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.

MINISTRY OF EDUCATION AND TRAINING VIETNAM ACADEMY OF 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 ENVIROMENT Major: 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 Reviewer 1: Reviewer 2: Reviewer 3: The doctoral thesis will be defended with the Evaluation Committee at Graduate University of Science and Technology, Vietnam Academy of Science and Technology Time: Date… month … 2018 This thesis can be found at: - The library of Graduate University of Science and Technology; - National Library of Vietnam INTRODUCTION 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, irradiation ultraviolet etc In particular, the titanium dioxide (TiO2) 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, easyto-look and low cost However, TiO2 has some disadvantages as follows: the large 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 nonmetals is often utilized on the crystal structure of TiO2 to obtain a 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 TiO2 is able to strongly oxidized – reduce, but has low capability of adsorption absorption, while hydroxyl apatite (HA) is a good adsorbent but has a poor oxidation – reduction feature There has been a lot of studies on HA/TiO2 composite from HA with TiO2 that is highly photo-catalytic and has good adsorption properties In addition, the HA coated on the TiO2 surface creates a space that allows TiO2 to perform the photo-catalytic properties without destroying other materials In particular, the HA/TiO2 composite is dispersed as a suspension in water and as a result, it is environmentally friendly However, TiO2 is a dense but not a microporous structure and it is necessary to investigate the stability of suspended solid TiO2 coated on metal aluminum oxide (TiO2/Al2O3) and HA coated on titanium dioxide nanoparticles (HA/TiO2) are promising materials for the treatment of some pollutants such as VOCs, CxHy, NOx, CO, bacteria in the air If being doped with nitrogen, these two materials are able to effectively treat the airborne contaminants in the visible light, thereby increasing the applicability in the practical cases The nano N-TiO2 rod has a larger specific surface area than that of the granular one, therefore the HA/N-TiO2 nanocomposite from N-TiO2 rod is more efficient and easier to have the stability in the suspension than that from the granular N-TiO2 For the above reasons, the thesis is proposes as "Research on the synthesis and characterization of structure and properties of TiO2-based nanocomposite for the treatment of some pollutants in air environment " The topic has practical significance, contributing to the reduction of the air pollution caused by chemicals and bacteria The objectives of the thesis The objective of the thesis is to produce two types of materials: Nano N-TiO2 coated on metal oxide aluminum (N-TiO2/Al2O3) used as membrane for air purification and hydroxyl apatite nano-composite coating on TiO2 doped Nitrogen (HA/N-TiO2) coated on the wall for the treatment of toluene, bacteria and fungal contamination in the air The main research activities - The synthesis of two nanostructured TiO2 photocatalyst materials (N-TiO2/Al2O3 and HA/N-TiO2) - Characterization of the structure, properties and composition of N-TiO2/Al2O3 and HA/N-TiO2 - Investigate the catalytic activity of the material through toluene treatment, B.cereus, S areus, E coli, B cepacia and Candida albicans The content The thesis is composed of 117 pages, 28 tables, 77 figures, 117 references and 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 TiO2 nanomaterial 1.3 TiO2 nanoparticles coated on aluminum oxide 1.4 HA/TiO2 nanocomposite 1.5 Evaluation of the photo-catalyst activity of the material CHAPTER 2: METHODOLOGY 2.1 Chemicals, apparatus and equipment 2.2 Synthesis of materials 2.2.1 Synthesis of N- TiO2/Al2O3 N- TiO2/Al2O3 material was synthesized by sol-gel method from 2-phase metal alkoxide, including: N-TiO2 solubilization stage and N-TiO2 nanofiltration stage on aluminum fiber oxide 2.2.2 Synthesis of HA/N-TiO2 nanocomposite HA/N-TiO2 materials were synthesized in two phases, including N-TiO2 powder phase and HA/N-TiO2 powder phase 2.3 Characterization of materials The state-of-the-art technique and equipment such as: thermal analysis (TGA), X-ray diffraction (XRD), IR spectroscopy, energydispersive X-ray spectroscopy (EDX), ICP-MS mass spectrometry were employed to determine the structure, the nature and composition of N- TiO2/Al2O3 and HA/N-TiO2 Morphology 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/Al2O3 on toluene treatment The 1m³ test chamber performs the experiments to evaluate the efficiency of the toluene treatment corresponding to the actual room but at a small scale N-TiO2/Al2O3 material is used as a filter membrane in the air purifier, dimension: 370×100×6mm/membrane, the comparison sample is unmodified TiO2/Al2O3 The thesis 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-TiO2 on toluene treatment The HA/N-TiO2 material is coated on a brick surface of 40cm  40cm, using 4brick/1experiment/1m3 chamber TiO2-P25 and HA/TiO2-P25 were used to compare The investigated parameters are: the role of HA in HA/N-TiO2 material, the effect of HA/N-TiO2 content in suspension solution, HA/N-TiO2 content, light, initial 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 determination method is 3.33 μg/m3 2.4.4 Testing the bactericidal capability of HA / N-TiO2 material HA/N-TiO2 material is coated on 10×10cm bricks The 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-TiO2/Al2O3 material 3.1.1 Synthesis of N-TiO2/Al2O3 material The sol solutions and the materials N-TiO2/Al2O3 are denoted as Sa-b Where (a) is the mole of TTIP, (b) is the mole of DEA Table 3.1 Composition of sol N-TiO2 Number Notation S1-1 S1-2 S2-1 S2-2 S3-1 S3-2 Composition (mole) TTIP DEA 1 2 2 3 EtOH 34 34 34 34 34 34 Table 3.2 N-TiO2/Al2O3 - The effect of time Num Notation Immersio ber n time S1-1-30’ 30 S1-1-60’ 60 S1-1-90’ 90 S1-1-120’ 120 S1-1-24h 24 hour Turn of immersion 1- 10 1- 10 1- 10 1- 10 1- 10 Calcination time (hour) 3 3 Calcination temprature (ºC) 470 470 470 470 470 Table 3.3 N-TiO2/Al2O3 - The effect of concentration Number Notation Immersion time Turn of immersion 5 5 5 S1-2 S2-1 S2-2 S3-1 S3-2 60 60 60 60 60 Calcination Calcination time (hour) temprature (ºC) 470 470 470 470 470 3.1.2 Structure and properties of N-TiO2/Al2O3 3.1.2.1 Effect of time and turn of dip coatings 2000 Al(200) Al(202) 1500 A(101) A(004) Cps A(200) 1000 A(105) A(211) S 1-1-24h S 1-1-120' S 1-1-90' 500 S 1-1-60' S 1-1-30' 20 25 30 35 40 45 –Theta-Scale 50 55 Fig 3.2 XRD patterns of N-TiO2/Al2O3 samples 30 - 24 hour Fig 3.3 SEM of Al2O3 before coating and after coating with N-TiO2 60 Figure 3.2 shows that there are two large peaks: Al (200) and Al (202) of the carrier material The diffraction peaks occurring at 2θ  25.3°(101); 37.8°(004); 48°(200), 54º(105); 55°(211) are the anatase phase of TiO2, and the peak A (101) at 2θ  25.3° has the strongest 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 dipping time of Al2O3 fiber in N-TiO2 sol is 60 minutes The surface of the Al2O3 fiber is initially rough like fish scales After turns of dip-coating and incubation, the surface of the Al2O3 fiber has become almost flat with the N-TiO2 layer formed and there are some indications of the N-TiO2 cracking (Fig 3.3) Thus, the optimized turn of dipping is times 3.1.2.2 Effect of composition of N-TiO2 solutions N-TiO2 crystals are granular in all samples (Fig 3.5) The particle size of N-TiO2 increases when the mole of TTIP is higher (in 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 to mol From the width of the diffraction peak at 2θ  25.3° on the face (101) described in Figure 3.6A, the average N-TiO2 particle size of samples is calculated in the range 12-33 nm from the Scherrer's formulation The N-TiO2 particle size increased rapidly (8-12nm) by increasing the amount of TTIP mole per unit and decreasing slowly (1-2nm) by increasing DEA from mole to moles (Fig 3.6B) The sharpness of peaks also differed between the samples, especially with the small peak such as A(004) at 2θ  37.8° which is easily observed in sample S1-2 but are difficult to recognize in the remaining samples Thus, the S1-2 has the highest crystallinity S1-1 S1-2 S2-1 S2-2 S3-1 S3-2 Fig 3.5 SEM picture of N-TiO2/Al2O3 sample with different sol Kích thước hạt (nm) concentration (A) S 3-2 S3-1 S 2-2 S2- S1-2 S1-1 23 24 25 26 27 (B) 40 30 DEA DEA 20 10 0 Nồng độ TTIP (mol) 28 Cps A(004) S 3-2 S 3-1 S 2-2 S 2-1 S 1-2 S 1-1 20 25 30 35 40 45 50 55 60 - Theta - Scale Fig 3.6 XRD patterns of N-TiO2/Al2O3 samples in different sol concentration 10 UV365nm lamp 80 70 60 50 40 30 20 10 S1-1 100 S1-2 80 Efficiency, (%) Efficiency, (%) Fluorescent lamp TiO2/Al2O3 S1-1 60 S1-2 40 TiO2/Al2O3 20 8 Time, (hour) Time, (hour) Fig 3.8 Performance of toluene Fig 3.9 Performance of toluene treatment N-TiO2/Al2O3 and treatment N-TiO2/Al2O3 and the fluorescent light light UV365nm 3.1.3.3 Effect of photo-catalyst weight The weight of N-TiO2/Al2O3 catalyst varied from 10-60g The experiment conditions are: C° ≈ 400μg/m3, fluorescent, t = hours As can be seen from the Figure 3.10, the optimized weight of NTiO2/Al2O3 is 40 g for both S1-1 and S1-2 1000 800 100µg/m3 300ug/m3 C, (µg/m ) Efficiency, (%) 100 S1-1 50 S1-2 600 500µg/m3 700µg/m3 400 200 900µg/m3 0 10 20 30 40 50 60 mcat , (gr) Time, (hour) Fig 3.10 Performance of toluene decomposition N-TiO2/Al2O3 in different catalyst weight Fig 3.11 The correlation between C0 and the photocatalyst activity of NTiO2/Al2O3 3.1.3.4 Effect of initial toluene concentration In the initial toluene concentration range of 100-500 μg/m3, when C0 increases, the frequency of collisions between free radicals and toluene molecules is high, thus the rate of toluene degradation increases (Figure 3.11) If the initial toluene concentration is in the range of 700-900μg/m3, the light can be absorbed by toluene in the 11 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-TiO2/Al2O3 Table 3.11 The rate constant (kobs) initial speed (r0) of the toluene decomposition equals NC0 kobs (µg/m ) 1/r0, (min.µg/m ) 3,5 TiO2/Al2O3 r0 -1 (minute ) -1 (µg/m minute ) 100 0,0026 2,354118 300 0,0025 1,766800 500 0,0018 0,904428 700 0,0044 1,338744 900 0,0034 0,343808 3,0 2,5 2,0 1,5 y = 269,49x + 0,1972 1,0 R = 0,9373 0,5 0,0 0,005 0,01 0,015 1/C0, µg/m Fig 3.13 The dependence of 1/r0 in 1/C0 in toluene decomposition by N-TiO2/Al2O3 Figure 3.13 indicates that the kinetics of the toluene decomposition by N-TiO2/Al2O3 conforms to the LangmuirHinshelwood model The value of k-1 is 0.1972 and the slope (269.49) is the value of k-1K-1L-H Thus, the rate constant is k = 5.0710 (min-1μg/m3) and the adsorption constant is KL-H = 7.32 × 10-4 (μg/m3) 3.1.3.5 The stability of photo-catalyst activity of N- TiO2/Al2O3 The investigation shown that after 2-6 months, the toluene treatment efficiency of N-TiO2/Al2O3 are relatively stable over 80% (sample S1-1) and over 90% (sample S1-2) After 12-24 months, the efficiency decreases to 60-70% and 70-80%, respectively with S1-1 and S1-2 3.2 HA/N- TiO2 nanocomposite 3.2.1 Synthesis of HA/N- TiO2 nanocomposite 12 3.2.1.1 Production results of N- TiO2 powder Analysis of SEM and XRD shows that the commercial TiO2 powders are particle, larger than 100 nm, single-phase anatase TiO2 After the hydrothermal and calcination at 800ºC, TiO2 was obtained 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 800 d=3.505 700 600 Lin (Cps) 500 400 d=1.363 d=1.491 d=1.479 100 d=1.698 d=2.425 d=2.327 d=2.372 200 d=1.664 d=1.889 300 10 20 30 40 50 60 70 2-Theta - Scale File: Thu MT mau B.r aw - Type: 2Th/Th loc ked - Start: 10.000 ° - End: 70.000 ° - Step: 0.030 ° - Step time: 0.8 s - Temp.: 25 °C (Room) - Time Started: 14 s - 2-Theta: 10.000 ° - Theta: 5.000 ° - Chi: 0.00 ° 01-078-2486 (C) - Anatase, syn - TiO2 - Y: 77.17 % - d x by: - 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) - Fig 3.15 SEM picture of the commercial TiO2 Fig 3.16 XRD commercial TiO2 1500 patterns of A A 1000 A R A A R A R 2,0 R Cps RA 1,0 500 0,5 0,25 TiO 20 25 30 35 40 45 50 55 60 - Theta - Scale Fig 3.20 SEM picture of TiO2 Fig 3.21 XRD patterns of TiO2 after the hydrothermal and after the doping nitrogen calcination at 800ºC There are two phases (anatase and rutile) in the TiO2 samples after being doped with nitrogen The result of EDX and UV-Vis show that the N-ratio represents over 2% of the N-TiO2 weight, the critical wavelength of the N-TiO2 samples is 410-460nm, in which the sample with mTiO2: mure = 1: absorbs the high quantity of visible light 13 3.2.1.2 Synthesis of HA/N-TiO2 materials Table 3.12 The HA/N-TiO2 samples – Effect of time Number Notation Immersion time Concentration Concentration of N-TiO2 Ca2+ PO43powder (hour) (mmol/L) (mmol/L) HA/N-TiO2 1h 25 10 HA/N-TiO2 3h 25 10 HA/N-TiO2 6h 25 10 HA/N-TiO2 12h 12 25 10 HA/N-TiO2 24h 24 25 10 Table 3.13 The HA/N-TiO2 samples – Effect of concentration Number Notation Immersion time of Concentration Concentration N-TiO2 powder Ca2+ PO43(hour) (mmol/L) (mmol/L) S5 12,5 S7 17,5 S10 25 10 S15 37,5 15 3.2.2 Characteristics of HA/N-TiO2 materials 3.2.2.1 Effect of N-TiO2 immersion time in the stock solution 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 14 2000 A A 1500 A A A R R RA Cps HA A R R 24 h R 1000 12 h 6h 500 3h 1h N - TiO 20 25 30 35 40 45 50 55 60 - Theta - Scale Fig 3.24 XRD patterns of HA/N- TiO2 samples 1-24 hour N-TiO2 HA/N-TiO2 – 1h HA/N-TiO2 – 3h HA/N-TiO2 – 6h HA/N-TiO2 – 12h HA/N-TiO2 – 24h Fig 3.25 SEM picture of HA/N- TiO2 samples 1-24 hour 15 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 N-TiO2 rod in the HA/N-TiO2 samples does not change (Figure 3.25) In the 1h sample, there are some small HA crystals located on the edge and on the surface of N-TiO2 In the 3h- and 6h-samples, the surface of the specimen is smooth, and the HA coated on the N-TiO2 is very uniformed However, in the 6h-sample, there is some accumulation between the N-TiO2 rods via the HA crystals and this phenomenon gradually increases in samples longer than 6h This prevents the uniformed distribution of material when mixing the HA/N-TiO2 in water Thus, the optimized crystallization time of HA is in the range of to hours 3.2.2.2 Effect of concentrations of Ca2 + and PO43- in the stock solution 2000 A A 1500 A A A Cps R RA A HA 1000 R R R S-15 S-10 500 S-7 S-5 20 25 30 35 40 45 50 55 60 - Theta - Scale Fig 3.26 XRD patterns of HA/N-TiO2 samples from S5-S15 16 Figure 3.26 shows that at 2θ  31.6°, the intensity of the diffraction peak of HA increases with increasing concentration of Ca2 + and PO43- proving that the higher the concentration of Ca2 + and PO43- in the stock solution, the higher the content of HA in the nanocomposite The results of EDX, ICP-MS, IR and SEM showed that the S10 possesses the highest purity Besides the elements such as Ti, Ca, P, O, N, the HA/N-TiO2 samples have Mg, Na as well OH-, PO43- and CO32- The concentration of HA is approximately 30% of HA/N-TiO2 Thus, the synthesized HA is not completely pured as the Ca(PO4)6(OH)2 molecular formula; therefore it is suggested that the approximate chemical formula of HA of this thesis is (Ca, Mg, Na)10 (PO4,CO3)6 (OH)2 Fig 3.33 UV-Vis spectrum of HA/N-TiO2 and HA/TiO2 – P25 The capability of absorbing the visible light of the 3h-HA/NTiO2 sample is better than that of the 6h-sample (Fig 3.33) The critical wavelength of the HA/N-TiO2 was reduced to 34-37 nm in compared with the untreated N- TiO2 sample Through BET analysis, the surface area of pre- and post-HA-coated N- TiO2 samples are larger than that of TiO2-P25 Specifically, the surface area of the NTiO2, HA/N-TiO2-3h and 6h samples are 231m2/g, 298m2/g and 17 385m2/g respectively Comparing to other studies, the surface area of the HA/N-TiO2 nanocomposite of this thesis is almost seven times higher than that of TiO2 - P25 and is times higher than that of HA/TiO2 material prepared by Soysal (78.4 - 80.2 m2/g), and Anastasios Mitsionis (60.4 - 78.8 m2/g) 3.2.3 Results of photo-catalyst activity evaluation of HA/N-TiO2 3.2.3.1 The role of HA in HA/N-TiO2 materials The experiment conditions are: density 10mL/brick/time, PVC ≈ 10/1000 (g/ml), C0 ≈ 400μg/m3, fluorescent lamp, t = hours Figure 3.34 shows that adsorption of TiO2-P25 is negligible, around 0.01%, HA/TiO2-P25 adsorbed by 2.88%, and HA/N-TiO2 adsorbed by 5.16% The toluene adsorption capacity of HA/N-TiO2 is stronger than that of TiO2-P25 and HA/TiO2 - P25 samples because the surface area of the rod TiO2 is higher than that of the granule TiO2 The main cause was the increase of OH groups on the surface of TiO2 and HA resulting in the increase in number of the adsorption site per unit mass 80 C, (µg/m ) Efficiency, (%) 500 T iO2 - P25 HA/T iO2 - P25 HA/N-T iO2 100 60 40 400 Brick 300 Brick + Lamp PVC 10 200 20 100 0 Tim e , ( ho u r) PVC 25 PVC 50 PVC 75 0,5 Time, (hour) Fig 3.34 The efficiency of toluene Fig 3.35 Effect of HA/N-TiO2 treatment of HA/N-TiO2 under content on toluene degradation irradiation with fluorescent lamps 3.2.3.2 Effect of HA/N-TiO2 content in suspension solution 18 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 or After the second coating, the efficiency of photo-catalyst reduces As a result, the two-time coated sample gives the optimized weight for the HA/N-TiO2 photo-catalyst when being coated on primer bricks From the experiment, the optimum surface of HA/N-TiO2 material on the tile is approximately 3.125 (g/m2) 3.2.3.4 Effect of light intensity The photo-catalyst efficiency is almost unchanged when the density of light is increased from 10 - 40w/m2 It can be seen that 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-TiO2 Figure 3.38 shows that in the range C0 = 300-500 μg/m3 the slope of graph is high, indicating that the concentration of toluene in this range greatly decreases At lower concentrations (100μg/m3) or higher (900μg/m3), the graphs showed a lower slope This can be 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 19 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 treatment efficiency is lower than that of with N-TiO2/Al2O3 being actively used in an air purifier 1000 3,0 1/r0 , (min.µg/m ) C, (µg/m ) 900µg/m3 800 700µg/m3 600 500µg/m3 300µg/m3 400 100µg/m3 200 2,5 2,0 1,5 y = 229,9x + 0,1009 1,0 R = 0,988 0,5 0,0 0 100 200 300 400 500 Time, (hour) 0,005 0,01 0,015 1/C0, (µg/m3) Fig 3.38 Correlation between Fig 3.39 The graph shows C0 and photochemical dependence 1/r0 on 1/C0 with capacities of HA/N-TiO2 initial toluene concentrations 100- 900μg/m3 3.2.3.6 The stability of photo-catalyst activity of HA/N-TiO2 material The results of investigating the photo-catalytic durability of HA/N-TiO2 on the brick surface showed that the adsorption 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 years of use, the efficiency dropped to 70.5% 3.2.3.7 Results of bacterial and fungal treatment of HA/N-TiO2 Bacteria treatment The bacterial killing efficiency of HA/N-TiO2 is higher than that of HA/TiO2-P2, with or without being illuminated After hours of illumination, the bacteria were completely destroyed by HA/N-TiO2 material When not being illuminated, HA/N-TiO2 materials inhibits the development and gave 59% efficiency Fungus treatment 20 At the time of hours, the fungus was completely eliminated by HA/N-TiO2 This may be explained by the bar-shaped structure and porous of material, leading to the higher contact surface; therefore, the fungus treatment of HA/N-TiO2 is more efficient than that of the HA/TiO2- P25 CONCLUSION From the results, there are some following conclusions: Ten (10) samples of nitrogen-doped TiO2 nanoparticles coated with metal oxide (N-TiO2/Al2O3) were synthesized via the sol-gel 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 N-TiO2 sol and N-TiO2 coating on Al2O3 fibers Nitrogen is directly doped into TiO2 crystals via the hydrolysis and condensation The XRD, SEM, UV-Vis, ICP-MS techniques have been employed to evaluate the structure, properties and composition of NTiO2/Al2O3 material The N-TiO2 has single-phase anatase structure and its particles size is from 15nm to 30 nm, and absorbs light with the wavelength of 439nm The content of N-TiO2 accounts for approximately 6% of the material’s weight The photo-catalyst activities of N-TiO2/Al2O3 material (being 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 toluene concentration of 400 μg/m3, treatment time of hours 21 Nine (9) samples of HA/N-TiO2 nanocomposite were synthesized via the method of HA deposition on the surface of TiO2 in the stock solution containing Ca2+ and PO43- ions After being doped with nitrogen, the structure of TiO2 was changed from anatase single-phase to anatase and rutile-phase The synthesis conditions of HA/N-TiO2 material are: the TiO2/urea ratio is 1: (g/g), Ca2+ and PO43- concentrations in the stock solutions are 25 and 10 (mmol/L) respectively, the immersion time of N-TiO2 in the stock solution is hours The TGA, XRD, SEM, EDX, IR, BET, UV-Vis techniques were employed to evaluate the structure, properties and composition of HA/N-TiO2 The TiO2 rods have a ratio of anatase/rutile approximately 80/20, average size 10 × 10 nm, length of 10 - 500nm, doped with N ratio of 2% by weight HA is coated on the TiO2 surface The content of HA in the material accounts for 30% of the weight The surface area of the material is about 385m2/g, the average size of the pore is 78.3929Å, absorption wavelength at 429nm The capability of adsorption and photo-catalysis of HA/NTiO2 material were tested in the visible light Under the investigated condition, the HA/N-TiO2 is optimally used as a suspension at the content of the photo-catalyst of 25/1000g/ml and the surface area of the photo-catalyst of 3.125 g/m2 If being illuminated by the fluorescent light, the HA/N-TiO2 is able to completely eliminate the bacteria after hours and the fungus after hours with an initial microorganism concentration of 105CFU/ml 22 CONTRIBUTION OF THESIS N-TiO2/Al2O3 nanomaterials are synthesized by sol-gel method from tetraisopropyl orthotitanate, diethanolamine and ethanol The synthesis process is simple and highly stable with two stages includes the preparation of N-TiO2 sol and N-TiO2 coating on Al2O3 fibers The N-TiO2 has single-phase anatase structure and its particles size is from 15nm to 30nm; and absorbs light with the wavelength 439nm N-TiO2/Al2O3 nanomaterials is capable of treating organic compounds if being used as a filter membrane in an air purifier The combination of the structure change of TiO2 nano from particle to rod and the precipitation of HA on the surface N-TiO2 has formed the pores in the HA/N-TiO2 nanocomposite material As a result, the material is not sedimented when being suspended in the aqueous solution The average size of the pores is 78.3929Å and the size of N-TiO2 rods is × 10nm and 10 - 500nm length HA/N-TiO2 absorbs light at 429nm wavelength with surface area is 385m2/g HA/N-TiO2 nanocomposite materials has adsorption and photocatalytic properties and is able to treat toluene as well as bacteria, fungi in the visible light This material has the potential in being used to treat the pollutant the air environment 23 PUBLICATION Nguyen Thi Hue, Tran Thi Duc, Ma Thi Anh Thu, Dinh Thi Thuy Hang, Synthesis and application of nano TiO2 to treat the toxic substances in the air in Vietnam, The Scientific Conference for 35 years of the establishment of Vietnam Academy of Science and Technology 1975-2010, Subcommittee on Environment and Energy, 2010, ISBN: 978-604-913-013-7, 220-225 Nguyen Thi Hue, Ma Thi Anh Thu, Study on fabrication of apatite/TiO2 suspension and assessment of its ability of disintegrating toxic substances in the air environment, The 3rd International Workshop on Nanotechnology and Application, November 10-12, Vung Tau, Vietnam, 2011, 960-963 Nguyen Manh Nghia, Nguyen Thi Hue, Ma Thi Anh Thu, Synthesis and study on TiO2/Al2O3 to decompose formaldehyde in air environment, Journal of Chemical, Physical and Biological Analysis, ISSN-0868-3224, 16 (3), 2011, 38-42 Nguyen Thi Hue, Nguyen Thi Ha Giang, Ma Thi Anh Thu, Tran Thi Thu Huong, Research on the treatment of benzene, toluene and xylene in air environment by apatite/TiO2 nano paint, Journal of Science and Technology, 2012, ISSN 0866 708X, 50 (2B), 213-220 Ma Thi Anh Thu, Nguyen Thi Hue, Au Duy Tuan, Research on the fabrication for air purifier using TiO2/Al2O3, TiO2/SiO2 materials for the treatment of NO, CO, Journal of Chemical, Physical and Biological Analysis, 2013, ISSN-0868-3224,18 (3), 48-53 Ma Thi Anh Thu, Nguyen Manh Nghia, Nguyen Thi Hue, Fabrication and study on structure, photocatalysis of TiO2: N/Al2O3 24 material for NO, CO degradation, Journal of Science, HNUE, 2013, 7, 94-99 Ma Thi Anh Thu, Nguyen Thi Hue, Research on the sysnthesis and the evaluation of the fungal elimination of apatite/TiO2 nano coating in the hospital, National Conference of Biotechnology, Hanoi, 2013, 563-567 Ma Thi Anh Thu, Nguyen Manh Nghia, Nguyen Thi Hue, Application of hydroxylapatite-coated titanium dioxide suspension for air purification, International Symposium on Nano-Materials, Technology and Application (NANOMATA), 2014, 15 - 17 October, Hanoi, Vietnam Nguyen Thi Hue, Ma Thi Anh Thu, Nguyen Manh Nghia, The toluene treatment with nano titanium dioxide doped nitrogen coating on alumina oxide fiber (N-TiO2/Al2O3), Journal of Chemical, Physical and Biological Analysis, 2017, ISSN-0868-3224, 22 (4), 115-120 10 Ma Thi Anh Thu, Nguyen Manh Nghia, Nguyen Thi Hue, The kinetics of toluene degradation using visible light in the presence of nano N-TiO2/Al2O3 photocatalyst, Journal of Chemical, Physical and Biological Analysis, 2018, ISSN-0868-3224, 23 (1), 94-99 ... 31.6°, the intensity of the diffraction peak of HA increases with increasing concentration of Ca2 + and PO43- proving that the higher the concentration of Ca2 + and PO43- in the stock solution, the. .. structure and properties of TiO2-based nanocomposite for the treatment of some pollutants in air environment " The topic has practical significance, contributing to the reduction of the air pollution... efficient and easier to have the stability in the suspension than that from the granular N-TiO2 For the above reasons, the thesis is proposes as "Research on the synthesis and characterization of structure