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Photocatalytic degradation of an azo textile dye (C.I. Reactive Red 195 (3BF)) in aqueous solution over copper cobaltite nanocomposite coated on glass by Doctor Blade method
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 147 (2015) 173–177
Contents lists available at ScienceDirect
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy journal homepage: www.elsevier.com/locate/saa
Photocatalytic degradation of an azo textile dye (C.I. Reactive Red 195 (3BF)) in aqueous solution over copper cobaltite nanocomposite coated on glass by Doctor Blade method Mohammad Hossein Habibi ⇑, Zoya Rezvani Nanotechnology Laboratory, Department of Chemistry, University of Isfahan, Isfahan 81746-73441 Islamic Republic of Iran
h i g h l i g h t s
g r a p h i c a l a b s t r a c t
Photocatalytic degradation of reactive
brilliant red X-3B was studied. Copper cobaltite nanocomposite was
coated on glass by Doctor Blade method. UV-DRS, XRD and FESEM measurements were performed for structural and optical properties.
a r t i c l e
i n f o
Article history: Received 22 June 2014 Received in revised form 4 August 2014 Accepted 6 March 2015 Available online 25 March 2015 Keywords: Photocatalytic Nanocomposite Doctor Blade Brilliant red
a b s t r a c t The degradation of C.I. Reactive Red 195 (3BF) in aqueous solution using copper cobaltite nanocomposite coated on glass by Doctor Blade method was studied. Structural, optical and morphological properties of nanocomposite coatings were characterized by X-ray powder diffractometry (XRD), diffuse reflectance spectroscopy (DRS) and field emission scanning electron microscopy (FESEM). The nanoparticles exhibit a particle size of 31 nm, showing a good nanoscale crystalline morphology. The photocatalytic activity of copper cobaltite nanocomposite coated on glass was studied by performing the photocatalytic degradation of 3BF at different irradiation time. The effect of irradiation time on the degradation of 3BF was studied and the results showed that more than 85% of the 3BF was degraded in 45 min of irradiation. The pseudo-first-order kinetic models were used and the rate constants were evaluated with pseudo first order rate constants of 4.10 10 2 min 1. The main advantage of the photocatalyst coated on glass overcomes the difficulties in separation and recycle of photocatalyst suspensions. Ó 2015 Elsevier B.V. All rights reserved.
Introduction Worldwide industries have used different kind of dyes and large amounts of dyes are released into the water environment which causes severe health problems [1–4,5]. Industrial waste water must be treated prior to discharging them into the water environment. Advanced oxidation processes are the most useful methods for mineralizing pollutants rather than non-destructive methods ⇑ Corresponding author. Tel.: +98 313 7932707; fax: +98 313 6689732. E-mail address: [email protected] (M.H. Habibi). http://dx.doi.org/10.1016/j.saa.2015.03.077 1386-1425/Ó 2015 Elsevier B.V. All rights reserved.
which transfer pollutants from water to sludge. Semiconductor photocatalysts are the most favorite choice for mineralizing pollutants. The photocatalysts must be stable, low-cost, and non-toxic with good photo-catalytic activity [6–9]. Spinel cobaltites have narrow band gap with promising photocatalytic activity. For scale up purposes there are needs to synthesize copper cobaltites at moderate condition such as co-precipitation. Co-precipitation process is favored for its reduced temperature of processing [10–12]. When the suspension of photocatalyst is used for photodegradation of pollutants, the suspended photocatalyst must be separated after each reaction. Coating and immobilization of photocatalyst
174
M.H. Habibi, Z. Rezvani / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 147 (2015) 173–177
overcomes the difficulties in separation and recycle of photocatalyst. Photocatalyst coating films can be prepared by various techniques [13,14]. Some spinel-type oxides [15] are semiconductor materials with narrow band gap and could be used in the degradation of environmental pollutants. Copper cobaltite, (CuCo2O4) is a typical spinel material and it has also attracted growing interest in diverse applications such as catalyst, refractory material, microwave dielectric and ceramic capacitor, and humidity sensors and a candidate for anode materials of lithium battery [16–18]. Most of the methods for preparation of copper cobaltite are either difficult, needs high temperature or costly which diminishes preparation of the nano-sized materials in a large scale as compared to the co-precipitation synthesis. We had conducted deposition of new copper cobaltite nanocomposite on commercial borosilicate glass substrates using spin-coating and Doctor Blade method. Our study revealed that copper cobaltite nanocomposite coatings exhibited favorable optical properties as photocatalyst. To the best our knowledge, Doctor Blade coated copper cobaltite on glass and photocatalytic performance of nanocomposite in 3BF aqueous solution is not reported. The objectives of the study were to optimize the photocatalytic performance of nanocomposite oxides coating. The film surface was characterized using diffuse reflectance spectroscopy (DRS), X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM). In this research copper cobaltite nanocomposite was synthesized via a co-precipitation method using copper nitrate, cobalt nitrate and sodium carbonate as precursors. Structural, optical and morphological properties of nanocomposite coatings were characterized by X-ray powder diffractometry (XRD), diffuse reflectance spectroscopy (DRS) and field emission scanning electron microscopy (FESEM). The effect of irradiation time on the degradation of 3BF has been studied and the results showed that more than 85% of the 3BF (Fig. 1) was degraded in 45 min. The degradation mechanism of 3BF was also discussed with the change of UV–vis spectra of 3BF at different degradation time. Materials and methods Chemicals The 3BF used for photocatalytic degradation was obtained from local textile dye industries and was utilized without further purification. Copper nitrate and cobalt nitrate was obtained from Merck Company (Germany). Sodium carbonate was supplied by Sigma Chemicals Company. Other reagents were all analytical grade.
60 °C. The precipitate was filtered, washed thoroughly with distilled water, dried at 120 °C for 24 h and annealed at 350 °C for 4 h (Fig. 2). Coating of nanostructure copper cobaltite on glass by Doctor Blade method Preparation of copper cobaltite paste and coating the paste on glass by Doctor Blade were performed by our previous reports [19–22]. Photocatalytic degradation of C.I. Reactive Red 195 (3BF) by copper cobaltite coated on glass by Doctor Blade method The paste of copper cobalt oxide coated on a glass slide (6 cm 2 cm and 2 mm thickness) by Doctor-Blade method and the thin film annealed at 400 °C for 1 h. The B3F solution as dye with a concentration of 10 mg/L (ppm) prepared as an initial solution. This solution exposed at O2 gas for 30 min. The copper cobalt oxide thin film immersed into a petri dish with 25 ml of the initial B3F solution (Fig. 1) and maintained at dark conditions for 1 h. The concentration of this solution determined by measuring the absorbance by UV–vis spectrophotometer was 9.57 mg/L (ppm) after remaining at dark condition (calculated from standard curve). The reaction system illuminated by a 230 W Hg (g) lamp at different times and the concentration of the B3F solution determined by measuring the absorbance by a Cary 500 UV–vis spectrophotometer for photocatalytic activity examination. Apparatus Copper cobaltite was characterized by UV-DRS, XRD and FESEM analysis. Diffuse reflectance spectra (DRS) were collected with a V670, JASCO spectrophotometer and transformed to the absorption spectra according to the Kebelka relationship. The structure and crystal phase composition of the composites were determined by XRD patterns with a X-ray diffractometer (D8 Advance, BRUKER) in the diffraction angle range 2h = 20–60°, using Cu Ka radiation. The crystallite size D of the sample was estimated using the Scherer’s equation, (0.9k)/ (bcosh), by measuring the line broadening of main intensity peak, where k is the wavelength of Cu Ka radiation, b is the full width at half-maximum, and h is the Brag’s angle. Morphology was measured by using a FE-SEM, Hitachi, and model S-4160. The borosilicate glass substrates coated using spin coating method (Spin Coater, Modern Technology Development Institute, Iran).
Preparation of nanostructure copper cobaltite
Results and discussion
The nanostructure copper cobaltite was synthesized following the procedure: a solution (0.7 M) of Cu(NO3)23H2O was mixed with a solution (2.3 M) of Co(NO3)26H2O. To this mixture was added a saturated solution of Na2CO3 dropwise, stirred for 1 h at
Characterization The crystal phase structures of prepared copper cobaltite nanocomposite was characterized by XRD measurements (Fig. 3) and
Fig. 1. Chemical structure of 3BF.
M.H. Habibi, Z. Rezvani / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 147 (2015) 173–177
175
Fig. 4. FESEM image of copper cobaltite nanocomposite coated on glass by Doctor Blade.
Fig. 2. Flow chart for preparation of copper cobaltite nanocomposite.
Fig. 5. DRS of copper cobaltite nanocomposite coated on glass by Doctor Blade.
Fig. 3. XRD pattern of nanostructure copper oxocobaltate using co-precipitation route and copper and cobalt nitrate as precursors calcined at 350 °C for 2 h.
the results confirmed the crystalline nature of copper cobaltite. The peaks at 2h = 22.1°, 36.5°, 43.1°, 45.1°, 52.6°, 65.7°, 70.2° and 77.6° can be assigned to the diffractions of (1 1 1), (2 2 0), (3 1 1), (2 2 2), (4 0 0), (4 2 2), (5 1 1), and (4 4 0) crystal planes of the spinel. The crystalline size of the prepared copper cobaltite nano-composite was determined using Debye–Scherrer equation: D = Kk/b cos h, where D is the crystal size of the catalyst, K is dimensionless constant (0.9). k is the wavelength of X-ray, b is the full width at halfmaximum (FWHM) of the diffraction peak and h is the diffraction angle. The average crystalline size of copper cobaltite nano-composite was 35.8 nm. Morphology of the composite photo-catalyst which affects the photocatalytic activity was determined by FESEM with 60,000 magnifications (Fig. 4). As shown in Fig. 4, the prepared composite photo-catalyst particles are nearly
Fig. 6. Kubelka–Munk plot of copper cobaltite nanocomposite coated on glass by Doctor Blade.
spherical in shapes. The nano-particles exhibit a particle size of 31 nm, showing a good nanoscale crystalline morphology, which corresponds well with their XRD results. The diffuse reflectance spectra of copper cobaltite nano-composite are displayed in Fig. 5. As shown in Fig. 5, copper cobaltite nano-composite shows absorption in entire visible region. Fig. 6 presents the Kubelka– Munk plot of the sample for determination of the band gap. The result shows that the band gap of copper cobaltite nano-composite is 1.45 eV (675 nm) in the visible region.
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M.H. Habibi, Z. Rezvani / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 147 (2015) 173–177
Photocatalytic activity
Fig. 7. The changes in UV–vis spectra of C.I. Reactive Red 195 (3BF) in aqueous solution in the presence of copper cobaltite nanocomposite coated on glass on different irradiation time 0 min, 5 min, 10 min, 15 min, 20 min, 25 min, 35 min and 45 min.
Moreover, to study the effect of the copper cobaltite nano-composite on the photocatalytic activity of 3BF as an azo textile dye was carried out at room temperature. Fig. 7 shows the changes in UV–vis spectra of 3BF in aqueous solution in the presence of copper cobaltite nanocomposite coated on glass on different irradiation time from zero to 45 min. The results showed that more than 85% of 3BF was degraded in 45 min of irradiation. Degradation of 3BF solution in the presence of catalyst alone (dark) and irradiation alone (without catalyst) was negligible. Degradation vs time of irradiation in the photocatalytic decomposition of 3BF in the presence of copper cobaltite coated on glass by Doctor Blade method is shown in Fig. 8. The results showed that most of the dye pollutant was degraded in a short time of irradiation. Under UV irradiation, copper cobaltite acts as a barrier to prevent the migration of electrons/holes generated. Fig. 9 shows the reaction kinetics of photocatalytic degradation of C.I. Reactive Red 195 (3BF) over copper cobaltite nanocomposite coated on glass. The plot of Ln (Co/Ct) vs time shows straight line with the rate constant of 4.10 10 2 min 1. It is clear that there is a linear relationship between ln (Co/ Ct) value and the irradiation time, where Ct is the actual dye concentration at irradiation time t, and Co is the dye concentration after the adsorption/desorption equilibrium and before the irradiation process. The good correlations are indicating that the reaction kinetics follows a pseudo first order rate law. Conclusion
Fig. 8. The degradation vs. time dependency 3BF (10 mg/L) over copper cobaltite nanocomposite coated on glass at room temperature.
Copper cobaltite nanocomposite coated on glass has been prepared via a simple modified co-precipitation method. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and UV–vis diffuse reflectance (UV-DRS) revealed the successful coating of copper cobaltite on glass surface by Doctor Blade method which is simple with scale-up capability. Structural, optical and morphological properties of nanocomposite coatings were characterized by X-ray powder diffractometry (XRD), diffuse reflectance spectroscopy (DRS) and field emission scanning electron microscopy (FESEM). The nano-particles exhibit a particle size of 31 nm, showing a good nanoscale crystalline morphology, which corresponds well with their XRD results. The as-prepared nanocomposites consisted of copper cobaltite showed photocatalytic activity in photodegradation of an azo textile dye (3BF) under UV irradiation. The kinetic studies revealed that the pseudo first-order kinetic model is better degradation kinetics. Acknowledgments The authors wish to thank the University of Isfahan for financially supporting this work. References
Fig. 9. Reaction kinetics of photocatalytic degradation of 3BF over copper cobaltite nanocomposite coated on glass.
[1] L.F.M. Ismail, M.M. Emara, M.M. El-Moselhy, N.A. Maziad, O.K. Hussein, Spectrochim. Acta A 131 (2014) 158–168. [2] Y. Mostafa, I.S. Nassar, I.S. Ahmed, Spectrochim. Acta A 131 (2014) 329–334. [3] B. Ismail, S.T. Hussain, S. Akram, Chem. Eng. J. 219 (2013) 395–402. [4] J.S. Piccin, C.S. Gomes, L.A. Feris, M. Gutterres, Chem. Eng. J. 183 (2012) 30–38. [5] M.N. Chong, B. Jin, C.W.K. Chow, C. Saint, Water Res. 44 (2010) 2997–3027. [6] J. Yan, H. Yang, Y. Tang, Z. Lu, S. Zheng, M. Yao, Y. Han, Renewable Energy 34 (2009) 2399–2403. [7] S. Saadi, A. Bouguelia, M. Trari, Renewable Energy 31 (2006) 2245–2256. [8] M.H. Khedr, M. Bahgat, W.M. Rouby, Mater. Technol. 33 (2008) 27–32. [9] G. Fortunato, H.R. Oswald, A. Reller, J. Mater. Chem. 11 (2001) 905–911. [10] P.B. Pandya, H.H. Joshi, R.G. Kulkarni, J. Mater. Sci. Lett. 10 (1991) 474–478. [11] S.W. Tao, F. Gao, X.Q. Liu, O.T. Sørensen, Mater. Sci. Eng., B 77 (2000) 172–176. [12] M.H. Habibi, Z. Rezvani, Spectrochim. Acta A 130 (2014) 309–312.
M.H. Habibi, Z. Rezvani / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 147 (2015) 173–177 [13] R.S. Sonawane, S.G. Hegde, M.K. Dongare, Mater. Chem. Phys. 77 (2002) 744– 750. [14] J. Wang, Y. Guo, P. Guo, J. Yu, W. Guo, X.i. Wang, Sep. Purif. Technol. 130 (2014) 1–6. [15] A. Amri, X.F. Duan, C.-Y. Yin, Z.-T. Jiang, M. Mahbubur Rahman, T. Pryor, Appl. Surf. Sci. 275 (2013) 127–135. [16] S. Sun, Z. Wen, J. Jin, Y. Cui, Y. Lu, Microporous Mesoporous Mater. 169 (2013) 242–247. [17] M.J. Iqbal, B. Ismail, C. Rentenberger, H. Ipser, Mater. Res. Bull. 46 (2011) 2271–2277.
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[18] T. Shiono, K. Shiono, K. Miyamoto, G. Pezzotti, J. Am. Ceram. Soc. 83 (2000) 235–237. [19] M.H. Habibi, A.H. Habibi, J. Ind. Eng. Chem. 20 (2014) 68–73. [20] M.H. Habibi, B. Karimi, M. Zendehdela, M. Habibi, J. Ind. Eng. Chem. 20 (2014) 1462–1467. [21] M.H. Habibi, B. Karimi, M. Zendehdela, M. Habibi, Spectrochim. Acta A 116 (2013) 374–380. [22] M.H. Habibi, A.H. Karimi, M. Zendehdela, M. Habibi, Spectrochim. Acta A 110 (2013) 226–232.
Contents lists available at ScienceDirect
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy journal homepage: www.elsevier.com/locate/saa
Photocatalytic degradation of an azo textile dye (C.I. Reactive Red 195 (3BF)) in aqueous solution over copper cobaltite nanocomposite coated on glass by Doctor Blade method Mohammad Hossein Habibi ⇑, Zoya Rezvani Nanotechnology Laboratory, Department of Chemistry, University of Isfahan, Isfahan 81746-73441 Islamic Republic of Iran
h i g h l i g h t s
g r a p h i c a l a b s t r a c t
Photocatalytic degradation of reactive
brilliant red X-3B was studied. Copper cobaltite nanocomposite was
coated on glass by Doctor Blade method. UV-DRS, XRD and FESEM measurements were performed for structural and optical properties.
a r t i c l e
i n f o
Article history: Received 22 June 2014 Received in revised form 4 August 2014 Accepted 6 March 2015 Available online 25 March 2015 Keywords: Photocatalytic Nanocomposite Doctor Blade Brilliant red
a b s t r a c t The degradation of C.I. Reactive Red 195 (3BF) in aqueous solution using copper cobaltite nanocomposite coated on glass by Doctor Blade method was studied. Structural, optical and morphological properties of nanocomposite coatings were characterized by X-ray powder diffractometry (XRD), diffuse reflectance spectroscopy (DRS) and field emission scanning electron microscopy (FESEM). The nanoparticles exhibit a particle size of 31 nm, showing a good nanoscale crystalline morphology. The photocatalytic activity of copper cobaltite nanocomposite coated on glass was studied by performing the photocatalytic degradation of 3BF at different irradiation time. The effect of irradiation time on the degradation of 3BF was studied and the results showed that more than 85% of the 3BF was degraded in 45 min of irradiation. The pseudo-first-order kinetic models were used and the rate constants were evaluated with pseudo first order rate constants of 4.10 10 2 min 1. The main advantage of the photocatalyst coated on glass overcomes the difficulties in separation and recycle of photocatalyst suspensions. Ó 2015 Elsevier B.V. All rights reserved.
Introduction Worldwide industries have used different kind of dyes and large amounts of dyes are released into the water environment which causes severe health problems [1–4,5]. Industrial waste water must be treated prior to discharging them into the water environment. Advanced oxidation processes are the most useful methods for mineralizing pollutants rather than non-destructive methods ⇑ Corresponding author. Tel.: +98 313 7932707; fax: +98 313 6689732. E-mail address: [email protected] (M.H. Habibi). http://dx.doi.org/10.1016/j.saa.2015.03.077 1386-1425/Ó 2015 Elsevier B.V. All rights reserved.
which transfer pollutants from water to sludge. Semiconductor photocatalysts are the most favorite choice for mineralizing pollutants. The photocatalysts must be stable, low-cost, and non-toxic with good photo-catalytic activity [6–9]. Spinel cobaltites have narrow band gap with promising photocatalytic activity. For scale up purposes there are needs to synthesize copper cobaltites at moderate condition such as co-precipitation. Co-precipitation process is favored for its reduced temperature of processing [10–12]. When the suspension of photocatalyst is used for photodegradation of pollutants, the suspended photocatalyst must be separated after each reaction. Coating and immobilization of photocatalyst
174
M.H. Habibi, Z. Rezvani / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 147 (2015) 173–177
overcomes the difficulties in separation and recycle of photocatalyst. Photocatalyst coating films can be prepared by various techniques [13,14]. Some spinel-type oxides [15] are semiconductor materials with narrow band gap and could be used in the degradation of environmental pollutants. Copper cobaltite, (CuCo2O4) is a typical spinel material and it has also attracted growing interest in diverse applications such as catalyst, refractory material, microwave dielectric and ceramic capacitor, and humidity sensors and a candidate for anode materials of lithium battery [16–18]. Most of the methods for preparation of copper cobaltite are either difficult, needs high temperature or costly which diminishes preparation of the nano-sized materials in a large scale as compared to the co-precipitation synthesis. We had conducted deposition of new copper cobaltite nanocomposite on commercial borosilicate glass substrates using spin-coating and Doctor Blade method. Our study revealed that copper cobaltite nanocomposite coatings exhibited favorable optical properties as photocatalyst. To the best our knowledge, Doctor Blade coated copper cobaltite on glass and photocatalytic performance of nanocomposite in 3BF aqueous solution is not reported. The objectives of the study were to optimize the photocatalytic performance of nanocomposite oxides coating. The film surface was characterized using diffuse reflectance spectroscopy (DRS), X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM). In this research copper cobaltite nanocomposite was synthesized via a co-precipitation method using copper nitrate, cobalt nitrate and sodium carbonate as precursors. Structural, optical and morphological properties of nanocomposite coatings were characterized by X-ray powder diffractometry (XRD), diffuse reflectance spectroscopy (DRS) and field emission scanning electron microscopy (FESEM). The effect of irradiation time on the degradation of 3BF has been studied and the results showed that more than 85% of the 3BF (Fig. 1) was degraded in 45 min. The degradation mechanism of 3BF was also discussed with the change of UV–vis spectra of 3BF at different degradation time. Materials and methods Chemicals The 3BF used for photocatalytic degradation was obtained from local textile dye industries and was utilized without further purification. Copper nitrate and cobalt nitrate was obtained from Merck Company (Germany). Sodium carbonate was supplied by Sigma Chemicals Company. Other reagents were all analytical grade.
60 °C. The precipitate was filtered, washed thoroughly with distilled water, dried at 120 °C for 24 h and annealed at 350 °C for 4 h (Fig. 2). Coating of nanostructure copper cobaltite on glass by Doctor Blade method Preparation of copper cobaltite paste and coating the paste on glass by Doctor Blade were performed by our previous reports [19–22]. Photocatalytic degradation of C.I. Reactive Red 195 (3BF) by copper cobaltite coated on glass by Doctor Blade method The paste of copper cobalt oxide coated on a glass slide (6 cm 2 cm and 2 mm thickness) by Doctor-Blade method and the thin film annealed at 400 °C for 1 h. The B3F solution as dye with a concentration of 10 mg/L (ppm) prepared as an initial solution. This solution exposed at O2 gas for 30 min. The copper cobalt oxide thin film immersed into a petri dish with 25 ml of the initial B3F solution (Fig. 1) and maintained at dark conditions for 1 h. The concentration of this solution determined by measuring the absorbance by UV–vis spectrophotometer was 9.57 mg/L (ppm) after remaining at dark condition (calculated from standard curve). The reaction system illuminated by a 230 W Hg (g) lamp at different times and the concentration of the B3F solution determined by measuring the absorbance by a Cary 500 UV–vis spectrophotometer for photocatalytic activity examination. Apparatus Copper cobaltite was characterized by UV-DRS, XRD and FESEM analysis. Diffuse reflectance spectra (DRS) were collected with a V670, JASCO spectrophotometer and transformed to the absorption spectra according to the Kebelka relationship. The structure and crystal phase composition of the composites were determined by XRD patterns with a X-ray diffractometer (D8 Advance, BRUKER) in the diffraction angle range 2h = 20–60°, using Cu Ka radiation. The crystallite size D of the sample was estimated using the Scherer’s equation, (0.9k)/ (bcosh), by measuring the line broadening of main intensity peak, where k is the wavelength of Cu Ka radiation, b is the full width at half-maximum, and h is the Brag’s angle. Morphology was measured by using a FE-SEM, Hitachi, and model S-4160. The borosilicate glass substrates coated using spin coating method (Spin Coater, Modern Technology Development Institute, Iran).
Preparation of nanostructure copper cobaltite
Results and discussion
The nanostructure copper cobaltite was synthesized following the procedure: a solution (0.7 M) of Cu(NO3)23H2O was mixed with a solution (2.3 M) of Co(NO3)26H2O. To this mixture was added a saturated solution of Na2CO3 dropwise, stirred for 1 h at
Characterization The crystal phase structures of prepared copper cobaltite nanocomposite was characterized by XRD measurements (Fig. 3) and
Fig. 1. Chemical structure of 3BF.
M.H. Habibi, Z. Rezvani / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 147 (2015) 173–177
175
Fig. 4. FESEM image of copper cobaltite nanocomposite coated on glass by Doctor Blade.
Fig. 2. Flow chart for preparation of copper cobaltite nanocomposite.
Fig. 5. DRS of copper cobaltite nanocomposite coated on glass by Doctor Blade.
Fig. 3. XRD pattern of nanostructure copper oxocobaltate using co-precipitation route and copper and cobalt nitrate as precursors calcined at 350 °C for 2 h.
the results confirmed the crystalline nature of copper cobaltite. The peaks at 2h = 22.1°, 36.5°, 43.1°, 45.1°, 52.6°, 65.7°, 70.2° and 77.6° can be assigned to the diffractions of (1 1 1), (2 2 0), (3 1 1), (2 2 2), (4 0 0), (4 2 2), (5 1 1), and (4 4 0) crystal planes of the spinel. The crystalline size of the prepared copper cobaltite nano-composite was determined using Debye–Scherrer equation: D = Kk/b cos h, where D is the crystal size of the catalyst, K is dimensionless constant (0.9). k is the wavelength of X-ray, b is the full width at halfmaximum (FWHM) of the diffraction peak and h is the diffraction angle. The average crystalline size of copper cobaltite nano-composite was 35.8 nm. Morphology of the composite photo-catalyst which affects the photocatalytic activity was determined by FESEM with 60,000 magnifications (Fig. 4). As shown in Fig. 4, the prepared composite photo-catalyst particles are nearly
Fig. 6. Kubelka–Munk plot of copper cobaltite nanocomposite coated on glass by Doctor Blade.
spherical in shapes. The nano-particles exhibit a particle size of 31 nm, showing a good nanoscale crystalline morphology, which corresponds well with their XRD results. The diffuse reflectance spectra of copper cobaltite nano-composite are displayed in Fig. 5. As shown in Fig. 5, copper cobaltite nano-composite shows absorption in entire visible region. Fig. 6 presents the Kubelka– Munk plot of the sample for determination of the band gap. The result shows that the band gap of copper cobaltite nano-composite is 1.45 eV (675 nm) in the visible region.
176
M.H. Habibi, Z. Rezvani / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 147 (2015) 173–177
Photocatalytic activity
Fig. 7. The changes in UV–vis spectra of C.I. Reactive Red 195 (3BF) in aqueous solution in the presence of copper cobaltite nanocomposite coated on glass on different irradiation time 0 min, 5 min, 10 min, 15 min, 20 min, 25 min, 35 min and 45 min.
Moreover, to study the effect of the copper cobaltite nano-composite on the photocatalytic activity of 3BF as an azo textile dye was carried out at room temperature. Fig. 7 shows the changes in UV–vis spectra of 3BF in aqueous solution in the presence of copper cobaltite nanocomposite coated on glass on different irradiation time from zero to 45 min. The results showed that more than 85% of 3BF was degraded in 45 min of irradiation. Degradation of 3BF solution in the presence of catalyst alone (dark) and irradiation alone (without catalyst) was negligible. Degradation vs time of irradiation in the photocatalytic decomposition of 3BF in the presence of copper cobaltite coated on glass by Doctor Blade method is shown in Fig. 8. The results showed that most of the dye pollutant was degraded in a short time of irradiation. Under UV irradiation, copper cobaltite acts as a barrier to prevent the migration of electrons/holes generated. Fig. 9 shows the reaction kinetics of photocatalytic degradation of C.I. Reactive Red 195 (3BF) over copper cobaltite nanocomposite coated on glass. The plot of Ln (Co/Ct) vs time shows straight line with the rate constant of 4.10 10 2 min 1. It is clear that there is a linear relationship between ln (Co/ Ct) value and the irradiation time, where Ct is the actual dye concentration at irradiation time t, and Co is the dye concentration after the adsorption/desorption equilibrium and before the irradiation process. The good correlations are indicating that the reaction kinetics follows a pseudo first order rate law. Conclusion
Fig. 8. The degradation vs. time dependency 3BF (10 mg/L) over copper cobaltite nanocomposite coated on glass at room temperature.
Copper cobaltite nanocomposite coated on glass has been prepared via a simple modified co-precipitation method. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and UV–vis diffuse reflectance (UV-DRS) revealed the successful coating of copper cobaltite on glass surface by Doctor Blade method which is simple with scale-up capability. Structural, optical and morphological properties of nanocomposite coatings were characterized by X-ray powder diffractometry (XRD), diffuse reflectance spectroscopy (DRS) and field emission scanning electron microscopy (FESEM). The nano-particles exhibit a particle size of 31 nm, showing a good nanoscale crystalline morphology, which corresponds well with their XRD results. The as-prepared nanocomposites consisted of copper cobaltite showed photocatalytic activity in photodegradation of an azo textile dye (3BF) under UV irradiation. The kinetic studies revealed that the pseudo first-order kinetic model is better degradation kinetics. Acknowledgments The authors wish to thank the University of Isfahan for financially supporting this work. References
Fig. 9. Reaction kinetics of photocatalytic degradation of 3BF over copper cobaltite nanocomposite coated on glass.
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