial concentration of DDNP in the 
waste water. 
4. CONCLUSION 
The effects of initial DDNP concentration, pH, H2O2/TiO2 ratio, UV light 
wavelength and temperature showed that the DDNP decomposition efficiency in 
UV-H2O2/Nano TiO2 system at concentration C
o
DDNP = 370.9 mg/L reaches 
99.41% with optimal condition of pH = 3, ratio of H2O2/TiO2 = 20, UV 
wavelength = 185 nm. Temperature does not have a considerable effect on 
performance and decomposition rate of DDNP in waste water. 
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DNT, 2,4,6-TNR bằng phương pháp điện hóa và ứng dụng trong xử lý nước 
thải công nghiệp. Luận án TS Hoá học, Trung tâm KHKT - CNQS. 
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Thiệp, Nguyễn Văn Hoàng (2010), Nghiên cứu khả năng sử dụng một số loại 
thực vật thủy sinh để xử lý nước thải nhiễm thuốc nổ Trinitrophenol (Axit 
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TÓM TẮT 
NGHIÊN CỨU XỬ LÝ 2-DIAZO-4,6-DINITROPHENOL (DDNP) TRONG 
NƯỚC BẰNG HỆ UV-H2O2/Nano TiO2 
Nghiên cứu này tập trung vào việc khảo sát khả năng ứng dụng chất xúc 
tác quang Nano TiO2 vào quá trình oxy hóa nâng cao UV- H2O2 để xử lý 2-
Diazo-4,6-dinitrophenol (DDNP) trong nước thải của các cơ sở sản xuất 
thuốc phóng, thuốc gợi nổ quốc phòng. Các ảnh hưởng bởi thời gian phản 
ứng (0-120 phút), pH, bước sóng đèn UV, tỉ lệ mol H2O2/TiO2, nhiệt độ, nồng 
độ chất ban đầu đến hiệu suất xử lý DDNP được đánh giá. Kết quả nghiên 
cứu cho thấy tại điều kiện CoDDNP = 370.9 mg/L, tỉ lệ mol H2O2/TiO2 = 20, 
pH = 3,  = 185 nm, 99.41% DDNP bị xử lý sau thời gian phản ứng 120 
phút. Nhiệt độ không làm ảnh hưởng tới hiệu suất xử lý DDNP. 
Từ khóa: DDNP; UV- H2O2; Nano TiO2. 
Received 25th March 2019 
Revised 26th April 2019 
Accepted 15th May 2019 
Author affiliations: 
1Institute for New Technology, Academy of Military Science and Technology; 
2VNU University of Science, Vietnam National University - Hanoi; 
*Corresponding author: vanhuongvg@gmail.com.