Luận văn iron oxide nanostructures for organic dyes removal

Various transition metal oxides with different structure, size, and morphology have been recognized effective solid adsorbent for wastewater treatment because of their high surface are

TIANOI UNIVERSITY OF SCIENCE AND TECIINOLOGY

Supervisors: Dr Tran Thị Viet Nga

Dr Raja Das

Tustitute: TnlemaHonal Trang Tnstitule for Material and

Science

Hanoi, Apr.2021

TLANOI UNIVERSITY OF SCIENCE AND TECIINOLOGV

Material Science (Electronic Materials)

Supervisors: Dr Iran Thị Viet Nga Supervisor's signature

Dr Raja Das

Tnstitute: Tnlermalional Training Fustitute for Material and

Science

Hanoi, Apr.2021

ACKNOWLEDGEMENTS

Firstly, I would like to express my sincere gratitude to Dr Tran Thi Viet Nga,

Dr Raja Das and Dr Duong Anh Tuan for their valuable guides and advice All their support in the process of learning and research is the most important factor to

help me to complete this thesis

Tam profourelly gratefal Lo the lecturers al the International Training Institute for Materials and Science, Hanoi University of Science and Technology for enthusiastic teaching, guidance and giving me valuable expericnces during the process of learning and doing research

I would also like to thank the colleagues at the Nanomaterials Research

Group for Ulectronic Applications and Renewable Linergy, Phenikaa University for guiding and supportmg me during the research time and partial funding

Finally T would like to express my profound and hearlfell thanks to my

family Tam where T am today because of having Gamily’s support int the past T would also like to thank my [tends for their advices, sharing, help and friendship not only in my study but also in my life

‘This research is funded by Vietnam National Moundation for Science and

‘Technology Development (NAFOSTED) under grant number 103.02-2019.314

SUMMARY

‘The uncontrolled discharge of some organic dyes has contaminated the water Therefore, removing organic dyes from wastewater became crucial because of their adverse effect on human health and environment In this study, a-l'ex0s and Fes, nanoplates and nanorices has been synthesized by hydrothermal reaction and used for the adsorption studies for organic pollutant removal The morphology, crystal structure and dye removal ability of them were investigated The adsorption studies showed selective and very high adsorption capacity of a-FexCs nanoplates towards Congo Red dye a-Fe,O3 nanoplates showed excellent recyclability with negligible loss of adsorption capacity after three cycles owing to their stable morphology and crystal structure The reusability, rapid, selective and high adsorption capacity of a-Fez; nanoplates indicated that it could have potential

appheation in removing industrial wasle, Congo Red from polluted walter

Pham Kim Ngoc

3.2 Crystal structure of as-synthesized nanoparticles 2o

3.3 Adsorption study of as-synthesized iron oxide nanostructures 31

3.3.1 The effect of the adsorbate on the adsorption capacity 31 3.3.2 The effect of the adsorbent concentration 34

3.4 Mechanism oÊ đựe adsorption

INTRODUCTION

The development of industry brings many economic, social and life benefits

Promote of industries is an important direction for any country However, this

direction still has many negative effects, especially in environmental issues

Strongly industrial development but dealing with its influence on nature is not

enough that has become the human concern

The uncontrolled discharge of organic dyes usually azo-groups containing industrial waste from textile, plastic, printing, paper-pulp, paint, and leather

industries has contaminated the water [1]-{6] Removing organic dyes from wastewater became crucial because of their adverse effect on human health and environment Several methods such as electrochemical, chlorination, ozonation, flotation, chemical oxidation, filtration, membrane separation, coagulation, adsorption, biological treatment, and photodegradation using photocatalyst has been used till date to remove organic dyes from wastewater [7]}-{16] However,

these methods are expensive, time consuming, and difficult to apply in the field

Among various processes available for wastewater treatment, recent studies have

shown adsorption to be the most promising technique for dye removal due to its

convenience, high efficiency, easy operation, simplicity of design, minimum

energy requirement, and can remove different type of pollutants [17]-{24] Various transition metal oxides with different structure, size, and morphology have been

recognized effective solid adsorbent for wastewater treatment because of their high

surface area, and presence of active sites [6], [22], [25]-{33]

Among various transition metal oxides, iron oxide (a-FexO3 and Fe304)

nanoparticles are drawing substantial attention owing to their unique properties

such as excellent stability, biocompatibility, low synthesis cost, easy of synthesis

and functionalization [25]-(33] However, there are some major challenges

associated with iron oxide nanostructures such as limited adsorption capacity, poor selectivity and recyclability [31 ], [32] To achieve high adsorption capacity several strategies like functionalization with organic molecules, polymer, carbon

nanotubes, and nanocomposite with graphene, graphene oxide, transition metal

dichalcogenide (TMD) has been used [31], [34]-{37] Recently, Chatterjee et al

reported developed 1,2,4,5-Benzentetracarboxylic acid functionalized FesO nanoparticles exhibiting high selectivity towards Congo Red (C R.) and high adsorption capacity [31] The functionalization of the nanostructures improves the adsorption capacity, nevertheless the functionalization processes are complex and costly Although there are several studies on the adsorption of dye molecules using,

1

1.3 @-He20s, Fess materials and their ability for organic dye removal 7

1.4.2 Methylthioninium chloride (Methylene Blue)

1.4.3 Rhodamine B CHAPTER 2 EXPERIMENT METHOD!

2.1.2, Fabrication of a-Fe:s nanoplates using hydrothermal method 17

3 Dabrication of aes nanorices using hydrothermal method 17

2.1.4, Phase transformation from a@-t'e203s to less veces "`

- Characterization methods co ceniiree ¬" _

3, Lltraviolet-visible spectroscopy (UV-Vis) 21 2.2.4, Brunauer-Emmett-Teller nitrogen adsorption/desorption

technique (BEL), cssseseesssnsseetsersnestistu vastness 22 2.2.5 Dye adsorption oxporiments su ccocceeeseneeoseroeoeoe 29

CHAPTER 3 RESULTS AND DISCUSSION

3.1 Morphology of as-synthesized iron oxide nanoparticles - 36

LIST OF TABLES

Table 1 Prapertios of hemalile and magnetite [59] 161 |

Table 2 Size parmnciers and BET surlace arca of iron oxide nanoriees

Table 3 Size parameters and BET surface area of iron oxide nanoplates

LIST OF FIGURES

Figure 1.4, Schematic representation for the adsorption of Congo Red [58] 8

Figure 1.8, Ilustration for the fabrication of iron oxide nanoparticles 18

Figure 2.1 The radius changing off the crystal seed according lo the Gibbs free

Figure 2.2 A fully pack of stainless-steel autoclave [68] 16 Kigure 2.3 Phase transformation process of a-Ker0s iron oxide 18

igure 2.7 Different types of adsorption isotherms 23

Figure 3.1 SEM images of as-synthesized ab) a-FoxOs nanoplates aller hydrothermal reaction of 12 and 24 h, respectively, c,d) a-FesOs nanorices after hydrothermal reaction of 3 and 5h, respeetively ¢,0) Zoom views of a-FexOs nanorices and a-Fe2Ws nanoplates after hydrothermal reaction of 5h and 24 b,

Figure 3.2 SHM images of a) ¥esO4 nanoplates after hydrothermal reaction of 24

h, b) FesO4 nanorices after hydrothermal reaction of 5h 7 iguze 3.3, Transmission electron mieroscope (TIM) images ö£ ess nanotubes after different reaction thue a) 1 h, b) 3 h, e) 8b, d) 24h Scale bars a-c) 100 nm, d) 500 nm, Inset of a) shows the zoom view of the nanorods formed after 1 h of

‘MD ‘Transition metal dichaleogenide

XRD X-ray diffraction

3.2 Crystal structure of as-synthesized nanoparticles 2o

3.3 Adsorption study of as-synthesized iron oxide nanostructures 31

3.3.1 The effect of the adsorbate on the adsorption capacity 31 3.3.2 The effect of the adsorbent concentration 34

3.4 Mechanism oÊ đựe adsorption

LIST OF FIGURES

Figure 1.4, Schematic representation for the adsorption of Congo Red [58] 8

Figure 1.8, Ilustration for the fabrication of iron oxide nanoparticles 18

Figure 2.1 The radius changing off the crystal seed according lo the Gibbs free

Figure 2.2 A fully pack of stainless-steel autoclave [68] 16 Kigure 2.3 Phase transformation process of a-Ker0s iron oxide 18

igure 2.7 Different types of adsorption isotherms 23

Figure 3.1 SEM images of as-synthesized ab) a-FoxOs nanoplates aller hydrothermal reaction of 12 and 24 h, respectively, c,d) a-FesOs nanorices after hydrothermal reaction of 3 and 5h, respeetively ¢,0) Zoom views of a-FexOs nanorices and a-Fe2Ws nanoplates after hydrothermal reaction of 5h and 24 b,

Figure 3.2 SHM images of a) ¥esO4 nanoplates after hydrothermal reaction of 24

h, b) FesO4 nanorices after hydrothermal reaction of 5h 7 iguze 3.3, Transmission electron mieroscope (TIM) images ö£ ess nanotubes after different reaction thue a) 1 h, b) 3 h, e) 8b, d) 24h Scale bars a-c) 100 nm, d) 500 nm, Inset of a) shows the zoom view of the nanorods formed after 1 h of

INTRODUCTION

The development of industry brings many economic, social and life benefits

Promote of industries is an important direction for any country However, this

direction still has many negative effects, especially in environmental issues

Strongly industrial development but dealing with its influence on nature is not

enough that has become the human concern

The uncontrolled discharge of organic dyes usually azo-groups containing industrial waste from textile, plastic, printing, paper-pulp, paint, and leather

industries has contaminated the water [1]-{6] Removing organic dyes from wastewater became crucial because of their adverse effect on human health and environment Several methods such as electrochemical, chlorination, ozonation, flotation, chemical oxidation, filtration, membrane separation, coagulation, adsorption, biological treatment, and photodegradation using photocatalyst has been used till date to remove organic dyes from wastewater [7]}-{16] However,

these methods are expensive, time consuming, and difficult to apply in the field

Among various processes available for wastewater treatment, recent studies have

shown adsorption to be the most promising technique for dye removal due to its

convenience, high efficiency, easy operation, simplicity of design, minimum

energy requirement, and can remove different type of pollutants [17]-{24] Various transition metal oxides with different structure, size, and morphology have been

recognized effective solid adsorbent for wastewater treatment because of their high

surface area, and presence of active sites [6], [22], [25]-{33]

Among various transition metal oxides, iron oxide (a-FexO3 and Fe304)

nanoparticles are drawing substantial attention owing to their unique properties

such as excellent stability, biocompatibility, low synthesis cost, easy of synthesis

and functionalization [25]-(33] However, there are some major challenges

associated with iron oxide nanostructures such as limited adsorption capacity, poor selectivity and recyclability [31 ], [32] To achieve high adsorption capacity several strategies like functionalization with organic molecules, polymer, carbon

nanotubes, and nanocomposite with graphene, graphene oxide, transition metal

dichalcogenide (TMD) has been used [31], [34]-{37] Recently, Chatterjee et al

reported developed 1,2,4,5-Benzentetracarboxylic acid functionalized FesO nanoparticles exhibiting high selectivity towards Congo Red (C R.) and high adsorption capacity [31] The functionalization of the nanostructures improves the adsorption capacity, nevertheless the functionalization processes are complex and costly Although there are several studies on the adsorption of dye molecules using,

1

1.3 @-He20s, Fess materials and their ability for organic dye removal 7

1.4.2 Methylthioninium chloride (Methylene Blue)

1.4.3 Rhodamine B CHAPTER 2 EXPERIMENT METHOD!

2.1.2, Fabrication of a-Fe:s nanoplates using hydrothermal method 17

3 Dabrication of aes nanorices using hydrothermal method 17

2.1.4, Phase transformation from a@-t'e203s to less veces "`

- Characterization methods co ceniiree ¬" _

3, Lltraviolet-visible spectroscopy (UV-Vis) 21 2.2.4, Brunauer-Emmett-Teller nitrogen adsorption/desorption

technique (BEL), cssseseesssnsseetsersnestistu vastness 22 2.2.5 Dye adsorption oxporiments su ccocceeeseneeoseroeoeoe 29

CHAPTER 3 RESULTS AND DISCUSSION

3.1 Morphology of as-synthesized iron oxide nanoparticles - 36

3.2 Crystal structure of as-synthesized nanoparticles 2o

3.3 Adsorption study of as-synthesized iron oxide nanostructures 31

3.3.1 The effect of the adsorbate on the adsorption capacity 31 3.3.2 The effect of the adsorbent concentration 34

3.4 Mechanism oÊ đựe adsorption

LIST OF FIGURES

Figure 1.4, Schematic representation for the adsorption of Congo Red [58] 8

Figure 1.8, Ilustration for the fabrication of iron oxide nanoparticles 18

Figure 2.1 The radius changing off the crystal seed according lo the Gibbs free

Figure 2.2 A fully pack of stainless-steel autoclave [68] 16 Kigure 2.3 Phase transformation process of a-Ker0s iron oxide 18

igure 2.7 Different types of adsorption isotherms 23

Figure 3.1 SEM images of as-synthesized ab) a-FoxOs nanoplates aller hydrothermal reaction of 12 and 24 h, respectively, c,d) a-FesOs nanorices after hydrothermal reaction of 3 and 5h, respeetively ¢,0) Zoom views of a-FexOs nanorices and a-Fe2Ws nanoplates after hydrothermal reaction of 5h and 24 b,

Figure 3.2 SHM images of a) ¥esO4 nanoplates after hydrothermal reaction of 24

h, b) FesO4 nanorices after hydrothermal reaction of 5h 7 iguze 3.3, Transmission electron mieroscope (TIM) images ö£ ess nanotubes after different reaction thue a) 1 h, b) 3 h, e) 8b, d) 24h Scale bars a-c) 100 nm, d) 500 nm, Inset of a) shows the zoom view of the nanorods formed after 1 h of

1.3 @-He20s, Fess materials and their ability for organic dye removal 7

1.4.2 Methylthioninium chloride (Methylene Blue)

1.4.3 Rhodamine B CHAPTER 2 EXPERIMENT METHOD!

2.1.2, Fabrication of a-Fe:s nanoplates using hydrothermal method 17

3 Dabrication of aes nanorices using hydrothermal method 17

2.1.4, Phase transformation from a@-t'e203s to less veces "`

- Characterization methods co ceniiree ¬" _

3, Lltraviolet-visible spectroscopy (UV-Vis) 21 2.2.4, Brunauer-Emmett-Teller nitrogen adsorption/desorption

technique (BEL), cssseseesssnsseetsersnestistu vastness 22 2.2.5 Dye adsorption oxporiments su ccocceeeseneeoseroeoeoe 29

CHAPTER 3 RESULTS AND DISCUSSION

3.1 Morphology of as-synthesized iron oxide nanoparticles - 36

INTRODUCTION

The development of industry brings many economic, social and life benefits

Promote of industries is an important direction for any country However, this

direction still has many negative effects, especially in environmental issues

Strongly industrial development but dealing with its influence on nature is not

enough that has become the human concern

The uncontrolled discharge of organic dyes usually azo-groups containing industrial waste from textile, plastic, printing, paper-pulp, paint, and leather

industries has contaminated the water [1]-{6] Removing organic dyes from wastewater became crucial because of their adverse effect on human health and environment Several methods such as electrochemical, chlorination, ozonation, flotation, chemical oxidation, filtration, membrane separation, coagulation, adsorption, biological treatment, and photodegradation using photocatalyst has been used till date to remove organic dyes from wastewater [7]}-{16] However,

these methods are expensive, time consuming, and difficult to apply in the field

Among various processes available for wastewater treatment, recent studies have

shown adsorption to be the most promising technique for dye removal due to its

convenience, high efficiency, easy operation, simplicity of design, minimum

energy requirement, and can remove different type of pollutants [17]-{24] Various transition metal oxides with different structure, size, and morphology have been

recognized effective solid adsorbent for wastewater treatment because of their high

surface area, and presence of active sites [6], [22], [25]-{33]

Among various transition metal oxides, iron oxide (a-FexO3 and Fe304)

nanoparticles are drawing substantial attention owing to their unique properties

such as excellent stability, biocompatibility, low synthesis cost, easy of synthesis

and functionalization [25]-(33] However, there are some major challenges

associated with iron oxide nanostructures such as limited adsorption capacity, poor selectivity and recyclability [31 ], [32] To achieve high adsorption capacity several strategies like functionalization with organic molecules, polymer, carbon

nanotubes, and nanocomposite with graphene, graphene oxide, transition metal

dichalcogenide (TMD) has been used [31], [34]-{37] Recently, Chatterjee et al

reported developed 1,2,4,5-Benzentetracarboxylic acid functionalized FesO nanoparticles exhibiting high selectivity towards Congo Red (C R.) and high adsorption capacity [31] The functionalization of the nanostructures improves the adsorption capacity, nevertheless the functionalization processes are complex and costly Although there are several studies on the adsorption of dye molecules using,

1

INTRODUCTION

The development of industry brings many economic, social and life benefits

Promote of industries is an important direction for any country However, this

direction still has many negative effects, especially in environmental issues

Strongly industrial development but dealing with its influence on nature is not

enough that has become the human concern

The uncontrolled discharge of organic dyes usually azo-groups containing industrial waste from textile, plastic, printing, paper-pulp, paint, and leather

industries has contaminated the water [1]-{6] Removing organic dyes from wastewater became crucial because of their adverse effect on human health and environment Several methods such as electrochemical, chlorination, ozonation, flotation, chemical oxidation, filtration, membrane separation, coagulation, adsorption, biological treatment, and photodegradation using photocatalyst has been used till date to remove organic dyes from wastewater [7]}-{16] However,

these methods are expensive, time consuming, and difficult to apply in the field

Among various processes available for wastewater treatment, recent studies have

shown adsorption to be the most promising technique for dye removal due to its

convenience, high efficiency, easy operation, simplicity of design, minimum

energy requirement, and can remove different type of pollutants [17]-{24] Various transition metal oxides with different structure, size, and morphology have been

recognized effective solid adsorbent for wastewater treatment because of their high

surface area, and presence of active sites [6], [22], [25]-{33]

Among various transition metal oxides, iron oxide (a-FexO3 and Fe304)

nanoparticles are drawing substantial attention owing to their unique properties

such as excellent stability, biocompatibility, low synthesis cost, easy of synthesis

and functionalization [25]-(33] However, there are some major challenges

associated with iron oxide nanostructures such as limited adsorption capacity, poor selectivity and recyclability [31 ], [32] To achieve high adsorption capacity several strategies like functionalization with organic molecules, polymer, carbon

nanotubes, and nanocomposite with graphene, graphene oxide, transition metal

dichalcogenide (TMD) has been used [31], [34]-{37] Recently, Chatterjee et al

reported developed 1,2,4,5-Benzentetracarboxylic acid functionalized FesO nanoparticles exhibiting high selectivity towards Congo Red (C R.) and high adsorption capacity [31] The functionalization of the nanostructures improves the adsorption capacity, nevertheless the functionalization processes are complex and costly Although there are several studies on the adsorption of dye molecules using,

1

LIST OF TABLES

Table 1 Prapertios of hemalile and magnetite [59] 161 |

Table 2 Size parmnciers and BET surlace arca of iron oxide nanoriees

Table 3 Size parameters and BET surface area of iron oxide nanoplates

Figure 3.6 UV-Vis absorbance spectra of as-aynihesized 12 h a-Fe2Os temoplales

Figure 3.7 UV-Vis speetra of a) Congo Red (C R.), b) Rhodamine B (Rh B.), &) Methyfene Blue (M B.) aqueous solution before and after incubation wilh ax-

Figure 3.8 ac) Dye removal (maxim absorbance) afler different times of incubation and d) Bar diagram of percentage removal of C R., Rh B., and M B

Figure 3.9 Percentage C R dye removal efficiency of different concentration of as-synthesized a-Fe20s nanoplates (24 h) 34 Figure 3.10 Recycability of as-synthesized a-He20s nanoplates (24h) for removal

of C R dye after 10 min of contact time and initial concentration of 10 mg L 7

35 Figure 3.11 Effect of pH on adsorption of C R dye by a-Ke2Os nanoplates (24 h)

at pila) 3, b) 7, e) 10 and d) percentage C R dye removal efficiency after 60min

Figure 3.12 Bar diagram for the percentage removal of C R., Rh B and M B

dyes after 60 min of incubation with a-l’e:0s nanoplates (12, 24 h) 38 Figure 3.13 Bar diagram for the percentage removal of C.R., Rh B., and M B dyes after 60 min of incubation with a-Fe:0; nanarices (3, 5 h) 39

Tigure 3.14 Bar diagram for the percentage removal of a) C.R., Rh B and M B

dyes after 60 min of incubation with a-FezO; nanoplates (24 h) and ø-Fe:O; nanorioes (3 bh), b} C R dye after 60 and 120 min of incubation with a-EezO; and

Figure 3.15 UV-Vis spectra of mixture of CR, Rh B MB dyes, (thin lines)

and C R, Rh B., M B (thick red, onmge, bluc lines) aqueous solution before and

Figure 3.6 UV-Vis absorbance spectra of as-aynihesized 12 h a-Fe2Os temoplales

Figure 3.7 UV-Vis speetra of a) Congo Red (C R.), b) Rhodamine B (Rh B.), &) Methyfene Blue (M B.) aqueous solution before and after incubation wilh ax-

Figure 3.8 ac) Dye removal (maxim absorbance) afler different times of incubation and d) Bar diagram of percentage removal of C R., Rh B., and M B

Figure 3.9 Percentage C R dye removal efficiency of different concentration of as-synthesized a-Fe20s nanoplates (24 h) 34 Figure 3.10 Recycability of as-synthesized a-He20s nanoplates (24h) for removal

of C R dye after 10 min of contact time and initial concentration of 10 mg L 7

35 Figure 3.11 Effect of pH on adsorption of C R dye by a-Ke2Os nanoplates (24 h)

at pila) 3, b) 7, e) 10 and d) percentage C R dye removal efficiency after 60min

Figure 3.12 Bar diagram for the percentage removal of C R., Rh B and M B

dyes after 60 min of incubation with a-l’e:0s nanoplates (12, 24 h) 38 Figure 3.13 Bar diagram for the percentage removal of C.R., Rh B., and M B dyes after 60 min of incubation with a-Fe:0; nanarices (3, 5 h) 39

Tigure 3.14 Bar diagram for the percentage removal of a) C.R., Rh B and M B

dyes after 60 min of incubation with a-FezO; nanoplates (24 h) and ø-Fe:O; nanorioes (3 bh), b} C R dye after 60 and 120 min of incubation with a-EezO; and

Figure 3.15 UV-Vis spectra of mixture of CR, Rh B MB dyes, (thin lines)

and C R, Rh B., M B (thick red, onmge, bluc lines) aqueous solution before and

INTRODUCTION

The development of industry brings many economic, social and life benefits

Promote of industries is an important direction for any country However, this

direction still has many negative effects, especially in environmental issues

Strongly industrial development but dealing with its influence on nature is not

enough that has become the human concern

The uncontrolled discharge of organic dyes usually azo-groups containing industrial waste from textile, plastic, printing, paper-pulp, paint, and leather

industries has contaminated the water [1]-{6] Removing organic dyes from wastewater became crucial because of their adverse effect on human health and environment Several methods such as electrochemical, chlorination, ozonation, flotation, chemical oxidation, filtration, membrane separation, coagulation, adsorption, biological treatment, and photodegradation using photocatalyst has been used till date to remove organic dyes from wastewater [7]}-{16] However,

these methods are expensive, time consuming, and difficult to apply in the field

Among various processes available for wastewater treatment, recent studies have

shown adsorption to be the most promising technique for dye removal due to its

convenience, high efficiency, easy operation, simplicity of design, minimum

energy requirement, and can remove different type of pollutants [17]-{24] Various transition metal oxides with different structure, size, and morphology have been

recognized effective solid adsorbent for wastewater treatment because of their high

surface area, and presence of active sites [6], [22], [25]-{33]

Among various transition metal oxides, iron oxide (a-FexO3 and Fe304)

nanoparticles are drawing substantial attention owing to their unique properties

such as excellent stability, biocompatibility, low synthesis cost, easy of synthesis

and functionalization [25]-(33] However, there are some major challenges

associated with iron oxide nanostructures such as limited adsorption capacity, poor selectivity and recyclability [31 ], [32] To achieve high adsorption capacity several strategies like functionalization with organic molecules, polymer, carbon

nanotubes, and nanocomposite with graphene, graphene oxide, transition metal

dichalcogenide (TMD) has been used [31], [34]-{37] Recently, Chatterjee et al

reported developed 1,2,4,5-Benzentetracarboxylic acid functionalized FesO nanoparticles exhibiting high selectivity towards Congo Red (C R.) and high adsorption capacity [31] The functionalization of the nanostructures improves the adsorption capacity, nevertheless the functionalization processes are complex and costly Although there are several studies on the adsorption of dye molecules using,

1

INTRODUCTION

The development of industry brings many economic, social and life benefits

Promote of industries is an important direction for any country However, this

direction still has many negative effects, especially in environmental issues

Strongly industrial development but dealing with its influence on nature is not

enough that has become the human concern

The uncontrolled discharge of organic dyes usually azo-groups containing industrial waste from textile, plastic, printing, paper-pulp, paint, and leather

industries has contaminated the water [1]-{6] Removing organic dyes from wastewater became crucial because of their adverse effect on human health and environment Several methods such as electrochemical, chlorination, ozonation, flotation, chemical oxidation, filtration, membrane separation, coagulation, adsorption, biological treatment, and photodegradation using photocatalyst has been used till date to remove organic dyes from wastewater [7]}-{16] However,

these methods are expensive, time consuming, and difficult to apply in the field

Among various processes available for wastewater treatment, recent studies have

shown adsorption to be the most promising technique for dye removal due to its

convenience, high efficiency, easy operation, simplicity of design, minimum

energy requirement, and can remove different type of pollutants [17]-{24] Various transition metal oxides with different structure, size, and morphology have been

recognized effective solid adsorbent for wastewater treatment because of their high

surface area, and presence of active sites [6], [22], [25]-{33]

Among various transition metal oxides, iron oxide (a-FexO3 and Fe304)

nanoparticles are drawing substantial attention owing to their unique properties

such as excellent stability, biocompatibility, low synthesis cost, easy of synthesis

and functionalization [25]-(33] However, there are some major challenges

associated with iron oxide nanostructures such as limited adsorption capacity, poor selectivity and recyclability [31 ], [32] To achieve high adsorption capacity several strategies like functionalization with organic molecules, polymer, carbon

nanotubes, and nanocomposite with graphene, graphene oxide, transition metal

dichalcogenide (TMD) has been used [31], [34]-{37] Recently, Chatterjee et al

reported developed 1,2,4,5-Benzentetracarboxylic acid functionalized FesO nanoparticles exhibiting high selectivity towards Congo Red (C R.) and high adsorption capacity [31] The functionalization of the nanostructures improves the adsorption capacity, nevertheless the functionalization processes are complex and costly Although there are several studies on the adsorption of dye molecules using,

1

1.3 @-He20s, Fess materials and their ability for organic dye removal 7

1.4.2 Methylthioninium chloride (Methylene Blue)

1.4.3 Rhodamine B CHAPTER 2 EXPERIMENT METHOD!

2.1.2, Fabrication of a-Fe:s nanoplates using hydrothermal method 17

3 Dabrication of aes nanorices using hydrothermal method 17

2.1.4, Phase transformation from a@-t'e203s to less veces "`

- Characterization methods co ceniiree ¬" _

3, Lltraviolet-visible spectroscopy (UV-Vis) 21 2.2.4, Brunauer-Emmett-Teller nitrogen adsorption/desorption

technique (BEL), cssseseesssnsseetsersnestistu vastness 22 2.2.5 Dye adsorption oxporiments su ccocceeeseneeoseroeoeoe 29

CHAPTER 3 RESULTS AND DISCUSSION

3.1 Morphology of as-synthesized iron oxide nanoparticles - 36

Figure 3.6 UV-Vis absorbance spectra of as-aynihesized 12 h a-Fe2Os temoplales

Figure 3.7 UV-Vis speetra of a) Congo Red (C R.), b) Rhodamine B (Rh B.), &) Methyfene Blue (M B.) aqueous solution before and after incubation wilh ax-

Figure 3.8 ac) Dye removal (maxim absorbance) afler different times of incubation and d) Bar diagram of percentage removal of C R., Rh B., and M B

Figure 3.9 Percentage C R dye removal efficiency of different concentration of as-synthesized a-Fe20s nanoplates (24 h) 34 Figure 3.10 Recycability of as-synthesized a-He20s nanoplates (24h) for removal

of C R dye after 10 min of contact time and initial concentration of 10 mg L 7

35 Figure 3.11 Effect of pH on adsorption of C R dye by a-Ke2Os nanoplates (24 h)

at pila) 3, b) 7, e) 10 and d) percentage C R dye removal efficiency after 60min

Figure 3.12 Bar diagram for the percentage removal of C R., Rh B and M B

dyes after 60 min of incubation with a-l’e:0s nanoplates (12, 24 h) 38 Figure 3.13 Bar diagram for the percentage removal of C.R., Rh B., and M B dyes after 60 min of incubation with a-Fe:0; nanarices (3, 5 h) 39

Tigure 3.14 Bar diagram for the percentage removal of a) C.R., Rh B and M B

dyes after 60 min of incubation with a-FezO; nanoplates (24 h) and ø-Fe:O; nanorioes (3 bh), b} C R dye after 60 and 120 min of incubation with a-EezO; and

Figure 3.15 UV-Vis spectra of mixture of CR, Rh B MB dyes, (thin lines)

and C R, Rh B., M B (thick red, onmge, bluc lines) aqueous solution before and

LIST OF TABLES

Table 1 Prapertios of hemalile and magnetite [59] 161 |

Table 2 Size parmnciers and BET surlace arca of iron oxide nanoriees

Table 3 Size parameters and BET surface area of iron oxide nanoplates

LIST OF TABLES

Table 1 Prapertios of hemalile and magnetite [59] 161 |

Table 2 Size parmnciers and BET surlace arca of iron oxide nanoriees

Table 3 Size parameters and BET surface area of iron oxide nanoplates

LIST OF TABLES

Table 1 Prapertios of hemalile and magnetite [59] 161 |

Table 2 Size parmnciers and BET surlace arca of iron oxide nanoriees

Table 3 Size parameters and BET surface area of iron oxide nanoplates

‘MD ‘Transition metal dichaleogenide

XRD X-ray diffraction

1.3 @-He20s, Fess materials and their ability for organic dye removal 7

1.4.2 Methylthioninium chloride (Methylene Blue)

1.4.3 Rhodamine B CHAPTER 2 EXPERIMENT METHOD!

2.1.2, Fabrication of a-Fe:s nanoplates using hydrothermal method 17

3 Dabrication of aes nanorices using hydrothermal method 17

2.1.4, Phase transformation from a@-t'e203s to less veces "`

- Characterization methods co ceniiree ¬" _

3, Lltraviolet-visible spectroscopy (UV-Vis) 21 2.2.4, Brunauer-Emmett-Teller nitrogen adsorption/desorption

technique (BEL), cssseseesssnsseetsersnestistu vastness 22 2.2.5 Dye adsorption oxporiments su ccocceeeseneeoseroeoeoe 29

CHAPTER 3 RESULTS AND DISCUSSION

3.1 Morphology of as-synthesized iron oxide nanoparticles - 36

1.3 @-He20s, Fess materials and their ability for organic dye removal 7

1.4.2 Methylthioninium chloride (Methylene Blue)

1.4.3 Rhodamine B CHAPTER 2 EXPERIMENT METHOD!

2.1.2, Fabrication of a-Fe:s nanoplates using hydrothermal method 17

3 Dabrication of aes nanorices using hydrothermal method 17

2.1.4, Phase transformation from a@-t'e203s to less veces "`

- Characterization methods co ceniiree ¬" _

3, Lltraviolet-visible spectroscopy (UV-Vis) 21 2.2.4, Brunauer-Emmett-Teller nitrogen adsorption/desorption

technique (BEL), cssseseesssnsseetsersnestistu vastness 22 2.2.5 Dye adsorption oxporiments su ccocceeeseneeoseroeoeoe 29

CHAPTER 3 RESULTS AND DISCUSSION

3.1 Morphology of as-synthesized iron oxide nanoparticles - 36

Figure 3.6 UV-Vis absorbance spectra of as-aynihesized 12 h a-Fe2Os temoplales

Figure 3.7 UV-Vis speetra of a) Congo Red (C R.), b) Rhodamine B (Rh B.), &) Methyfene Blue (M B.) aqueous solution before and after incubation wilh ax-

Figure 3.8 ac) Dye removal (maxim absorbance) afler different times of incubation and d) Bar diagram of percentage removal of C R., Rh B., and M B

Figure 3.9 Percentage C R dye removal efficiency of different concentration of as-synthesized a-Fe20s nanoplates (24 h) 34 Figure 3.10 Recycability of as-synthesized a-He20s nanoplates (24h) for removal

of C R dye after 10 min of contact time and initial concentration of 10 mg L 7

35 Figure 3.11 Effect of pH on adsorption of C R dye by a-Ke2Os nanoplates (24 h)

at pila) 3, b) 7, e) 10 and d) percentage C R dye removal efficiency after 60min

Figure 3.12 Bar diagram for the percentage removal of C R., Rh B and M B

dyes after 60 min of incubation with a-l’e:0s nanoplates (12, 24 h) 38 Figure 3.13 Bar diagram for the percentage removal of C.R., Rh B., and M B dyes after 60 min of incubation with a-Fe:0; nanarices (3, 5 h) 39

Tigure 3.14 Bar diagram for the percentage removal of a) C.R., Rh B and M B

dyes after 60 min of incubation with a-FezO; nanoplates (24 h) and ø-Fe:O; nanorioes (3 bh), b} C R dye after 60 and 120 min of incubation with a-EezO; and

Figure 3.15 UV-Vis spectra of mixture of CR, Rh B MB dyes, (thin lines)

and C R, Rh B., M B (thick red, onmge, bluc lines) aqueous solution before and

Figure 3.6 UV-Vis absorbance spectra of as-aynihesized 12 h a-Fe2Os temoplales

Figure 3.7 UV-Vis speetra of a) Congo Red (C R.), b) Rhodamine B (Rh B.), &) Methyfene Blue (M B.) aqueous solution before and after incubation wilh ax-

Figure 3.8 ac) Dye removal (maxim absorbance) afler different times of incubation and d) Bar diagram of percentage removal of C R., Rh B., and M B

Figure 3.9 Percentage C R dye removal efficiency of different concentration of as-synthesized a-Fe20s nanoplates (24 h) 34 Figure 3.10 Recycability of as-synthesized a-He20s nanoplates (24h) for removal

of C R dye after 10 min of contact time and initial concentration of 10 mg L 7

35 Figure 3.11 Effect of pH on adsorption of C R dye by a-Ke2Os nanoplates (24 h)

at pila) 3, b) 7, e) 10 and d) percentage C R dye removal efficiency after 60min

Figure 3.12 Bar diagram for the percentage removal of C R., Rh B and M B

dyes after 60 min of incubation with a-l’e:0s nanoplates (12, 24 h) 38 Figure 3.13 Bar diagram for the percentage removal of C.R., Rh B., and M B dyes after 60 min of incubation with a-Fe:0; nanarices (3, 5 h) 39

Tigure 3.14 Bar diagram for the percentage removal of a) C.R., Rh B and M B

dyes after 60 min of incubation with a-FezO; nanoplates (24 h) and ø-Fe:O; nanorioes (3 bh), b} C R dye after 60 and 120 min of incubation with a-EezO; and

Figure 3.15 UV-Vis spectra of mixture of CR, Rh B MB dyes, (thin lines)

and C R, Rh B., M B (thick red, onmge, bluc lines) aqueous solution before and

INTRODUCTION

The development of industry brings many economic, social and life benefits

Promote of industries is an important direction for any country However, this

direction still has many negative effects, especially in environmental issues

Strongly industrial development but dealing with its influence on nature is not

enough that has become the human concern

The uncontrolled discharge of organic dyes usually azo-groups containing industrial waste from textile, plastic, printing, paper-pulp, paint, and leather

industries has contaminated the water [1]-{6] Removing organic dyes from wastewater became crucial because of their adverse effect on human health and environment Several methods such as electrochemical, chlorination, ozonation, flotation, chemical oxidation, filtration, membrane separation, coagulation, adsorption, biological treatment, and photodegradation using photocatalyst has been used till date to remove organic dyes from wastewater [7]}-{16] However,

these methods are expensive, time consuming, and difficult to apply in the field

Among various processes available for wastewater treatment, recent studies have

shown adsorption to be the most promising technique for dye removal due to its

convenience, high efficiency, easy operation, simplicity of design, minimum

energy requirement, and can remove different type of pollutants [17]-{24] Various transition metal oxides with different structure, size, and morphology have been

recognized effective solid adsorbent for wastewater treatment because of their high

surface area, and presence of active sites [6], [22], [25]-{33]

Among various transition metal oxides, iron oxide (a-FexO3 and Fe304)

nanoparticles are drawing substantial attention owing to their unique properties

such as excellent stability, biocompatibility, low synthesis cost, easy of synthesis

and functionalization [25]-(33] However, there are some major challenges

associated with iron oxide nanostructures such as limited adsorption capacity, poor selectivity and recyclability [31 ], [32] To achieve high adsorption capacity several strategies like functionalization with organic molecules, polymer, carbon

nanotubes, and nanocomposite with graphene, graphene oxide, transition metal

dichalcogenide (TMD) has been used [31], [34]-{37] Recently, Chatterjee et al

reported developed 1,2,4,5-Benzentetracarboxylic acid functionalized FesO nanoparticles exhibiting high selectivity towards Congo Red (C R.) and high adsorption capacity [31] The functionalization of the nanostructures improves the adsorption capacity, nevertheless the functionalization processes are complex and costly Although there are several studies on the adsorption of dye molecules using,

1

Figure 3.6 UV-Vis absorbance spectra of as-aynihesized 12 h a-Fe2Os temoplales

Figure 3.7 UV-Vis speetra of a) Congo Red (C R.), b) Rhodamine B (Rh B.), &) Methyfene Blue (M B.) aqueous solution before and after incubation wilh ax-

Figure 3.8 ac) Dye removal (maxim absorbance) afler different times of incubation and d) Bar diagram of percentage removal of C R., Rh B., and M B

Figure 3.9 Percentage C R dye removal efficiency of different concentration of as-synthesized a-Fe20s nanoplates (24 h) 34 Figure 3.10 Recycability of as-synthesized a-He20s nanoplates (24h) for removal

of C R dye after 10 min of contact time and initial concentration of 10 mg L 7

35 Figure 3.11 Effect of pH on adsorption of C R dye by a-Ke2Os nanoplates (24 h)

at pila) 3, b) 7, e) 10 and d) percentage C R dye removal efficiency after 60min

Figure 3.12 Bar diagram for the percentage removal of C R., Rh B and M B

dyes after 60 min of incubation with a-l’e:0s nanoplates (12, 24 h) 38 Figure 3.13 Bar diagram for the percentage removal of C.R., Rh B., and M B dyes after 60 min of incubation with a-Fe:0; nanarices (3, 5 h) 39

Tigure 3.14 Bar diagram for the percentage removal of a) C.R., Rh B and M B

dyes after 60 min of incubation with a-FezO; nanoplates (24 h) and ø-Fe:O; nanorioes (3 bh), b} C R dye after 60 and 120 min of incubation with a-EezO; and

Figure 3.15 UV-Vis spectra of mixture of CR, Rh B MB dyes, (thin lines)

and C R, Rh B., M B (thick red, onmge, bluc lines) aqueous solution before and

‘MD ‘Transition metal dichaleogenide

XRD X-ray diffraction

‘MD ‘Transition metal dichaleogenide

XRD X-ray diffraction