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The design and synthesis of graphene oxide at iron oxide (GOFexOy) for catalytic application

THAI NGUYEN UNIVERSITY
UNIVERSITY OF AGRICULTURE AND FORESTRY

XAYALACK LASY

THE DESIGN AND SYNTHESIS OF GRAPHENE OXIDE
AT IRON OXIDE (GO@FEXOY) FOR CATALYTIC APPLICATION

BACHELOR THESIS

Study Mode: Full-time
Major: Environmental science and management
Faculty: International Training and Developing center
Batch: 43 Advance Education Program

Thai Nguyen, October 2015


DOCUMENTATION PAGE WITH ABSTRACT
Thai Nguyen University of Agriculture and Forestry
Degree Program


Bachelor of Environment science and Management

Student name

Xayalack Lasy

Student ID

DTN1153110275

Thesis title

The design and synthesis of graphene oxide at iron
oxide (GO@FexOy) for catalytic application
Assoc. Prof. DR Tran Van Dien

Supervisors

Assoc. Prof. Yu-Fen Huang
PhD. Student. He Yue
PhD. Student. Celeste

Abstract:
The thesis describes the oxidation of methylene blue, a basic dye of thiazine series
using a Fenton reaction at normal laboratory temperature and at atmospheric
pressure and the advantages in use of magnetic nanoparticles (MNPs), graphene
oxide @iron oxide nanoparticles(GO@FexOy) in the reaction. Oxidation by Fenton
reactions is proven and economically feasible process for destruction of a variety of
hazardous pollutants in wastewater. MNPs were synthesis via a thermal
decomposition method and (GO@FexOy) via electrooxidation procedure. The
synthesis of MNPs and (GO@FexOy) was characterized by several techniques,
Ultraviolet–visible spectroscopy (UV-Vis), and Transmission Electron Microscopy
(TEM).
The concentrations of dye degradation were determined ectrophotometrically using
Plate Readers at 665 nm, the absorption maximum of the dye.
Keywords:
Fenton reaction, nanocomposite, magnetic
nanocomposites, Graphene oxide @ iron oxide
nanoparticles, absorption, methylene blue, H2O2.


Number of pages:

40 pages

Date of submission:
Supervisor’s signature

September 30, 2015


ACKNOWLEDGEMENT

First of all, we know that knowledge is just only can be proved by our works,
and internship is one of the best opportunity for student whose can do their first project
before they find their jobs to enroll in the future. Besides that, we are not only
improving ourselves by knowledge in company environment, institute or laboratory
but also making more friends whose are having many experiences in environment, and
it will help us in the near future. From my perspective, this internship is absolutely
needed, helpful and important.
Because of that, and be assigned by the International Training Center and also
the allowed of Department of Biomedical Engineering and Environmental Science
(National Tsing Hua University, Taiwan). To well done this thesis, I want to express
profound gratitude to Advanced Education Program, the school administrators, the
staffs in Department of Biomedical Engineering and Environmental Science, the staffs
of YF laboratory, and particularly my supervisor, Associate. Prof. DR Tran Van Dien
and Associate Professor Huang Yu Fen whose is always support me every single time
I got troubles. I would like to send both of supervisor a warmly thanks for the
supporting me, and for their sacrifice for education, as same as environmental issues in
Taiwan and Vietnam as all countries in the world.
Finally, I would like to say that I have tried my best to finish this thesis in the
best way, I guess. However, to be honest, I partly believe that my thesis still have
some problems because of the limitation of knowledge and reality experiences,
especially in our environmental circumstances these days. It is totally happy if I can
get feedbacks and comments from you, my teachers, Professor, and Supervisor, to
finish my thesis in a fantastic way, to get the best results.
Sincerely,
Thai Nguyen, October, 2015
Student

Xayalack Lasy


STATEMENT BY THE AUTHOR

I hereby declare that this submission is my own work from doing my
experimental research and to the best of my knowledge, it contains no material
previously published, nor material which to a substantial extent has been accepted for
the award of any other degree or diploma at any educational institution, except where
due acknowledgement is made in the thesis.


TABLE OF CONTENTS
CHAPTER I. INTRODUCTION .............................................................................1
1.1. Rationale...........................................................................................................1
1.2 Objectives. .........................................................................................................2
CHAPTER II. LITERATURE REVIEW .................................................................3
2.1 Nanotechnologies and Nanomaterial. .................................................................3
2.1.1 Nanotechnologies............................................................................................3
2.1.2 Nanomaterial. .................................................................................................4
2.1.3 Methods synthesis of nanomaterial. ................................................................6
2.1.4 Overview of research and application of nanomaterial and nanocomposite. ....8
2.1.5 Magnetic NPs and application of magnetic NPs in wastewater treatment. ..... 11
2.2 Fenton reaction in the degradation of methylene blue. ..................................... 13
2.3 The use of magnetic nanocomposites in catalytic degradation of methylene blue....... 14
2.4 The equipment used to determine the properties of gold nanoparticles and
methylene blue degradation. .................................................................................. 15
2.4.1 Ultraviolet–visible spectroscopy (UV-Vis).................................................... 15
2.4.2 Transmission Electron Microscopy (TEM). .................................................. 15
CHAPTER III. METHODOLOGY ........................................................................ 18
3.1 Preparation of magnetic nanoparticles and Graphene oxide@iron oxide .......... 18
3.1.1 Method synthesis Fe3O4 NPs. ........................................................................ 18
3.1.2 Method synthesis FeOx, GO@FexOy andGO-Au,FeOx. ................................ 19
3.2 Fenton reaction and the use of Magnetic NPs and Graphene oxide@
iron oxide NPs in in Fenton reaction for catalytic degradation of dye. ................... 21
3.2.1 Chemicals and equipment. ............................................................................ 21
3.2.2 Method preparation stock solution: ............................................................... 22
3.2.3 Procedure. ..................................................................................................... 25
CHAPTER IV. RESULTS AND DISCUSSIONS.................................................. 26
4.1 Characterizations. ............................................................................................ 26
4.1.1 Magnetic nanoparticles. ................................................................................ 26


4.2 Magnetic NPs and Graphene@iron oxide NPs apply in Fenton reaction
degradation of methylene blue. .............................................................................. 27
4.2.1 Standard Fenton-like reaction for degradation of methylene blue. ................. 27
4.2.2 Application of magnetic nanoparticles,graphene oxide @iron-oxide on
degradation of MB. ................................................................................................ 31
4.2.3 The use of MNC, GO-FeOx in degradation of dye. ....................................... 34
CHAPTER V. CONCLUSIONS AND RECOMMENDATION ............................ 36
5.1 Conclusions. .................................................................................................... 36
5.2 Recommendation. ............................................................................................ 36
REFERENCE ........................................................................................................ 37


LIST OF FIGURES

Figure 1.1 Diagram of principle synthesis of nanomaterial............................. 6
Figure 1.2 Ultraviolet–visible spectroscopy (UV-Vis).................................. 15
Figure 1.3 Schematic diagram of a TEM. Generally, TEM is divided into two
main parts: illumination and imaging. .......................................................... 17
Figure 1.4 Setup for synthesis MNC............................................................. 18
Figure 1.5 Setup usingsonicators method ..................................................... 19
Figure 1.6 Setup for extract Fe3O4 NPs by centrifuging. ............................. 19
Figure 1.7 Scheme for synthesis iron oxide, Graphen at iron
oxide and Graphen at gold,iron oxide nanoparticles ..................................... 20
Figure 1.8 Using plastic tubes to containing the solutions of MB
degradation on the magnetic stirrer .............................................................. 25
Figure 1.9 TEM images of Fe3O4 NPs in different scale bar:
(a) 50 nm; (b) 100 nm. ................................................................................. 26
Figure 2.0 dynamic light-scattering (DLS). .................................................. 27
Figure 2.1 UV–Vis spectra of 3.13×10-5 M methylene blue solution at 0 min
(control) with absorption maximum at 665 nm. ............................................ 27
Figure 2.2 Temporal UV–Vis spectra absorption showing
changes the concentration of methyleneblue during Fenton reaction: a)
at 0min; b) at 60min. .................................................................................... 28
Figure 2.3 Degradation of methylene blue by Fe (II) (pH 2-3) ..................... 28
Figure 2.4 Effect of [Fe2+] on degradation of MB at 60 minutes. .................. 29
Figure 2.5 Effect of [H2O2] on degradation of MB at 30 minutes. ................ 30
Figure 2.6 Effect of pH on degradation of MB ............................................. 30
Figure 2.7 Degradation of methylene blue by Fe (II); Fe (II) + Fe (III) and Fe
(III) at pH 2-3. .............................................................................................. 31
Figure 2.8 the degradation of MB by GO-FeOx 3h ...................................... 32
Figure 2.9 the degradation of MB by GO-Au,FeOx 5V ................................ 32


Figure 3.0 Detection of Concentration of GO-FeOx 3h
and GO-Au, FeOx 5V .................................................................................. 34
Figure 3.1 UV-vis absorption spectra of GO and GO-FeOx ......................... 35
Figure 3.2 recycle the degradation of GO-FeOx on MB ............................... 35


LIST OF TABLES

Table 1.1 Chemicals used in the experiment................................................. 21
Table 1.2 Preparation of Methylene blue stock solution ............................... 22
Table 1.3 Preparation of H2SO4 stock solution ............................................ 22
Table 1.4 Preparation of Fe2+ within H2SO4(0.1M)stock solution .............. 23
Table 1.5 Preparation of Fe2+ without H2SO4stock solution ....................... 23
Table 1.6 Preparation stock solution of Fe2+ ................................................. 24
Table 1.7 Preparation stock solution of H2O2 ............................................... 25
Table 1.8 detection concentration of GO-FeOx 3h and GO-Au,FeOx 5V. .... 33


LIST OF ABBREVIATIONS

AOP

oxidation processes

AFM

The atomic force microscope

Conc.

Concentration

(GO@FeOx)

Graphene oxide@iron oxide

MNC

Magnetic nanoclusters

MNPs

magnetic nanoparticles Concentration

MB

Methylene Blue

OH•

Radical

Ppb

Part per billion

Ppm

Part per million

RO

reverse osmosis

SAM

the scanning acoustic microscope

STM

Scanning Tunneling Microscope

TEM

Transmission Electron Microscopy

UV-Vis

Ultraviolet–visible spectroscopy


CHAPTER I
INTRODUCTION

1.1. Rationale
The Environment includes the natural resources and the artificial material
factors, and they have a close relationship with each other, surrounded by humans,
affecting to productive life, and the survival and the development of human and
natural course.
These days, with the advancement of science, engineering and technology, human
has made great achievements in various fields. As the increase of industrialization and
urbanization in many developed cities, the requirement of removal of small amounts of
toxic pollutants in the ppm or ppb level from industrial wastewater and contaminated
groundwater is increasingly becoming significant. Chemical industries, such as oil
refineries, petrochemical units, dye and dye intermediate manufacturing industries,
textile units, industries making paper, pharmaceuticals,cosmetics and synthetic
detergents, and tanneries are the typical industries that discharge toxic organic
compounds at low concentrations, thus making the water polluted (Kabita Dutta et. al.,
2001).
In this context, a new process for wastewater treatment in order to degrade or
removing these compounds in textile industryeffluents is an important issue. An
extensively studied is the use of advanced oxidation processes (AOP). These processes
are based on the formation of hydroxyl radicals, which are capable of oxidizing
contaminutesants to smaller and less polluting molecules or even minuteseralize them,
turning them into CO2, H2O, and inorganic ions from atoms. Fenton’s chemistry is
very well known and it is one of the high potential oxidation technologies because it
produces a highly reactive species [OH•].
Currently, there is a lot of wastewater from industries causes the problem of the
environmental management in the world in general and Vietnam in particular. We have
to design collection systems and processing, and it is not only necessary for residential
areas or factory area but also even the new place area planning to improve the urban
environment and sustainable development. nanotechnology is gradually changing

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people's lives. With its small nanometer size nanomaterials have very unique
characteristics than other bulk materials with less mechanical strength, strong catalytic
activity and the ability to absorb excess.
According to the research results from domestic and foreign authors about the
catalytic capacity of the magnetic nanocomposite preform good in Fenton reaction; the
aim in this study was about to using the magnetic nanocomposite and Fenton reaction
to demonstrate the degradation in water pollutants, a study: “THE DESIGN AND
SYNTHESIS OF GRAPHENE OXIDE AT IRON OXIDE (GO@ FexOy) FOR CATALYTIC
APPLICATION" was conducted.

1.2 Objectives
* Determine optimum concentration of Iron ion and Graphene oxide at Iron
oxide.
* Design and synthesis to use Physical materials and Chemical materials on
degradation of methylene blue.
* Determine optimum of H2O2 concentration on degradation of methylene blue
by magnetic nanocomposite for degradation of dye in textiles industry.
* Determine optimum of new chemical materials that suitable with researching
experiment on degradation of Methylene blue.
* Assess the efficiency of use magnetic nanocomposite in Fenton’s reaction to
orientate the application in wastewater treatment technology.

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CHAPTER II
LITERATURE REVIEW

2.1 Nanotechnologies and Nanomaterial
2.1.1 Nanotechnologies
Nanotechnology

(nanotech)

is

the

manipulation

of

matter

on

an atomic, molecular, and supramolecular scale. The earliest, widespread description
of nanotechnology (Drexler & Eric, 1986) referred to the particular technological goal
of precisely manipulating atoms and molecules for fabrication of macro scale products,
also now referred to as molecular nanotechnology. A more generalized description of
nanotechnology was subsequently established by the National Nanotechnology
Initiative, which defines nanotechnology as the manipulation of matter with at least
one dimension sized from 1 to 100 nanometers. This definition reflects the fact
that quantum mechanical effects are important at this quantum-realm scale, and so the
definition shifted from a particular technological goal to a research category inclusive
of all types of research and technologies that deal with the special properties of matter
that occur below the given size threshold. It is therefore common to see the plural form
"nanotechnologies" as well as "Nanoscale technologies" to refer to the broad range of
research and applications whose common trait is size. Because of the variety of
potential applications (including industrial and military), governments have invested
billions of dollars in nanotechnology research. Until 2012, through its National
Nanotechnology Initiative, the USA has invested 3.7 billion dollars; the European
Union has invested 1.2 billion and Japan 750 million dollars (Daily Star, 2012).
Nanotechnology as defined by size is naturally very broad, including
fields of science as diverse as

surface science, organic chemistry, molecular

biology, semiconductor physics, Microfabrication, etc. (Saini et. al, 2010). The
associated research and applications are equally diverse, ranging from extensions of
conventional device physics to completely new approaches based upon molecular selfassembly, from developing new materials with dimensions on the Nanoscale to direct
control of matter on the atomic scale.

3


As a whole nanotechnology are technology sectors relevant to the analysis,
design, fabrication and application of structures, devices and systems by controlling
shape, size on the nanometer scale.
According to National Nanotechnology Initiative-NNI of United State of
America, nanotechnology includes:
- Research and development technology at the nanoscale with diameter size
range from 1 nm to 100 nm.
- Generating and use the structures, devices and systems with new properties and
functions due to their very small size.

2.1.2 Nanomaterial
Nanomaterials are materials in which at least one-dimensional nano-meter size.
Regarding the states of the material is divided into three states: solid, liquid and gas.
Currently, nanomaterials are studied mainly in solid state.
About the shape material, it's splited into the following categories: threedimension with nanoscale (nanoparticles, nano clusters), two-dimension with
nanoscale (film), one-dimensional (thin wire). In addition, there are nanostructured
materials or nanocompozit in which only a portion of nanoscale materials or its nano
structures have no dimensional nanoscale.
Therefore the nonmaterial includes subfields which develop or study materials
having unique properties arising from their nanoscale dimensions (Narayan et. al,
2004).


Interface and colloid science has given rise to many materials which may be

useful in nanotechnology, such as carbon nanotubes and other fullerenes, and various
nanoparticles and nanorods. Nanomaterials with fast ion transport are related also to
nanoionics and nanoelectronics.


Nanoscale materials can also be used for bulk applications; most present

commercial applications of nanotechnology are of this flavor.


Progress has been made in using these materials for medical applications;

see Nanomedicine.

4




Nanoscale materials such as nanopillars are sometimes used in solar cells which

combats the cost of traditional Silicon solar cells.


Development of applications incorporating semiconductor nanoparticles to be

used in the next generation of products, such as display technology, lighting, solar
cells and biological imaging; see quantum dots.


Recent applicationof nanomaterials include a range of biomedical applications,

such as tissue engineering, drug delivery, andbiosensors (David et. al., 2015).
2.1.2.1 Characteristics and properties of nanomaterials
An extremely important characteristic of nanomaterials is that the diameter size
is only in nanoscale. Therefore, the total number of atoms on the surface distribution
of nanomaterials and the total surface area of the material is much greater than with
conventional materials. This has appeared in many feature nanomaterials anomalies,
especially the ability to absorb catalyst. With its small size at the molecular level,
nanomaterials appear three main effects: quantum effects, surface effects, effect size.
2.1.2.2 Nanocomposite
The term "nanocomposite" describes a group of composite materials, in which
enhanced phase only at nanometer dimensions. The presence of this enhanced phase
was to generate major improvements in the physical and mechanical properties of
nanocomposite materials (Kumar & Krishnamoorti, 2010).The nanocomposite either
combining the precious nature of nanomaterials anomalies or it has separate nature of
each of the constituents. In composite materials based on goals that people made use
of different materials. The presence of enhanced phase generates the products which
their properties of the components are not at the original. The nanocomposite is a
material with many applications in many fields. So studying on nano composite
materials is an important direction and being strongly developed. Enhanced phases in
the nanocomposite usually are nanoparticles, colloidal particles, nano membrane
fibers. Carriers in the nanocomposite material often are polymers, carbon fiber, the
salt, zeolite and silica, bentonite (Anh, 2007).
.

5


2.1.3 Methods synthesis of nanomaterial
Nanomaterials are made using two methods.
- Top-down method (top-down), the method of nanoparticles from particles of
larger size.
- Bottom-up method (bottom-up), methods formed nanoparticles from atoms.

Figure 1.1 Diagram of principle synthesis of nanomaterial
2.1.3.1 Top-down method
The principle of this method is crushing and deformation techniques for
processing materials with organizing mass of coarse grain size of nanoparticles. This
method is simple, inexpensive but very effective, can be carried out for a variety of
materials with relatively large size. In the method of crushing, material in powder form
mixed with balls made of very hard material and placed in a mortar. Crusher can be
crushed shaking, vibrating mill or mill spinning. The hard balls collide and break
down powders to nanoscale. The result is non-dimensional nanomaterials
(nanoparticles). Deformation method is used with a special technique to create
extremely large deformation without destroying the material (probably > 10 nm). The
temperature can be adjusted depending on each specific case. If the process
temperature is greater than the crystallization temperature is called the hot
deformation, while the opposite is called cold deformation. The result is a onedimensional nanomaterials (nanowires) or bidirectional (nm layer thickness).

6


However, the disadvantage of this method is that generate materials that are not
homogeneous high energy-consuming and complex equipment (Bönnemann et. al,
2004).
2.1.3.2 Bottom-up method
The principle of this method is the formation of nano materials from atoms or
ions. The method was developed from the bottom- up very strongly for flexibility and
quality of the final product. Most of the nanomaterials that we use today are made by
this method. The advantage of this method: convenience, the size of nanoparticles
generated relatively small, uniform, equipment and service for this method is very
simple. Bottom-up method can be physical methods, chemical or a combination of
both physico-chemical methods.
* Physical methods:The method of creating nanomaterials from atoms or
transition. Atoms to form nanomaterials are created from physical methods such as
thermal evaporation. Method transition: the material is heated and then allowed to cool
at a faster rate in order to obtain an amorphous state, heat treatment to occur
transformation of amorphous - crystalline (crystallized). Physical methods are often
used to create nanoparticles, nano film.
* Chemical methods: the method of creating nanomaterials from the ion.
Chemical methods are characterized by very diverse because, depending on the
specific material that they have technical changes made accordingly. However, we can
classify the chemical methods into two categories: nanomaterials formed from the
liquid phase (precipitation, sol-gel), and from the gas phase (pyrolysis). This method
can produce nanoparticles, nanowires, nanotubes, nano film, nano powder...
* Combined method: the method to create nanomaterials based on the principles
of physics and chemistry, such as electrolytic condensation from the gas phase ..this
method

can

produce

nanoparticles,

nanowires,

nanotubes,

nano

thin-film,

nanopowders.

7


2.1.3.3 Functional approaches
These seek to develop components of a desired functionality without regard to
how they might be assembled.
• Molecular

scale electronics seeks to develop molecules with useful electronic

properties. These could then be used as single-molecule components in a
nanoelectronic device (Gates et. al., 2007).
• Synthetic

chemical methods can also be used to create synthetic molecular

motors, such as in a so-called nanocar.
2.1.3.4 Biomimetic approaches


nature,

Bionics or biomimicry seeks to apply biological methods and systems found in
to

the

study

and

design

of

engineering

systems

and

modern

technology.Biomineralization is one example of the systems studied.


Bionanotechnology is

the

use

of biomolecules for

applications

in

nanotechnology, including use of viruses and lipid assemblies (Mashaghi et. al., 2013).
Nanocellulose is a potential bulk-scale application.

2.1.4 Overview of research and application of nanomaterial and nanocomposite
Nowadays, the research and applications of nanotechnology in the world are
interested in many countries. Some powers dominate the technology market currently
such as the US, Japan, Taiwan, China, Germany, Russia and some European countries
... In these countries, government devoted a significant budget support for the research
and practical applications of nano technology. Not only laboratories in the universities
with equipment-study scale but the production corporations also conduct research and
development of nanotechnology with laboratory with total cost studies equivalent the
government budget for nanotechnology.
In Vietnam as in some countries that located in Asia, tend to approaching with
nanotechnology in recent years has generated very charismatic movement on this field.
The government has spent a large budget for research programs nanotechnology
national level with the participation of many universities and research institutes in the
country, initially gained encouraging results. The reason that nanotechnology is
focused on developing due to magic applications that nanotechnology has been

8


achieved in the field of science and technology. The following is the application of
nanotechnology has the advantage.
2.1.4.1 Tool and Electronic Technology, Information Technology
There are several important modern developments. The atomic force
microscope (AFM) and the Scanning Tunneling Microscope (STM) are two early
versions of scanning probes that launched nanotechnology. There are other types of
scanning probe microscopy. Although conceptually similar to the scanning confocal
microscope developed

by Marvin

Minskyin

1961

and

the scanning

acoustic

microscope (SAM) developed by Calvin Quate and coworkers in the 1970s, newer
scanning probe microscopes have much higher resolution, since they are not limited by
the wavelength of sound or light.
The tip of a scanning probe can also be used to manipulate nanostructures (a process
called positional assembly). Feature-oriented scanning methodology may be a
promising way to implement these Nano manipulations in automatic mode (Lapshin,
2004). However, this is still a slow process because of low scanning velocity of the
microscope.
In the information technology needs to use large memory capacity increasing.
Scientists have researched and generated computer chips with quantum dots called
nano chip with very high integration level, allowing increased memory capacity of the
computer. Nanotechnology can also be applied in the fabrication of optoelectronic
components in the liquid crystal display, laser transmitters, sensors... with the
precision of a few nanometers (Komatsu & Ogasawara, 2015).
* Biomedical
- Separation and selective cell: Based on the characteristic superparamagnetic of
magnetite nanoparticles, researchers have used it to conduct cell separation. The
process is split into two phases: biological marker that really need to study through the
magnetic nanoparticles. Then separating the entities marked out by an external
magnetic field environment.
- Drug delivery: When entering the body, drug is often scattered and unfocused
affect healthy cells, producing side effects. Therefore scientist use magnetic particles

9


as drug carriers to the desired location on the body (tumors, cancer ...) by an external
magnetic field.
- Local hyperthermia: This method is used in cancer treatment. The magnetic
nanoparticles are dispersed in the diseased tissue, then use an external alternating
magnetic field of sufficient intensity and frequency is applied to the ferromagnetic
nanoparticles, the nanoparticles do respond and make the local thermal heating cancer
cells (about 42°C). At this local temperature can kill the cancer cells (Cu & Chanh,
2004).
* New energy
With nanotechnology, it is possible to generate new battery capable of artificial
photosynthesis, helping human to produce clean energy, or generate these devices
consume less energy by using these materials soft material. The film nano (with low
production costs) promising absorb more solar energy than current photovoltaic
materials. This is the start of a revolution in the use of solar energy.
2.1.4.2 Environmental treatment technology
Environmental treatment material is being concerned, especially materials used
for water purification technology. The filter was created by nanotechnology with the
filter diameter hole just like nano film for reverse osmosis (RO), microfiltration
membrane... can filter bacteria and viruses in water and separated on 99.8% of all
types of water-soluble substances (Tam, 2014).
Recently, Japanese scientists have discovered a bacteria eating substancessuspended in water and the magnetic nanoparticles. When the organisms were fed
(organic pollutants and the magnetic nanoparticles) full, they will be deposited and
separated from the water by an external magnetic field.
Nanomaterials have area and electronic distribution on the surface is much larger
than the bulk materials. Thus, nanomaterials appear more outstanding features,
especially the ability to catalyze, absorb ... Taking advantage of that advantages,
scientists have been studying in depth to explore generating advanced materials, used
in the field of environmental treatment: adsorbent, the material capable of catalytic
processing of inorganic and organic compounds, and volatile gases.

10


2.1.5 Magnetic NPs and application of magnetic NPs in wastewater treatment
2.1.5.1 Magnetic nanoparticles
Nanoparticles are submicron moieties (diameters ranging from 1 to 100 nm
according to the used term, although there are examples of NPs several hundreds of
nanometers in size) made of inorganic or organic materials, which have many novel
properties compared with the bulk materials (Conte & Nitin, 2005). On this basis,
MNPs have many unique magnetic properties such as superparamagnetic, high
coercivity, low Curie temperature, high magnetic susceptibility, etc. MNPs are of great
interest for researchers from a broad range of disciplines, including magnetic fluids,
data storage, catalysis, and bioapplications (Kim et. al., 2008; Josephson et. al, 2003).
In environmental treatment technology, MNPs have absorbed capacity of two
states of arsenate - As (III) and arsenit-As (V), capacity to absorb 200 times higher
than bulk material (World Bank, 2005). Especially, it has catalytic capacity in
wastewater treatment for degradation of organic pollutants in water.
2.1.5.2 Application of Magnetic nanoparticles in wastewater treatment
Selection of the best method and material for wastewater treatment is a highly
complex task, which should consider a number of factors, such as the quality standards
to be met and the efficiency as well as the cost (Huang et al., 2008). Therefore, the
following four conditions must be considered in the decision on wastewater treatment
technologies: (1) treatment flexibility and final efficiency (2) reuse of treatment
agents, (3) environmental security and friendliness, and (4) low cost (Zhang & Fang
M, 2010). Fe3O4 MNPs are promising for industrial scale wastewater treatment, due to
their low cost, strong adsorption capacity, easy separation and enhanced stability
(Kumpiene et. al., 2009). The ability of Fe3O4 MNPs to remove contaminants has been
demonstrated at both laboratory and field scale tests (Mater, 2009). Current
applications of Fe3O4 MNPs in contaminated water treatment can be divided into two
groups: (a) technologies which use Fe3O4 MNPs as a kind of nanosorbent or
immobilization carrier for removal efficiency enhancement (referred to here as
adsorptive/ immobilization technologies), and (b) those which use Fe3O4 MNPs as
photocatalysts to break down or to convert contaminants into a less toxic form (i.e.

11


photocatalytic technologies). However, it should be noted that many technologies may
utilize both processes.
* Adsorptive technologies
- Magnetic NPs as nanosorbents for heavy metals:The majority of bench-scale
research and field applications of materials for wastewater treatment has currently
focused on magnetic NPs, carbon nanotubes, activated carbon, and zero-valent iron.
Among these, it seems that Fe3O4 MNPs, possessing the capability to treat large
volume of wastewater and being convenient for magnetic separation, are most
promising materials for heavy metal treatment ( Wang et. al., 2010).
Fe3O4 MNPs could illustrate excellent superiority. In a study performed by
Nassar (2010), it was found that the maximum adsorption capacity for Pb (II) ions was
36.0 mg g−1 by Fe3O4 nanoparticles, which was much higher than that of reported low
cost adsorbents. The small size of Fe3O4 nanosorbents was favorable for the diffusion
of metal ions from solution onto the active sites of the adsorbents surface. It
recommended that Fe3O4 nanosorbents were effective and economical adsorbents for
rapid removal and recovery of metal ions from wastewater effluents.
- Magnetic NPs as nanosorbents for organic contaminants:as a well-known
separation process, adsorption has been widely applied to remove chemical pollutants
from water. It has numerous advantages in terms of cost, flexibility and simplicity of
design/operation, and insensitivity to toxic pollutants. Therefore, an effective and lowcost adsorbent with high adsorption capacity for organic pollutants removal is
desirable. Fe3O4 MNPs are currently being explored for organic contaminant
adsorption, particularly for the efficient treatment of large-volume water samples and
fast separation via employing a strong external magnetic field. A lot of experiments
have been undertaken to examine the removal efficiency of organic pollutants by using
Fe3O4 MNPs for organic pollutants (Zeng et al, 2007). For example, Fe3O4 hollow
nanospheres were shown to be an effective sorbent for red dye (with the maximum
adsorption capacity of 90 mg g−1) (Iram et al., 2010). The saturation magnetization of
prepared nanospheres was observed to be 42 emu g−1, which was sufficient for
magnetic separation with a magnet (critical value at 16.3 emu g−1). These proved that

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magnetic NPs technology was a novel, promising and desirable alternative for organic
contaminant adsorption.
* Photocatalytic technology
Photocatalysis, one of the advanced physico-chemical technology applicable in
photodegradation of organic pollutants has attracted much attention in recent years
(Akhavan & Azimirad, 2009). However, some obstacles hinder the wide application of
Fe3O4 MNPs for the photocatalysis of toxic compounds: (a) the separation of materials
after the treatment process tends to be expensive owing to man power, time and
chemicals used for precipitation followed by centrifugation or decantation at the end of
treatment process, and (b) the low quantum-yield of treatment process restricts the
kinetics and efficiency.
Fe3O4 MNPs can be a good photocatalyst absorbing visible light. Compared with
commonly applied TiO2, which mainly absorbs UV light with wavelengths of b380
nm (covering only 5% of the solar spectrum) due to its wide band-gap of 3.2 eV,
Fe2O3 with band-gap of 2.2 eV is an interesting n-type semiconducting material and a
suitable candidate for photodegradation under visible light condition. The better
photocatalytic performance of Fe3O4 MNPs than TiO2 can be attributed to considerable
generation of electron–hole pairs through the narrow band-gap illumination (Bandara
et. al., 2007).
* Immobilization carriers
Fe3O4 MNPs have also shown considerable potential in the immobilization of
biomass. The biosorption capacity of a variety of macro and microbial biomass has
been widely used to remove various pollutants. Fe3O4 MNPs can offer larger surface
areas and multiple sites for interaction or adsorption. In particular, due to the
advantage of chemical inertness and favorable biocompatibility, Fe3O4 MNPs has been
widely used in immobilization technology.

2.2 Fenton reaction in the degradation of methylene blue
A variety of physical, chemical and biological methods are presently available
for the treatment of polluted water. Biological treatment is a good and promising as
well as cost effective technology but it has a number of disadvantages. Physical

13


methods such as liquid-liquid extraction, ion exchange, GAC adsorption, air stripping
etc. are ineffective for pollutants which are not adsorbable or volatile similarly these
technologies only transfer the pollutant from one phase to another phase. In the light of
limitations of these methods, the chemical oxidation methods are capable to almost
complete mineralization of organic pollutants and effective to the wider range of
pollutants (Sanjay, 2004).
Among the chemical oxidation methods, oxidation by Fenton’s reagent is
popular method. Advantages of Fenton’s reagent over other oxidizing treatment are
numerous, including simplicity, suitability to treat a wide range of substance, no
special equipment is needed etc. (Arnold, 1995). Generally in Fenton’s process ferrous
ion is commonly used with the H2O2 as a source of OH• radical in presence or absence
of light.
The method of Fenton’s oxidation may not be applicable to alkaline solutions or
sludges with strong buffering capacities. Another disadvantage of Fenton’s treatment
is the production of iron sludge, which must be disposed (Bull & Zeff, 1992). Costs of
application of Fenton’s reagent are expected to be quite low as compared to other
oxidation processes, such as UV radiation/hydrogen peroxide process. The main
chemical cost of Fenton’s reagent is the cost of H2O2. So, it is important to optimize
the amount of H2O2 in the Fenton’s oxidation technology.
Methylene blue has been selected a refractory model compound in this
oxidation process. Methylene blue is a basic dye extensively used for dying and
printing cotton, silk, etc. It is also used as a medicinal dye because of its antiseptic
properties (Sanjay, 2004).

2.3 The use of magnetic nanocomposites in catalytic degradation of methylene blue
Magnetic field was tentatively introduced into Fenton reactions system for the
degradation and discoloration of methyl blue as the represent of organic chemical dye,
which was a bio-refractory organic pollutant in industry wastewater. It was found that
under optimal Fenton reaction conditions, with the assistant of magnetic field in
Fenton reactions, the degradation rate of methyl blue, the decomposition rate of H2O2

14


and the conversion rate of Fe2+ were accelerated, the extent of them would be
improved by the increase of magnetic field intensity (Hao et. al., 2009).

2.4 The equipment used to determine the properties of gold nanoparticles and
methylene blue degradation
2.4.1 Ultraviolet–visible spectroscopy (UV-Vis)
The analytical method is widely used for a long time. Ultraviolet and visible
spectrum (UV-Vis) of organic compounds associated with electron transition between
the energy levels of electrons in the molecule when the electron transfers from the
energy low energy level high.

Figure 1.2 Ultraviolet–visible spectroscopy (UV-Vis)
Energy transition: under normal conditions, the electrons in the molecule is in the
ground state, the light stimulus with appropriate frequency, the electron will absorb
energy and transfer to the excited state have a higher energy level.
2.4.2 Transmission Electron Microscopy (TEM)
Transmission electron microscopy is a microscopy technique in which a beam of
electrons is transmitted through an ultra-thin specimen, interacting with the specimen
as it passes through. An image is formed from the interaction of the electrons
transmitted through the specimen; the image is magnified and focused onto an imaging

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