Abstract of Doctoral thesis: Research on the synthesis and characterization of structure and properties of TiO2-based Nanocomposite for the treatment of some pollutants in air enviroment

The objective of the thesis is to produce two types of phase-phase Nano TiO2 materials Nitrogen inclusion on aluminum oxide metal (N-TiO2 / Al2O3) applied as a filter for air purifiers and nanocomposit hydroxyl apatite coated on nitrogen doped TiO2 (HA / N-TiO2) on the wall to treat toluene, Bacteria and fungi contaminate the air.

AND TRAINING SCIENCE AND TECHNOLOGY

GRADUATE UNIVERSITY OF SCIENCE AND TECHNOLOGY

-MA THI ANH THU

RESEARCH ON THE SYNTHESIS AND

CHARACTERIZATION OF STRUCTURE AND PROPERTIES OF TiO2-BASED NANOCOMPOSITE FOR THE TREATMENT OF SOME POLLUTANTS IN

AIR ENVIROMENTMajor: Theoretical Chemistry - Physical Chemistry

Code: 62.44.01.19

ABSTRACT OF DOCTORAL THESIS

Hanoi - 2017

The thesis was completed at Graduate University of Science and Technology, Vietnam Academy of Science and Technology

Supervisor: Assoc Prof Dr Nguyen Thi Hue

Time: Date… month … 2018

This thesis can be found at:

- The library of Graduate University of Science and Technology;

- National Library of Vietnam

INTRODUCTION

1 The rationale of the thesis

Nowadays, the transportation, the industry activities, craft villages, etc has emitted many high-toxic compounds and harmful bacteria harmful to human health into the air Therefore, the polluted air is an urgent issue that needs to be studied and solved

A variety of methods has been employed to treat the polluting substances in the air such as membrane filtration, adsorption by activated carbon, thermophilization, ionization, ozone, photocatalyst,

photocatalyst possesses many outstanding advantages such as complete conversion of toxic compounds into carbon dioxide, water, and salts but no by-products, the ambient operation conditions, easy-to-look and low cost

band gap (Eg 3,2eV), the reaction occurring only when the radiation

is in the ultraviolet area, the high rate of the combination of high electron-hole pair leads to the low efficiency of photochemical quantification and photocatalysis Thus, doping of metals or

catalyst that is operable in the visible light region In all of the used elements, nitrogen is the most frequently employed because the process is very simple but effective

of adsorption absorption, while hydroxyl apatite (HA) is a good adsorbent but has a poor oxidation – reduction feature There has

is highly photo-catalytic and has good adsorption properties In

destroying other materials In particular, the HA/TiO2 composite is dispersed as a suspension in water and as a result, it is

micro-porous structure and it is necessary to investigate the stability of suspended solid

materials are able to effectively treat the airborne contaminants in the visible light, thereby increasing the applicability in the practical

reasons, the thesis is proposes as "Research on the synthesis and

characterization of structure and properties of TiO 2 -based composite for the treatment of some pollutants in air environment

nano-" The topic has practical significance, contributing to the reduction

of the air pollution caused by chemicals and bacteria

2 The objectives of the thesis

The objective of the thesis is to produce two types of materials:

as membrane for air purification and hydroxyl apatite nano-composite

the treatment of toluene, bacteria and fungal contamination in the air

3 The main research activities

- Characterization of the structure, properties and composition of

- Investigate the catalytic activity of the material through toluene

treatment, B.cereus, S areus, E coli, B cepacia and Candida

albicans

4 The content

The thesis is composed of 117 pages, 28 tables, 77 figures, 117 references and 3 appendixes There are following chapters: Introduction (2 pages); chapter 1: Literature review (39 pages); chapter 2: Methodology (22 pages); chapter 3: Resutl and discussion

(52 pages); Conclusion (2 pages)

CHAPTER 1: LITERATURE REVIEW

1.1 Introduction of some air pollutants and treatment methods 1.2 TiO 2 nanomaterial

1.3 TiO 2 nanoparticles coated on aluminum oxide

2.2.1 Synthesis of N- TiO2/Al 2 O 3

2.2.2 Synthesis of HA/N-TiO2 nanocomposite

2.3 Characterization of materials

The state-of-the-art technique and equipment such as: thermal analysis (TGA), X-ray diffraction (XRD), IR spectroscopy, energy-dispersive X-ray spectroscopy (EDX), ICP-MS mass spectrometry were employed to determine the structure, the nature and

specific surface area of the samples were determined by SEM and BET method The critical absorption wavelength of the material is determined by UV-Vis absorption spectrometry

2.4 Catalyst activity testing

2.4.1 Test of N-TiO2/Al 2 O 3 on toluene treatment

The 1m³ test chamber performs the experiments to evaluate the efficiency of the toluene treatment corresponding to the actual room

membrane in the air purifier, dimension: 370×100×6mm/membrane,

investigated the effect of light source, the weight of material, initial toluene concentration, photo-catalyst activity, kinetics of toluene

oxidation and the adsorption capacity of the material via the toluene

degradation

2.4.2 Test of HA/N-TiO 2 on toluene treatment

toluene concentration, kinetics of toluene oxidation and catalytic stability of the material

2.4.3 Toluene concentration analysis method

Toluene concentration was analyzed on the gas chromatograph GC-FID Shimadzu 2010, Japan The quantitative limit of the toluene

2.4.4 Testing the bactericidal capability of HA / N-TiO 2 material

experiments were performed with four bacteria strains: B.cereus, S

areus, E.coli, B cefalacia and a fungal strain of Candida

CHAPTER 3: RESULTS AND DISCUSSION

3.1 N-TiO 2 /Al 2 O 3 material

3.1.1 Synthesis of N-TiO 2 /Al 2 O 3 material

Composition (mole) Number Notation

Calcination time (hour)

Calcination temprature (ºC)

Table 3.3 N-TiO 2 /Al 2 O 3 - The effect of concentration

Number Notation Immersion

time

Turn of immersion

Calcination time (hour)

Calcination temprature (ºC)

3.1.2 Structure and properties of N-TiO 2 /Al 2 O 3

3.1.2.1 Effect of time and turn of dip coatings

Figure 3.2 shows that there are two large peaks: Al (200) and Al

25.3°(101); 37.8°(004); 48°(200), 54º(105); 55°(211) are the anatase

intensity The small peaks indicate that the pattern of the 60-minute immersed sample is very strong, suggesting that the 60-minute samples are more crystallized than the other ones Thus, the

optimized turn of dipping is 5 times

3.1.2.2 Effect of composition of N-TiO 2 solutions

the column from top to bottom) When the samples had the same TTIP ratio (in left to right row), the particle size of 2mol-DEA sample is more uniformed than that of 1mol-DEA sample This conclusion is proved from the XRD spectrum (Fig 3.6) The intensity of the X-ray diffraction peak of the samples increases with the increase of TTIP concentration from 1 to 3 mol From the width

calculated in the range 12-33 nm from the Scherrer's formulation

the amount of TTIP mole per unit and decreasing slowly (1-2nm) by increasing DEA from 1 mole to 2 moles (Fig 3.6B) The sharpness of peaks also differed between the samples, especially with the small

Fig 3.5 SEM picture of N-TiO 2 /Al 2 O 3 sample with different sol

Nồng độ TTIP (mol)

Fig 3.7 The UV-Vis spectra of N-TiO 2 in N-TiO 2 /Al 2 O 3 material

work effectively with the visible light

3.1.3 Results of the photo-catalyst activity of N-TiO 2 /Al 2 O 3

3.1.3.1 Investigate the adsorption capacity of N-TiO 2 /Al 2 O 3

Light sources are used in two types of lamp: 10w fluorescent daylight and 8w UV365nm lamp In each experiment, the initial

with or without nitrogen express the weak adsorption of toluene

3.1.3.2 Effect of the light source

If being illuminated by the fluorescent lamp (Figure 3.8),

non-doped sample (14%) In case with the 365nm UV lamp (Figure

UV365nm lamp

0 20 40 60 80 100

Fig 3.8 Performance of toluene

treatment N-TiO 2 /Al 2 O 3 and

fluorescent light

Fig 3.9 Performance of toluene treatment N-TiO 2 /Al 2 O 3 and the light UV365nm

3.1.3.3 Effect of photo-catalyst weight

As can be seen from the Figure 3.10, the optimized weight of TiO2/Al2O3 is 40 g for both S1-1 and S1-2

0 200 400 600 800 1000

Fig 3.10 Performance of toluene

decomposition N-TiO 2 /Al 2 O 3 in

different catalyst weight

N-TiO 2 /Al 2 O 3 3.1.3.4 Effect of initial toluene concentration

In the initial toluene concentration range of 100-500 μg/m3, when

toluene molecules is high, thus the rate of toluene degradation increases (Figure 3.11) If the initial toluene concentration is in the

gas, reducing the light density on the surface of the TiO2 particles, resulting in a reduction in the efficiency of toluene decomposition

3.1.3.5 Kinetics of toluene oxidation using N-TiO 2 /Al 2 O 3

Table 3.11 The rate constant

(k obs ) initial speed (r 0 ) of the

toluene decomposition equals

decomposition by N-TiO 2 /Al 2 O 3

Figure 3.13 indicates that the kinetics of the toluene

The investigation shown that after 2-6 months, the toluene

3.2 HA/N- TiO2 nanocomposite

3.2.1 Synthesis of HA/N- TiO2 nanocomposite

3.2.1.1 Production results of N- TiO 2 powder

in the form of rods of 5×10nm, with a length of about 10-500nm, two phases: anatase and rutile with the anatase/rutile ratio of about 80/20

Faculty of Chemistry, HUS, VNU, D8 ADVANCE-Bruker - Sample B

01-078-2486 (C) - Anatase, syn - TiO2 - Y: 77.17 % - d x by: 1 - WL: 1.5406 - Tetr agonal - a 3.78450 - b 3.78450 - c 9.51430 - alpha 90.000 - beta 90.000 - gamma 90.000 - Body-centered - I41/amd ( 141) -

0 100 200 300 400 500 600 700 800

A

A A A

A R

Fig 3.20 SEM picture of TiO 2

after the hydrothermal and

calcination at 800ºC

Fig 3.21 XRD patterns of TiO 2

after the doping nitrogen

after being doped with nitrogen The result of EDX and UV-Vis

light

3.2.1.2 Synthesis of HA/N-TiO 2 materials

Table 3.12 The HA/N-TiO 2 samples – Effect of time

Number Notation Immersion time

Table 3.13 The HA/N-TiO 2 samples – Effect of concentration

Number Notation Immersion time of

N-TiO 2 powder (hour)

3.2.2 Characteristics of HA/N-TiO2 materials

Figure 3.24 shows the results of XRD analysis of HA/N-TiO2 samples at different HA formation times Diffraction peaks of anatase and rutile phases of TiO2 appear in all samples A small but clearly visible peak at 2θ31.6° is the

face (211) of the HA crystals This peak represents a small crystalline HA The intensity of the HA peak increased sharply from 1h to 6h, then 12h and 24h showed no increase in intensity

A A R

R

R R

HA

The original N-TiO2 powder (without HA) had large slots between the rods If the HA is coated on the surface, the size of the

3.25) In the 1h sample, there are some small HA crystals located on

is very uniformed However, in the 6h-sample, there is some

phenomenon gradually increases in samples longer than 6h This prevents the uniformed distribution of material when mixing the

is in the range of 3 to 6 hours

3.2.2.2 Effect of concentrations of Ca 2 + and PO 4

in the stock solution

A

A A

A A A

A R

R R R

R

HA

Fig 3.26 XRD patterns of HA/N-TiO 2 samples from S 5 -S 15

Figure 3.26 shows that at 2θ31.6°, the intensity of the

diffraction peak of HA increases with increasing concentration of

PO4

2- The concentration of HA is approximately 30% of

Ca(PO4)6(OH)2 molecular formula; therefore it is suggested that the

(PO4,CO3)6 (OH)2

The capability of absorbing the visible light of the

385m2/g respectively Comparing to other studies, the surface area of

3.2.3 Results of photo-catalyst activity evaluation of HA/N-TiO 2

3.2.3.1 The role of HA in HA/N-TiO 2 materials

The experiment conditions are: density 10mL/brick/time, PVC ≈

The main cause was the increase of OH groups on the surface of

Fig 3.34 The efficiency of toluene

treatment of HA/N-TiO 2 under

irradiation with fluorescent lamps

Fig 3.35 Effect of HA/N-TiO 2

content on toluene degradation 3.2.3.2 Effect of HA/N-TiO 2 content in suspension solution

The optimal content of HA/N-TiO2 was determined by the toluene treatment with suspension solution that has the solid content (notated as PVC) from 10/1000 (g/ml) to 75/1000 (g/ml) The efficiency of photo-catalyst from PVC10 to PVC25 was 74.92% - 82.84% After PVC25, the photo-catalyst efficiency decreases The optimal PVC value is 25/1000 (g/ml) under the experiment conditions (Fig 3.35)

3.2.3.3 Effects of material weight

The photo-catalyst efficiency increased from 82.84% to 92.92% when the number of coating is 1 or 2 After the second coating, the efficiency of photo-catalyst reduces As a result, the two-time coated

when being coated on primer bricks From the experiment, the

3.2.3.4 Effect of light intensity

The photo-catalyst efficiency is almost unchanged when the

density of light does not greatly affect the photo-catalyst activity of the material under experiment conditions

3.2.3.5 Kinetics of photo-catalytic oxidation of toluene by HA/N-TiO 2

slope of graph is high, indicating that the concentration of toluene in

explained by the fact that high toluene concentrations may interfere with the movement of reactants and products from the pores inside the material to the surface, if the initial toluene concentration is too low (under the lowest value of the standard) Comparing this with the

results shown in Figure 3.11, although HA/N-TiO2 has a high specific surface area and porosity, due to the passive use, the toluene

actively used in an air purifier

y = 229,9x + 0,1009

R2 = 0,988 0,0

0,5 1,0 1,5 2,0 2,5 3,0

3.2.3.6 The stability of photo-catalyst activity of HA/N-TiO 2 material

The results of investigating the photo-catalytic durability of

efficiency of the material decreases with the time and the number of consumption After 20 times of use, the efficiency decreased from 93.5% to 78.6% After 2 years of use, the efficiency dropped to 70.5%

3.2.3.7 Results of bacterial and fungal treatment of HA/N-TiO 2 Bacteria treatment

the development and gave 59% efficiency

Fungus treatment

At the time of 3 hours, the fungus was completely eliminated by

porous of material, leading to the higher contact surface; therefore,

CONCLUSION

From the results, there are some following conclusions:

method, starting from precursors: tetraisopropyl orthotitanate, diethanolamine and ethanol, synthesized The synthesis process is simple and highly stable with two stages includes the preparation of

2 The XRD, SEM, UV-Vis, ICP-MS techniques have been employed to evaluate the structure, properties and composition of N-

and its particles size is from 15nm to 30 nm, and absorbs light with

approximately 6% of the material’s weight

used as a filter membrane) was investigated via the air purifier for toluene treatment The toluene treatment efficiency of 30% was obtained with both 365nm UV light and fluorescent lamp at the conditions: 40g catalyst, the ambient temperature and pressure, initial