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Synthesis and Characterization of Photocatalytic MnFe2O4 Nanoparticles
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ScienceDirect Materials Today: Proceedings 21 (2020) 1905–1910
www.materialstoday.com/proceedings
ISFM-2018
Synthesis and Characterization of Photocatalytic MnFe2O4 Nanoparticles Harshal B. Desaia, Laxmi J. Hathiyab, Hiren H. Joshib, Ashish R. Tannaa* a
b
School of Science, RK University, Rajkot-360020, India Department of Physics, Saurashtra University, Rajkot-360005, India
Abstract Nanoparticles of manganese ferrite are successfully synthesized by auto combustion technique. The chemical stoichiometry of the sample is checked by Energy Dispersive X-ray (EDAX). The structure of prepared ferrite is confirmed through X-ray Diffraction (XRD) method and is endorsed by Fourier Transform Infrared (FTIR) Spectra. The range of crystallite size is obtained 20-40 nm from Transmission Electron Microscopy (TEM). Photocatalytic dye degradation of methylene blue is carried out under the Sunlight using MnFe2O4 and different mM solutions of H2O2. The minimum 10 mM concentration of H2O2 is required for the photocatalitic dye degradation of the MnFe2O4 nanoparticles. © 2019 Elsevier Ltd. All rights reserved. Peer-review under responsibility of the scientific committee of the International Symposium on Functional Materials (ISFM-2018): Energy and Biomedical Applications. Keywords: Auto combustion method; Nanoparticles; Photocatalysis; TEM; Dye degradation.
1. Introduction Spinel ferrites are fascinating materials which have ferrimagnetic properties as well as semiconducting properties. The chemical compositions formula of spinel ferrite is MO·Fe2O3. This structure has a fcc cage of oxygen ions and the metallic cations are distributed among tetrahedral (A) and octahedral [B] interstitial sites. This MO·Fe2O3 structure can be derived from Fe2+O·(Fe3+)2O3 while Fe2+ replaced by other divalent ions like Cd, Cu, Zn, Mn, etc.
* Corresponding author. E-mail address: [email protected] 2214-7853 © 2019 Elsevier Ltd. All rights reserved. Peer-review under responsibility of the scientific committee of the International Symposium on Functional Materials (ISFM-2018): Energy and Biomedical Applications.
1906
H.B. Desai et al. / Materials Today: Proceedings 21 (2020) 1905–1910
These ferrites are extensively useful for the mankind due to their irreplaceable properties and multiple applications towards the fields of science and technology [1]. Water resources can be affected by synthetic dyes which are byproduct of certain processes. Decompositions of these dyes occur either aerobically or anaerobically methods which can form carcinogenic compounds. Synthetic dye can be decomposed by several advanced oxidation processes to convert dyes into carbon dioxide and water i.e. biodegradation, photo-Fenton, photocatalytic, radiation, sonolysis, Fenton and UV photocatalytic processes [2]. Magnetic spinel ferrites are known catalyst for oxidation and dye degradation process [3]. Magnetic nanoparticles of spinel ferrites can separate by external magnetic field which is economical and promising technique for industrial applications. There are several methods to synthesize spinel ferrites like solid-state reactions, co-precipitation technique, microemulsion method, hydrothermal method, sol-gel auto combustion method and many more. Sol-gel auto combustion method is easy, low cost and requires low temperature to prepare nano-materials in large quantity. To synthesis nano-particles of spinel ferrites nitrate salts can be used. These salts are water-soluble at low temperature and known to use as precursors for this method [4-6]. The content of cations and synthesis methods play important role for photocatalysis properties of ferrite nanoparticles. The ferrites can also be used in odor control, bacterial inactivation, elimination of contaminants from water and air [7]. In photocatalysis process solar energy is used and performed simple oxidation and reduction process [8,9]. In present case, MnFe2O4 (MNF) nanoparticles have been synthesized by sol-gel auto-combustion method and studied by means of various physical properties like XRD, TEM, SEM, EDX, BET analysis. Photocatalytic dye degradation of methylene blue under the influence of sun light in H2O2 has been carried out for the prepared nanoparticles. 2. Experimental To synthesize nanoparticles of MnFe2O4, 50 ml of nitrate salts of Mn (II), Fe (III) and citric acid were added at molar ratio 1:2:2.2 for sol-gel auto-combustion method. This ratio was calculated by the principle used in propellant chemistry [10]. According to this principle, the reducing and oxidizing valences are considered as follows: H = 1, C = 4, O = -2, N = 0, M = 2,3 etc. Here, the chemical formula of ferrite is M2+Fe23+O4. The oxidizing valency of Mn (II) nitrate becomes -10, Fe (III) nitrate becomes -15. This should be balanced by total valences of citric acid which was used as fuel in the synthesis process that is +18. Citric acid was added in nitrate salts for the synthesis of MnFe2O4. Therefore, the stoichiometric composition for the redox mixture could be calculated by -40+18n = 2.22 mole of citric acid. Initially, the pH of this mixture was ~ 2. The pH of this mixture was adjusted 9 by slowly adding ammonia solution. Simultaneously, the mixture was stirred at 80 ℃ constant temperature on magnetic stirrer. After certain time lapsed, the mixture became dark brown viscous gel and MNF nanoparticles were obtained [11,12]. These nanoparticles were sintered at 500ºC for 4 hrs in muffle furnace to remove impurities. The Energy Dispersive Analysis of X-ray (EDAX) analysis was used to check proportion of Mn, Fe and O in prepared sample. The internal structure of MNF observed with the help of SEM images. The lattice parameters, particle size and crystal structure were obtained by X-ray diffraction (XRD) characterization. The force constants between metal-oxygen bond was calculated with the help of FTIR spectroscopy. The crystallite size was calculated by Debye-Scherer formula using highest peak (311) of XRD. The range of crystallite size distribution was derived by the ImageJ software using TEM images [13]. The surface area of MNF was obtained by BET analysis. For dye degradation study, methylene blue to H2O2 ratio was fixed by 9:1. The different combinations of 10 mg MNF + methylene blue and H2O2 solutions were kept under sunlight to carry out the experiments of dye degradation. Also, same combinations were used in UVVisible spectrophotometer for the absorbance of light and dye degradation test. 3. Result and Discussion The stoichiometric proportion of the prepared sample is confirmed through EDAX as shown in Fig. 1. It can be observed from SEM image that the grains of MNF are having nano size with uniform distribution as shown in Fig. 2 (a). It can also be observed that there are voids, pores and the fractured surface formed due to escape of large amount of gases during auto combustion process as shown in Fig. 2 (b). This is the one of the reasons, that nanoferrites can be worked as photocatalytic materials.
H.B. Desai et al. / Materials Today: Proceedings 21 (2020) 1905–1910
1907
Fig. 1. EDAX of MNF.
Fig. 2. (a) SEM image of the MNF for grain size; (b) SEM fracture image of the MNF.
The X-ray diffraction (XRD) patterns for MNF is recorded at 300 K as shown in Fig. 3. The XRD pattern of Mn spinel ferrite is indexed for fcc-Fd3m space group using standard data file obtained from PCPDFWIN program (JCPDS card number: 74-2403). Further, crystallite size of MNF is calculated using Debye-Scherrer formula by sharp Bragg reflection corresponding to intense peak (311) about 33 nm [13,14]. The infrared absorption spectrum is recorded at room temperature in the range of 400-800 cm-1. The three main metal-oxygen bonds are seen in the FTIR spectrum for MNF as shown in Fig. 4. The higher absorption band is at 634 cm-1 which is due to stretching vibrations of the tetrahedral metal-oxygen bond and lowest band observed at 573 cm-1 due to metal-oxygen vibrations in the octahedral sites and one shoulder at 596 cm-1 [15]. The force constant can be calculated for tetrahedral site (kt) = 140 N/m and octahedral site (ko) = 119 N/m using the standard formulae [16] from the IR absorption spectra.
900
(533)
(400)
3000
(440)
4500
(422) (333)
(311)
MNF
(220)
Intensity (counts)
6000
JCPDS card no. 74-2403
600 300 0 20
40
2θ (degree)
60
Fig. 3. XRD pattern of MNF
80
1908
H.B. Desai et al. / Materials Today: Proceedings 21 (2020) 1905–1910
60 55
45 400
500
600
634 _
50
573 _ 596 _
Transmittance (%)
65
700
-1
800
Wave number (cm ) Fig. 4. FTIR spectrum of MNF.
Fig. 5. (a) TEM image of MNF; (b) HRTEM image of MNF.
Fig. 5 (a) and (b) show the TEM and HRTEM images of MNF specimen respectively. The lattice planes have been observed by HRTEM image of prepared nano-ferrites. The range of crystallite size of synthesized MNF is obtained 20-40 nm from TEM. The average crystallite size is deduced using ImageJ software which is matched with values of crystallite size calculated by Debye-Scherrer method [13]. Fig. 6 shows the particle size histogram and the fitting by Gaussian function deduce through TEM measurement. The average particle size is 32.66 nm and the standard deviation reads 4.87 nm. Particles frequncy Gaussian fitting
20
Frequency (%)
16 12 8 4 0
20
25
30
35
Particle size (nm)
40
Fig. 6. Crystallite size distribution from TEM image.
The porosity of MNF can be recognized by nitrogen adsorption-desorption isotherm curve. The surface area of MNF can be measured by the BET surface area analyzer. Fig. 7 shows the nitrogen adsorption-desorption isotherm
H.B. Desai et al. / Materials Today: Proceedings 21 (2020) 1905–1910
1909
3 -1
Volume adsorbed (cm g )
curve of nano-ferrite. This exhibits a type IV isotherm with an H3 type hysteresis loop [17, 18]. From BrunauerEmmett-Teller (BET) analysis values of the surface area, pore diameter and pore volume are 93.19 m2/g, 70.02 Å and 0.3506 cm3/g respectively. The synthesized MNF have a mesoporous structure which is responsible for the dye degradation process.
28 21 14 7
0.0
0.3
0.6
0.9
Relative pressure (P / P0)
Fig. 7. Nitrogen adsorption-desorption isotherm curve for MNF.
Spinel ferrite materials can be effectively worked as photocatalyst using electromagnetic radiation to create electron-hole pairs on the Photocatalytic surface. Due to this electron-hole pairs, reduction and oxidation process occur in the solution and finally, it produces radicals ●OH and O2-●. These radicals can be utilized for decomposition process of organic dye. Furthermore, to enhance the formation of reactive oxygen species, H2O2 oxidant can be added to the reaction mixture. According to these reactions, iron cations react with H2O2 results formation of highly reactive ●OH radicals. Both these electrons and holes interact with surface bound H2O or OH− to produce ●OH radicals. These radicals are main active species in the photocatalytic degradation process [19]. In the presence of solar radiation, Fig. 8 (a) shows the mixture of 10 ppm Methylene blue and 10 mM H2O2 in a sample holder. Fig. 8 (b) shows the mixture of 10 ppm Methylene blue+10 mM H2O2 and 10 mg MNF powder in a sample holder. Due to nano-ferrite particles photo catalysis process has occurred in the sample holder and bubbles formed within 1 min of time. Further, magnetic nano-particles can be separated from mixture after removal of dye through external magnets as shown in Fig. 8 (c). Fig. 8 (d) shows the complete removal of Methylene blue dye from the mixture where the contact time of prepared sample was 80 mins.
Fig. 8. The mixture of (a) 10 ppm Methylene blue+10 mM H2O2; (b) 10 ppm Methylene blue+10 mM H2O2+10 mg MNF, ~1 min; (c) 10 ppm Methylene blue+10 mM H2O2 + 10mg MNF, ~ 3 mins with magnet; (d) 10 ppm Methylene blue+10 mM H2O2 + 10mg MNF, time ~ 80 mins.
Fig. 9 shows the plots of absorbance of visible light versus contact time of nano-ferrite with the mixture of 10 ppm Methylene blue by variation of H2O2 solution in the UV-Vis spectrophotometer. It shows that minimum 10 mM concentration of H2O2 required for dye degradation.
1910
H.B. Desai et al. / Materials Today: Proceedings 21 (2020) 1905–1910
Absorbance
0.45
5 mM H2O2
0.30
10 mM H2O2 20 mM H2O2 30 mM H2O2
0.15
40 mM H2O2 50 mM H2O2
0.00 0
20
40
60
Contact time (min)
80
Fig. 9. Methylene blue removal using MNF.
4. Conclusion MnFe2O4 nanoparticles are successfully synthesized by auto combustion technique. The X-ray diffraction study reveals the formation of spinel structure and FTIR measurement supports the structure of the prepared sample. The crystallite size of nano-ferrites is calculated from Debye-Scherrer equation using intense peak of XRD. The transmission electron microscopy measurement gives the rang of prepared nano-particles from 20 nm to 40 nm. The HRTEM image of nano-particle reflects the crystalline nature of spinel ferrite. The synthesized sample has mesoporous structure which observed from BET analysis. These properties make the nano-particles excellent photocatalytic material for water treatment. Consequently, the prepared sample is successfully used as catalyst for methylene blue dye degradation by means of photocatalytic activity. The rate of reaction and photocatalysis process of nano catalyst can be enhanced by adding H2O2 under the visible light irradiation. The dye degradation process is established due to the porous structure of the photocatalyst nanoparticles which adsorbed the dye molecules and generated transparent mixture. References [1] S.M. Chavan, M.K. Babrekar, S.S. More. J Allo. Comp. 507(1) (2010) 21-25. [2] I. Ullah, S. Ali, M. A. Hanif, S.A. Shahid, Int. J. Chem. Biochem. Sci. 2(2012) 60-67. [3] N. Ma, Y. Yue,W. Hua and Z. Gao, Appl. Cataly. A: Gen.l 251 (2003) 39–47. [4] R.K. Salvan, C.O. Augustin, L.J. Berchmans, Mater. Res. Bulle. 38(1)(2003) 41-54. [5] A. K. Bedyal, V. Kumar, V.Sharma, S. S. Pitale, E. Coetsee, M. M. Duvenhage, O. M. Ntwaeaborwa, H. C. Swart, J Mater Sci 48 (2013) 33 27–3333 [6] V. Sharma, A. Das, V. Kumar, V. Kumar, K. Verma, H.C. Swart, Physica B: Phys. Conden. Matter. 535(2018) 149-156. [7] E. Casbeer, V.K. Sharma, X. Li, Sep. Purif. Technol. 87 (2012) 1-14. [8] N.M. Mahmoodi, Desalin. Water Treat. (2013) 1-7. [9] T. Valde´s-Solıs, P. Valle-Vigo´n, S. lvarez, G. Marba´n, A. B. Fuertes, Catal. Commun. 8 (2007) 2037–2042. [10] R.C. Kambale, P.A. Shaikh, N.S. Harale, V.A. Bilur, Y.D. Kolekar, C.H. Bhosale, K.Y. Rajpure, J. All. Comp.490(2010) 568-571. [11] A. Sukta, G. Mezinskis, Front. Mater. Sci. 6(2) (2012) 128–141. [12] N.S. Gajbhiye, U. Bhattacharya, V.S. Darshane, Thermochim. Acta. 264 (1995) 219-230. [13] A.R. Tanna, K.M. Sosa, H. H. Joshi, Mater. Res. Express. 4 (2017) 115010-1-7. [14] I. Soibam, Angom D. Mani, Mater. Today: Proc. 5 (2018) 2064–2073. [15] R. D. Waldron, Phys. Rev. 99 (6) (1955) 1727-1735. [16] K.P. Thummer, A.R. Tanna, H.H. Joshi, AIP Conf. Proc. 1837 (2017) 040058-1-4. [17] L. Yang, F. Wang, Y. Meng, Q. Tang, Z. Liu, Journal of Nanomaterials. (2013) 1-5. [18] B. Sahoo, S. K. Sahoo, S. Nayak, D. Dhara, P. Pramanik, Cat. Sci. Techno. 2(2012), 1367-1374 [19] T.K. Pathak, N.H. Vasoya, T.S. Natarajan, K.B. Modi, R.J. Tayade, Mater. Sci. Forum. 764 (2013) 116-129.
ScienceDirect Materials Today: Proceedings 21 (2020) 1905–1910
www.materialstoday.com/proceedings
ISFM-2018
Synthesis and Characterization of Photocatalytic MnFe2O4 Nanoparticles Harshal B. Desaia, Laxmi J. Hathiyab, Hiren H. Joshib, Ashish R. Tannaa* a
b
School of Science, RK University, Rajkot-360020, India Department of Physics, Saurashtra University, Rajkot-360005, India
Abstract Nanoparticles of manganese ferrite are successfully synthesized by auto combustion technique. The chemical stoichiometry of the sample is checked by Energy Dispersive X-ray (EDAX). The structure of prepared ferrite is confirmed through X-ray Diffraction (XRD) method and is endorsed by Fourier Transform Infrared (FTIR) Spectra. The range of crystallite size is obtained 20-40 nm from Transmission Electron Microscopy (TEM). Photocatalytic dye degradation of methylene blue is carried out under the Sunlight using MnFe2O4 and different mM solutions of H2O2. The minimum 10 mM concentration of H2O2 is required for the photocatalitic dye degradation of the MnFe2O4 nanoparticles. © 2019 Elsevier Ltd. All rights reserved. Peer-review under responsibility of the scientific committee of the International Symposium on Functional Materials (ISFM-2018): Energy and Biomedical Applications. Keywords: Auto combustion method; Nanoparticles; Photocatalysis; TEM; Dye degradation.
1. Introduction Spinel ferrites are fascinating materials which have ferrimagnetic properties as well as semiconducting properties. The chemical compositions formula of spinel ferrite is MO·Fe2O3. This structure has a fcc cage of oxygen ions and the metallic cations are distributed among tetrahedral (A) and octahedral [B] interstitial sites. This MO·Fe2O3 structure can be derived from Fe2+O·(Fe3+)2O3 while Fe2+ replaced by other divalent ions like Cd, Cu, Zn, Mn, etc.
* Corresponding author. E-mail address: [email protected] 2214-7853 © 2019 Elsevier Ltd. All rights reserved. Peer-review under responsibility of the scientific committee of the International Symposium on Functional Materials (ISFM-2018): Energy and Biomedical Applications.
1906
H.B. Desai et al. / Materials Today: Proceedings 21 (2020) 1905–1910
These ferrites are extensively useful for the mankind due to their irreplaceable properties and multiple applications towards the fields of science and technology [1]. Water resources can be affected by synthetic dyes which are byproduct of certain processes. Decompositions of these dyes occur either aerobically or anaerobically methods which can form carcinogenic compounds. Synthetic dye can be decomposed by several advanced oxidation processes to convert dyes into carbon dioxide and water i.e. biodegradation, photo-Fenton, photocatalytic, radiation, sonolysis, Fenton and UV photocatalytic processes [2]. Magnetic spinel ferrites are known catalyst for oxidation and dye degradation process [3]. Magnetic nanoparticles of spinel ferrites can separate by external magnetic field which is economical and promising technique for industrial applications. There are several methods to synthesize spinel ferrites like solid-state reactions, co-precipitation technique, microemulsion method, hydrothermal method, sol-gel auto combustion method and many more. Sol-gel auto combustion method is easy, low cost and requires low temperature to prepare nano-materials in large quantity. To synthesis nano-particles of spinel ferrites nitrate salts can be used. These salts are water-soluble at low temperature and known to use as precursors for this method [4-6]. The content of cations and synthesis methods play important role for photocatalysis properties of ferrite nanoparticles. The ferrites can also be used in odor control, bacterial inactivation, elimination of contaminants from water and air [7]. In photocatalysis process solar energy is used and performed simple oxidation and reduction process [8,9]. In present case, MnFe2O4 (MNF) nanoparticles have been synthesized by sol-gel auto-combustion method and studied by means of various physical properties like XRD, TEM, SEM, EDX, BET analysis. Photocatalytic dye degradation of methylene blue under the influence of sun light in H2O2 has been carried out for the prepared nanoparticles. 2. Experimental To synthesize nanoparticles of MnFe2O4, 50 ml of nitrate salts of Mn (II), Fe (III) and citric acid were added at molar ratio 1:2:2.2 for sol-gel auto-combustion method. This ratio was calculated by the principle used in propellant chemistry [10]. According to this principle, the reducing and oxidizing valences are considered as follows: H = 1, C = 4, O = -2, N = 0, M = 2,3 etc. Here, the chemical formula of ferrite is M2+Fe23+O4. The oxidizing valency of Mn (II) nitrate becomes -10, Fe (III) nitrate becomes -15. This should be balanced by total valences of citric acid which was used as fuel in the synthesis process that is +18. Citric acid was added in nitrate salts for the synthesis of MnFe2O4. Therefore, the stoichiometric composition for the redox mixture could be calculated by -40+18n = 2.22 mole of citric acid. Initially, the pH of this mixture was ~ 2. The pH of this mixture was adjusted 9 by slowly adding ammonia solution. Simultaneously, the mixture was stirred at 80 ℃ constant temperature on magnetic stirrer. After certain time lapsed, the mixture became dark brown viscous gel and MNF nanoparticles were obtained [11,12]. These nanoparticles were sintered at 500ºC for 4 hrs in muffle furnace to remove impurities. The Energy Dispersive Analysis of X-ray (EDAX) analysis was used to check proportion of Mn, Fe and O in prepared sample. The internal structure of MNF observed with the help of SEM images. The lattice parameters, particle size and crystal structure were obtained by X-ray diffraction (XRD) characterization. The force constants between metal-oxygen bond was calculated with the help of FTIR spectroscopy. The crystallite size was calculated by Debye-Scherer formula using highest peak (311) of XRD. The range of crystallite size distribution was derived by the ImageJ software using TEM images [13]. The surface area of MNF was obtained by BET analysis. For dye degradation study, methylene blue to H2O2 ratio was fixed by 9:1. The different combinations of 10 mg MNF + methylene blue and H2O2 solutions were kept under sunlight to carry out the experiments of dye degradation. Also, same combinations were used in UVVisible spectrophotometer for the absorbance of light and dye degradation test. 3. Result and Discussion The stoichiometric proportion of the prepared sample is confirmed through EDAX as shown in Fig. 1. It can be observed from SEM image that the grains of MNF are having nano size with uniform distribution as shown in Fig. 2 (a). It can also be observed that there are voids, pores and the fractured surface formed due to escape of large amount of gases during auto combustion process as shown in Fig. 2 (b). This is the one of the reasons, that nanoferrites can be worked as photocatalytic materials.
H.B. Desai et al. / Materials Today: Proceedings 21 (2020) 1905–1910
1907
Fig. 1. EDAX of MNF.
Fig. 2. (a) SEM image of the MNF for grain size; (b) SEM fracture image of the MNF.
The X-ray diffraction (XRD) patterns for MNF is recorded at 300 K as shown in Fig. 3. The XRD pattern of Mn spinel ferrite is indexed for fcc-Fd3m space group using standard data file obtained from PCPDFWIN program (JCPDS card number: 74-2403). Further, crystallite size of MNF is calculated using Debye-Scherrer formula by sharp Bragg reflection corresponding to intense peak (311) about 33 nm [13,14]. The infrared absorption spectrum is recorded at room temperature in the range of 400-800 cm-1. The three main metal-oxygen bonds are seen in the FTIR spectrum for MNF as shown in Fig. 4. The higher absorption band is at 634 cm-1 which is due to stretching vibrations of the tetrahedral metal-oxygen bond and lowest band observed at 573 cm-1 due to metal-oxygen vibrations in the octahedral sites and one shoulder at 596 cm-1 [15]. The force constant can be calculated for tetrahedral site (kt) = 140 N/m and octahedral site (ko) = 119 N/m using the standard formulae [16] from the IR absorption spectra.
900
(533)
(400)
3000
(440)
4500
(422) (333)
(311)
MNF
(220)
Intensity (counts)
6000
JCPDS card no. 74-2403
600 300 0 20
40
2θ (degree)
60
Fig. 3. XRD pattern of MNF
80
1908
H.B. Desai et al. / Materials Today: Proceedings 21 (2020) 1905–1910
60 55
45 400
500
600
634 _
50
573 _ 596 _
Transmittance (%)
65
700
-1
800
Wave number (cm ) Fig. 4. FTIR spectrum of MNF.
Fig. 5. (a) TEM image of MNF; (b) HRTEM image of MNF.
Fig. 5 (a) and (b) show the TEM and HRTEM images of MNF specimen respectively. The lattice planes have been observed by HRTEM image of prepared nano-ferrites. The range of crystallite size of synthesized MNF is obtained 20-40 nm from TEM. The average crystallite size is deduced using ImageJ software which is matched with values of crystallite size calculated by Debye-Scherrer method [13]. Fig. 6 shows the particle size histogram and the fitting by Gaussian function deduce through TEM measurement. The average particle size is 32.66 nm and the standard deviation reads 4.87 nm. Particles frequncy Gaussian fitting
20
Frequency (%)
16 12 8 4 0
20
25
30
35
Particle size (nm)
40
Fig. 6. Crystallite size distribution from TEM image.
The porosity of MNF can be recognized by nitrogen adsorption-desorption isotherm curve. The surface area of MNF can be measured by the BET surface area analyzer. Fig. 7 shows the nitrogen adsorption-desorption isotherm
H.B. Desai et al. / Materials Today: Proceedings 21 (2020) 1905–1910
1909
3 -1
Volume adsorbed (cm g )
curve of nano-ferrite. This exhibits a type IV isotherm with an H3 type hysteresis loop [17, 18]. From BrunauerEmmett-Teller (BET) analysis values of the surface area, pore diameter and pore volume are 93.19 m2/g, 70.02 Å and 0.3506 cm3/g respectively. The synthesized MNF have a mesoporous structure which is responsible for the dye degradation process.
28 21 14 7
0.0
0.3
0.6
0.9
Relative pressure (P / P0)
Fig. 7. Nitrogen adsorption-desorption isotherm curve for MNF.
Spinel ferrite materials can be effectively worked as photocatalyst using electromagnetic radiation to create electron-hole pairs on the Photocatalytic surface. Due to this electron-hole pairs, reduction and oxidation process occur in the solution and finally, it produces radicals ●OH and O2-●. These radicals can be utilized for decomposition process of organic dye. Furthermore, to enhance the formation of reactive oxygen species, H2O2 oxidant can be added to the reaction mixture. According to these reactions, iron cations react with H2O2 results formation of highly reactive ●OH radicals. Both these electrons and holes interact with surface bound H2O or OH− to produce ●OH radicals. These radicals are main active species in the photocatalytic degradation process [19]. In the presence of solar radiation, Fig. 8 (a) shows the mixture of 10 ppm Methylene blue and 10 mM H2O2 in a sample holder. Fig. 8 (b) shows the mixture of 10 ppm Methylene blue+10 mM H2O2 and 10 mg MNF powder in a sample holder. Due to nano-ferrite particles photo catalysis process has occurred in the sample holder and bubbles formed within 1 min of time. Further, magnetic nano-particles can be separated from mixture after removal of dye through external magnets as shown in Fig. 8 (c). Fig. 8 (d) shows the complete removal of Methylene blue dye from the mixture where the contact time of prepared sample was 80 mins.
Fig. 8. The mixture of (a) 10 ppm Methylene blue+10 mM H2O2; (b) 10 ppm Methylene blue+10 mM H2O2+10 mg MNF, ~1 min; (c) 10 ppm Methylene blue+10 mM H2O2 + 10mg MNF, ~ 3 mins with magnet; (d) 10 ppm Methylene blue+10 mM H2O2 + 10mg MNF, time ~ 80 mins.
Fig. 9 shows the plots of absorbance of visible light versus contact time of nano-ferrite with the mixture of 10 ppm Methylene blue by variation of H2O2 solution in the UV-Vis spectrophotometer. It shows that minimum 10 mM concentration of H2O2 required for dye degradation.
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H.B. Desai et al. / Materials Today: Proceedings 21 (2020) 1905–1910
Absorbance
0.45
5 mM H2O2
0.30
10 mM H2O2 20 mM H2O2 30 mM H2O2
0.15
40 mM H2O2 50 mM H2O2
0.00 0
20
40
60
Contact time (min)
80
Fig. 9. Methylene blue removal using MNF.
4. Conclusion MnFe2O4 nanoparticles are successfully synthesized by auto combustion technique. The X-ray diffraction study reveals the formation of spinel structure and FTIR measurement supports the structure of the prepared sample. The crystallite size of nano-ferrites is calculated from Debye-Scherrer equation using intense peak of XRD. The transmission electron microscopy measurement gives the rang of prepared nano-particles from 20 nm to 40 nm. The HRTEM image of nano-particle reflects the crystalline nature of spinel ferrite. The synthesized sample has mesoporous structure which observed from BET analysis. These properties make the nano-particles excellent photocatalytic material for water treatment. Consequently, the prepared sample is successfully used as catalyst for methylene blue dye degradation by means of photocatalytic activity. The rate of reaction and photocatalysis process of nano catalyst can be enhanced by adding H2O2 under the visible light irradiation. The dye degradation process is established due to the porous structure of the photocatalyst nanoparticles which adsorbed the dye molecules and generated transparent mixture. References [1] S.M. Chavan, M.K. Babrekar, S.S. More. J Allo. Comp. 507(1) (2010) 21-25. [2] I. Ullah, S. Ali, M. A. Hanif, S.A. Shahid, Int. J. Chem. Biochem. Sci. 2(2012) 60-67. [3] N. Ma, Y. Yue,W. Hua and Z. Gao, Appl. Cataly. A: Gen.l 251 (2003) 39–47. [4] R.K. Salvan, C.O. Augustin, L.J. Berchmans, Mater. Res. Bulle. 38(1)(2003) 41-54. [5] A. K. Bedyal, V. Kumar, V.Sharma, S. S. Pitale, E. Coetsee, M. M. Duvenhage, O. M. Ntwaeaborwa, H. C. Swart, J Mater Sci 48 (2013) 33 27–3333 [6] V. Sharma, A. Das, V. Kumar, V. Kumar, K. Verma, H.C. Swart, Physica B: Phys. Conden. Matter. 535(2018) 149-156. [7] E. Casbeer, V.K. Sharma, X. Li, Sep. Purif. Technol. 87 (2012) 1-14. [8] N.M. Mahmoodi, Desalin. Water Treat. (2013) 1-7. [9] T. Valde´s-Solıs, P. Valle-Vigo´n, S. lvarez, G. Marba´n, A. B. Fuertes, Catal. Commun. 8 (2007) 2037–2042. [10] R.C. Kambale, P.A. Shaikh, N.S. Harale, V.A. Bilur, Y.D. Kolekar, C.H. Bhosale, K.Y. Rajpure, J. All. Comp.490(2010) 568-571. [11] A. Sukta, G. Mezinskis, Front. Mater. Sci. 6(2) (2012) 128–141. [12] N.S. Gajbhiye, U. Bhattacharya, V.S. Darshane, Thermochim. Acta. 264 (1995) 219-230. [13] A.R. Tanna, K.M. Sosa, H. H. Joshi, Mater. Res. Express. 4 (2017) 115010-1-7. [14] I. Soibam, Angom D. Mani, Mater. Today: Proc. 5 (2018) 2064–2073. [15] R. D. Waldron, Phys. Rev. 99 (6) (1955) 1727-1735. [16] K.P. Thummer, A.R. Tanna, H.H. Joshi, AIP Conf. Proc. 1837 (2017) 040058-1-4. [17] L. Yang, F. Wang, Y. Meng, Q. Tang, Z. Liu, Journal of Nanomaterials. (2013) 1-5. [18] B. Sahoo, S. K. Sahoo, S. Nayak, D. Dhara, P. Pramanik, Cat. Sci. Techno. 2(2012), 1367-1374 [19] T.K. Pathak, N.H. Vasoya, T.S. Natarajan, K.B. Modi, R.J. Tayade, Mater. Sci. Forum. 764 (2013) 116-129.