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International Journal of ChemTech Research CODEN (USA): IJCRGG, ISSN: 0974-4290, ISSN(Online):2455-9555 Vol.10 No.2, pp 24-31, 2017
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Synthesis Beads Photocatalyst TiO2/N-zeolite/chitosan to photodegradation Methylene Blue with Sunlight
Sri Wardhani1*, Danar Purwonugroho1, Rachmat Triandi Tjahtjanto
1Faculty of Mathematics and Natural Sciences, Brawijaya University, Jl. Veteran Malang, 65145, Indonesia
Abstract : The purpose of this study was to synthesize a photocatalyst to form a ball making it easy to reuse activity is still high. Photocatalyst which has been synthesized then performed to characterize and test activities on various parameters include the concentration of methylene blue, while irradiation, the effect of pH methylene blue and reuse photocatalyst. Characterization is done by using FTIR, SEM and UV-Vis spectrometer Diffuse Reflactance. The concentration of methylene blue test is 10-25 ppm, long irradiation with sunlight 1-5 hours. Based on an analysis by FTIR, the N atom in TiO2 is shown in wave numbers from 1520 to 1570 cm-1. The results of the analysis with Diffuse Reflectance Spectroscopy is the energy band gap of TiO2, TiO2-N, TiO2-N/zeolite, and TiO2-N/zeolite-chitosan respectively are 3,28; 3.09; 3.3; 3.25 eV. The specific surface area of zeolite, zeolite activation, TiO2, TiO2-N, TiO2-N/zeolite, and TiO2-N/zeolite-chitosan is determined by the surface area analyzer with successive BET method was 224.233; 251.686; 119.42; 273.997; and 306.275 m2/g. Based on the research showed that the concentration of MB is the effect on the degradation rate constant. Constant rate of degradation is increasing at a concentration of methylene blue from 10, 15 and 20 mg/L. The highest rate constant was 0.5198 h-1, these constants is generated from MB 20mg/L.
Keywords : photocatalyst; methylene blue; TiO2/N-zeolite; sunlight.
The use of photocatalysts are Often known as "advanced oxidation processes" (AOPs) can Facilitate the degradation of organic waste that can accelerate the declining value of the COD of the waste. Vinu, R. and Madars, G. have been using TiO2 as a photocatalyst for the degradation and mineralization of various toxic organic compounds such as chloro phenol, phenolic, dyestuffs, pesticides, and pharmaceuticals1. Ibhadon suggested that the TiO2 photocatalyst can degrade organic waste in the water efficiently, because the strong oxidizing ability of TiO2 when irradiated with light corresponding to the band gap of TiO22. This process Organic Pollutants can degrade into harmless inorganic materials items, namely CO2 and H2O3.
The catalytic activity of a semiconductor can be enhanced through the developing of a porous material, such as zeolite4,5,6. Distribution of TiO2 in the inner and outer surface of the zeolite results in specific surface area and total pore volume increases5. Research Faghihian and Bahranifard mentions that the developing of TiO2 in the zeolite can improve percent degradation safranin-O by 69% compared with TiO2 without entrusted4.
TiO2 has an energy band gap in the region of UV light, so the ability to absorb light in the visible region (visible) is still relatively low. UV rays from the sun is only about 5-8%2. The use of the sun as an energy source
becomes less efficient at using TiO2 photocatalytic process, so that the necessary modifications to the other on TiO2 photocatalyst-zeolite that can absorb light in the visible light region. The addition of non-metal N can cause the photocatalyst TiO2-zeolite provides absorption at the wavelength of visible light). According Gandhe addition of N in TiO2 lowers the band gap of the photocatalyst is originally 3.26 to 2.35 eV7. This decrease causes the photocatalysts can use sunlight evidenced by decreasing the concentration of the dye to be close to 0 after irradiation for 2 hours.
Based on research Pekakis TiO2 to degrade reusable textile waste to use all three8. Despite the decline in the efficiency of photocatalytic degradation but the user back to the third still shows the percentage of degradation is quite high. Photocatalyst is effective, it can be reused but there are constraints on the separation process. Photocatalyst in powder form is difficult to be separated from the filtrate before reuse. This problem can be solved if the photocatalyst is made in the form of beads to be easily separated from the filtrate but have the same catalytic activity in powder form. Based on these facts, this research photocatalyst is made in the form of a ball. Although UV light provides increased efficiency degradation dye, sunlight as an effective substitute because of the cost and abundant presence in nature. Photodegradation reached 96% after 300 minutes of solar radiation9.
Materials and Methods
The materials used in this study include natural zeolites Turen, TiO2 (pharmacy grade), demineralised water (aqua DM), distilled water, urea pa (CH4N2O), CH3COOH technical (98%, bj = 1.049), chitosan (food grade), absolute ethanol (96%, bj = 1.36), HCl (32% bj = 1.16 g/mL), NaOH and methylene blue dye (Uni Chem).
3. Photodegradation Methylene Blue
4. Photocatalyst Characterization
The surface structure and morphology of the pothocatalyst were capture by using Scaning Electron Microscopy (SEM-EDX) Hitachi TM 3000, Brunaurer-Emmet-Teller (BET) Analysis was carried out using NOVA 1000 to determine the spesifik surface area of the pothocatalyst where liquid N2 was used as adsorbate.
Results and Discussion
Zeolite and photocatalyst characterized using FTIR, XRD, spectroscopy and diffuse Reflactance. The results of characterization by FTIR presented in Figure 1 and 2. The results of the characterization by diffuse UV
Spectroscopy Reflactance presented in Figure 3. Levels of N contained in the photocatalyst was conducted by Kjeldhal. Results of analysis of the N content contained in Table 1.
FTIR spectra for the activation of zeolite contained in Figure 1, the measurements are made at wave number 4000-500 cm-1. Peak at 3620.14 and 3419.56 cm-1 is an OH group on the hydrated zeolite, 1026.06 cm-1 is an asymmetric range of O-Si-O or O-Al-O, 765.59 cm-1 is a bond peak the main structure of the zeolite unit symmetrical10.
At the height of 466.74 cm-1 and 430.10 cm-1 indicate the presence of vibration and bending vibration T-O bond11, there are peaks OH buckling wave number 1514.02 cm-1. Type of change and movement intratetrahedral symmetric Si-O-Al indicated by the peak at 646.11 cm-1, a peak at 578.60 and 528.4 cm-1 is the vibration of Si-O / Al-O buckling12,13.
FTIR characterization results for TiO2, TiO2N, TiO2N-zeolite, zeolite-chitosan-TiO2N contained in Figure 2. The typical zeolite absorption shown by the vibrations of Si, O, and Al. Zeolite at wave number 1026.06 cm-1 is an asymmetric range of O-Si-O/O-Al-O, 765.59 cm-1 is a unit structure of zeolite asymmetric14. Movement of Si-O-Al intratetrahedral contained in 646.11 cm-1 12, 578.60 and 528.46 cm-1 is Si-O/Al-O buckling 13 while at 466.74 cm-1 and 430.10 cm-1, which is symmetrical movement of Si-O-Al 15. Uptake typical TiO2 contained in 676.97; 669.25; 684.86 cm-1, the N on the surface of TiO2 detected at wave number 1525.59 cm-1 (TiO2N), 1523.66 cm-1 (TiO2N-zeolite), 1645.17 and 1569.95 cm-1 TiO2N-zeolite-chitosan11. The presence of chitosan on zeolites characterized by absorption at 3411.84 cm-1 numbers which are hydrated OH groups of chitosan14. FTIR spectra of TiO2-N/zeolite-chitosan (Figure 2 D) there NH stretching vibration absorption at wave number 3743.57 cm-1, the wave number 3411.84 and 1645.17 cm-1 are OH stretching and bending OH deformation of H2O. N-TiO2 bond shown in absorption wave number 1514.02 cm-1. Wavenumber 1033.77 cm-1 and 765.69 to 655.75 cm-1 is a strain uptake asymmetry and symmetry of the O-Si-O and O-Al-O. Characteristics of TiO2 is shown on the uptake from 516.89 to 430.10 cm-1 which is a Ti-O stretching vibration on TiO2. Their uptake of N-H stretching vibration which is an active group of chitosan indicating that chitosan has been tied into the pores of the photocatalyst TiO2-N/zeolite15.
Measurements to determine the characteristics of the specific surface area of solids photocatalysts can show photocatalyst contact with the reactants. The solids from the photocatalyst is assumed as a solid monolayer will adsorb N2 gas at very low pressure. The pressure before and after the N2 gas adsorption is determined16. The method used to determine the surface area, pore diameter and pore volume are the Branauer-Emmet-Teller (BET ) method. On the results of the analysis of data obtained with this method the specific surface area, mean pore and total pore volume of the photocatalyst are shown in Table 1.
Natural zeolite has a specific surface area and total pore volume smaller than the zeolite activation, due to the pore surface of zeolite is still contained impurities which cover while the zeolite compound impurity activation is lost on the activation process. TiO2-N/ zeolite has a specific surface area and total pore volume greater than pure TiO2 as the catalyst TiO2-N/zeolite are zeolites that can increase the surface area and total pore volume. In catalyst TiO2-N/zeolites made possible aggregation and cause the formation of cavities characterized by an increased average pore. catalyst TiO2-N/zeolite-chitosan has a specific surface area greater than the catalyst TiO2-N/zeolite, it indicates that the addition of chitosan on the catalyst TiO2-N/zeolite may increase the specific surface area of the catalyst. TiO2-N/zeolite particles associated with chitosan as a binder so that TiO2-N/zeolite- chitosan have cavities larger. This is consistent with the SEM results indicate the presence of fibers binder particles TiO2-N/zeolite.
In Figure 3 a on the leading TiO2 adsorption isotherms classification of type III which shows the increasing pressure the more the quantity adsororbat. In this type of interaction is smaller than the adsorbent adsorbate-adsorbate interactions. Figure 3 b, c, and d is the type IV adsorption isotherm profile which has a characteristic similar to the type II and shows the size of the mesoporous (2-50 nm)17. Increasing the relative pressure accompanied with increasing adsorbate that goes into the pore material18. Desorption isotherms are formed leads to Type C, which in this type produced by the type of taper-shaped pores and is open at both ends.
The structure and morphology of photocatalysts can be known through characterization by Electrone Scanning Microscope (SEM). Morphology and structure of zeolite activation, TiO2, TiO2-N, N-TiO2/zeolite and TiO2-N/zeolite-chitosan is known that the morphology is different from one another. The morphology of the N
atom is known that already in the TiO2, TiO2N already bound in the zeolite, and the chitosan causes TiO2N/zeolite can be spread out evenly. Morphology of the results of characterization using Electrone Scanning Microscope (SEM) is shown in Figure 4. Activation of zeolite morphology Figure 4.a shows that zeolite activation has many pores and forming clots. Morphology of TiO2 in Figure 3.b with 5.000x magnification showed that the TiO2 in the form of balls that belong together and have pores that quite a lot. TiO2-N in Figure 4.c with a magnification of 5.000x morphology in the form of a set of balls possible of TiO2 and there is a section which dominates with a diameter greater than the morphology of TiO2. In morphology TiO2-N has a surface which is denser than TiO2 because the pores that exist in TiO2 has been filled with N. Morphology of TiO2-N is not much different from the TiO2, TiO2 is more dominating, This is due to the basic material is TiO2 and TiO2 have a ratio of more than N. TiO2 and urea has been calcined at a temperature of 300o C, the morphology of TiO2-N shows the aggregate particles19. In Figure 4.d morphology of TiO2-N/zeolite through magnification 4.000x there are several forms including some lumps which come from TiO2-N and shapes with diameters wide, rectangular shape is derived from the zeolite. Morphology of TiO2-N/zeolite-chitosan in Figure 4.e with 5.000x magnification can be seen that each TiO2, N, zeolite and chitosan have been distributed evenly on the surface of the photocatalyst. Long form that resembles a needle is chitosan contained in the photocatalyst
The energy band gap of a material can be measured using the DRS (Diffuse Reflactance Spectroscopy), which is the distance between the valence band and the conduction band. Data obtained from the characterization is then processed by making the curve relationship between wavelength and K/S to determine the equation of a straight line with R2 close to 120.
Characterization of DRS is able to provide great information value of the band gap of the photocatalyst. Data absorbance, % R, and the wavelength can be processed using Kubelka-Munk equation and made the curve relationship between the wavelength and the value of K/S with R2 close to 1, the point of intersection on the wavelength axis (x axis) is the wavelength edge. Wavelength edge obtained is converted into energy band gap (eV). Based on the calculation, the energy band gap of the photocatalyst is as follows TiO2 3.28 eV, 3.09 eV TiO2-N, TiO2-N/zeolite of 3.3 eV, TiO2-N/zeolite-chitosan 3.25 eV. The addition of N dopant capable of lowering the energy band gap of TiO2. The addition of chitosan, a large energy bandgap decreased, Chitosan itself has an energy band gap in the range of 1.6 to 2.3 eV 21.
TiO2 band gap 3.28 eV according to the literature, namely 3.2 eV (387 nm)22,23. The presence of dopant N in TiO2 causes a shift to larger wavelengths called Red Shift shift the band gap value is down. It is due to the formation of mid gap between the valence band and the conduction band of the TiO2 semiconductor. The formation of mid gap is the result of a 2p orbital hybridization N and O 2p24. TiO2N lower band gap of TiO2 may be caused by a deficiency of stoichiometric TiO2 by N or due to the formation of defects energy levels25. Decreased energy band gap in the presence of N dopants according to research Permatasari9.
TiO2-N/zeolite-chitosan beads photocatalyst tested for their ability to degrade MB at various concentrations and various long irradiation. The constant rate of degradation is presented in Figure 5 and Table 2. Based on Figure 5 and Table 2 that the initial concentration of MB affect the degradation rate constant. Based on research from Hasan (2016) showed that the initial concentration of the dye will affect the speed of degradation of congo red, the rate of degradation is decreased with increasing the initial concentration of congo red26. While in this study for methylene blue at a concentration range of 10-25 ppm, a concentration of 20 ppm gives a constant degradation of the greatest. Degradation rate constant at MB was increased to concentrations of 10-20 ppm MB whereas when the concentration increased further degradation rate constant is decreased.
Research Wardhani27 stated that constant rate degradation is decreased with increasing concentrations of 10-40 ppm MB using powder photocatalyst TiO2/zeolite and UV rays. Increased degradation rate constant at higher concentrations caused more chances OH radicals and MB to interact. In the MB concentration increased, the more MB adsorbed on the photocatalyst so MB which exist on the surface of the catalyst is more likely to interact with OH radicals, which are produced by the photocatalyst. Degradation rate constant is decreased at MB concentrations were higher due to the increased intensity of the color of the MB. The intensity of this color affects the intensity of light that interacts with photocatalysts. So this will affect the OH radicals are generated so that the number of MB degraded decline.
Conclusion
Beads photocatalyst TiO2-N/zeolite-chitosan have can be made of TiO2, urea, zeolite and chitosan. Beads photocatalyst characterized by FTIR and showed absorption at wave number range of 1520 cm-1 which showed absorption bond of N-TiO2. The specific surface area of TiO2 will increase when TiO2 is added bearers of zeolite and increase even more when added to chitosan. The specific surface area, average pore radius and total pore volume of TiO2-N / zeolite chitosan are respectively 306.275 (m2/g), 29.13 (Å) 4,462x10-1 (cm3/g). The energy band gap of TiO2 decreased when TiO2 is implied by N. Energy band gap of TiO2, TiO2-N, N-TiO2/zeolite, TiO2-N/zeolite-chitosan are respectively 3.28; 3.09; 3.3 and 3.25 eV. MB degradation rate constant is affected by the concentration of MB.
Table 1 specific surface area, mean pore and total pore volume by the BET method.
The catalyst |
specific surface area (m2/g) |
Average pore (Å) |
Total pore volume (cm3/g) |
natural zeolite |
224,233 |
30,03 |
3,668x10-1 |
zeolite activation |
251,686 |
30,23 |
3,804x10-1 |
TiO2 |
119,42 |
23,40 |
1,395 |
TiO2-N/zeolite |
273,997 |
38,37 |
5,257x10-1 |
TiO2-N/zeolite-chitosan |
306,275 |
29,13 |
4,462x10-1 |
Figure 1. FTIR spectra of Zeolite Activation
D
Figure 2. FTIR Spectra of (A) TiO2, (B) TiO2N, (C)TiO2N-Zeolite, (D) TiO2N-Zeolite-Chitosan
Relative Pressure, P/POPressure, P/Po
Relative Pressure, P/POPressure, P/Po
Relative Pressure, P/POPressure, P/Po
Relative Pressure, P/POPressure, P/Po
Relative Pressure, P/POPressure, P/Po
(d) (e)
Figure 3: Graph adsorption-desorption isotherms of N2 (a) TiO2, (b) the natural zeolite, (c) zeolite activation, (d) TiO2-N/zeolite, and (e) TiO2-N/zeolite-chitosan
Figure 4: Morphology SEM results. (A) Zeolite activation, (b) TiO2, (c) TiO2-N, (d) TiO2-N zeolite, (e) TiO2-N/zeolite-chitosan.
Figure 5 Correlation of irradiation time and ln (C0/ Ct) at various initial concentration of MB
Table 2 Degradation rate constant at various concentrations MB
MB ppm |
Rate constant (h-1) |
10 |
0.3193 |
15 |
0.3471 |
20 |
0.5198 |
25 |
0.1989 |
References
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