Nghiên cứu tổng hợp vật liệu MIL 101(cr) biến tính bằng oxit sắt và ứng dụng tt tiếng anh

1 I INTRODUCTION OF THESIS 1.The imperativeness of thesis Nowadays, porous solids materials are known to possess numerous practical applications, including zeolite, activated carbon , and their values on the market Also, there are applications in many fields: adsorption, catalysis, gas separation, ion exchange These materials have a porous structure and large specific surface, with specific surface area of 904 m2.g-1, zeolite of 1030 m2.g-1 The study of these materials has attracted many scientists over the past decades The continuous development of science has done various researches which indicates that there is a new material having many superior characteristics than zeolites, activated carbon or other microporous materials, that is, metal–organic framework material This material also has a porous structure and an extremely large specific surface area (can reach 2000 m2.g-1 to 6500 m2.g-1) built on the metal-organic frameworks, abbreviated as MOFs Metal–organic frameworks (MOFs) are porous crystal materials, with the structures extending from one to three dimensions in space, formed from the "assembly" of metal ions or oxide clusters associated with ligands which are organic bridge This material has attracted considerable attention due to its large surface area, heat resistance, diversity in structure as well as order structure, resulting in many applications in various areas such as: gas storage, catalyst, sensor, drug delivery, biomedical Especially in the synthesis process, the physical and chemical properties of MOFs could be adjusted by combining functional groups on organic bonding or on unsaturated metal positions in the network frame of the MOFs MIL-101 (Cr) (Matérial Institute Lavoisier) with the formula: [Cr3O(F,OH)(H2O)2(bdc)3.nH2O] (bdc = 1,4 - benzendicarboxylate, n ~ 2,5), first published by Férey and his co-workers in 2005, with high stability in heat and chemistry The positions of Cr(III) in the network frame form particularly attractive potentials of MIL-101(Cr) in many areas: gas adsorption, catalysis, CO2 and H2 storage Especially, the study of denatured MIL-101(Cr) materials still have interest in its synthesis process and applications It can be said that nowadays there are usually two ways to denature materials: (i) transfer metal or metal oxide into materials, (ii) attach organic functional groups to the surface capillary face Therefore, the potential uses of MIL-101(Cr) when being attached with some oxide types have not been vastly exploited Applications of this metal– organic framework materials for heavy metal adsorption, adsorption of dyed products in solution, catalyzing oxidation reactions of organic compounds and photocatalysts, are promisingly full of practical significance From the above problems, we was carried the thesis with the title of “Iron modified MIL-101(Cr) materials and their application” The task of the thesis - Iron modified MIL-101(Cr) materials (Fe2O3/MIL-101(Cr)), application in adsorption Pb(II) and oxidations catalysis of oct-1ene; - Iron modified MIL-101(Cr) materials (Fe3O4/MIL-101(Cr)) and application photocatalyst for MB degradation Scope and object of the thesis In the thesis, scope and object of the study are selected: - MIL-101(Cr) and Fe2O3/MIL-101(Cr) were synthesised using the hydrothermal process; - Fe3O4/MIL-101(Cr) is synthesized by co-precipitation method; - Heavy metal Pb(II); - The oct-1-ene and methylene blue(MB) solution Scientific and practical meaning of the thesis - MIL-101(Cr) was synthesized by hydrothermal method; - Modification Fe2O3/MIL-101(Cr) materials for used for Pb(II) adsorption from aqueous solutions (study of equilibrium, adsorption kinetics and thermodynamic parameters); - Using method for direct oxidation of oct-1-ene with H2O2 as envirommental friendly oxidant by Fe2O3/MIL-101(Cr) catalyst; - Modification Fe3O4/MIL-101(Cr) materials for used for photocatalytic for MB degradation From the results of the thesis show that the practical study could be opened to potentially toxic metals removal and dyes from aqueous solutions; catalytic reactions oxidation of organic compounds Originality of the thesis - MIL-101(Cr) and Fe2O3/MIL-101(Cr) were used for Pb(II) adsorption from aqueous solutions Kinetic study of Pb(II) adsorption from aqueous solution by non-linear models, be opened to potentially toxic metals removal - The oxidation reaction for direct oxidation of oct-1-ene onto Fe2O3/MIL-101(Cr); - Proposing a kinetic Langmuir - Hinshelwood model of methylene blue degradation over this Fe3O4/MIL-101(Cr) heterogeneous catalyst, could be opened to potentially toxic dyes from aqueous solutions The lay-out of the thesis The thesis possesses 117 pages, includes: Introduction (2 pages); Chapter 1: Theory overview (31 pages); Chapter 2: Content and methods (17 pages); Chapter 3: Results and discussion (47 pages); Conclusion (01 pages); List of publishing manuscripts (2 page); Reference (16 pages) 4 II CONTENT OF THE THESIS Chapter Theory overview Searching and collect scientific information related to metal organic frame materials on synthetic methods and applications From that choose the suitable methods and application for the thesis Finding originality that did not mention in reference to carry out the thesis Theory overview show that modified MIL-101(Cr) materials have been extensively studied Special modified MIL-101(Cr) has metal oxides or functional groups applied in adsorption and catalysis In which, the applications iron modified MIL-101(Cr) in the field adsorption, photocatalytic and catalyzing oxidation reactions of organic compounds is limited Therefore, the thesis also aims to study the applications of this material in the fields of adsorption and catalysis CHAPTER OBJECTIVES AND METHODS 2.1 Objectives The thesis concentrated to large objectives: - Investigating iron modified MIL-101(Cr) materials (Fe2O3/MIL101(Cr)) and use as adsorbent for removal of Pb(II) from aqueous solution - Investigating ferromagnetic oxide modified MIL-101(Cr) materials (Fe3O4/MIL-101(Cr)) and application photocatalyst for MB degradation 2.2 Methods The thesis has used structural characteristics methods includes: includes: X-ray diffraction (XRD) studying crystal phase composition, Fourier-transform infrared spectroscopy (FT-IR) realizing oxygen containing groups on the surface of material, X-ray photoelectron spectroscopy (XPS) is spectroscopic technique that measures chemical state and electronic state of the elements that exist within a material, energy-dispersive X-ray spectroscopy (EDS) analyzing atomic compostion, nitrogen adsorption/desorption isotherms analyses determining surface area, canning electron microscope (SEM) and transmission electron microscope (TEM) observing morphology and size of particle, Thermogravimetric analysis (TG-DTA), Raman spectrum and Magnetic method (vibrating sample magnetometer); Group of analytical methods includes: atomic absorption spectroscopy (AAS) and UV-VIS spectroscopy (quantifying heavy metals), High-performance liquid chromatography (HPLC) used to separate, identify, and quantify each component in a mixture 2.3 Experimental - Synthetic MIL-101 (Cr) material; - Synthetic Fe2O3/MIL-101(Cr) material; - MIL-101(Cr) and Fe2O3/MIL-101(Cr) used for Pb(II) adsorption; - MIL-101(Cr) and Fe2O3/MIL-101(Cr) used for direct oxidation of oct-1-ene; - Synthetic Fe3O4/MIL-101 (Cr) material; - Fe3O4/MIL-101(Cr) materials for used for photocatalytic for MB degradation CHAPTER RESULTS AND DISCUSSION 3.1 Synthesizing MIL-101(Cr), Fe2O3/MIL-101(Cr) and application 3.1.1 Characterization of MIL-101(Cr) and Fe2O3/MIL-101(Cr) Fig 3.1 represents the XRD patterns (2θ = 1÷ 20o ) of MIL101(Cr) (M0) and Fe2O3/MIL-101(Cr) sample using different molar ratios of Cr(III)/Fe(III) (M9:1, M8:2, M7:3, M5:5) As seen from the figure, characteristic diffractions with high intensity of MIL–101(Cr) corresponding to Miller indices (111), (220), (311), (511), (852), (753) [13] were observed, indicating that the obtained MIL–101 as reported earlier The characteristic peak of H2BDC acid at 17o was not observed in these samples, which proved that residual H2BDC acid was completely removed (1000 cps) M8:2 (112) (200) M7:3 (880) (822) (753) M9:1 (511) (111) (220) (311) Intensity/ arb (cps) M5:5 M0 10 12 14 16 18 20 theta (degree) Fig 3.1 XRD patterns of M0 and the sample modifile using different molar ratios of Cr(III)/Fe(III) SEM images in Figure 3.2 showed that the samples M0 and M9:1 still kept octahedron shaped structure of MIL-101(Cr) When the ratio of Fe (III) increases, the octahedral structure gradually breaks down, the particle shape begins to elongate and stick tends Fig 3.2 SEM images of M0 and the sample modifile using different molar ratios of Cr(III)/Fe(III) As for TEM, the samples M0 and M9:1 consisted of octahedron shaped crystals with smooth facets and well-faceted ∼ 300- 500 nm crystals, while the samples M8:2, M7:3 and M5:5 particles tend to cohesion and have no fixed structure (Fig 3.3) Fig 3.3 TEM images of M0 and the sample modifile using different molar ratios of Cr(III)/Fe(III) Fig 3.4 shows the nitrogen adsorption/desorption isotherms of M0, M9:1 and M8:2 All the samples exhibited type IV with the H4 curve,which is characteristic of mesoporous materials, this also gave the evidence of the encapsulation of iron oxides within the pores of the framework MIL-101(Cr) The curves of the samples M7:3 and M5:5 are almost non-observable and not belong to IUPAC 8 1200 Adsorption Desorption Adsorbed (cm /g STP) 1000 MO 800 M9:1 600 M8:2 400 M7:3 200 M5:5 0.0 0.2 0.4 0.6 0.8 1.0 Relative presure (P/Po) Fig 3.4 Nitrogen adsorption/desorption isotherms M0 and the sample modifile using different molar ratios of Cr(III)/Fe(III) The functional groups on the surface of M0 and M9:1 were determined by FT-IR spectra as shown in Fig 3.5a For M9:1, peak band at wavenumber of 632 cm-1 was referred to the variation of FeO bond a) M0 Intensity (cps) Transmittance (%) C- H Cr-O M9:1 C=O C-C O-H C-H C-H Fe-O 5000 4000 3000 2000 Wavenumber (cm1-) 1000 O1s C1s 160000 120000 MO 80000 40000 C=O C-C O-H b) 200000 C-H Cr2p3 M 9:1 Fe2p3 0 1200 1000 800 600 400 200 Binding Energy (eV) Fig 3.5 (a) FT-IR spectra; (b) XPS spectra of M0 and M9:1 The XPS survey spectrum (Fig 3.5b) shows that Cr, C and O exist in M0 and M9:1 at binding energies of around 577.7 eV; 284.6 eV and 530.02 eV, respectively For M9:1 the peak at 724.9 eV is contributed to Fe2p3 These results confirmed that Fe2O3 has been included in frame MIL-101 (Cr) 9 3.1.2 Pb(II) adsorption studies onto MIL-101(Cr) and Fe2O3/MIL101(Cr) 3.1.2.1 Kinetic study of Pb(II) adsorption 60 Fe2O3/ MIL-101(Cr) 60 MIL-101(Cr) 9,12 mg.L-1 -1 19,36 mg.L -1 31,00 mg.L 40,33 mg.L-1 -1 50,01 mg.L 70,02 mg.L-1 -1 80,02 mg.L -1 90,12 mg.L -1 30 20 ) -1 qt (mg.g-1) 40 50 qt (mg.g 9,12 mg.L -1 19,36 mg.L 31,00 mg.L-1 -1 40,33 mg.L 50,01 mg.L-1 -1 70,02 mg.L -1 80,02 mg.L 90,12 mg.L-1 50 40 30 20 10 10 0 50 100 150 200 250 Time (min) 50 100 150 200 250 Time (min) Fig 3.6 Effect of concentration on the adsorption of Pb(II) 20 20 MIL-101(Cr) Fe2O3/ MIL-101(Cr) 16 qt (mg.g-1) qt (mg.g-1) 15 12 10 20oC 30oC 40oC 50oC 60oC 20oC 30oC 40oC 50oC o 60 C 0 50 100 150 Time (min) 200 250 40 80 120 160 200 240 Time (min) Fig 3.7 Effect of temperature on adsorption of Pb(II) Fig 3.6 and 3.7 shows the Pb(II) adsorption capacity versus the contact time at initial Pb(II) concentrations and various temperatures The Pb(II) adsorption capacity of Fe2O3/MIL-101(Cr) was higher than that of MIL-101(Cr) with the same initial concentration The equilibrium adsorption capacity increased with the increase in temperature, indicating the endothermic nature of the adsorption reaction between Pb(II) and the adsorbents (MIL-101(Cr) and Fe2O3/MIL-101(Cr)) 10 The values of ΔG#, ΔH# and ΔS# were obtained from non-linear regression from the plot of Eyring’s The positive value of ΔH# confirmed an endothermic process The negative value of ΔS# indicated that the adsorption occurred through the formation of an activated complex, suggesting that the Pb(II) adsorption on the surface had an associated mechanism ΔG# for MIL-101(Cr) was higher than that for Fe2O3/MIL-101(Cr) at the same temperature, therefore, the energy required for Fe2O3/MIL-101(Cr) to enable the adsorption reaction to proceed was lower than that for MIL-101(Cr) The values of ΔGo, ΔH° and ΔS° were determined from the slope and intercept of plot Van’t Hoff The sign of ΔH° and ΔS° was positive for the endothermic nature of the adsorption and replaced more than one water molecule previously adsorbed on the adsorbent ΔS°was positive since the displaced water molecules obtained more translational entropy than what was lost by the Pb(II) ions attachment, thus resulting in increasing randomness at the solid solution interface The negative value of ΔG° indicates the feasibility of the process and the spontaneous nature of the adsorption It could be seen that the value of ΔG° for Fe2O3/MIL-101(Cr) was more negative than that for MIL-101(Cr) The more negative ΔG° the more favorable thermodynamics 3.1.2.2 Equilibrium studies The equilibrium data of adsorption show that over MIL-101(Cr) were more compatible with the Langmuir model; Fe2O3/MIL-101 (Cr) is suitable for both Langmuir and Freundlich models It is worth noting that the maximum monolayer adsorption capacity for Fe2O3/MIL-101(Cr) based on the Langmuir model was 1.5 times as high as that for MIL-101(Cr) (86.20 mg·g–1 versus 57.96 mg·g–1) 3.1.3 Catalytic ability of MIL-101(Cr) and Fe2O3/MIL-101(Cr) for oxidation of oct-1-en 11 3.1.3.1 Affecting factors for oxidation of oct-1-en The catalyst effect is shown in Fig 3.8, when the amount of catalyst 20 g.mol-1 for MIL-101(Cr) and 15 g.mol-1 for Fe2O3 / MIL101 (Cr), then the yield tend to increase Reaction yield decreases as the catalyst continues to increase for both types MIL-101(Cr) 80 80 Yield (%) 70 Yield (%) Fe2O3/MIL-101(Cr) 70 60 50 60 50 40 30 40 20 30 10 15 20 25 30 mcatalyst (g.mol-1) 35 40 10 15 20 25 30 mcatalyst (g.mol-1) Fig 3.8 Shows the yield of HC formation with diffeerent catalysts The influencing factors of the ratio of H2O2/oct-1-en and pH in Fig 3.9 showed that when increasing the amount of H2O2 to 2.0 and pH = 6, the conversion efficiency of heptanoic acid increased, 77.4% and 82.4% for MIL-101(Cr), Fe2O3/MIL-101(Cr), respectively a) 75 b) 80 70 Yield (%) Yield (%) 60 45 30 MIL-101(Cr) Fe2O3/MIL-101(Cr) 15 60 50 40 MIL-101(Cr) Fe2O3/MIL-101(Cr) 30 20 10 1.2 1.6 2.0 VH2 O2 (mL) 2.4 2.8 pH Fig 3.9 (a) Effect of volume ratio H2O2/oct-1-en ; (b) Effect of pH on reaction efficiency 12 To estimate the heterogeneity of MIL-101(Cr) or Fe2O3/MIL101(Cr) catalyst shown in Fig 3.10 90 70 Fe2O3/MIL-101(Cr) Có xúc tác Khơng xúc tác 80 70 60 HiƯu st (%) HiƯu st (%) 90 MIL-101(Cr) Có xúc tác Khơng xúc tác 80 50 Läc xóc t¸c 40 30 60 Läc xóc t¸c 50 40 30 20 20 10 10 Time (h) 10 Time (h) Fig 3.10 A hot experiment to check the heterogeneity of catalysts MIL-101(Cr) and Fe2O3/MIL-101(Cr) The results showed that the catalysts were filtered out of liquid phase reaction, the product performance was almost unchanged in the range of 37.1 to 36% with Fe2O3/MIL-101(Cr) and 29 - 28.1 % with MIL-101(Cr) Proving that if no catalytic oxidation reaction will occur relatively slowly and firmly indicating that the observed catalysis is truly heterogeneous 3.1.3.2 Reusability a) MIL-101(Cr) MIL-101(Cr) b) C- H C- H Transmittance (%) Transmittance (%) C- H C=O O-H C=O C-C Cr-O Fe2O3/MIL-101(Cr) C- H C- H Fe-O C- H C=O O-H C=O C-C Fe2O3/MIL-101(Cr) Cr-O Fe-O C- H O-H C=O C- H C=O O-H 5000 4000 3000 C-C C-C 2000 Wavenumber (cm1-) 1000 4000 3000 2000 1000 Wavenumber (cm1-) Fig 3.11 FT-IR spectra of MIL-101(Cr) and Fe2O3/MIL-101(Cr) : a) original; b) recovered 13 50 cps 1000 cps The nature of the used catalysts were studied by means of FT-IR spectroscopy and XRD measurment In the infrared spectrum (Fig 3.11) after regeneration, the peaks has caused the oscillation bands of the bonding groups to be lower This is due to the oxidative degradation of the MIL-101 structure may be because the degradation of the MIL-101 (Cr) structure Moreover, the XRD pattern of the recovered catalyst is as same as the fresh catalyst but the peaks intensity has been decreased (Fig 3.12) 2nd cycle 1st cycle 3rd cycle Intensity (arb) Intensity (arb) 3rd cycle 2nd cycle 1st cycle Fe2O3/MIL-101(Cr) MIL-101(Cr) 10 12 14 16 18 20 theta (degree) 10 12 14 16 18 20 theta (degree) (311) Fig 3.12 XRD patterns of MIL-101(Cr) and Fe2O3/MIL-101(Cr) recovered catalyst 3.2 Synthesizing Fe3O4/MIL-101(Cr) and application 3.2.1 Synthesizing Fe3O4/MIL-101(Cr) (422) (511) (400) Intensity (cps) (440) Fe3O4/ MIL-101(Cr) (220) 500 cps MIL-101(Cr) 10 20 30 40 50 60 70 theta (degree) Fig 3.13 XRD patterns of MIL-101(Cr) and Fe3O4/MIL-101(Cr) 14 Figure 3.13 represents the XRD patterns of MIL-101(Cr) and Fe3O4/MIL-101(Cr) The difractions of Fe3O4 appear at Miller indicesm 31,7o (220); 35,8o (311); 42,5o (400); 54,1 o (422); 57,5o (511) and 63,7o (440) (JCPDS No: 00-001-1111) The results show that Fe3O4 is encapsulated into MIL-101(Cr) No typical hysteresis loop of the Fe3O4/MIL-101(Cr) nanocomposite is observed, suggesting the superparamagnetic behavior of the material (Fig 3.14) The morphology of Fe3O4/MIL101(Cr) was observed using SEM (Fig 3.15) show that Fe3O4/MIL101 provides the octahedral particles with rough facets because the fine particles of Fe3O4 with into the MIL-101(Cr) surface Fe3O4/MIL-101(Cr) 15 M (emu/ g) 10 -5 -10 -15 -20000 -10000 10000 20000 H (Oe) Fig 3.14 Magnetic hysteresis Fig 3.15 SEM observation of loops of Fe3O4/MIL-101(Cr) Fe3O4/MIL-101(Cr) The functional groups on the surface of Fe3O4/MIL-101(Cr) were determined by FT-IR spectra as shown in Fig 3.16 show that confrming the presence of the dicarboxylate moieties within MIL101(Cr), besides characteristic broad band at 586 cm−1 for proves the incorporation of Fe - O groups The XPS survey spectrum (Fig 3.17) shows that C, O, Cr, and Fe exist in Fe3O4/MIL-101(Cr) at binding energies of around 711,4 eV; 576,37 eV; 284,6 eV 531,7 eV, respectively All of these results clearly confrm the formation of Fe3O4/MIL-101(Cr) 15 60000 C-H C-H Fe-O C=O O-H Cr-O C-C MIL-101(Cr) C-H C-H O-H Intensity®é (cps) Transmittance (%) Fe3O4/MIL-101(Cr) O1s 48000 Fe2p3 36000 24000 Cr2p3 C1s 12000 C=O C-C 4000 3000 2000 1200 1000 1000 800 600 400 200 Binding energy (eV) -1 wavenumber (cm ) Fig 3.16 FT-IR spectra of Fe3O4/MIL-101(Cr) Fig 3.17 XPS spectra of Fe3O4/MIL-101(Cr) Intensity (cps) Raman spectra were employed to study the intensity ratio of the D and G bands (ID/IG) is used to estimate the disorder in the materials Fig 3.18 show that the ID/IG ratio of Fe3O4/MIL101(Cr) (1.43) is higher than that of pure MIL-101(Cr) (1.37), which implies that magnetic iron oxide has successfully been tailored in Fe3O 4/MIL-101(Cr) MIL-101(Cr) ID/IG = 1.37 I D/IG = 1.43 Fe3O4/MIL-101(Cr) 400 800 1200 1600 2000 2400 Raman shift (cm-1) Fig 3.18 Raman spectra of MIL-101(Cr) and Fe3O4/MIL-101(Cr) Evaluation of visible light absorption capacity of materials MIL101(Cr) and Fe3O4/MIL-101(Cr) shown in Fig 3.19 From KubelkaMunk function show that decrease in the band gap energy of the irondoped MIL-101 may be attributed to the excitation of the 3d electrons of 16 Fe(III) or Fe(II) to the conduction band level of Cr by a charge transfer transition The low band gap at 2.4 eV enables Fe3O4/MIL-101(Cr) to exhibit the photocatalytic activity under visible light MIL-101(Cr) Hµm Kubelka - Munk (nm) Hµm Kubelka - Munk (nm) 10000 a) 13200 11000 8800 6600 4400 4,19 3,70 2200 Fe 3O4/MIL-101(Cr) b) 8000 6000 4000 2000 2,4 3,48 Binding energy (ev) Binding energy (ev) Fig 3.19 Kubelka–Munk plot of: (a) MIL-101(Cr) (b) Fe3O4/MIL-101(Cr) 3.2.2 Visible-light-driven photocatalytic degradation of MB over Fe3O4/MIL-101(Cr) - Catalytic kinetics Fig 3.20 shows the decolorization fraction for MB in dark adsorption and under the visible light illumination with and without the catalyst show that: dark light illumination 100 H (%) 80 60 Fe3 O4/MIL-101(Cr) 40 Fe3 O4 /MIL-101(Cr) filtrarated without MIL-101(Cr) and Fe3 O4/MIL-101(Cr) MIL-101(Cr) 20 0 100 200 300 400 500 600 700 Time (min) 800 Fig 3.20 Effect of time degradation of MB reaction efficiency with diffeerent catalysts 17 The MB solution was not decolorized under visible light after 700 mim the absence of catalysts, indicating that the photolysis of MB under this condition could be ignored MIL-101(Cr) exhibits in 300 a higher adsorption capacity than Fe3O4/MIL-101(Cr) with the equilibrium decolorization fraction at 73.5% and 57.3% in dark adsorption, respectively However, the MB solution decolorizes with Fe3O4/MIL-101(Cr) after 650 of illumination; meanwhile, the decolorization is not observed in the MB solution containing MIL-101(Cr) under the same condition This suggests that MIL-101(Cr) is not a photocatalyst for MB degradation The leaching experiment, in which Fe3O4/MIL-101(Cr) was fltered after 420 min, was also conducted The decolorization of MB does not take place under illumination, confrming that Fe3O4/MIL101(Cr) is a heterogeneous photocatalyst in the degradation of MB 90 0.25 b) 80 COD (mg.L-1) 0.20 Absorb (Abs) a) 720 540 300 120 Start 0.15 0.10 70 60 50 40 0.05 30 0.00 300 400 500 600 wavelegth (nm) 700 800 50 100 150 200 250 Time (min) Fig 3.21 (a) UV-Vis spectra; (b) COD value of MB under conditions light over Fe3O4/MIL-101(Cr) The UV-Vis spectra for MB solution MB under conditions light show that the adsorption band peaks at 650 nm (Fig 3.21 a) The of COD of the reaction products with time was analyzed The results COD analysis in conditions light and catalyst Fe3O4/MIL-101(Cr) in Fig 3.21 b showed decrease from 82.6 mg.L -1 to 35.2 mg.L-1 This 18 decrease proves that Fe3O4/MIL-101(Cr) is an efcient photocatalyst for MB degradation and decomposition product is CO2 and H2O 50 350 dark light illumination -1 Ct (mg.L-1) 40 31,38 mg.L -1 41,82 mg.L -1 51,98 mg.L 76,53 mg.L-1 Coe 30 280 210 ln C  C K 140 20 70 10 31,38 40,38 51,98 76,53 mg.L-1 -1 mg.L mg.L-1 -1 mg.L -70 150 300 450 600 Time (min) 750 900 100 200 300 400 500 600 Time (min) Fig 3.22 Adsorption and Fig 3.23 Modifed Langmuir– photocatalytic decolorization Hinshelwood’s plot at diferent kinetics of MB over initial concentrations of Fe3O4/MIL-101(Cr) in dark and catalyst under visible light Figure 3.22 presents the kinetics of adsorption and photocatalytic decolorization of MB show that the adsorption is saturated between 240 and 300 depending on the initial MB concentration When visible light to 840 the concentration of MB solution reduced quickly The value of k2 decreases with the increase of the initial MB concentration (Fig 3.23) A higher MB concentration can shield the light from interacting with the catalyst, resulting in a lower rate coefcient - Mechanisms of MB degradation: In the study are selected radical scavengers such as tert-butanol (TB), 1,4-benzoquinone (BQ), dimethyl sulfoxide (DMSO), and ammonium oxalate (AO) were used to quench hydroxyl radicals show that in Fig 3.24 19 100 dark light illumination wiouth scavengers 80 Amoni oxalate (AO) H (%) tert-butanol (TB) 1,4-benzoquinone (BQ) 60 dimetyl sulfoxide (DMSO) 40 20 0 100 200 300 400 500 600 Time (min) Fig 3.24 Efects of radical scavengers on the degradation efciency of MB The MB degradation rate tends to decrease as the corresponding radical scavenger is added to the reaction solution AO and TB decrease the MB degradation rate signifcantly After 600 reaction, the MB decolorization fraction reaches 82% for the case without radical scavengers, and it only reaches 49.5% for AO and 43.8% for TB Meanwhile, BQ and DMSO slightly slow down the degradation rate of MB These findings imply that ⋅OH and h+ play a critical role in MB degradation although −·O2 and e- contribute to MB degradation as well Based on the photocatalyst mechanism of MOF-5 it is thought that the structure of MIL-101 (Cr) can be as semiconductor When the iron oxides are added to the MIL-101(Cr) appear electron energy levels the lowest unoccupied molecular orbital (LUMO) and highest occupied molecular orbital (HOMO) creating drum trap area between energy levels The continuously transfer of electron over holes reduce reunion electron in Fe3O4/MIL-101(Cr) and increase the photocatalytic activity under visible light From the above understands, this explain were mechanisms of MB degradation investigation semiconductor mechanism following reactions (1) - (9) and Fig 3.25 20 The edge of the valence band (VB) and conduction band (CB) for MIL-101(Cr) is + 0.49 eV, and - 1.57 eV; and for Fe3O4 is 0.48 and 2.08 eV, respectively Firstly, MB molecules adsorb quickly onto Fe3O4/MIL-101(Cr) to form MBads (reaction (1)) Both MIL101(Cr) and Fe3O4 could absorb visible light to generate the pairs of e- and h+ at CB and VB, respectively, according to reaction (2) CB of MIL-101(Cr) is more negative than that of Fe3O4, then it will transfer the excited electrons to CB of Fe3O4 that is believed to prevent the fast recombination of the photo-excited e- and h+ pairs The LUMO (lowest unoccupied molecular orbital) of photo-excited MB· (–3.81 eV) is more negative than CB of Fe3O4 Therefore, MB could act as the photosensitizer to favorably provide additional photogenerated electrons into CBs of Fe3O4 through the formed downstream channel (reaction (3) and (4)) The energy of h+ of Fe3O4 (2.08 V) is more positive than the potential of H2O/OH· (+1.9 V) Then, h+ could be quickly converted to the hydroxyl radical upon oxidation of surface water, according to reaction (5) The potential of e- in MIL-101 (–1.57 V) is more negative than that of O2/-·O2 (–0.28 V), then introduced oxygen forms the free radicals -·O2, as reaction (6) These radicals are responsible for MB degradation (reaction (7), (8) and (9)) According to the published articles, the reactions could be illustrated as follows: • (1) Fe3O4 /MIL-101(Cr) + MB  MB(hp)  MB(hp) Fe3O4 /MIL-101(Cr) + hν  Fe3O4 /MIL-101(e- + h+ ) (2) MB•(hp)  e- + MB•+ (3) MB•+  MB + h+ Fe3O4 (h ) + H2O(hp)  OH (4) (5) MIL-101(Cr) (e- ) + O2(hp)  • O-2 (6) • (7) + • (hp) OH + MB(hp)  Phân hủy MB 21 Fe3O4 (h + ) + MB(hp)  Phân hủy MB (8) • (9) O2- + MB(hp)  Phân hủy MB Hình 3.25 Proposed mechanism of MB degradation over Fe3O4/MIL-101(Cr) under visible light IV CONCLUSION 1) Fe2O3/MIL-101(Cr) (with 10% Fe) material were successfully synthesised using the hydrothermal process The obtained material has homogeneous size with a typical octahedral structure, high crystallinity, and significant BET surface area of 2440 m2.g–1 2) The adsorption was controlled by physico-chemisorption for both MIL-101(Cr) and Fe2O3/MIL-101(Cr) The equilibrium data for MIL-101(Cr) followed the Langmuir mode while Fe2O3/MIL101(Cr) adsorption followed both the Langmuir and Freundlich isotherm models The value of ΔG° for Fe2O3/MIL-101(Cr) was more negative than that for MIL-101(Cr) The more negative ΔG° the more favorable thermodynamics is The maximum monolayer adsorption capacity of Pb(II) on Fe2O3/MIL-101(Cr) (86.20 mg·g–1) was approximately 1.5 times as high as that for MIL-101(Cr) (57.96 22 mg·g–1) This means that the iron introduction into MIL-101(Cr) enhanced adsorption in terms of material After the three cycles reusability seemed to be unchanged 3) Using method for direct oxidation of oct-1-en with H2O2 by MIL101(Cr) and Fe2O3/MIL-101(Cr) catalyst indicated that the yield of heptanoic formation on Fe2O3/MIL-101(Cr) (82,4%) higher than MIL-101(Cr) (77,4%) catalyst The results show that with the dosage of Fe-MIL-101/oct-1-en: 15 (g.mol-1), molar ratio of H2O2/oct-1-ene: 2, reaction temperature: 700C, reaction time: hours 4) Fe3O4/MIL-101(Cr) material were successfully synthesised with high crystallinity, and significant BET surface area of 1860 m2.g–1; superparamagnetic and enhanced visible-light absorption 5) This is the first investigated the photocatalytic activity of methylene blue decomposition on Fe3O4/MIL-101(Cr) material according to modified Langmuir- Hinshelwood model: the degradation efficiency reached 93.9% under lighting conditions with incandescent lamps of 60W in 800 minutes The photocatalytic decomposition that is exhibits goodness of fit for modified Langmuir- Hinshelwood model with a high determination coefficient (R2 = 0.95 - 0.97) Fe3O4/MIL-101(Cr) material are stable in photochemical reaction environment, their catalytic activity and structure are almost unchanged after three times of reuse V PAPERS CONCERNING TO THE THESIS Vietnam Journals Huynh Thi Minh Thanh, Tran Thanh Tam Toan, Tran Ngoc Tuyen, Đinh Quang Khieu (2018), Study on determination of appropriate conditions for oct-1-en oxidation reaction over Fe-MIL101 catalyst using experimental design., Vietnam Journal of Chemistry 56(3E12), pp 241-245 23 Huynh Thi Minh Thanh, Tran Ngoc Tuyen, Đinh Quang Khieu(2018), Synthesis of Fe-MIL-101 material and evaluation of photocatytic activity under visible light, Vietnam Journal of Catalysis and Adsorption, Volume 2, pp 50-54 Huynh Thi Minh Thanh, Tran Ngoc Tuyen, Đinh Quang Khieu (2018), Synthesis and characterization of metal-organic framework Fe-MIL-101, Journal of Science and Technology, Hue University of Sciences 127(1), pp 05-15 Huynh Thi Minh Thanh, Tran Ngoc Tuyen, Đinh Quang Khieu (2019), Synthesis and characterization of metal-organic framework Fe3O4/MIL-101(Cr), Journal of Analytical Sciences, No 24, Volume 5, pp 106-111 International Journals Huynh Thi Minh Thanh, Tran Thi Thu Phuong, Phan Thi Le Hang, Tran Thanh Tam Toan,Tran Ngoc Tuyen, Tran Xuan Mau, Dinh Quang Khieu, Comparative study of Pb(II) adsorption onto MIL–101 and Fe–MIL–101 from aqueous solutions, Journal of Environmental Chemical Engineering, (2018), pp 4093- 4102 Vo Thi Thanh Chau, Huynh Thi Minh Thanh, Pham Dinh Du, Tran Thanh Tam Toan, Tran Ngoc Tuyen, Tran Xuan Mau, and Dinh Quang Khieu, Metal-Organic Framework-101 (MIL-101): synthesis, kinetics, thermodynamics, and equilibrium isotherms of Remazol deep black RGB adsorption,Journal of Chemistry, Volume 2018, Article ID 8616921, 14 pages Pham Dinh Du, Huynh Thi Minh Thanh, Thuy Chau To, Ho Sy Thang, Mai Xuan Tinh, Tran Ngoc Tuyen, Tran Thai Hoa, and Dinh Quang Khieu, Metal-Organic Framework MIL-101: synthesis and photocatalytic degradation of Remazol black B dye, Journal of Chemistry, Volume 2019, Article ID 6061275, 15 pages Huynh Thi Minh Thanh, Nguyen Thi Thanh Tu, Nguyen Phi Hung, Tran Ngoc Tuyen, Tran Xuan Mau and Dinh Quang Khieu, 24 Magnetic iron oxide modified MIL-101 composite as an efficient visible-light-driven-photocatalyst for methylene blue degradation, Journal of Porous materials, Volume 2019, 14 pages  ... 77.4% and 82.4% for MIL- 101(Cr), Fe2O3 /MIL- 101(Cr), respectively a) 75 b) 80 70 Yield (%) Yield (%) 60 45 30 MIL- 101(Cr) Fe2O3 /MIL- 101(Cr) 15 60 50 40 MIL- 101(Cr) Fe2O3 /MIL- 101(Cr) 30 20 10 1.2... Experimental - Synthetic MIL- 101 (Cr) material; - Synthetic Fe2O3 /MIL- 101(Cr) material; - MIL- 101(Cr) and Fe2O3 /MIL- 101(Cr) used for Pb(II) adsorption; - MIL- 101(Cr) and Fe2O3 /MIL- 101(Cr) used for direct... (degree) Fig 3.13 XRD patterns of MIL- 101(Cr) and Fe3O4 /MIL- 101(Cr) 14 Figure 3.13 represents the XRD patterns of MIL- 101(Cr) and Fe3O4 /MIL- 101(Cr) The difractions of Fe3O4 appear at Miller indicesm