Research Journal of Chemical Sciences 
______
______________________________
______
____
 
ISSN 2231
-
606X
 
 
 
Vol. 
2
(
5
), 
72
-
7
7
, 
May 
(201
2
)
 
 
Res.J.Chem.Sci.
 
 
 
International Science Congress Association
 
 
 
 
    
72
 
Photocatalytic 
Degradation 
of Violet GL2B 
A
zo dye by using Calcium 
A
luminate 
N
anoparticle in presence of 
S
olar light
 
 
Narayanappa Madhusudhana
1
,
 
Kambalagere Yogendra*
1
 
and
 
 
Kittappa M Mahadevan
2
 
*
1
Department of P.G studies and Research in Environmental Science, Kuvempu University, Jnana Sahyadri, Shankaraghatta, Shivamog
ga, INDIA
 
2
Department of Chemistry, Kuvempu University, Jnana Sahyadri, Shankaraghatta, Shivamogga, INDIA
 
 
 
Available online at: 
www.isca.in
 
(Received
 
 
8
th
 
March 
201
2
, revised
 
 
20
th
 
March 
201
2
, accepted
 
22
nd
 
March 
201
2
)
 
 
 
 
 
 
Abstract
 
The present study deals with the photocatalytic degradation of Violet GL2B an azo
 
dye, using Calcium aluminate (CaAl
2
O
4
) 
nanoparticles. SEM and XRD studies were carried out to determine the size of the nanoparticle. UV
–
VIS spectroscopy method 
was selected to evaluate the degradation efficiency at 545nm. The results indicated that at al
l pH levels ~100% degradation was 
achieved in 120 minutes irrespective of amount of catalyst load. The results revealed the efficiency of the present photocata
lytic 
process for the effective degradation of dye effluents.
 
 
Keywords:
 
Violet GL2B, Degradation
, Nanoparticle, Photocatalyst, Calcium aluminate
 
 
 
Introduction
 
Different types of dyes are used in many industries such as 
textile, paint, ink, plastics and cosmetics. About half of global 
production of synthetic textile dyes (700000 tons per year) are 
classified into azo
 
compounds that have the chromophore of 
-
N=N
-
 
unit in their molecular structure and over 15% of the 
textile dyes are lost in wastewater stream during dyeing 
operation
1
. It is well known that when accumulated into the 
body the soluble azo dyes split into co
rresponding aromatic 
amines by liver enzymes and intestinal flora, which can cause 
cancer in human. The textile industry produces large quantity of 
highly coloured effluents, which are generally toxic and 
resistant to destruction by biological treatment me
thods. 
Therefore, it is necessary to find an effective method to remove 
colour from textile effluents
2
-
4
. 
 
 
Various chemical and physical processes such as coagulation, 
electro coagulation and adsorption on activated carbon are not 
destructive but only tra
nsfer dye from one phase to another; 
hence, there is a need for developing treatment technologies for 
eliminating contaminants from wastewater. Photocatalytic 
degradation by semiconductors is a new and effective technique 
for the removal of pollutants from
 
water
5,6
. Although the 
process of UV
-
irradiated photocatalytic decolourization of azo 
dyes has proved to be effective, the direct use of clean and 
renewable solar light and active photocatalysts for 
decolourization and degradation of azo dyes has attracte
d great 
interest in recent years
7
–
9
.
 
 
Very recently, Ali Mahyar 
et al., 
reported the degradation of 
C.I. Basic Violet 2 (BV2; New Fuchsin) by preparing TiO
2
–
SiO
2
 
nanoparticles by the sol
-
gel method using Titanium 
tetraisopropoxide as a titanium source and 
used as a 
photocatalyst for the photodegradation of BV2
10
. In another 
research work, photocatalyst Zinc oxide (ZnO), which is one of 
the most important semiconductors with a direct wide band gap 
of  ~3.37 eV and large excitation binding energy of 60 meV at
 
room temperature
11
. ZnO has promising applications in 
electrical engineering, catalysis, ultraviolet (UV) absorption, 
and optical and optoelectronic devices. 
One of the most 
important and surface
-
dependant properties of ZnO 
nanoparticles is their photocat
alytic behavior under UV 
electromagnetic irradiation. Hence, ZnO can be used for 
degradation and removal of environmental pollutants, especially 
organic dye contaminants, from water
12
.
 
 
 
Similar work has been reported such as, 
degradation of azo dyes 
by us
ing synthesized nanoparticles (ZnO, CaAl
2
O
4
, and 
CaZnO
2
) as photocatalysts under natural sunlight
13
-
15
. These 
nanoparticles have been reported as efficient photocatalysts 
against Coralene Red F3BS and Coralene Dark Red 2B dyes at 
different conditions such 
as optimum catalyst dosage and 
effective pH level. 
 
 
This study reports CaAl
2
O
4 
nanoparticles mediated 
photocatalytic destruction of dyes. The textile azo
 
dye Violet 
GL2B is selected for the degradation studies under natural 
sunlight and it gives dark Violet colour when dissolved in water. 
The structure is as shown in 
f
igure 1.
 
 
Materials and Reagents:
 
Metal nitrates were chosen for the 
preparation of the CaAl
2
O
4
 
nanoparticle, as the NO
3
 
groups of 
metal nitrates act as oxidizing agents and also their high 
solubility in water allows a proper homogenization. Urea seems 
to be the most convenient fuel which
 
can be used for the 
synthesis of CaAl
2
O
4
. The commercially available azo dye 
Violet GL2B was procured. 
 
The chemicals like Calcium nitrate 
Research Journal of Chemical Sciences 
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ISSN 2231
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606X
 
 
Vol. 
2
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), 
72
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7, 
May 
(201
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)
 
  
Res.J.Chem.Sci
 
International Science Congress Association
 
 
73
 
(Ca (NO
3
)
2
. 4H
2
O) (99%, AR), Aluminium nitrate (Al
 
(NO
3
)
3.
9H
2
O) (95%, AR), Urea (NH
2 
CO NH
2
) (99%, AR), 
were obtaine
d from Hi
-
media chemicals, Mumbai and used as 
received.
 
 
 
 
 
 
 
 
 
 
 
Figure
-
1
 
Chemical structure of Violet GL2B
 
 
The UV
-
VIS single beam spectrophotometer 119 (Systronics
) 
has been used for recording absorbance at λ
max
, Later the 
absorbance was recorded in UV
-
VIS spectrophotometer 169 
(Systronics).
 
 
Synthesis of Calcium aluminate nanoparticle:
 
The Calcium 
aluminate nanoparticle was prepared
 
by solution combustion 
method, using procured 
c
alcium nitrate, 
a
luminium nitrate
, and 
Urea (Fuel).
 
Stoichiometric amounts of 
c
alcium nitrate, 
a
luminium nitrate
 
and fuel Urea were calculated using the total 
oxidizing and reducing valencies
 
of the compounds which serve 
as numerical coefficients for Stoichiometric balance. Here Ca 
(NO
3
)
2
.4H
2
O (3.54 g) and Al (NO
3
)
3
. 9H
2
O (11.255 g) were 
dissolved in minimum quantity of water along with Urea (24 g) 
in a silica 
c
rucible (with volume of 100 cm
3
). The resulting 
mixture was introduced into the muffle furnace which was 
preheated to 600
0
C. The solution boils and undergoes 
dehydration followed by decomposition along with the release 
of certain amounts of gases it froths and swells forming foam 
which
 
ruptures with a flame and glows to incandescence
16,17
. 
The product after combustion is a voluminous and foamy 
CaAl
2
O
4
. The obtained Calcium aluminate was crushed in a 
mortar to make it amorphous. According to propellant chemistry 
the reaction is as shown.
 
3 Ca (NO
3
)
2
 
+ 6 Al (NO
3
)
3
 
+ 20 NH
2
CONH
2
  
 
3 CaAl
2
O
4
 
+ 20 CO
2
 
+ 40 H
2
O + 32 N
2
 
 
SEM and XRD of prepared Calcium 
Aluminate 
Nanoparticles
:
 
XRD analysis was carried out on fresh sample 
to assess the purity of the expected phases and the degree of 
crystallization, i.e., size, composition and crystal structure. XRD 
was performed by Rigaku diffractometer using Cu
-
K
α
 
radiation 
(1.5406 Å) in a θ
-
2θ
 
configuration. The XRD pattern of the 
prepared CaAl
2
O
4
 
nanoparticle was as shown in Figure 2. 
According to the Debye
–
Scherrer’s formula (D = Kλ/ (βcosθ), 
where K is the Scherrer’s constant, λ the X
-
ray wavelength, β is 
the peak width at half
-
maximum and θ
 
is the Bragg diffraction 
angle) the average crystallite size D is 38.55 nm. 
 
 
The SEM images of prepared CaAl
2
O
4
 
nanoparticle have shown 
the typical texture and morphology. SEM images obtained were 
depicted that the synthesized nanoparticles were crystal 
like 
structures.
 
 
 
 
                                                                                                                             
                                      
 
 
 
 
 
 
 
 
 
 
 
 
 
Figure
-
2
 
X
-
ray diffractograms of the nanoparticle CaAl
2
O
4
 
 
 
Figure
-
3
 
SEM micrographs of the nanoparticle CaAl
2
O
4
 
Research Journal of Chemical Sciences 
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ISSN 2231
-
606X
 
 
Vol. 
2
(
5
), 
72
-
7
7, 
May 
(201
2
)
 
  
Res.J.Chem.Sci
 
International Science Congress Association
 
 
74
 
Material and Methods
 
Experimental Procedure
: 
The photocatalytic experiments 
were carried out in presence of direct sunlight of intensity at 
1125 lux (using Lux
 
meter). The experiments were carried out 
between 10.30 am to 1.30 pm. In all photocatalytic experiments, 
100 ml of 30 ppm Violet GL2B solution was taken in 100 ml 
Borosil beakers. The UV
-
VIS spectrophotometer 119 
(Systronics) was used for the determinatio
n of absorbance in the 
range of 200 to 800 nm. The λ
max
 
of Violet GL2B was found to 
be 545 nm. The photocatalytic suspensions of 100 mg, 200 mg, 
300 mg, 400 mg and 500 mg were tested on the dye samples. 
The suspension pH values were adjusted by using NaOH/
 
HCl 
solutions using pH meter. Before irradiation, photocatalyst 
suspension was stirred in the dark to ensure the adsorption 
equilibrium and it was kept in sunlight for the photocatalytic 
degradation. The suspension was sampled at regular time 
intervals of
 
30 minutes and centrifuged using (EBA
-
Hetlich) at 
2500 rpm for 10 min to remove photocatalyst particles. The 
residual concentration of the solution samples was monitored by 
using UV
-
VIS spectrophotometer 169 (Systronics) at 545 nm. 
The 
v
iolet GL2B experim
ents were conducted at pH range of 
2.5 to 9.5 in order to study the efficiency of the nanoparticle on 
Acidic, 
a
lkaline and 
n
eutral conditions. The data obtained from 
the photocatalytic degradation experiments were then used to 
calculate the degradation eff
iciency D. 
 
=
(
(
0
−
)
÷
0
)
×
100
 
 
Where, 
A
0
 
is the initial absorbance of dye solution and A
t 
is 
absorbance at time ‘t’.
 
 
Results and Discussion
 
Effect of Sunlight and Catalyst
: 
Figure 4 illustrate the 
photocatalytic
 
degradation of Violet GL2B dye in aqueous 
solution under three different experimental conditions; Sunlight 
alone, Dark/ CaAl
2
O
4
 
and Sunlight/CaAl
2
O
4
. The degradation 
rate was found to increase with increase in irradiation time and 
100% degradation was ach
ieved within 120 min for Violet 
GL2B. When 30 ppm of the dye along with CaAl
2
O
4
 
was 
magnetically stirred for the same optimum dosage in the 
absence of sunlight, for pH 7 achieved degradation was 38.56%, 
whereas, when the dye was directly exposed to the sun
light 
without adding the photocatalyst decolourization was not 
observed. Similar results have been reported for ZnO
-
assisted 
photocatalytic degradation of azo dyes such as Red 3BL and 
Remazol Red RR
18
-
20
.
 
 
Effect of catalyst loading on the rate of degradat
ion
: 
The 
catalytic dosage was varied from 100 mg 
-
 
500 mg for 30 ppm 
(30 mg/L) against Violet GL2B at three different pH levels. 
After adding the catalyst, the solution was stirred to disperse the 
catalyst throughout the solution and kept in sunlight and 
i
mmediately it started degrading. For all the pH levels in the 
first 30 minutes the average percentage of degradation was 
found to be 53.34% for minimum dosage and 83.71% for the 
maximum dosage (Figure 5), after 120 min it was degraded upto 
~100 % for minim
um dosage and ~100% for maximum dosage 
(Figure 6). Degradation efficiency was equal for all the catalytic 
dosages at 120 minutes. The photonic absorption has helped the 
reaction to a great extent and an increase in catalyst loading 
greatly enhances the pro
cess performance with respect to time. 
 
 
 
 
Figure
-
4
 
Photocatalytic degradation of Violet GL2B under different 
experimental conditions ([CaAl
2
O
4
]=0.1gm,0.2 gm,0.3 
gm,0.4 gm and 0.5gm, [Violet GL2B]= 30 ppm, neutral 
pH 
=7, T=1125 lux, λmax=545 nm)
 
 
 
Figure
-
5
 
The average percentage of degradation at the first 30 
minutes time interval for all the pH parameters
 
0
20
40
60
80
100
120
Blank
0.1
0.2
0.3
0.4
0.5
% DEGRADATION
DOSAGE
V GL2B/SUNLIGHT
V GL2B/ CaAl2O4/SUNLIGHT
V GL2B/CaAl2O4/DARK
0
10
20
30
40
50
60
70
80
90
Blank
0.1
0.2
0.3
0.4
0.5
DEGRADATION (%)
DOSAGE
DEGRADATION (30 min)
For all pH values
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Vol. 
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-
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Res.J.Chem.Sci
 
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75
 
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0
30
60
90
120
ABSORBANCE
TIME
pH 7
Blank
0.1
0.2
0.3
0.4
0.5
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0
30
60
90
120
ABSORBANCE
TIME
pH 9.5
Blank
0.1
0.2
0.3
0.4
0.5
 
 
Figure
-
6
 
The average percentage of degradation at 120 minutes time 
interval for all the pH parameters
 
Effect of pH Solution
: 
In order to study
 
the effect of pH on the 
degradation efficiency of CaAl
2
O
4
 
catalyst on
 
photocatalytic 
degradation of v
iolet GL2B dye, experiments were carried out at 
varied pH ranging from 2.5 to 9.5. As shown in 
f
igure 7, for 
Violet GL2B, the degradation rate increased to 100% for 300 
mg, 400 mg and 500 mg in 60 minutes as the pH was increased 
from 7 to 9.5. The maximum degradation rate of 
v
iolet GL2B 
(100%) was achieved at all pH ranges at the end of 120 minutes. 
The experimental data revealed that higher degradation rate of 
v
iolet GL2B was observed in all the pH conditions. However in 
alkaline medium, the maximum colour degradation was attained 
at 60 minutes for 300mg, 400mg and 500mg dosages. In 
alkaline medium, 
excess of hydroxyl ions facilitate 
photogeneration of OH radicals which is accepted as primary 
oxidizing species responsible for photocatalytic degradation, 
resulting in enhancement of the efficiency of the process. 
 
`
 
 
 
 
 
 
 
 
 
 
7(a)   
 
 
 
 
 
 
 
7(b)
 
 
7(c)
 
Figure
-
7
 
Effect of catalyst loading on Violet GL2B 30mg/L at different pH levels, pH 7 
7
(a), pH 9.5 
7
(b) and pH 2.5 
7
(c) with respect 
to time interval 120 minutes
 
 
0
10
20
30
40
50
60
70
80
90
100
Blank
0.1
0.2
0.3
0.4
0.5
DEGRADATION (%)
DOSAGE
DEGRADATION (120 min)
FOR ALL pH LEVELS
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0
30
60
90
120
ABSORBANCE
TIME
pH 2.5 
Blank
0.1
0.2
0.3
0.4
0.5
Research Journal of Chemical Sciences 
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ISSN 2231
-
606X
 
 
Vol. 
2
(
5
), 
72
-
7
7, 
May 
(201
2
)
 
  
Res.J.Chem.Sci
 
International Science Congress Association
 
 
76
 
31
32
33
34
35
36
37
38
39
40
41
0
30
60
90
120
% OF COD REMOVED
TIME
COD 
Blank
0.1
0.2
0.3
0.4
0.5
COD removal
: 
It is observed that the COD decreases slower 
than the decolourization of the solution (
f
igure 8). This is 
because of the fact that the dyes are not directly mineralized, but 
transformed in intermediate photoproducts. These generated 
photoproducts may submi
t other cycles of degradation to 
complete total mineralization. The initial COD of the dye was 
found to be 39.9 mg/L and after degradation the final COD was 
found to be 34.3 mg/L.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Figure
-
8
 
Percentage of COD removal by photocatalytic
 
activity
 
 
Mechanism
 
CaAl
2
O
4
 
+ hν → CaAl
2
O
4
•+
 
(e
-
CB
 
+ h
+
VB
) ………….…..…..(1)
 
e
-
CB 
+ O
2
 
→ O
2
•−
……………………………………..…..….(2)
 
H
2
O + 
O
2
•− 
→ OOH
•
 
+ OH
−
………………………….…..…(3)
 
2OOH
•
 
→ O
2
 
+ H
2
O
2
 
……………………………………….(4)
 
O
2
•−
 
+ Violet GL2B 
→ 
Violet GL2B 
-
OO
•
 
…………….…..(5)
 
OOH
•
 
+ H
2
O + 
e
-
CB
 
 
→ H
2
O
2
 
+ OH
−
 
……………….……....(6)
 
H
2
O
2
 
+ 
e
-
CB
 
 
→ OH
•
 
+ OH
−
……………………………….…(7)
 
H
2
O
2
 
+ 
O
2
•−
 
→ OH
•
 
+ OH
−
 
+ O
2
 
………………………..…..(8)
 
OH
•
 
/
 
O
2
•−
/ 
CaAl
2
O
4
•+
 
+ Violet GL2B
 
→ Dye degradation…(9)
 
 
The mechanism of photocatalytic activity of CaAl
2
O
4 
nanoparticle
 
can be explained as shown above.
 
Under sunlight 
irradiation CaAl
2
O
4 
molecules get excited and transfer electron 
to the conduction band (
e
quation 1). Electron in the conduction 
band of CaAl
2
O
4 
can reduce molecular oxygen and produce the 
super oxide radical
 
(
e
quation 2). This radical may form 
hydrogen peroxide or organic peroxide in the presence of 
oxygen and organic molecule (
e
quation 3,4,5). Hydrogen 
peroxide can be generated in another part (Equation 6). 
Hydrogen peroxide can form hydroxyl radicals which 
are 
powerful oxidizing agents (
e
quation 7,8). The radicals produced 
are capable of attacking dye molecules and degrade them 
(
e
quation 9).
 
 
Conclusion
 
Photocatalysis is a very effective method for the degradation of 
azo dyes. In this study, Calcium aluminat
e nanoparticles were 
synthesized and characterized by SEM and XRD studies. It was 
observed that the synthesized Calcium aluminate (average 
particle size 38.55 nm) is photosensitive and effective in 
degrading selected azo dye (
v
iolet GL2B) completely in a s
hort 
interval of time (120 minutes). The protocol developed may be 
employed effectively in the treatment of textile dye effluents 
which are hazardous to the environment. It is also economically 
feasible compared to other oxidative processes since it involv
es 
natural sunlight for photodegradation of dyes thereby saving 
energy.
 
 
Acknowledgements
 
This work was supported  by University Grants Commission, 
New Delhi, India under 
M
ajor 
R
esearch 
P
roject scheme.
 
 
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ISSN 2231
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Vol. 
2
(
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), 
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-
7
7, 
May 
(201
2
)
 
  
Res.J.Chem.Sci
 
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77
 
9
 
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