Rapid visible light induced photocatalytic degradation of orange-II using H2O2 sensitized Cu2O

Article abstract of DOI:10.14233/ajchem.2017.20320

Photocatalytic degradation of orange II has been studied using H₂O₂ sensitized Cu₂O and visible light. Complete degradation of orange II is achieved for 90 min of irradiation. Addition of external oxidant H₂O

Full text of DOI:10.14233/ajchem.2017.20320

Asian Journal of Chemistry; Vol. 29, No. 4 (2017), 817-820
A
SIAN
J
OURNAL OF HEMISTRY
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https://doi.org/10.14233/ajchem.2017.20320
Rapid Visible Light Induced Photocatalytic Degradation of Orange-II Using H2O2 Sensitized Cu2O
*
T. NARASIMHA MURTHY, A.M. UMABALA and A.V. PRASADA RAO
Department of Inorganic and Analytical Chemistry, Andhra University, Visakhapatnam-530 003, India
*Corresponding author: E-mail: prasadraoav53@gmail.com
Received: 30 September 2016;
Accepted: 9 December 2016;
Published online: 31 January 2017;
AJC-18250
Photocatalytic degradation of orange II has been studied using H2O2 sensitized Cu2O and visible light. Complete degradation of orange II
is achieved for 90 min of irradiation.Addition of external oxidant H2O2 is found to be enhancing the rate of degradation. Formation of •OH
free radicals during irradiation is ascertained with photoluminescence studies using terephthalic acid as probe molecule.
Keywords: Orange II, Photocatalytic degradation, Synergetic effect, Cu2O.
the influence of anatase to rutile mixing ratio on the photo-
catalytic degradation of orange II under UV light. Stengl
and Bakardjieva [16] reported that Mo-doped anatase could
degrade orange II to an extent of 40 % under visible light.Yang
et al. [17] reported the photocatalytic performance of BiOCl/
ZnO heterojunction for degradation of orange II under UV
irradiation. Susmitha and coworkers [18] reported effective
catalytic performance of Mn and P-codoped TiO2 for the
degradation of orange-II under visible light.
The above literature reports indicate that the photocatalytic
degradation of orange II is more extensively studied under
UV irradiation than under visible light that are confined to
doped or coupled TiO2 [14,16,18]. Though TiO2 mediated
photocatalysis has been reported to be potentially advanta-
geous, the main drawback is its wide band gap limiting the
absorption to UV region which is hardly < 5 % in solar radia-
tion. In order to exploit 45 % of visible light in solar radiation,
search for suitable non-TiO2 type semiconductor metal oxides
has been in progress [19]. Cuprous oxide (Cu2O) is a p-type
semiconductor with a band gap in the region of 2.0 to 2.2 eV.
Photocatalytic degradation of several organic dye pollutants
like rhodamine-B, methylene blue and methyl orange [20],
bromocresol green, rosaniline and eosin blue [21] as well as
aromatic derivatives like nitrophenols [22] and nitrobenzene
[23] has been recently reported from this laboratory. Present
paper describes a simple inexpensive method for 100 % photo-
catalytic degradation of orange II using H2O2 sensitized Cu2O
under visible light irradiation.
INTRODUCTION
Azo-dyes constitute a major portion of synthetic organic
dyes commonly used in textile industries. Waste water exhausts
from these industries contain large amounts of remnant azo-
dyes and pose a potential threat to human health due to their
toxic nature. Direct exposure to either UV or visible light has
been reported to be ineffective in inducing photo degradation
of azo dyes [1]. Similarly, biological degradation also is either
slow or does not proceed for many of azo dyes [2,3]. Orange
II is an azo-dye and degradation of orange II was reported
using Fenton process [4], photo assisted Fenton method [5],
microwave electrode less photocatalytic degradation [6], photo-
catalytic [7] and electrochemically assisted photocatalytic
degradation methods [8]. Photocatalytic degradation of orange
II was reported by Lucarelli and coworkers [9] using TiO2 and
UV radiation. These investigators reported that when H2O2
was initially added as an oxidant to the photo degradation
process, the rate of dye removal from solution was accelerated
significantly and orange II got degraded more readily over anatase
than on rutile. Fernandez et al. [10] reported photocatalytic
degradation of orange II using Degussa P25 under UV light.
Feng et al. [11] developed a clay based Fe nano composite for
the degradation of orange II in presence of H2O2 and UV light.
Mu et al. [12] investigated degradation of orange II in aqueous
dispersions of TiO2 using UV light as irradiation source. Stylidi
and coworkers [13] reported visible light induced degradation
of orange II in aqueous TiO2 suspensions in presence of added
H2O2 in 47 h. Bessekhouad et al. [14] made a comparative
study of UV-visible versus visible light degradation of orange
II in a coupled CdS/TiO2 suspension and noticed only 40 %
degradation under visible light. Bojinova et al. [15] studied
EXPERIMENTAL
As purchasedAR grade Cu2O (99 %) obtained from Sigma
Aldrich and Orange-II was obtained from Merck India Ltd.

818 Murthy et al.
Asian J. Chem.
Phase purity of Cu2O is ascertained using X-ray diffractometer
(PANalytical-X’ Pert PRO, Japan) at room temperature with
Ni filtered Cu-Kα radiation and a scan rate of 2° min–1.
Photocatalytic studies: 100 mg of catalyst powder was
added into 100 mL aqueous solution containing 10 ppm orange
II. The suspension was magnetically stirred for 30 min in dark.
The suspension was then exposed to 400 W metal halide lamp;
5 mL aliquots were pipetted at periodic time intervals and filtered
through 0.45 µ Millipore filters to remove the suspended
particles. Extent of degradation was followed by recording
the corresponding absorption spectra. All experiments were
conducted under ambient conditions. Percent degradation of
the dye is calculated by using the formula:
to respectively the two tautomeric forms of orange II-hydra-
zone form and azo form of orange II shown in Scheme-I.
SO3Na
SO3Na
N
N
N
H
O
N
H
O
(A0 − At )
Degradation (%) =
×100
Hydrazone form
Azo form
A0
Scheme-I: Tautomeric forms of orange II in solutions
where A0 and At are respectively initial absorbance and
absorbance at time ‘t’.
Photolysis due to irradiation for 120 min indicated no
significant change in the absorption intensity of orange II as
seen from Fig. 2a. In presence of H2O2, photo degradation to
an extent of about 8 % is observable from Fig. 2b. In presence
of Cu2O photo degradation of orange II is effected with pro-
gressive irradiation and for irradiation of 180 min nearly 21 %
photocatalytic degradation is noticeable from Fig. 2c. However,
in presence of both Cu2O + H2O2, rapid photo degradation is
seen as a function of irradiation time and complete degradation
of orange II is achieved for 90 min of irradiation as seen from
Fig. 2d.
Photoluminescence study: 50 mg Cu2O catalyst is added
to the beaker containing 100 mL of terephthalic acid (TPA)
solution (0.25 mmol L-1 in 1 mmol L-1 NaOH solution) and 10
µmol H2O2. The solution is stirred for 30 min in dark followed
by irradiation by 400 w metal halide lamp for 30 min. The
reacted solution was centrifuged and the clear solution is used
for photoluminescence measurements in a fluorescence spectro-
flourometer (Flouromax 4) with the excitation wavelength of
315 nm.
RESULTS AND DISCUSSION
In order to establish optimum conditions in terms of the
amount of catalyst and the amount of H2O2 for the photocata-
lytic degradation of orange II using Cu2O, photo degradation
studies are performed with different amounts of catalyst. Fig. 3
depicts variation of spectral intensities as a function of irradia-
tion time for varying amounts of catalysts – 50, 100 and 150
mg. Catalytic degradation with 50 mg of catalyst around 90 %
degradation is observed. With 100 mg catalyst 100 % degra-
dation is observed for 90 min of irradiation. For the degradation
study using 150 mg catalyst, 100 % degradation is observed
for 120 min of irradiation.
Fig. 1 gives X-ray diffraction pattern of Cu2O sample used
in the present study. The diffraction peaks can be indexed to
cubic Cu2O of JCPDS File No. 78-2076. In the absence of any
extra peaks that could not be assigned, the sample is ascertained
to be phase pure Cu2O.
From these spectra, it is established that 100 mg is the
optimum amount of catalyst. Fig. 4 shows variation of spectral
intensities as a function irradiation time for differing amounts
of H2O2, keeping the amount of catalyst (100 mg) and orange-
II (10 ppm) constant. With 8 µmol of H2O2, photocatalytic
degradation is incomplete for 90 min of irradiation. Similarly
for 10 µmol of H2O2, the observed degradation is not 100 %
for 90 min of irradiation. However, with 12 µmol H2O2, complete
100 % photocatalytic degradation of orange-II is observed for
90 min of irradiation. The observed spectra therefore suggest
that 100 mg catalyst and 12 µmol H2O2 are the optimum condi-
tions for the photocatalytic degradation of 10 ppm orange-II.
Present result is significant since effective photocatalytic
degradation of orange II has so far been achieved only with
modified TiO2 photocatalysts under UV irradiation only. It is
also observed that Cu2O or H2O2 individually did not show
any significant photo degradation, but combindly Cu2O + H2O2
showed a synergetic effect which may be explained with the
possible photocatalytic mechanism indicated below:
20
30
40
50
(°)
Fig. 1. X-ray diffraction pattern of Cu2O sample
60
70
80
2θ
Fig. 2 shows the UV-visible absorption spectra of aqueous
solution of orange II as a function of irradiation time. From
the figure, it can be seen that orange II shows two characteristic
absorption peaks at λ = 485 and 430 nm which can be attributed

Vol. 29, No. 4 (2017)
Rapid Visible Light Induced Photocatalytic Degradation of Orange-II Using H2O2 Sensitized Cu2O 819
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Wavelength (nm)
Fig. 2. Temporal variation of spectral contours for photocatalytic degra-dation of (a) orange-II, (b) orange-II + H2O2, (c) orange-II + Cu2O
and (d) orange-II + Cu2O + H2O2
0.4
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350 400 450 500 550 600 650
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Wavelength (nm)
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Wavelength (nm)
Fig. 3. Variation of spectral intensities as a function of irradiation time for 10 ppm orange-II + H2O2 with (a) 50 mg, (b) 100 mg and (c) 150
mg of Cu2O
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Wavelength (nm)
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Wavelength (nm)
Fig. 4. Time dependent variation of spectral contours for 10 ppm aqueous orange-II solution + 100 mg Cu2O with (a) 8 µmol, (b) 10 µmol and
(c) 12 µmol of H2O2

820 Murthy et al.
Asian J. Chem.
Cu2O + hv → e–CB + h+
photocatalyst. Rate of degradation is found to be enhanced in
presence of external electron acceptor H2O2 which gives rise
to •OH free radicals that disintegrate the molecular structure.
Formation of •OH free radicals is confirmed by photolumine-
scence studies using terephthalic acid as probe molecule.
VB
e–CB + H2O2 → •OH + OH–
h+VB + OH– → •OH
•OH + orange II → Degradation products
Formation of •OH free radicals due to addition of external
oxidant H2O2 during irradiation process is ascertained in terms
of photoluminescence studies using terephthalic acid (TPA)
as probe molecule. Terephthalic acid is known to react with
•OH free radicals to yield 2-hydroxy terephthalic acid (HTPA)
which exhibits a characteristic luminescence peak around 420
nm. Fig. 5 depicts photoluminescence spectra of Cu2O + TPA
aqueous suspension with and without addition of H2O2 prior
to and after irradiation. Intense peak observed for Cu2O + TPA
aqueous suspension in presence of H2O2 after irradiation is a
REFERENCES
1. M.R. Hoffmann, S.T. Martin, W. Choi and D.W. Bahnemann, Chem. Rev.,
95, 69 (1995);
https://doi.org/10.1021/cr00033a004.
2. G. Helz, R. Zepp and D. Crosby, Aquatic and Surface Chemistry, Lewis
Publishers: Boca Raton, FL (1995).
3. M. Halmann, Photodegradation of water pollutants; CRS Press: Boca
Raton, FL (1996).
4. J. Bandara, C. Morrison, J. Kiwi, C. Pulgarin and P. Peringer, J. Photochem.
Photobiol. Chem., 99, 57 (1996);
https://doi.org/10.1016/1010-6030(96)04339-0.
5. J. Fernandez, J. Bandara, A. Lopez, Ph. Buffat and J. Kiwi, Langmuir,
15, 185 (1999);
•
clear indication of formation of OH free radicals from an
important part in the photocatalytic degradation of orange II.
https://doi.org/10.1021/la980382a.
6. X. Zhang, G. Li, Y. Wang and J. Qu, J. Photochem. Photobiol. Chem.,
184, 26 (2006);
https://doi.org/10.1016/j.jphotochem.2006.03.021.
7. M. Stylidi, D.I. Kondarides and X.E. Verykios, Int. J. Photoenergy, 5, 59
(2003);
https://doi.org/10.1155/S1110662X0300014X.
8. G. Li, J. Qu, X. Zhang, H. Liu and H. Liu, J. Mol. Catal. Chem., 259,
238 (2006);
(a) TPA + Cu2O prior to irradiation
(b) TPA + Cu2O after 60 min irradiation
(c) TPA + Cu2O + H2O2 after 60 min irradiation
https://doi.org/10.1016/j.molcata.2006.06.038.
9. L. Lucarelli, V. Nadtochenko and J. Kiwi, Langmuir, 16, 1102 (2000);
https://doi.org/10.1021/la990272j.
(c)
10. J. Fernandez, J. Kiwi, C. Lizama, J. Freer, J. Baeza and H.D. Mansilla,
J. Photochem. Photobiol. Chem., 151, 213 (2002);
https://doi.org/10.1016/S1010-6030(02)00153-3.
11. J. Feng, X. Hu, P.L. Yue, H.Y. Zhu and G.Q. Lu, Chem. Eng. Sci., 58,
679 (2003);
https://doi.org/10.1016/S0009-2509(02)00595-X.
12. Y. Mu, H.Q. Yu, J.C. Zheng and S.J. Zhang, J. Photochem. Photobiol.
Chem., 163, 311 (2004);
https://doi.org/10.1016/j.jphotochem.2003.08.002.
13. M. Stylidi, D.I. Kondarides and X.E. Verykios, Appl. Catal. B, 47, 189
(2004);
https://doi.org/10.1016/j.apcatb.2003.09.014.
14. Y. Bessekhouad, N. Chaoui, M. Trzpit, N. Ghazzal, D. Robert and J.V.
Weber, J. Photochem. Photobiol. Chem., 183, 218 (2006);
https://doi.org/10.1016/j.jphotochem.2006.03.025.
15. A. Bojinova, R. Kralchevska, I. Poulios and C. Dushkin, Mater. Chem.
Phys., 106, 187 (2007);
https://doi.org/10.1016/j.matchemphys.2007.05.035.
16. V. Stengl and S. Bakardjieva, J. Phys. Chem. C, 114, 19308 (2010);
https://doi.org/10.1021/jp104271q.
(b)
(a)
350
400
450
500
550
600
Wavelength (nm)
Fig. 5. Photoluminescence spectra of terephthalic acid solutions containing
Cu2Oin presence and in absence of H2O2 before and after irradiation
Rate constants computed from respective slopes for plots
of ln (Ct/C0) versus time for the degradation of orange II under
different conditions are given in Table-1.
17. K. Yang, C.L. Yu, L.N. Zhang and J.M. Yu, J. Synth. Cryst., 41, 171
(2012).
18. T. Susmitha, T. Siva Rao and B. Sreedhra, J. Environ. Chem. Eng., 2,
1505 (2014).
TABLE-1
CALCULATED RATE CONSTANTS FOR
PHOTODEGRADATION OF orange-II, orange-II + H2O2,
orange-II + Cu2O AND orange-II + H2O2 + Cu2O
19. A.V. Prasada Rao, A.M. Umabala and P. Suresh, J. Appl. Chem., 4, 1145
(2015).
20. T. Narasimha Murthy, P. Suresh, A.M. Umabala and A.V. Prasada Rao,
J. Appl. Chem., 4, 1751 (2015).
21. T. Narasimha Murthy, K. Deepthi, A.M. Umabala, A.V. Prasada Rao,
Der Pharma Chem., 8, 140 (2016).
Photodegradation
Dye alone
Dye + H2O2
Dye + Cu2O
Dye + Cu2O + H2O2
Rate constant korange-II (min–1)
0.0
2.0 × 10-5
3.0 × 10-5
6.7 × 10-4
22. T. Narasimha Murthy, P. Suresh, A.M. Umabala, A.V. Prasada Rao,
Der Pharma Chem., 8, 228 (2016).
23. T. Narasimha Murthy, P. Suresh, A.M. Umabala and A.V. Prasada Rao,
Int. J. Recent Sci. Res., 7, 10895 (2016).
Conclusion
The above experimental results suggest that orange-II can
be successfully degraded under visible light using Cu2O as