MINISTRY OF EDUCATION
AND TRAINING

VIETNAM ACADEMY OF
SCIENCE AND TECHNOLOGY

GRADUATE UNIVERSITY OF SCIENCE AND TECHNOLOGY
----------------&---------------

NGUYEN THANH THAO

STUDY ON PHENOL TREATMENT IN COKING
WASTEWATER BY OZONATION PROCESS COMBINED
WITH CATALYST

Major: Environmental Engineering
Code: 9.52.03.20

SUMARY OF DOCTORAL THESIS OF
ENVIRONMENTAL ENGINEERING

Hanoi, 2019


The work was completed at Graduate University of Science and
Technology – Vietnam Academy of Science and Technology

Scientific Supervisor 1: PGS.TS. Trinh Van Tuyen
Scientific Supervisor 2: PGS.TS. Lê Truong Giang

1st Reviewer:…

nano composite as efficient catalyst for phenol removal in
ozonation process. Materials Research Express. Volume 5, Number
9, 095603, 2018.
5. Hoang Hai Linh, Nguyen Quang Trung, Nguyen Thanh Thao.
Removal phenol in coke wastewater by ozone combine with
modified laterit. Jounal of Analytical Sciences, ISSN 0868-3224,
(23), number 4/2018, pages 295-304.
6. Nguyen Thanh Thao, Trinh Van Tuyen, Nguyen Quang Trung.
Simultaneous determination of hydroquinone, catachol and
benzoquinone during phenol ozonation by high-perfomance
liquid chromatoghaphy. Jounal of Analytical Sciences, ISSN 08683224,
(21), number 3/2016, pages15-24.


7. Nguyen Thanh Thao, Trinh Van Tuyen, Le Truong Giang.
Study on the kinetics of phenol degradation in aqueous solution
by ozonation process at neutral media. Jounal of Analytical
Sciences, ISSN 0868-3224 (has been approved for publishment).
8. Thao Nguyen Thanh, Tuyen Trinh Van, Giang Le Truong,
Tuan Vu Anh. Study on Phenol treatment by Catalytic Ozonization
using Modified dolomite. Jounal of Analytical Sciences, ISSN
0868-3224 (has been approved for publishment).
9. Nguyen Thanh Thao, Trinh Van Tuyen, Le Truong Giang.
Study on degradation of phenol in aqueous solution by ozonation
combined with FeMgO/CNT. Jounal of Analytical Sciences, ISSN
0868-3224 (has been approved for publishment).


1
INTRODUCTION



2
are the first time to be evaluated for catalytic role for the removal
phenol in water by heterogeneous catalytic ozonation process.The thesis
with the title "Study on phenol treatment in coking wastewater by
ozonation process combined with catalyst” has been conducted to study
the treatment of coking wastewater containing toxic phenol compound
by ozonationprocess combined with heterogeneous catalysts, using
available catalyst materials produced in Vietnam with low cost and
environmentally friendly.
Objectives of thesis:
Study on phenol treatment in water by ozonation process
combined with catalysts. An empirical kinetic model and one quadratic
regression equations were built based on experimental data for
destroying phenol by heterogeneous catalytic ozonation process with
response variables (initial pH, ozone concentration, catalyst
concentration and reaction time). Application of phenol treatment in
coking wastewater.
Contents:
1. Overview of phenol pollution status in coking effluent, sources,
composition, toxicity and phenol treatment technologies in these kinds
of wastewater.
2. Study on phenol treatment in water by heterogeneous catalytic
ozonation process with two catalytic materials selected: FeMgO/CNT
and M-Dolomite. From studied results, select one best catalytic material
for further phenol treatment.
3. Develop the empirical kinetic model and quadratic regression
equations for decomposing phenol by O3/FeMgO/CNT process with
response variables (initial pH, ozone concentration, catalyst

2.3.1.2. Evaluation on the catalytic activity of materials
2.3.1.3. Study on phenol treatment in water by ozone and heterogeneous
catalytic ozonation processes
2.3.1.4. Development of an empirical kinetic model for treatment of
phenol by O3/FeMgO/CNT process
2.3.1.5. Development of a quadratic regression equations for treatment
of phenol by O3/FeMgO/CNT process


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2.3.1.6. Treatment of coke wastewater of Thai Nguyen Iron and Steel
Joint Stock Company by O3/FeMgO/CNT process
2.3.2. Field survey and sampling methods
2.3.3. Analysis methods
2.3.4. Data processing methods
2.3.4.1. Efficiency of pollutants removal
2.3.4.2.
Method of calculating pseudo first order reaction rate
constant
2.3.4.3. Method of developing an empirical kinetic model
2.3.4.4. Method of developing a quadratic regression equation
CHAPTER 3. RESULTS AND DISCUSSIONS
3.1. Characteristics of coking waste water
The analysis results of 16 samples of coking wastewater were
taken from Thai Nguyen Iron and Steel Joint Stock Company and Fomosa
Ha Tinh Steel Corporation show that this wastewater has a pungent odor
(smell of phenol) and many parameters with high concentration such as
color, COD, BOD5, CN-, phenols (phenol and total derivatives), phenol,
total nitrogen, NH4-N. Other parameters such as heavy metals, total grease,
total phosphorus, Cl-, S2-, residual chlorine are quite low. The pH of the

3.2.1. Evaluation of adsorption capacity of dissolved O3 on material
surfaces

Fig 3.1: Dissolved O3
concentration in solution with
and without catalyst

Fig 3.2: The effects of tert-butanol on the efficiency of
phenol decomposition with and without catalyst

The results show that the concentration of dissolved O 3 in the
solution with catalysts were always higher than without catalyst. When


6
there is no catalyst, the measured concentration are 2.8; 3.6; 3.2; 3 mg/L
at 5; 10; 15; 20 minutes, higher than 2.4; 3.2; 2.7; 2.5 mg/L in the
presence of M-Dolomite and 2; 2.8; 2.5; 2.2 mg/L with FeMgO/CNT
catalyst (Fig 3.1). That indirectly proves the selected materials have
catalytic activities. The dissolved O3 produced in the solution has been
adsorbed and decomposed on the surfaces of the material to form free
•

radicals OH. The analytical results of phenol adsorption capacity on the
surface of FeMgO/CNT and M-Dolomite catalyst in 60 minutes show
that phenol is not adsorbed on the surface of catalysts.
3.2.2. Evaluation of the role of free hydroxyl radicals contribute to
phenol treatment by heterogeneous catalytic ozonation process
The presence of tert-butanol in solution reduced the efficiency
of phenol decomposition in both cases with and without catalyst. Fig 3.2

show the catalytic activity of decomposing phenol by homogeneous
catalytic ozonation process. In contrast, mixtures of Ca, K, Mg metals in
M-Dolomite material composition at concentrations of 0.35; 1.19 and
26.4 mg/L represent catalytic activity. After 60 minutes of reaction,
phenol decomposition efficiency reached 64.8%, an increase of 8.8%
compared to the efficiency achieved by O3 process.
3.2.4. Evaluate the ability of adsorption of phenol on the surface of
the catalysts
Results of the investigation of phenol adsorption capacity on the
surface of FeMgO/CNT and M-Dolomite materials in 60 minutes
showed that phenol is almost unabsorbed on the surface of materials.
This proves that the adsorption process does not contribute to the phenol
decomposition efficiency for O3/FeMgO/CNT and O3/M-Dolomite
processes.
3.3. Study on phenol treatment in water by ozone and
heterogeneous catalytic ozonation processes
The removal efficiency of phenol, COD, TOC and apparent
reaction rate constant with (kcata) and without catalyst (k) tend to
increase with increasing pH solution. When there is no catalyst, k
increases 2.8 times when the pH of the solution increases from 3 to 11.
kcata increase gradually from 0.0122 - 0.0312 (1/min) in O3/M-Dolomite


8
process when increasing pH from 3-11 but increase from 0.022 to
0.0392 (1/min) with O3/FeMgO/CNT process.
The presence of FeMgO/CNT catalyst has accelerated the
decomposition rate of phenol with kcata fold 1.4 - 2.5 times higher than k
without catalyst when increasing pH from 3-11 but only fold 1.1- 1.4
times with M-Dolomite catalyst (Fig 3.8). The increasing k value when

reaction rate constants of phenol decomposition tend to increase with
increasing catalysts concentration. Figure 3.12 shows the removal
efficiency of phenol after 60 minutes with O 3/FeMgO/CNT process with
increasing catalyst concentrations: 0; 0.5; 1; 2; 3; 3.5 g/L corresponds to 56;
72.1; 78.1; 79.2; 86.3; 87.3%. The cause of increased removal efficiency of
phenol when increasing FeMgO/CNT catalyst concentration is due to: 1)
The surface area of catalysts increases with higher amount of catalyst,
increasing the amount of O3 molecules adsorbed on the surface. The
hydroxyl radicals •OH produced by the O3 self-decomposition reaction
increased [110, 112]. 2) The amount of CNT material participating in the
reaction is higher, leading to an increase in the amount of •OH producing
the reduction reaction (e) of O 3 on the CNT surface, increasing the solution
pH. Increased pH increases
•

OH produced by the O3 self-decomposition reaction increased. 3). The
number of ions Fe2+, Fe3+ and MgO in FeMgO/CNT material also
increase when the amount of catalyst increased. The chain of reactions
produced •OH is more due to the reaction of O 3 with the active
components of the catalyst. The amount of •OH in the solution
increases, increasing the efficiency of phenol decomposition. Phenol
decomposition efficiency reaches 56; 59.4; 63.7; 70.1; 80.3; 81% in the
O3/M-Dolomite process corresponds to a catalyst concentration of 0; 1;
2; 3; 4; 5 g/L. kcata fold 1.8 and 2.2 times corresponding to O 3/MDolomite process (4 g/L) and O3/FeMgO/CNT process (3.5 g/L)
compared with k obtained by ozone process.
COD removal efficiency after 60 minutes increased from 18 to
41.5%, corresponding to increasing the catalyst concentration from 0 to
3.5 g / L for O3/FeMgO/CNT process but only increased from 18 to
35% with O3/M-Dolomite process when increasing the catalyst
concentration from 0 - 5 g/L. Similar to COD, the efficiency of TOC

treating phenol by ozone process but the influence is not significantly
increased when the stirring speed increased from 200 to 300 rpm.

Fig 3.15: Influence of speed
stirring to removal efficiency of
phenol with and without catalyst

Fig 3.16: Influence of speed stirring to
apparent reaction rate constants of phenol
removal with and without catalyst


11
In the presence of FeMgO/CNT and M-Dolomite catalysts, the
efficiency of phenol decomposition increased from 64.2 to 86.3% and
60 - 80.3% respectively when increasing the stirring speed from 150 to
300 rpm.
Increased phenol decomposition efficiency when accelerating
the stirring process is due to the increased ability to diffuse O 3 from the
gas phase to the liquid phase increases and increases the collision
between the substances in the solution to increase the reaction rate.
Phenol decomposition effects [92, 94, 96]. However, the efficiency of
decomposing phenol only increases to a maximum value and does not
increase further because at this stirring speed the ability to diffuse O 3
from the gas phase to the maximum liquid phase, the concentration of
O3 dissolves in the solution saturated.
k increase from 0.01 to 0.015 (1/min) when increasing the
stirring speed from 150 - 300 rpm with O 3 process but increases from
0.016 to 0.026 (1/min) with O3/FeMgO/CNT process and 0,018 - 0,032
(1/min) with O3/M-Dolomite process. COD removal efficiency


Fig 3.20: Effect of solution
temperature on the apparent
reaction rate constant of phenol
removal with and without catalyst

Figure 3.20 shows the effect of temperature on k with and
without the catalyst. In O3 process, the value of k increased from 0.011
to 0.015 (1/min) corresponding to the temperature increase of 10 - 25 oC
but decreases to only 0.006 (1/min) at 35 oC and 0.005 (1/min) at 45 °C
after 60 minutes of reaction. The k cata value of O3/FeMgO/CNT process
is quite stable at all investigated temperature. In contrast, the O 3/MDolomite process depends on temperature. The k cata values decrease
from 0.03 (1/min) to 0.025 (1/min), correspondingly increasing the
solution temperature from 10°C to 45°C. The thesis selected phenol
solution at 25oC for further studies of phenol decomposition with O 3
and catalytic ozonation processes because this temperature is favorable
for temperature regulation during the study.
3.3.5. Effect of ozone concentration on phenol treatment efficiency


13
The O3 concentration is selected from 0,152 to 1,216 g/L. The
study results show the removal efficience of phenol, COD, TOC, and
apparent reaction rate constants tend to increase when increasing the
ozone concentration.

Fig 3.23: Effect of O3 concentration on
the removal efficiency of phenol after 60
minutes with and without catalyst


process and increase sharply from 0.0162 (1/min) to 0,1064 (1/min)
with O3/FeMgO/CNT process (Fig 24). kcata increased by 1.6 - 2.6 times
compared to k achieved in the presence of FeMgO/CNT catalyst but
only increase by 1.3 -1.9 times with M-Dolomite catalyst.
The removal efficiency of COD and TOC tends to increase
when O3 concentration increases. After 60 minutes, COD removal
efficiency by O3 process increased from 14.9 to 32.6% when increasing
O3 concentration from 0.152 g/L to 1.216 g/L. Efficiency of phenol
removal increased from 28.3 to 64.8% with O 3/FeMgO/CNT process
and 23 - 55.4% for O3/M-Dolomite process. The ability of TOC
mineralization is only from 7.8 to 15% in O 3 process when increasing
O3 concentration from 0.152 to 1,216 g/L but increased to 13.5 - 32.5%
and 18.4 - 39.5% corresponds to O3/M-Dolomite, O3/FeMgO/CNT
processes. The thesis selected 0.304 g/L O 3 as the concentration of O 3
applied for further studies in this thesis because at this concentration,
phenol decomposition rate occurs at a moderate speed, convenient for
sampling, calculating of kinetic constants with and without catalysts.
3.3.4. Effect of phenol concentration on phenol treatment efficiency
The study results show the removal efficiency of phenol,
COD, TOC and apparent reaction rate constants of phenol
decomposition tend to decrease when increasing the initial phenol
concentration. After 60 minutes of reaction at 0.1 g/L phenol
concentration, only 86.4% of phenol was decomposed by O 3 process but
increased to 100% after 25 minutes of reaction by O 3/FeMgO/CNT
process or 35 minutes by O 3/M-Dolomite process. The presence of
catalysts increases the removal efficiency of phenol at the same initial


15
phenol concentration. After 55 minutes, phenol is completely



16
3.3.5. Influence of NH4+, CN-, HCO3- on phenol treatment efficiency

NH4+, CN-, HCO3- are influencing factors selected because they
have a high concentration in coking wastewater and reacting with O 3 in
solution. NH4+ 0.5 g/L concentration; CN- 0.03 g/L; HCO3- 1 g/L are
chosen because these are the average values detected in 16 wastewater
samples in this thesis.
The results show that the presence of NH 4+ in solution does not
affect the efficiency of phenol decomposition in both cases with and
without catalyst at pH=7. This proves that O 3 competition between
phenol, NH4+ and intermediate products is produced in the reaction
process. However, it is possible that the concentration of O 3 in the
reactor is not high enough so that NH4+ has not been decomposed.
Studies have shown that NH4+ decomposition efficiency increases when
the solution pH increases and this process consumes high amounts of O 3
concentration.
The results of the influence investigation of 1 g/L HCO 3- in the
solution containing 0.4 g/L phenol show the presence of HCO 3- ions
without affecting the removal efficiency of phenol. The results reveal
that the competition for oxidation agents between phenol, HCO 3- as well
as byproducts in solution. Phenol concentration at the time of sampling
is similar to the initial phenol concentration.
Variation of CN- concentration after 60 minutes of reaction in
phenol solution with and without catalyst under conditions pH=7; O 3
0.304 g/L with the optimal concentration of catalyst determined. The
results show that O3 competition between phenol and CN- that reduced
the removal efficiency of phenol in solution (Table 3.3).

ozonation process.
3.4.Establishment of the empirical kinetic mode for phenol
treatment in water by O3/FeMgO/CNT process
3.4.1. Effect of catalytic concentration on apparent reaction rate
constants of phenol decomposition at pH 7
kcata reaches the values: 0,0109; 0.0175; 0.0210; 0.0490; 0.027;
0.0313 (1/min) corresponds to FeMgO/CNT concentrations: 0; 0.5; 1; 2;


18
3; 3.5 g/L. The relationship between the k cata reaction rate constant and
the FeMgO/CNT catalytic amount is shown in Figure 3.33 b.
The line y = 0.0158x + 0.0578 with tagα = 0.0158 and R 2 = 0.93.
We have: α3 = k2k5 = 0,0158 (L2/g2.min); α2_pH7 = 0,0578 (L/g.min).

Fig 3.33: Effect of catalytic concentration on kcata (a); The
relationship between α1 and the catalytic concentration (b) at pH=7

3.4.2. Effect of catalytic concentration on apparent reaction rate
constants of phenol decomposition at pH 5; 9; 11
Similar to pH = 7, the apparent rate constant for phenol
degradation when changing the catalyst concentration at pH = 5 tends to
increase when the FeMgO/CNT catalyst concentration increases. k cata
reaches 0.0109 values; 0.0175; 0.0210; 0.0490; 0.027; 0.0313 (1/min)
corresponds to FeMgO/CNT concentration: 0; 0,5; 1; 2; 3; 3.5 g/L
(Figure 3.34 b). The line: y = 0.0164 [cata] +0,0453 with R2 = 0.93.
We have: α2_pH5 = 0.0453 (L/min).

Fig 3.34: The relationship between α1
and catalytic concentration (b) at pH=5


[P]

= exp{−(0,0081[O3 ] + 0,0073[O3 ]× pH + 0,0158[cata][O3 ])}× t
[Po ]
The empirical kinetic mode shows that the process of

decomposing phenol in water with O3/FeMgO/CNT process depends on
pH, O3 concentration and catalyst concentration. Relative error between
experimental and predicted phenol concentration by empirical mode at
5.7%.


20
3.5. Establishment of the quadratic regression equation for phenol
treatment in water by O3/FeMgO/CNT process
The results of phenol concentration treated after conducting 31
experiments in the correct order and experimental conditions given by
Modde 12.1 software. The regression coefficient values for coded
variables of the polynomial function is shown in Table 3.11.
Table 3.1. Regresstion coefficients values (coded variables) of the
polynomial model of responses for phenol treatment
Coded
variables

Regression
coefficients

Variations


28,889

11

1,329

b

0,962

22

-2,296

33

16,204

1,663
11,735

44

8,204

5,941

12

0,813


-0,937

34

-6,937

0,508
3,763

3

.

b
b
b
b
b
b
b
b

Y

*
*

*


The result of calculating the F value for Ct-phenol is 3 (