Nghiên ứu thiết kế quá trình và thiết kế cơ sở hệ thống phản ứng xúc tác quang hóa xử lý nước thải dệt nhuộm =

MINISTRY OF EDUCATION AND TRAINING
HANOI UNIVERSITY OF SCIENCE AND TECHNOLOGY
--------------------------------------VŨ VIỆT THẮNG

STUDY ON PROCESS DESIGN AND BASIC DESIGN
OF A PHOTOCATALYTIC REACTION SYSTEM
FOR TREATMENT OF TEXTILE WASTEWATER

CHEMICAL ENGINEERING

MASTER THESIS OF CHEMICAL ENGINEERING
…......................................

SUPERVISOR
DR. TA HONG DUC

Hanoi – 2019

Tai ngay!!! Ban co the xoa dong chu nay!!! 17051113887301000000


STATEMENT
I do hereby declare that all the data in this Master thesis is the results of
investigation carried out by me in the Leibniz-Institut für Katalyse, Rostock,
Germany, and that all direct and indirect sources are acknowledged as references.
Hanoi, March 27th, 2019

Vũ Việt Thắng

1

ACKNOWLEDGEMENTS
First of all, I would like to express my deepest appreciation to my supervisor, Dr. Ta
Hong Duc, for pursuing my Master study at School of Chemical Engineering, Hanoi
University of Science and Technology, granting me his endless patience, invaluable
guidance and consideration at all times.
I would also like to extend my sincere thanks to Dr. Norbert Steinfeldt, Ms. Pritzkow,
Mr. Michael Sebek and my helpful friend, Mr. Karl Friedrich Iffländer for all sharing
knowledges and research experiences when I was working on my topic at the LeibnizInstitut für Katalyse for six-month stay in Rostock, Germany.
I really appreciate Prof. Dr. Le Minh Thang, Dr. Dirk Hollmann and Dr. Esteban
Mejia as the DAAD – ROHAN SDG Schoolarship’s co-ordinator for their helpful
support and consideration so that I could have a precious opportunity to go study
abroad in Rostock and could complete my thesis.
Last but not least, I would like to thank my parents for their endless love, support,
and patience during all my stay abroad. I never thought that I could do it without you
all. Though I cannot list all the names in this section, I feel myself very lucky when I
have them, teachers, colleagues, and friends throughout my life.

2


CONTENTS
STATEMENT ............................................................................................................1
LIST OF ABBREVIATIONS AND SYMBOLS USED ........................................ I
LIST OF TABLES .................................................................................................. II
LIST OF FIGURES ............................................................................................... III
INTRODUCTION .....................................................................................................1
Chapter 1. LITERATURE REVIEW .....................................................................2
1.1 Textile operations ..............................................................................................3
1.1.1 Sizing and desizing .....................................................................................4

1.1.2 Bleaching....................................................................................................4
1.1.3 Mercerization .............................................................................................4
1.1.4 Dyeing and printing ...................................................................................5
1.1.5 Finishing ....................................................................................................6
1.2 Classifications, properties and applications of textile dyes ..............................7
1.2.1 Azoic dyes ...................................................................................................9
1.2.2 Reactive dyes ............................................................................................10
1.2.3 Vat dyes ....................................................................................................11
1.2.4 Sulphur dyes .............................................................................................12
1.2.5 Acid dyes ..................................................................................................13
1.2.6 Disperse dyes ...........................................................................................14
1.2.7 Basic dyes .................................................................................................15
1.2.8 Direct dyes ...............................................................................................16
1.3. Carbon nitride material review ......................................................................16
1.3.1 Brief introduction of g-C3N4 ....................................................................18
3


1.3.2 Electronic structure of g-C3N4 .................................................................20
1.3.3 Application of g-C3N4 ...............................................................................22
1.3.4 Methods to improve g-C3N4 photocatalytic efficiency .............................28
Chapter 2. Materials and Methods ........................................................................33
2.1 Materials ..........................................................................................................33
2.1.1 Chemicals .................................................................................................33
2.1.2 Catalyst synthesis .....................................................................................33
2.2 Photoreaction apparatus and procedure ..........................................................34
2.3 Analytical Methods .........................................................................................35
2.3.1 X-ray Diffraction Analysis .......................................................................35
2.3.2 Attenuated total reflectance - Infrared spectroscopy ...............................35
2.3.3 Brunauer–Emmett–Teller method ............................................................35

2.3.4 Scanning transmission electron microscopy ............................................35
2.3.5 UV/Vis spectra .........................................................................................36
Chapter 3. Results and Discussion.........................................................................37
3.1 Characterization of materials .........................................................................37
3.1.1 The XRD results .......................................................................................37
3.1.2. The SEM/TEM images ............................................................................38
3.1.3 The BET method .......................................................................................41
3.1.4 The UV/Vis spectra materials ..................................................................42
3.1.5 The ATR – IR of catalysts .........................................................................43
3.1.6 The XPS analytic results ..........................................................................45
3.2 The photocatalytic activities of materials .......................................................48
Conclusions and outlook .........................................................................................53
4


1. Conclusions .......................................................................................................53
2. Outlook ..............................................................................................................54
REFERENCES ........................................................................................................55

5


LIST OF ABBREVIATIONS AND SYMBOLS USED
ATR

Attenuated total reflectance

BET

Brunauer–Emmett–Teller method

ESR

Electron spin resonance

IR

Infrared spectroscopy

MO

Methyl Orange

PL

Photoluminescence spectra

SEM

Scanning electron microscope

TEM

Transmission electron microscopy

XRD

X-ray Diffraction

UV

Ultra violet

VIS

Visible

XPS

X-ray photoelectron spectroscopy

Fe – gC3N4

Carbon nitride material doping Iron

gC3N4 – O
Fe – gC3N4 – O

Carbon nitride material oxidizing with Hydrogen
peroxide
Carbon nitride material doping with Iron and
oxidizing with Hydrogen peroxide

I


LIST OF TABLES
Table 1.1. Classification and examples of dyes according to the chromophore present
[19] ..............................................................................................................................7
Table 1.2. Catalytic activity of mpg-C3N4 in the Friedel–Crafts acylation of benzene

[47] ............................................................................................................................23
Table 3.1 Summary of general characteristics of the different g-C3N4 samples .....42
Table 3.2 Near surface composition of the different catalysts determined by XPS .46

II


LIST OF FIGURES
Figure 1.1. A flow diagram for steps involved in wet processing of fabric ...............3
Figure 1.2. Dyes for different fibers ...........................................................................5
Figure 1.3. The component of major pollutants involved at various stages of a textile
manufacturing industry ...............................................................................................6
Figure 1.4. Example of azo dye ................................................................................10
Figure 1.5. Example of reactive dye (C. I. Reactive Red 198) .................................11
Figure 1.6. Chemical structure of vat dyes ...............................................................12
Figure 1.7. Two sulfur dyes very used ......................................................................13
Figure 1.8. C. I. Acid Blue 25 ...................................................................................14
Figure 1.9. Chemical structure of C. I. Disperse Red 8 ............................................15
Figure 1.10. Basis Blue 22 ........................................................................................15
Figure 1.11. C. I. Direct Red 2 ..................................................................................16
Figure 1.12. The schematic diagram of the s-heptazine unit and s-triazine unit
structure [45] .............................................................................................................19
Figure 1.13. TG-DSC thermograms for heating the melamine [55] .........................20
Figure 1.14. Postulated condensation of melamine 1a [79]......................................20
Figure 1.15. Electronic structure of polymeric melon. (a) Density-functional-theory
band structure for polymeric melon; (b) the Kohn–Sham orbitals for the valence band
of polymeric melon; (c) the corresponding conduction band [44]. ..........................22
Figure 1.16. (a) Stacked g-C3N4 sheets function as an all-organic solidstatephotocatalyst promoting redox reactions with visible light; (b) chemical
interaction of benzene and defective g-C3N4 via HOMO–LUMO hybridization of
melem and benzene [99] ...........................................................................................24

Figure 1.17. (a) Electron transfer reactions with mpg-C3N4; (b) kinetic isotope effect
[108] ..........................................................................................................................25
Figure 1.18. Schematic representation of the oxidation mechanism [111]...............26
Figure 1.19. Proposed pathway for the photocatalytic H2 production by.
[M(TEOA)2]2+/gC3N4 systems [117] ......................................................................27
III


Figure 1.20. Comparison of the XRD spectra of g-C3N4 with those of Fe/g-C 3N4
hybrids with varying Fe contents. .............................................................................30
Figure 1.21. (a, b) Typical TEM images of CNS–CN; (c) high-resolution XPS spectra
of S2p recorded from CN, CNS–CN and CNS; (d) room temperature EPR spectra of
CNS–CN. Arrow direction in (d): CN, CNS–CN-1, CNS–CN-2, CNS–CN-3, CNS–
CN-4; (e) schematic illustration of organic heterojunction formed between CN and
CNS. D = donor [136]. ..............................................................................................31
Figure 2.1. The photocatalytic testing system...........................................................34
Figure 3.1. XRD pattern of the prepared g-C3N4 – samples which differ in
composition and/or post-treatment (* - Fe3 O4 phase) ...............................................37
Figure 3.2. SEM images of the prepared g-C 3N4 – materials: g-C3N4 (a,b); g-C3N4 –
O (c,d); Fe – g-C3N4 (e,h) and Fe – g-C3N4 – O (g,h)………………………………39
Figure 3.3. HAADF_STEM images of g-C3N4 - O (a,b) and Fe – g C 3N4 – O (c,d)
with different magnification………………………………………………………..40
Figure 3.4. a) N2 adsorption-desorption isotherms for the different samples and b)
BJH pore size-distribution………………………………………………………….41
Figure 3.5. a) UV-Vis spectra and b) Tauc plots from the spectra of the all g-C3N4 –
samples……………………………………………………………………………..43
Figure 3.6. ATR-IR spectra of the different g-C 3N4 – samples…………………….44
Figure 3.7. XPS spectra (C1s, N1s, O1s and Fe2p) of different catalysts: pure g-C3N4,
g-C3N4-O, Fe-gC3N4, and Fe-gC3N4-O……………………………………………..45
Figure 3.8. ESR spectra of A) g-C3N4 and g-C3N4-O and B) Fe-g-C 3N4 and Fe-gC3N4O (10 mg, 298 K)…………………………………………………………………..47

Figure 3.9. The UV-Vis spectra of MO degradation process: (a) no catalyst; (b) gC3N4; (c) Fe – g-C 3N4; (d) g-C 3N4 – O; (e) Fe – g-C3N4 – O and (f) the HPLC
determination………………………………………………………………………50
Figure 3.10. The PL spectra of g-C3N4 based materials……………………………51

IV


INTRODUCTION
Nowadays, water pollution is becoming more severe. One of the reasons
comes from organic wastes and residues in industrial textile wastewater, which
contains approximately 1 – 20% of the total world production of dyes compound. In
fact, from textile plants, the effluent streams have to be treated to eliminate the
poisonous dye residues. Furthermore, an effective dye wastewater decolorization is
usually required due to most government regulations. For dyes compound
degradation, an outstanding trend in recent years is using Advanced Oxidation
Processes method (AOPs), as developing photocatalysts which can degrade organic
pollutant well under light energy (Ultra violet or Visible light). It opens many
directions of selecting and modification semi-conductors materials as photocatalysts.
Graphitic carbon nitride (g-C3N4), a fascinating polymeric organic
semiconductor, is attracting worldwide attention. g-C3N 4 possesses appropriate band
positions, a band gap of 2.70 eV, high thermal stability, excellent chemical stability,
and special optical features, which make it a promising metalfree photocatalyst for
organic pollution degradation or water reduction under visible light irradiation.
However, the photocatalytic efficiency of pure g-C3N4 is far from satisfaction due to
not only the large optical band gap with limited utilization of solar energy ( λ ˂ 460
nm) but also the high recombination rate of photogenerated electron–hole pairs.
From the reason above, the topic of this thesis was selected as “Study on
process design and basic design of a photocatalytic reaction system for treatment
of textile wastewater”, working on study and investigating the influence of iron
doping and oxidation by using hydrogen peroxide on the graphitic carbon nitride

based materials for organic dye compound degradation process.

1


Chapter 1. LITERATURE REVIEW
Industrialization

plays

an

important

role

in

the

development

of

any country. Textile industry is a vital and quickly emerging industrial segment in
India. The textile industry uses different resources/raw materials such as cotton,
woolen and synthetic fibers. Cotton based textile industries are considered in this
study. The textile industries can also be classified into two groups viz dry and
wet fabric industry. Solid wastes are generated in dry fabric industry while liquid
wastes are generated in wet fabric industries. Processing operation such as desizing,

scouring, bleaching, mercerizing, dying, printing and finishing stages are included in
wet fabric processing industry. During fabric formation, the water utilization and
waste water generation from a wet processing textile industry depends upon the
operations.
The textile industry is a main creator of effluent wastewater due to a more
consumption of water for its different wet processing operations. These effluent
wastewater contains chemicals like acids, alkalis, dyes, hydrogen peroxide, starch,
surfactants dispersing agents and soaps of metals [1]. So, in terms of its
environmental impact, the textile industry is estimated to use more water than any
other industry, globally and almost all wastewater discharged is highly polluted.
Average sized textiles mills consume water about 200 L per kg of fabric processed
per day [2]. According to the World Bank estimation, textile dyeing and finishing
treatment given to a fabric generates around 17 to 20 percent of industrial waste water
[2].
In India, the textiles industry consumes around 80% of the total production of
1,30,000 tons of dyestuff, due to high demand for polyester and cotton, globally [3].
These dyes in wastewater severely affect photosynthetic function in plant. They also
have an impact on aquatic life due to low light penetration and oxygen consumption.
They may also be lethal to certain forms of marine life due to the occurrence of
component metals and chlorine. Suspended particles can choke fish gills and kill
2


them. They also decrease the capacity of algae to make food and oxygen. Dyes are
also detected to hinder with certain municipal wastewater treatment operations such
as ultraviolet decontamination etc. [4]. At present, aromatic and heterocyclic dyes are
used in textile industry. The complicated and stable structure of dye is posing a
greater difficulty in degradation when present not only in textile wastewater but also
in any kind of complex matrix [5]. The mineralization of dyes, organic compounds
and hence the toxicity of the wastewater generated by textile industry and dyes

manufacturing industry is a main challenge and an ecological concern. Hence,
understanding and emerging real textile wastewater treatment is ecologically
noteworthy.
1.1 Textile operations
Textile industries prepare fibers; transform fibers into yarn and alter the yarn
into fabric and then these fabrics goes through several stages of wet processing. Some
of the stages in wet processing of textile fabrics are revealed in Figure 1.1 [6] and are
discussed in detail in the subsequent sections.

Figure 1.1. A flow diagram for steps involved in wet processing of fabric

3


1.1.1 Sizing and desizing
Textile wet processes like dyeing and printing are affected by the existence of
sizing chemicals in the fabric. For instance, the occurrence of starch hampers the
diffusion of the dye molecule into the yarn/fabric, which needs the elimination of
starch preceding to dyeing and then printing. Enzymatic or dilute mineral acid
hydrolysis or oxidation is used to remove such a sizing chemicals. Such a hydrolysis
or oxidation processes convert starch into simple water soluble products [7]. Effluent
from desizing has a more biological oxygen demand (BOD) in the range of 300 – 450
ppm and pH of 4 – 5 [8] that renders it out of use. An oxidation by hydrogen peroxide
can be used for the degradation of starch into CO2 and H2O. Alternatively, the
problem of starch can also be eased by using enzymes that covert it into ethanol.
Distillation is used to recover this ethanol which can be used as a fuel, thus reducing
the ultimate biological oxygen demand (BOD) load on the treatment [9].
1.1.2 Bleaching
Natural color substance in the fabric is responsible for the creamy look to the
fabric. In order to get a white fabric which enables the production of bright shades, it

is essential to remove natural color matter from the fabric by the process of bleaching.
In earlier days, hypochlorite was being used as bleaching agents. Now days,
hypochlorite is exchanged by another bleaching agents such as H2O2 and peracetic
acid. Peracetic acid is an environmentally benign alternative to hypochlorite
bleaching agent. Higher luster along with less yarn destruction of the processed fabric
is the one major benefits of peracetic acid [10, 11].
1.1.3 Mercerization
Mercerization of cotton fabrics are carried out after bleaching to give a shine
and advance dye uptake. Basically, it is done by treating cotton fabric with a high
concentration (about 18 – 24% by weight) of sodium hydroxide. In this process,
cotton fabric goes through the longitudinal shrinkage during impregnation in the

4


NaOH solution. Here, this longitudinal shrinkage can be avoided by elongating the
fabric or holding the fabric under tension. The excess caustic is washed off after 1e3
min, while holding the cotton fabric under stress. Then, the material gains the
preferred properties of luster, easy dye uptake and improved absorbency. Membrane
techniques or multiple effect evaporators can be used to recover the sodium
hydroxide in the wash water [12, 13].
1.1.4 Dyeing and printing
Dyeing is the treatment of fabric or yarn with a dye to impart color.
Chromophore groups such as azo (─N═N─), carbonyl (─C═O), nitro (─N═O),
quinoid groups and auxochrome groups like amine, carboxyl, sulphonate and
hydroxyl in the dyes are responsible for the color [14]. Azo and anthraquinone are
the most important groups. These chromophores also cause contamination rendering
unacceptable color to the textile wastewater. Figure 1.2 depicts the main types of dyes
used for dyeing different kinds of fibers [14].

Figure 1.2. Dyes for different fibers
The important reactions involved in printing process are similar to those in
dyeing process. In case of dyeing, dye is applied in a solution form, while in printing;
dye is applied in a thick paste form of the dye to prevent its spread. Printing effluent
also contains waste components similar to dyeing effluent [15].

5


1.1.5 Finishing
Here, fabrics are exposed to a several types of finishing processes. Finishing
process is used to improve definite properties in the fabric. Specific properties like
softening, waterproofing, antibacterial and UV protective are imparted to fabric in
the process of finishing. The finishing processes also contribute to water pollution.
List of some water pollutants that may be produced at different stage of wet
processing is depicted in Figure 1.3 [16, 17, 18].

Figure 1.3. The component of major pollutants involved at various stages of a
textile manufacturing industry

6


1.2 Classifications, properties and applications of textile dyes
Textile dyes have been classified according to their chemical structural (Azo
dyes, Nitro dyes, Indigo dyes, Anthraquinone dyes, Phthalein dyes, Triphenyl methyl
dyes, Nitrated dyes, etc.) or their industrial application. Table 1.1 presents the
classification of textile dyes according to their chromophore.
Table 1.1. Classification and examples of dyes according to the chromophore
present [19]

Class

Chromophore

Azo dyes

─N═N─

Example

Acid Red 337

Nitro dyes
Disperse Yellow 14

Indigoid dyes
C. I. Vat Blue 35

7


Anthraquinone dyes

Reactive Blue 4

Phthalein dyes

Phenolphtaleine

Triphenyl methyl

dyes

Basic Violet 2

Nitroso dyes

─N═O
Fluorescent-labeled nitroso
compound
8


1.2.1 Azoic dyes
Nowadays, the world production of azo dyes is assessed to be about 1 million
tons. It is found in diverse forms and natures and more than 2,000 fundamentally
different azo dyes are presently in use. Azo bond linkage (─N═N─) may be present
more than once, mono azo dyes have one azo linkage. While, there are two linkages
in diazo dyes and three in triazodyes respectively.
According to Lucas et al., [20] and other [21] have been reported to Azo dyes
are the largest class of synthetic dyes. Approximately 70% of all the dyes used in
industry are azo dyes. They are widely used in textile, cosmetic, leather,
pharmaceutical, paper, paint and food industries.
Sabnis et al., [22] have been confirmed to, the azo dyes represent the greatest
production volume in dyestuff chemistry today, and their relative importance may
even grow in the future. The huge success of azo dyes is due to several factors: the
simplicity of the coupling reaction, the immense possibilities for structural variations
and adaption to the needs of the most diverse applications for these dyes, and the
often very high molar extinction of azo compounds.
According to same authors have been reported to, about 50,000 tons of textile
dyes are discharged in the environment annually from dyeing processes globally.

Chang, et al., [23] have been confirmed to, the azo dyes make up about one
half of all dyes synthesized and are predominantly used synthetic dyes in the textile,
food, paper, printing, leather and cosmetic industries. Azo dyes have diversity in
structure but their most important structural feature is presence of azo linkage i.e.,
N═N. This linkage may be present more than one time and thus mono azo dyes have
one azo linkage while two in diazo and three in triazo, respectively.
According to zollinger et al., [24] have been reported to, these azo groups are
connected on both sides with aromatics like benzene and naphthalene moiety.
9


Sometimes aromatic heterocyclic units are also present being connected with azo
groups.
According to Rajaguru et al., [25] have been reported to, the azo dyes
containing sulfonate groups as substituent are called as sulphonated azo dyes. Azo
groups in conjugation with aromatic substituents or enolizable groups make a
complex structure which lead to huge expression of variation of colors in dyes.
Example of azo dyes is shown in Figure 1.4 following.

Figure 1.4. Example of azo dye
1.2.2 Reactive dyes
They make it possible to obtain a high wet strength (better than the less
expensive direct dyes), but their use is not always possible because of difficulty in
obtaining good unison. The chlorine-fastness is slightly lower than that of the vat
dyes, as is the light fastness under extreme conditions.
Farouk et al., [26] and others have been reported to, the reactive dyes are the
only textile colourants designed to form covalent bond with the substrate during the
application process, reactive dyes furnish a wide gamut of shades of good light
fastness and excellent wash fastness on cotton. Such properties place this class of
dyes at the quality end of the market.

According to Gao et al., [27] and authors have been reported to, the reactive
dyes used for cellulose are reactive and an increasing amount is used on wool and
nylon.

10