- Email: [email protected]
Fabrication and characterization of needle shaped CuO nanoparticles and their application as photocatalyst for degradation of organic pollutants
Journal Pre-proofs Fabrication and characterization of needle shaped CuO nanoparticles and their application as photocatalyst for degradation of organic pollutants Vandna Singh, Pratibha Bansal PII: DOI: Reference:
S0167-577X(19)31561-7 https://doi.org/10.1016/j.matlet.2019.126929 MLBLUE 126929
To appear in:
Materials Letters
Received Date: Revised Date: Accepted Date:
29 July 2019 30 October 2019 31 October 2019
Please cite this article as: V. Singh, P. Bansal, Fabrication and characterization of needle shaped CuO nanoparticles and their application as photocatalyst for degradation of organic pollutants, Materials Letters (2019), doi: https:// doi.org/10.1016/j.matlet.2019.126929
This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
© 2019 Published by Elsevier B.V.
Title: Fabrication and characterization of needle shaped CuO nanoparticles and their application as photocatalyst for degradation of organic pollutants
Vandna Singh* and Pratibha Bansal Department of Applied Chemistry Gautam Buddha University Greater Noida U.P. India Email: [email protected]* [email protected] *Corresponding author
Fabrication and characterization of needle shaped CuO nanoparticles and their application as photocatalyst for degradation of organic pollutants
Abstract Fabrication of nanomaterials for deprivation of organic pollutants like dyes is important. In present research work spotlight is on preparation of copper oxide (CuO) nano needles and characterized by using various techniques such as ultraviolet (UV)–visible spectroscopy, Xray diffraction (XRD) and Transmission electron microscopy (TEM). The photocatalytic efficiency of CuO nano needles has been examined on both kind of dyes such as cation dye (Victoria blue) and anionic dye (Direct Red 81). CuO nano needles catalytic efficiency in degradation of dye was measured by examining the change in absorbance of dye under UVspectrophotometer. The effects of functional parameters such as catalyst amount, pH and initial dye concentration were explored. CuO nano needles demonstrated brilliant degradation capacity in the existence of UV- visible radiations. Degradation processes follows pseudofirst order kinetics. The rate constant was fruitfully launched and reusability experiments were made to assure the steadiness of the used catalysts. Keywords: CuO nano needles, photocatalysis, Direct Red 81, Victoria Blue
1. Introduction Water is the most important natural resource which is required by human life to sustain on earth. But due to increase in urbanisation and population growth more and more industries are establishing. The waste water from industries such as textile, food, chemical processing, and cosmetics are released in various water bodies [1-3]. This waste water contains organic dyes which are highly harmful to living organism in water and human beings [1-3]. These organic dyes are highly stable due to complex molecular structure [4]. The waste water of industries should be treated well before releasing them into water bodies. In literature there are different methods used to treat the toxic dyes from waste water, one is adsorption of dyes by an appropriate substance and other is degradation of dyes by advanced oxidation process (AOPs) [5-7]. Adsorption of dyes has various disadvantages such as where to dispose the sludge which formed after adsorption of dye on the substance and substance cannot be used again once used [5]. In case of AOPs process all the disadvantages of adsorption technique is over come. Various AOPs used for degradation of dyes are chemical oxidation, biological oxidation, photocatalysis, sonocatalysis etc [8-10]. Out of various AOPs, photocatalytic degradation of dyes using nanopaticles is one of the best method to remove dyes from water [11-13]. In photocatalysis, radiations of energy greater than the band gap of photocatalyst is fallen on photocatalyst, it results in fabrication of electron and hole [11-13]. These electron and hole combine with water molecules to form reactive oxidative species ROS (.OH and .O). These ROS helps in degradation of dyes. If more amount of ROS is produced higher efficiency of degradation will be seen. In the present manuscript, copper oxide (CuO) nano needles were synthesized with very simple technique and time taken for synthesis was very less. Synthesized nano needles were characterized by using various techniques such as UV-visible spectroscopy, X-ray diffraction (XRD) and Transmission electron microscopy (TEM).
First time CuO nano needles were
used as photo catalyst for degradation of cationic dye (Victoria blue) and anionic dye (Direct Red). To analyse the efficiency of CuO nano needles as photocatalyst various parameters were studied such as effect of catalyst amount, effect of pH of dye solution, initial dye concentration, and reusability of catalyst and value of kinetic rate constant is calculated.
2. Experimental 2.1 Materials and techniques Dyes from Sigma-Aldrich (Direct Red 81and Victoria Blue) and Chemicals from Hi-media (absolute ethanol, NaOH, HCl and CuCl2) were utilized in the present research work. All the chemicals were consumed as received. For preparing all the solution double distilled water was used. Hitachi electron microscope (model H-7500) available at SAIF, Panjab university Chandigarh INDIA was employed to characterize CuO nano needles. Analytical X'Pert Pro X-ray diffractometer at SAIF, Panjab university Chandigarh INDIA was used to obtain XRD spectra of CuO nano needles. Ultraviolet (UV)–visible absorption spectra of CuO nano needles was obtained by using JascoV-530 spectrophotometer. Photocatalytic chamber has 125 W high pressure mercury lamp was employed as a UV-visible light source. PCi analytics ultrasonic bath apparatus with frequency 50 KHz was used to carry out sonocatalytic reactions. pH of dye solution was done by using pH meter cyberscan 510 pH meter. 2.2 Synthesis and characterization of CuO nano needles 10 ml of 0.01M CuCl2 was taken in beaker and 10 ml of 0.01M NaOH was taken in other beaker. Beaker containing CuCl2 solution is kept in sonicator, dropwise addition of NaOH solution is done to it. Addition of NaOH was completed in 2 minutes. Dark brown black precipitates appeared in the solution. Obtained solution was filtered and precipitates were washed with ethanol. The precipitates were dried at room temperature (rt). 2.3 Sonocatalytic and photocatalyst degradation reaction procedure Group tests were carried to know the reaction mechanism for the degradation of cationic and anionic dyes in the existence of CuO nano needles using UV-visible energy sources at rt. The mixture of CuO nano needles and dye solution was rotated in dark for 10 minutes before revelation to UV-visible radiations. This was done so that equilibrium was achieved between adsorption/desorption of the dye on the CuO nano needles. HCl and NaOH solution of concentration 0.1 molL-1 was utilized to set the pH of the dye solution. During photocatalysis, the formed suspension of dye solution was kept in UV-visible chamber of specification 125 W and 198.4 mW/S2 for fixed time interval. After desired time interval of UV-visible radiation, solution was taken out from the reaction mixture, centrifuged and variation in absorbance was calculated by the means of UV–visible spectrophotometer. The experimental circumstances set for all the research study was 20 ml of 10 x 10-5 M for DR and VB, added
quantity of CuO nano needle (40 mg), initial dye solution of pH 10 (VB) and pH 4.0 (DR). Energy source used in the experiments was UV-visible radiation (198.4 mW/S2 frequency and 125 W power). Percentage degradation efficiency (%) of dyes was analysed by the given equation 1:
Degradation %
C0 Ct 100 C0
(equation 1)
C0 initial concentration of dye and Cf is the final concentration of the dye solution after degradation. Concentration is directly proportional to absorbance of dye, therefore concentration can be calculated from absorbance. 3. Result and Discussion 3.1 Characterization of CuO NPs UV-visible spectra of nano needles were recorded (Figure S1, Supplementary information) which gives characteristic peak related to CuO nano needles [14]. In Figure 1(a) XRD pattern of CuO nano needles tells about the crystal phases as well as crystalanity. Diffraction peaks for CuO nano needles were obtained with (hkl) values as (110), (-111), (200), (-202), (020), (202), (-113), (022), (220), (311), (222), (322). These reflection peaks confirms the formation of single phase CuO nano needles with monoclinic structure [15]. Size was calculated by full width half maxima (FWHM) of two reflection peaks (-111) and (200) of highest intensity. The particle size calculated by using Debye Scherrer formula (equation 2) is 60.56 nm. No addition peak in XRD pattern is seen which confirms no impurity is present in the sample.
D=
K cos
(equation 2)
The morphology of CuO nano needles was determined from TEM micrograph. From Figure 1(b), it was illustrated that CuO were needle shape, particles has narrow range of size distribution. The average length of needle shape is 70 nm ± 10 nm and diameter is 5 nm ± 1 nm. 3.2 Photocatalytic efficiency of CuO nano needles under various conditions Photocatalytic efficiency of CuO nano needles was analysed on both VB and DR dyes. In Figure 2(a) it is seen that both the dyes does not degrade in the presence of UV-visible light if no CuO nano needles were added. The reason for no degradation of dyes is due to no
formation of ROS in the absence of nano needles [16]. It was seen that degradation of both the dyes increases as the reaction time increases in the presence of CuO nano needles and UV-visible light irradiation. The reason for degradation can be production of ROS radicals in the presence of nanoparticles and UV-visible light. Experiment was conducted to see the effect of catalyst dose on degradation of dye. It was observed that by increasing amount of catalyst (CuO nano needles) for 5 to 50 mg in 20 ml of 10 x 10-5 M dye solution (Figure S2, Supplementary information). The photocatalytic degradation first increases then become constant with increase in the amount of CuO nano needles [17]. Rate kinetic modelling of photocatalytic degradation was examined with initial concentration 10 x 10-5 M of VB or DR and 40 mg of CuO nano needles. In Figure 2(b) it was seen that the graph was straight line passing through origin when it was plotted between ln(Ct/C0) and time. From these results it was concluded that the kinetics followed by the photocatalytic degradation of dyes is pseudo first order [18]. The value of rate constant (k) is calculated by using equation 3. In table 1 all the values of K and regression (R) related to both the dyes are mentioned. ln(C0/Ct) = kt
(equation 3)
Effect of initial dye concentration on photocatalytic degradation of dye was examined (Figure S3, supplementary information). It was seen that with increase in initial dye concentration photocatalytic degradation decreases [18]. pH is one of the important operational parameter which effects the photocatalytic efficiency of nanoparticles, as it effects surface charge of nanoparticles [19]. Therefore effect of pH has been studied on degradation of dyes. The effect of pH value between 4 to 10 on photocatalytic degradation of VB and DR was analysed with 20 ml of 10 x10-5 M initial dye concentration, 40 mg of CuO nano needles under UV-visible radiations. In Figure 2(c) and 2(d) it has been seen that both the dyes follow pseudo first order kinetics at various pH (equation 3 was used) [16]. VB shows highest degradation at pH 10 whereas DR shows greatest degradation at pH 4. CuO nano needles has zero point charge at 6.5 to 8.5 pH, means CuO surface is neutral or there is no charge on the surface of CuO nano needles between 6.5 to 8.5 pH [19]. At higher pH, nanoparticles surface is negatively charged due to the presence of OH- ions on the surface [20]. Therefore at higher pH CuO nano needles will attract cationic dyes (VB). This results in higher degradation of VB at pH 10. At lower pH, CuO NPs is positively charged due to presence of H+ ions on the surface [21]. Therefore CuO nano
needles have maximum attraction for anionic dye (DR). This results in higher degradation of DR at pH 4. Mechanism of photocatalytic degradation of dyes involves equation 4 to equation 8. In equation 4, fall of UV-visible light on the surface of CuO nano needles (catalyst) produces electron and hole [22, 23]. In equation 5 hole combine with water molecule to produce ROS. Electron combine with O2 dissolved in water to form O.-2 as shown in equation 6 [22]. ROS (.OH, O2.-) which are produced in equation 5 and 6 helps in degradation of both dyes as shown in equation 7 and 8 [22, 23].
visible catalyst UV h e visible catalyst H 2O h UV catalyst OH H visible catalyst O2 e UV catalyst O2
visible VB / DR catalyst OH UV CO2 H 2O inorganic
visible VB / DR catalyst O2 UV CO2 H 2O inorganic
(equation 4) (equation 5) (equation 6) (equation 7) (equation 8)
Recyclability test of CuO nano needles was examined (Figure S4, Supplementary information). It was seen that there is no much decrease in efficiency of recycled nano needles till third recycle. 4. Conclusion In summary, CuO nano needles were fabricated, employing ultrasonic radiations without using any stabilizer resulting in nano needles and high mono disparity. The potential of synthesized CuO nano needles was discovered as photocatalyst, for degradation of VB and DR dyes in water. They confirmed brilliant results in degradation remediation of cationic (VB) and anionic (DR) dye in the presence of UV–visible irradiation. Group of the above examinations agree with the success of the CuO nano needles/US system for the decolouration of anionic and cationic dyes for large scale industrial applications. 5. Acknowledgement Pratibha Bansal is thankful to UGC, Delhi for UGC women postdoctoral fellowship and Department of Applied Chemistry, Gautam Buddha University for providing necessary research facilities.
References 1. S. Payra, S. Challagulla, Y. Bobde, C. Chakraborty, B. Ghosh, S. Roy, J. Hazard. Mater. 373 (2019) 377-388 2. J.R. Steter, W.R.P. Barros, M.R.V. Lanza, A.J. Motheo, Chemosphere 117 (2014) 200-207 3. A. Radon, S. Lonski, T. Warski, R. Babilas, T. Tanski, M. Dudziak, D. Lukowiec, Appl. Sur. Sci. 487 (2019) 1018-1025 4. M. Mirzaee, M. Faghani, Mater. Sci. Eng. B 246 (2019) 80-88 5. Y. Guan, H.Y. Yu, S.Y.H. Abdalkarim, C. Wang, F. Tang, J. Merek, W.L. Chen, J. Militky, J.M. Yao, Int. J. Biol. Macromol. 132 (2019) 51-62. 6. J. Liu, J. Zhou, Z. Ding, Z. Zhao, X. Xu, Z. Fang, Ultrason. Sonochem. 34 (2017) 953-959 7. A.R. Khataee, M.N. Pons, O. Zahraa, J. Hazard. Mater. 168 (2009) 451-457 8. A.A.P. Mansur, H.S. Mansur, F.P. Ramanery, L.C. Oliveira, P.P. Souza, Appl. Catal. B: Environ. 158–159 (2014) 269–279 9. J. Abdi, M. Vossoughi, N.M. Mahmoodi, I. Alemzadeh, Ultrason. Sonochem. 39 (2017) 550-564 10. S.A. Jadhav, H.B. Garud, A.H. Patil, G.D. Patil, C.R. Patil, T.D. Dongale, P.S.Patil, Colloid Interf. Sci. Comm. 30 (2019) 100181. 11. M. Sharma, T. Jain, S. Singh, O.P. Pandey, Solar Energy 86 (2012) 626–633 12. X. Li, J. Yu, G. Li, H. Liu, A. Wang, L. Yang, W. Zhou, B. Chu, S. Liu, J. Colloid Interf. Sci. 526 (2018) 158-166 13. Y. Zhu, R. Zhu, Y. Xi, T. Xu, L. Yan, J. Zhu, G. Zhu, H. He, Chem. Eng. J. 346 (2018) 567-577 14. Y. Zhao, J. Zhao, Y. Li, D. Ma, S. Hou, L. Li, X. Hao, Z. Wang, Nanotechnol. 22 (2011) 115604-115613 15. D. Han, H. Yang, C. Zhu, F. Wang, Powder Technol. 185 (2008) 286–290 16. P. Bansal, G.R. Chaudhary, S.K. Mehta Chem. Eng. J. 280 (2015) 475-485 17. X. Weng, L. Huang, Z. Chen, M. Megharaj, R. Naidu, Ind. Crop. Prod. 51 (2013) 342– 347 18. K. Hayat, M.A. Gondal, M.M. Khaled, Z.H. Yamani, S. Ahmed, J. Hazard. Mater. 186 (2011) 1226–1233 19. B.P. Nenavathu, A.V.R.K. Rao, A. Goyal, A. Kapoor, R.K. Dutta, Appl. Catal. A Gen. 459 (2013) 106-113.
20. Q.I. Rahman, M. Ahmad, S.K. Misra, M. Lohani, Mater. Lett. 91 (2013) 170–174 21. A.N. Ejhieh, M.K. Shamsabadi, Chem. Eng. J. 228 (2013) 631-641. 22. T.N. Ravishankar, K. Manjunatha, T. Ramakrishnappa, G. Nagaraju, D. Kumar, S. Sarakar, B.S. Anandakumar, G.T. Chandrappa, V. Reddy, J. Dupont, Mat. Sci. Semicon. Proc. 2014, 26, 7–17 23. P. Kumari, P. Chandran, S.S. Khan, J. Photochem. Photobiol. B: Biol. 141 (2014) 235–240
Figure captions Figure1 (a) XRD pattern of CuO nano needles (b) TEM image of CuO nano needles Figure 2 (a) Degradation of VB and DR dye treated with different process (b) Pseudo-first order kinetics of VB and DR under UV-visible irradiation. Effect of pH on degradation under UV-visible irradiation (c) VB (d) DR Table 1 Pseudo-first-order kinetics rate constants for degradation of VB and DR under UVvisible radiations
(a)
(200)
2000
(b)
(-111)
1800
1400
(110)
800
(100) 600
(322)
1000
(202) (-113) (022) (220) (311) (222)
(-202)
1200
(020)
Intensity (a.u.)
1600
400 20
40
60
80
2(degree)
Figure 1
100
(b)
Degradation (%)
5
80
4
60
3
20
0
VB DR
VB + UV light DR + UV light DR + UV light + CuO nano needles VR + UV light + CuO nano needles
40
0
3
6
9
12 15 18 21 24 27 30 33 36 39 42 45 48 51
Time (in minutes)
(c)
4
ln (C0/Ct)
(a) 100
2
1
0
40
20
60
80
Time (in minutes)
(d)
100
120
0
4 pH 4 pH 6 pH 8 pH 10
pH 4 pH 6 pH 8 pH 10
3
2
DR
3
2
1
0
1
0
20
40
60 80 Time (in minutes)
100
120 0
Figure 2
20
40 60 80 Time (in minutes)
100
120
0
ln(C0/Ct)
ln(C0/Ct)
VB
Table 1 Dyes
Photocatalysis k (min-1)
R
0.03451
Statistical error for k 5.21475 x 10-4
Victoria Blue (VB) 10 x 10-5 M Direct Red (DR) 10 x 10-5 M
0.03705
8.78375 x 10-4
0.99888
0.99954
Conflict of interest statement We declare that no conflict of interest exists.
Declaration of Interest The authors declare that they have no known competing financial or personal relationships that could have appeared to influence the work in this paper.
Graphical Abstract
Highlights
CuO nano
needles
(NNs) are
synthesized
by very easy
technique
NNs are used as
photocatalyst
for degradation of
Direct Red
and Victoria Blue
dyes
NNs proved excellent photocatalyst for the degradation of dyes
NNs have been successfully recovered and reused
Value of rate constant has been obtained for Direct Red and Victoria Blue dyes
S0167-577X(19)31561-7 https://doi.org/10.1016/j.matlet.2019.126929 MLBLUE 126929
To appear in:
Materials Letters
Received Date: Revised Date: Accepted Date:
29 July 2019 30 October 2019 31 October 2019
Please cite this article as: V. Singh, P. Bansal, Fabrication and characterization of needle shaped CuO nanoparticles and their application as photocatalyst for degradation of organic pollutants, Materials Letters (2019), doi: https:// doi.org/10.1016/j.matlet.2019.126929
This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
© 2019 Published by Elsevier B.V.
Title: Fabrication and characterization of needle shaped CuO nanoparticles and their application as photocatalyst for degradation of organic pollutants
Vandna Singh* and Pratibha Bansal Department of Applied Chemistry Gautam Buddha University Greater Noida U.P. India Email: [email protected]* [email protected] *Corresponding author
Fabrication and characterization of needle shaped CuO nanoparticles and their application as photocatalyst for degradation of organic pollutants
Abstract Fabrication of nanomaterials for deprivation of organic pollutants like dyes is important. In present research work spotlight is on preparation of copper oxide (CuO) nano needles and characterized by using various techniques such as ultraviolet (UV)–visible spectroscopy, Xray diffraction (XRD) and Transmission electron microscopy (TEM). The photocatalytic efficiency of CuO nano needles has been examined on both kind of dyes such as cation dye (Victoria blue) and anionic dye (Direct Red 81). CuO nano needles catalytic efficiency in degradation of dye was measured by examining the change in absorbance of dye under UVspectrophotometer. The effects of functional parameters such as catalyst amount, pH and initial dye concentration were explored. CuO nano needles demonstrated brilliant degradation capacity in the existence of UV- visible radiations. Degradation processes follows pseudofirst order kinetics. The rate constant was fruitfully launched and reusability experiments were made to assure the steadiness of the used catalysts. Keywords: CuO nano needles, photocatalysis, Direct Red 81, Victoria Blue
1. Introduction Water is the most important natural resource which is required by human life to sustain on earth. But due to increase in urbanisation and population growth more and more industries are establishing. The waste water from industries such as textile, food, chemical processing, and cosmetics are released in various water bodies [1-3]. This waste water contains organic dyes which are highly harmful to living organism in water and human beings [1-3]. These organic dyes are highly stable due to complex molecular structure [4]. The waste water of industries should be treated well before releasing them into water bodies. In literature there are different methods used to treat the toxic dyes from waste water, one is adsorption of dyes by an appropriate substance and other is degradation of dyes by advanced oxidation process (AOPs) [5-7]. Adsorption of dyes has various disadvantages such as where to dispose the sludge which formed after adsorption of dye on the substance and substance cannot be used again once used [5]. In case of AOPs process all the disadvantages of adsorption technique is over come. Various AOPs used for degradation of dyes are chemical oxidation, biological oxidation, photocatalysis, sonocatalysis etc [8-10]. Out of various AOPs, photocatalytic degradation of dyes using nanopaticles is one of the best method to remove dyes from water [11-13]. In photocatalysis, radiations of energy greater than the band gap of photocatalyst is fallen on photocatalyst, it results in fabrication of electron and hole [11-13]. These electron and hole combine with water molecules to form reactive oxidative species ROS (.OH and .O). These ROS helps in degradation of dyes. If more amount of ROS is produced higher efficiency of degradation will be seen. In the present manuscript, copper oxide (CuO) nano needles were synthesized with very simple technique and time taken for synthesis was very less. Synthesized nano needles were characterized by using various techniques such as UV-visible spectroscopy, X-ray diffraction (XRD) and Transmission electron microscopy (TEM).
First time CuO nano needles were
used as photo catalyst for degradation of cationic dye (Victoria blue) and anionic dye (Direct Red). To analyse the efficiency of CuO nano needles as photocatalyst various parameters were studied such as effect of catalyst amount, effect of pH of dye solution, initial dye concentration, and reusability of catalyst and value of kinetic rate constant is calculated.
2. Experimental 2.1 Materials and techniques Dyes from Sigma-Aldrich (Direct Red 81and Victoria Blue) and Chemicals from Hi-media (absolute ethanol, NaOH, HCl and CuCl2) were utilized in the present research work. All the chemicals were consumed as received. For preparing all the solution double distilled water was used. Hitachi electron microscope (model H-7500) available at SAIF, Panjab university Chandigarh INDIA was employed to characterize CuO nano needles. Analytical X'Pert Pro X-ray diffractometer at SAIF, Panjab university Chandigarh INDIA was used to obtain XRD spectra of CuO nano needles. Ultraviolet (UV)–visible absorption spectra of CuO nano needles was obtained by using JascoV-530 spectrophotometer. Photocatalytic chamber has 125 W high pressure mercury lamp was employed as a UV-visible light source. PCi analytics ultrasonic bath apparatus with frequency 50 KHz was used to carry out sonocatalytic reactions. pH of dye solution was done by using pH meter cyberscan 510 pH meter. 2.2 Synthesis and characterization of CuO nano needles 10 ml of 0.01M CuCl2 was taken in beaker and 10 ml of 0.01M NaOH was taken in other beaker. Beaker containing CuCl2 solution is kept in sonicator, dropwise addition of NaOH solution is done to it. Addition of NaOH was completed in 2 minutes. Dark brown black precipitates appeared in the solution. Obtained solution was filtered and precipitates were washed with ethanol. The precipitates were dried at room temperature (rt). 2.3 Sonocatalytic and photocatalyst degradation reaction procedure Group tests were carried to know the reaction mechanism for the degradation of cationic and anionic dyes in the existence of CuO nano needles using UV-visible energy sources at rt. The mixture of CuO nano needles and dye solution was rotated in dark for 10 minutes before revelation to UV-visible radiations. This was done so that equilibrium was achieved between adsorption/desorption of the dye on the CuO nano needles. HCl and NaOH solution of concentration 0.1 molL-1 was utilized to set the pH of the dye solution. During photocatalysis, the formed suspension of dye solution was kept in UV-visible chamber of specification 125 W and 198.4 mW/S2 for fixed time interval. After desired time interval of UV-visible radiation, solution was taken out from the reaction mixture, centrifuged and variation in absorbance was calculated by the means of UV–visible spectrophotometer. The experimental circumstances set for all the research study was 20 ml of 10 x 10-5 M for DR and VB, added
quantity of CuO nano needle (40 mg), initial dye solution of pH 10 (VB) and pH 4.0 (DR). Energy source used in the experiments was UV-visible radiation (198.4 mW/S2 frequency and 125 W power). Percentage degradation efficiency (%) of dyes was analysed by the given equation 1:
Degradation %
C0 Ct 100 C0
(equation 1)
C0 initial concentration of dye and Cf is the final concentration of the dye solution after degradation. Concentration is directly proportional to absorbance of dye, therefore concentration can be calculated from absorbance. 3. Result and Discussion 3.1 Characterization of CuO NPs UV-visible spectra of nano needles were recorded (Figure S1, Supplementary information) which gives characteristic peak related to CuO nano needles [14]. In Figure 1(a) XRD pattern of CuO nano needles tells about the crystal phases as well as crystalanity. Diffraction peaks for CuO nano needles were obtained with (hkl) values as (110), (-111), (200), (-202), (020), (202), (-113), (022), (220), (311), (222), (322). These reflection peaks confirms the formation of single phase CuO nano needles with monoclinic structure [15]. Size was calculated by full width half maxima (FWHM) of two reflection peaks (-111) and (200) of highest intensity. The particle size calculated by using Debye Scherrer formula (equation 2) is 60.56 nm. No addition peak in XRD pattern is seen which confirms no impurity is present in the sample.
D=
K cos
(equation 2)
The morphology of CuO nano needles was determined from TEM micrograph. From Figure 1(b), it was illustrated that CuO were needle shape, particles has narrow range of size distribution. The average length of needle shape is 70 nm ± 10 nm and diameter is 5 nm ± 1 nm. 3.2 Photocatalytic efficiency of CuO nano needles under various conditions Photocatalytic efficiency of CuO nano needles was analysed on both VB and DR dyes. In Figure 2(a) it is seen that both the dyes does not degrade in the presence of UV-visible light if no CuO nano needles were added. The reason for no degradation of dyes is due to no
formation of ROS in the absence of nano needles [16]. It was seen that degradation of both the dyes increases as the reaction time increases in the presence of CuO nano needles and UV-visible light irradiation. The reason for degradation can be production of ROS radicals in the presence of nanoparticles and UV-visible light. Experiment was conducted to see the effect of catalyst dose on degradation of dye. It was observed that by increasing amount of catalyst (CuO nano needles) for 5 to 50 mg in 20 ml of 10 x 10-5 M dye solution (Figure S2, Supplementary information). The photocatalytic degradation first increases then become constant with increase in the amount of CuO nano needles [17]. Rate kinetic modelling of photocatalytic degradation was examined with initial concentration 10 x 10-5 M of VB or DR and 40 mg of CuO nano needles. In Figure 2(b) it was seen that the graph was straight line passing through origin when it was plotted between ln(Ct/C0) and time. From these results it was concluded that the kinetics followed by the photocatalytic degradation of dyes is pseudo first order [18]. The value of rate constant (k) is calculated by using equation 3. In table 1 all the values of K and regression (R) related to both the dyes are mentioned. ln(C0/Ct) = kt
(equation 3)
Effect of initial dye concentration on photocatalytic degradation of dye was examined (Figure S3, supplementary information). It was seen that with increase in initial dye concentration photocatalytic degradation decreases [18]. pH is one of the important operational parameter which effects the photocatalytic efficiency of nanoparticles, as it effects surface charge of nanoparticles [19]. Therefore effect of pH has been studied on degradation of dyes. The effect of pH value between 4 to 10 on photocatalytic degradation of VB and DR was analysed with 20 ml of 10 x10-5 M initial dye concentration, 40 mg of CuO nano needles under UV-visible radiations. In Figure 2(c) and 2(d) it has been seen that both the dyes follow pseudo first order kinetics at various pH (equation 3 was used) [16]. VB shows highest degradation at pH 10 whereas DR shows greatest degradation at pH 4. CuO nano needles has zero point charge at 6.5 to 8.5 pH, means CuO surface is neutral or there is no charge on the surface of CuO nano needles between 6.5 to 8.5 pH [19]. At higher pH, nanoparticles surface is negatively charged due to the presence of OH- ions on the surface [20]. Therefore at higher pH CuO nano needles will attract cationic dyes (VB). This results in higher degradation of VB at pH 10. At lower pH, CuO NPs is positively charged due to presence of H+ ions on the surface [21]. Therefore CuO nano
needles have maximum attraction for anionic dye (DR). This results in higher degradation of DR at pH 4. Mechanism of photocatalytic degradation of dyes involves equation 4 to equation 8. In equation 4, fall of UV-visible light on the surface of CuO nano needles (catalyst) produces electron and hole [22, 23]. In equation 5 hole combine with water molecule to produce ROS. Electron combine with O2 dissolved in water to form O.-2 as shown in equation 6 [22]. ROS (.OH, O2.-) which are produced in equation 5 and 6 helps in degradation of both dyes as shown in equation 7 and 8 [22, 23].
visible catalyst UV h e visible catalyst H 2O h UV catalyst OH H visible catalyst O2 e UV catalyst O2
visible VB / DR catalyst OH UV CO2 H 2O inorganic
visible VB / DR catalyst O2 UV CO2 H 2O inorganic
(equation 4) (equation 5) (equation 6) (equation 7) (equation 8)
Recyclability test of CuO nano needles was examined (Figure S4, Supplementary information). It was seen that there is no much decrease in efficiency of recycled nano needles till third recycle. 4. Conclusion In summary, CuO nano needles were fabricated, employing ultrasonic radiations without using any stabilizer resulting in nano needles and high mono disparity. The potential of synthesized CuO nano needles was discovered as photocatalyst, for degradation of VB and DR dyes in water. They confirmed brilliant results in degradation remediation of cationic (VB) and anionic (DR) dye in the presence of UV–visible irradiation. Group of the above examinations agree with the success of the CuO nano needles/US system for the decolouration of anionic and cationic dyes for large scale industrial applications. 5. Acknowledgement Pratibha Bansal is thankful to UGC, Delhi for UGC women postdoctoral fellowship and Department of Applied Chemistry, Gautam Buddha University for providing necessary research facilities.
References 1. S. Payra, S. Challagulla, Y. Bobde, C. Chakraborty, B. Ghosh, S. Roy, J. Hazard. Mater. 373 (2019) 377-388 2. J.R. Steter, W.R.P. Barros, M.R.V. Lanza, A.J. Motheo, Chemosphere 117 (2014) 200-207 3. A. Radon, S. Lonski, T. Warski, R. Babilas, T. Tanski, M. Dudziak, D. Lukowiec, Appl. Sur. Sci. 487 (2019) 1018-1025 4. M. Mirzaee, M. Faghani, Mater. Sci. Eng. B 246 (2019) 80-88 5. Y. Guan, H.Y. Yu, S.Y.H. Abdalkarim, C. Wang, F. Tang, J. Merek, W.L. Chen, J. Militky, J.M. Yao, Int. J. Biol. Macromol. 132 (2019) 51-62. 6. J. Liu, J. Zhou, Z. Ding, Z. Zhao, X. Xu, Z. Fang, Ultrason. Sonochem. 34 (2017) 953-959 7. A.R. Khataee, M.N. Pons, O. Zahraa, J. Hazard. Mater. 168 (2009) 451-457 8. A.A.P. Mansur, H.S. Mansur, F.P. Ramanery, L.C. Oliveira, P.P. Souza, Appl. Catal. B: Environ. 158–159 (2014) 269–279 9. J. Abdi, M. Vossoughi, N.M. Mahmoodi, I. Alemzadeh, Ultrason. Sonochem. 39 (2017) 550-564 10. S.A. Jadhav, H.B. Garud, A.H. Patil, G.D. Patil, C.R. Patil, T.D. Dongale, P.S.Patil, Colloid Interf. Sci. Comm. 30 (2019) 100181. 11. M. Sharma, T. Jain, S. Singh, O.P. Pandey, Solar Energy 86 (2012) 626–633 12. X. Li, J. Yu, G. Li, H. Liu, A. Wang, L. Yang, W. Zhou, B. Chu, S. Liu, J. Colloid Interf. Sci. 526 (2018) 158-166 13. Y. Zhu, R. Zhu, Y. Xi, T. Xu, L. Yan, J. Zhu, G. Zhu, H. He, Chem. Eng. J. 346 (2018) 567-577 14. Y. Zhao, J. Zhao, Y. Li, D. Ma, S. Hou, L. Li, X. Hao, Z. Wang, Nanotechnol. 22 (2011) 115604-115613 15. D. Han, H. Yang, C. Zhu, F. Wang, Powder Technol. 185 (2008) 286–290 16. P. Bansal, G.R. Chaudhary, S.K. Mehta Chem. Eng. J. 280 (2015) 475-485 17. X. Weng, L. Huang, Z. Chen, M. Megharaj, R. Naidu, Ind. Crop. Prod. 51 (2013) 342– 347 18. K. Hayat, M.A. Gondal, M.M. Khaled, Z.H. Yamani, S. Ahmed, J. Hazard. Mater. 186 (2011) 1226–1233 19. B.P. Nenavathu, A.V.R.K. Rao, A. Goyal, A. Kapoor, R.K. Dutta, Appl. Catal. A Gen. 459 (2013) 106-113.
20. Q.I. Rahman, M. Ahmad, S.K. Misra, M. Lohani, Mater. Lett. 91 (2013) 170–174 21. A.N. Ejhieh, M.K. Shamsabadi, Chem. Eng. J. 228 (2013) 631-641. 22. T.N. Ravishankar, K. Manjunatha, T. Ramakrishnappa, G. Nagaraju, D. Kumar, S. Sarakar, B.S. Anandakumar, G.T. Chandrappa, V. Reddy, J. Dupont, Mat. Sci. Semicon. Proc. 2014, 26, 7–17 23. P. Kumari, P. Chandran, S.S. Khan, J. Photochem. Photobiol. B: Biol. 141 (2014) 235–240
Figure captions Figure1 (a) XRD pattern of CuO nano needles (b) TEM image of CuO nano needles Figure 2 (a) Degradation of VB and DR dye treated with different process (b) Pseudo-first order kinetics of VB and DR under UV-visible irradiation. Effect of pH on degradation under UV-visible irradiation (c) VB (d) DR Table 1 Pseudo-first-order kinetics rate constants for degradation of VB and DR under UVvisible radiations
(a)
(200)
2000
(b)
(-111)
1800
1400
(110)
800
(100) 600
(322)
1000
(202) (-113) (022) (220) (311) (222)
(-202)
1200
(020)
Intensity (a.u.)
1600
400 20
40
60
80
2(degree)
Figure 1
100
(b)
Degradation (%)
5
80
4
60
3
20
0
VB DR
VB + UV light DR + UV light DR + UV light + CuO nano needles VR + UV light + CuO nano needles
40
0
3
6
9
12 15 18 21 24 27 30 33 36 39 42 45 48 51
Time (in minutes)
(c)
4
ln (C0/Ct)
(a) 100
2
1
0
40
20
60
80
Time (in minutes)
(d)
100
120
0
4 pH 4 pH 6 pH 8 pH 10
pH 4 pH 6 pH 8 pH 10
3
2
DR
3
2
1
0
1
0
20
40
60 80 Time (in minutes)
100
120 0
Figure 2
20
40 60 80 Time (in minutes)
100
120
0
ln(C0/Ct)
ln(C0/Ct)
VB
Table 1 Dyes
Photocatalysis k (min-1)
R
0.03451
Statistical error for k 5.21475 x 10-4
Victoria Blue (VB) 10 x 10-5 M Direct Red (DR) 10 x 10-5 M
0.03705
8.78375 x 10-4
0.99888
0.99954
Conflict of interest statement We declare that no conflict of interest exists.
Declaration of Interest The authors declare that they have no known competing financial or personal relationships that could have appeared to influence the work in this paper.
Graphical Abstract
Highlights
CuO nano
needles
(NNs) are
synthesized
by very easy
technique
NNs are used as
photocatalyst
for degradation of
Direct Red
and Victoria Blue
dyes
NNs proved excellent photocatalyst for the degradation of dyes
NNs have been successfully recovered and reused
Value of rate constant has been obtained for Direct Red and Victoria Blue dyes