SYNTHESIS AND CHARACTERIZATION OF GOLD NANOPARTICLES FOR MERCURY ADSORPTION MAWARNI FAZLIANA BINTI MOHAMAD A thesis is submitted in fulfilment ofthe requirements for the award of the degree of Master of Engineering (Gas) Faculty of Petroleum and Renewable Energy Engineering Universiti Teknologi Malaysia MAY 2012
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SYNTHESIS AND CHARACTERIZATION OF GOLD NANOPARTICLES FOR
MERCURY ADSORPTION
MAWARNI FAZLIANA BINTI MOHAMAD
A thesis is submitted in fulfilment ofthe
requirements for the award of the degree of
Master of Engineering (Gas)
Faculty of Petroleum and Renewable Energy Engineering
Universiti Teknologi Malaysia
MAY 2012
iii
Dedicated to my beloved family…
ACKNOWLEDGEMENT
All praise is due to Allah, I have successfully completed my thesis. I am so
blessed to Allah who gave me tremendous courage and spirit while facing the entire
obstacle all this while. I would like to express my greatest gratitude to my supervisor
Assoc. Prof. Dr. Khairul Sozana Nor Kamarudin for her encouragement, guidance,
critics and friendship. Her valuable comments and suggestions are very much
appreciated. I would like to thanks the undergraduate students, Nik Nur Fazeera and
Nur Fadhilah who show their interest in this research. My sincere appreciation also
extends to all my colleagues and others who have provided assistance at various
occasions who had very supportive and thoughtful. Special thanks to Mr. Mohamad
at Ibnu Sina Institute, UTM and Mr. Yassin at Faculty Science, UTM for their kind
assistance helped me in sample analyzing. I also acknowledge the financial support,
from the Malaysia under Fundamental Research Grant Scheme (FRGS) and
Universiti Teknologi Malaysia. Last but certainly not least, I wish to express my
deepest gratitude to my lovely parent (Mohamad and Lailani), sister (Mawarni
Fazlaili), brothers (Amirru Luqman and Aliff Luqman) and family member (Ahmad
Danial Zulhilmi) for their prayers, loves, continuous moral, support and unending
encouragement. All peace is upon to all of you.
ABSTRACT
This research was carried out to synthesize and characterize different sizes and shapes of gold (Au) nanoparticles in order to find the optimum synthesis parameters for maximum mercury adsorption. The different sizes and shapes of Au nanoparticles were prepared using microwave (MW) polyol method. By using different polyvinylpyrrolidone (PVP) concentrations (1.9-33.3 mM), different concentration of sodium chloride (NaCl) (10-30 mM) and different amount of [Au]1/[Au]0 molar ratio (1-9), different sizes and shapes of Au nanoparticles were obtained. The Au nanoparticles were characterized using ultra violet-visible (UV-Vis) absorption spectroscopy and transmission electron microscopy (TEM). The different sizes and various mixtures of spherical, triangular, cubic, hexagonal, octahedral, decahedral, icosahedral and one-dimension (1-D) particles were obtained using those methods. Mercury adsorption was determined based on different sizes and shapes of Au nanoparticles and measured using atomic absorption spectrophotometer (AAS). The optimum PVP concentration is 22.2 mM for 92 % spherical particles of a size in range less than 10 nm. It was found that, using 11.1 mM of PVP solution, the sizes and shapes can be further reduced in the presence of chloride ions. It was also found that, 20 mM of NaCl is sufficient to produce stable Au nanoparticles with most of the particles are spherical in which 97 % of particles diameter is less than 10 nm. The different of [Au]1/[Au]0 molar ratio led to the high yield of polygonal nanoparticles and the size is increase with increasing [Au]1/[Au]0 molar ratio. However, the optimum values of [Au]1/[Au]0 molar ratio cannot be determined because the sizes and shapes are irregular. High mercury adsorption was obtained for spherical nanoparticles (263.18 mg/g) with 99 % particles size less than 10 nm. The defect on spherical nanoparticles surface contributes to high mercury adsorption. In addition, smaller sizes of Au nanoparticles increase the total surface area available for mercury adsorption. It was found that the formation of sizes and shapes of Au nanoparticles was depend on parameters such as the concentration of PVP, NaCl, as well as [Au]1/[Au]0 molar ratio, and thus affects the mercury adsorption.
ABSTRAK
Kajian ini telah dijalankan untuk mensintesis dan mencirikan saiz dan bentuk nanopartikel emas (Au) yang berbeza bagi mencari nilai parameter sintesis yang optimum untuk penjerapan merkuri yang maksimum. Saiz dan bentuk nanopartikel Au yang berbeza telah disediakan mengikut kaedah poliol gelombang mikro (MW). Dengan menggunakan kepekatan polyvinylprrolidone (PVP) (1.9-33.3 mM) yang berlainan, kepekatan natrium klorida (NaCl) (10-30 mM) yang berlainan dan pelbagai jumlah nisbah [Au]1/[Au]0 (1-9), pelbagai saiz dan bentuk nanopartikel Au yang berbeza telah diperolehi. Pencirian nanopartikel Au telah dilakukan dengan menggunakan spektroskopi IR (UV-Vis) dan mikroskop elektron penghantaran (TEM). Pelbagai saiz dan campuran partikel yang berbeza seperti sfera, segi tiga, kubik, heksagon, oktahedral, decahedral, icosahedral dan satu dimensi (1-D) partikel telah deperolehi menggunakan kaedah ini. Keputusan jerapan merkuri telah ditentukan berdasarkan saiz dan bentuk nanopartikel Au yang berbeza dan disukat menggunakan spektrofotometer penyerapan atom (AAS). Kepekatan PVP yang optimum ialah 22.2 mM dengan 92% zarah adalah sfera dengan julat saiz yang kurang daripada 10 nm. Didapati bahawa, dengan menggunakan larutan kepekatan PVP 11.1 mM, saiz dan bentuk boleh diturunkan lagi dengan wujudnya ion klorida. Didapati juga bahawa, 20 mM NaCl adalah mencukupi untuk menghasilkan Au nanopartikel yang stabil. Kebanyakan zarah sfera adalah 97% diameter adalah lebih kurang daripada 10 nm. Kepelbagaian nisbah molar [Au]1/[Au]0 membawa kepada hasil nanopartikel poligon yang tinggi dan saiz partikel yang lebih besar dengan peningkatan nisbah molar [Au]1/[Au]0. Walau bagaimanapun, nilai optimum nisbah molar [Au]1/[Au]0 tidak dapat ditentukan kerana saiz dan bentuk yang tidak menentu. Merkuri penjerapan yang tinggi telah diperolehi untuk nanopartikel sfera (263.18 mg/g) dengan 99% zarah saiz adalah kurang daripada 10 nm. Kecacatan permukaan pada nanopartikel sfera menyumbang kepada penjerapan merkuri yang tinggi. Di samping itu, saiz Au nanopartikel yang lebih kecil meningkatkan jumlah luas permukaan yang tersedia untuk penjerapan merkuri. Didapati bahawa pembentukan saiz dan bentuk Au nanopartikel bergantung kepada parameter seperti kepekatan PVP, NaCI, serta nisbah molar [Au]1/[Au]0, sekali gus memberi kesan kepada penjerapan merkuri.
TABLE OF CONTENTS
CHAPTER TITLE PAGE
DECLARATION ii
DEDICATION iii
ACKNOWLEDGEMENTS iv
ABSTRACT v
ABSTRAK vi
TABLE OF CONTENTS vii
LIST OF TABLES x
LIST OF FIGURES xi
LIST OF SYMBOLS xiii
LIST OF ABBREVIATIONS xiv
LIST OF APPENDICES xv
1 INTRODUCTION
1.1 Background 1
1:2 Problem Statement 2
1.3 Objective and Scopes 4
1.4 Thesis Outline 5
1.5 Summary 6
2 LITERATURE REVIEW
2.1 Introduction 7
2.2 Types of Mercury 8
2.2.1 Elemental mercury 8
2.2.2 Inorganic mercury compounds 9
viii
2.3 Mercury Emissions 10
2.4 Introduction to Natural Gas 13
2.5 Mercury in Natural Gas 15
2.6 Mercury Problem in Natural Gas Processing
Plant
16
2.6.1 Amalgation 16
2.6.2 Amalgam corrosion 17
2.6.3 Liquid metal embrittlement (LME) 18
2.7 Mercury Removal in Natural Gas Plant 19
2.8 Gold as Mercury Adsorber 22
2.9 Gold Nanoparticles 24
2.10 Characterization of Au Nanoparticles 28
2.10.1 UV-Vis absorption spectroscopy 28
2.10.2 Transmission electron microscopy 31
2.11 Summary 33
3 MATERIALS AND METHODS 34
3.1 Introduction 34
3.2 Chemicals 35
3.3 Experimental Procedure 36
3.3.1 Preparation of Au nanoparticles 36
3.3.2 Characterization of Au nanoparticles 37
3.3.3 Mercury adsorption measurement 38
3.4 Summary 39
4 RESULTS AND DISCUSSION 40
4.1 Introduction 40
4.2 Effect of PVP 41
4.3 Effects of PVP Concentrations 42
4.4 Visible wavelenght and Particle Shape 46
4.5 Effect of NaCl 51
iix
4.6 Effect of Different Amount of [Au]1/[Au]0 Molar
Ratio
56
4.7 Mercury Adsorption 67
4.7.1 Effect of particles sizes 67
4.7.2 Effects of particles shapes 68
5 CONCLUSIONS AND RECOMMENDATIONS 71
5.1 Introduction 71
5.2 Summary of Research Findings 71
5.2.1 Au nanoparticles synthesis and
characteristics
71
5.2.2 Mercury adsorption 72
5.3 Recommendations for Future Researchers 73
5.4 Concluding Remarks 74
REFERENCES 76
APPENDIX 87
LIST OF TABLES
TABLE NO. TITLE PAGE
2.1 Physical properties of mercury 9
2.2 Range of mercury content in oil and gas fields 12
2.3 Approximate mercury compound in natural gas and
gas condensate
13
2.4 Estimated mercury concentration in natural gas and
condensate
15
2.5 Mercury removal system for natural gas 20
2.6 Analytical technique available for the determination of
mercury content
21
2.7 Methods to synthesize Au nanoparticles 24
2.8 Absorbance and complementary color 29
4.1 Particle size calculated and estimation from TEM
images of Au nanoparticles
58
4.2 Mercury adsorption on different particle sizes of Au
nanoparticles
67
4.3 Mercury adsorption on different particle shapes of Au
nanoparticles with particle size ≤ 10 nm
68
4.4 Mercury adsorption on different particle shapes of Au
nanoparticles with particle size 11-20 nm
69
4.5 Mercury adsorption on different particle shapes of Au
nanoparticles with particle size 21-110 nm
70
LIST OF FIGURES
FIGURE NO. TITLE PAGE
2.1 The mercury emission to the environment 11
2.2 Schematic view of cryogenic heat exchanger
showing the manifolds (1) and nozzles (2)
14
2.3 Schematic flow diagram of a typical natural gas
processing plant
19
2.4 Schematic diagram of mercury monitoring system 22
2.5 Schematic illustration on preparation Au
nanoparticles with existing chloride ion
27
2.6 Photograph of Au nanoparticles solution with
increasing sizes for different sample of Au
nanoparticles solution (S1-S6)
30
2.7 Absorption spectra of Au nanoparticles from
different sample for different sample of Au
nanoparticles solution (S1-S6)
30
2.8 SEM photographs of (a) spherical (b) triangular (c)
hexagonal (d) octahedral (e) decahedral (f)
icosahedral Au nanoparticles prepared by MW-
polyol method
32
2.9 Definition of sizes of each particle 33
3.1 A flow diagram of experimental procedures used in
the study
35
4.1 Schematic diagram of Au nanoparticles growth 41
4.2 TEM images of Au nanoparticles with PVP 42
xii
4.3 TEM photographs of Au nanoparticles 43
4.4
4.5
Effect of PVP concentrations on particle size
distribution
Vis spectra of Au nanoparticle with different PVP
concentrations
44
47
4.6 Effect of concentration PVP on shape distribution of
Au nanoparticle
49
4.7 TEM images of Au nanoparticles (a) without addition
NaCl and with three different NaCl concentrations
(b) 10 mM (c) 20 mM and (d) 30 mM
52
4.8 Effect of NaCl concentrations on particle size
distribution
53
4.9 Effect of NaCl concentrations on particle shape
distribution
55
4.10 TEM images of Au nanoparticles obtained from Au
seeds and with various [Au]1/[Au]0 molar ratios
56
4.11 Size distribution of (a) Au seeds and [Au]1/[Au]0
molar ratios of (b) 1 (c) 3 (d) 5 (e) 7 and (f) 9
58
4.12 Shape distribution of (a) Au seeds and [Au]1/[Au]0
molar ratios of (b) 1 (c) 3 (d) 5 (e) 7 and (f) 9
61
4.13 SEM photographs of spherical nanoparticles 64
4.14 Mechanism of oxidative etching and growth of Au