Research Journal of 
Recent 
Sciences 
______
______________________________
______
____
___
 
ISSN 2277
-
2502
 
 
Vol. 
2
 
(
ISC
-
2012
), 
29
-
31
 
(201
3
)
 
Res.J.
Recent
.Sci.
 
 
 
International Science Congress Association
 
 
 
 
 
29
 
Short Communication 
 
Kinetic 
B
ehavior of 
P
hoto 
C
atalysts
 
 
S
ingh Bhoopendra
 
and
 
A
fridi
 
A
zrabegam
 
Department of 
C
hemistry, K.K.P.G. College, 
E
tawah 206001
, 
U
P, INDIA
 
 
Available online at: 
www.isca.in
 
Received
 
29
th
 
September
 
2
012
, revised
 
12
th
 
April
 
201
3
, accepted
 
17
th
 
April
 
201
3
 
 
 
 
Abstract
 
The photo catalytic degradation of methyl blue dye, over TiO
2
 
and ZnO were carried out in the presence of light to observe 
good semi conducting property. The photo catalytic degradation of
 
methyl blue was observed in the presence of both photo 
catalysts. Parameters like amount, band gap, intensity, sensitizer etc were also studied. Studies show that TiO
2
 
shows more 
photo catalytic activity than ZnO.
 
 
Keywords
:
 
Kinetic behavior, photo cataly
sts, dye, degradation. 
 
 
Introduction
 
Last few decades numerous research effect in the field of 
heterogeneous and homogeneous photo catalyst by semi 
conducting through particular system has been studied
1,2
.
 
However,  synthesized  degradation  of  o
-
 
nitr
o  phenol  that  
has  been  studied  in  the  presence  of  semi  conducting oxide
3
.
 
Kinetic  study  of  application  of  ZnO  as  photo  catalyst  in 
heterogeneous  medium  analyzed  recently
4
.  In  case  of  zinc  
oxide  the pure white compound turn yell
ow on heating because 
of deficit of oxygen has various uses, of which the most 
important is as co 
–
 
catalyst, with CuO  for  low  pressure  
synthesis  of  methanol  by  oxidation  of  methane
5
.When a 
semiconductor is irradiated with light having energy (E=
 
hv)  
equal to or more  than band  gap  energy,  a heterogeneous 
photo  catalyst reaction occur at the solid solution contact 
surface .The semi conducting forms  a  pair  of  volume  band  
(VB)  hole  and  conduction  band  (CB) electron as in case of 
zinc
 
oxide and titanium dioxide.
 
 
The titanium dioxide is used as white pigment
6
.
 
It also 
reacts 
with
 
glycol in the presence of alkali metal hydroxide to yield 
soluble titanium glaciates
7
.  The  dioxide  impregnated  with  
some  metal  complexes  has been  muc
h  studied  as  a  catalyst  
for  photodecomposition  of  water
8
. Ultraviolet irradiation of   a 
gas/solid interface of microcrystalline TiO
2
 
in the presence of 
H
2
O and CO
2
 
leads to formation of CO,
 
H
2 
and CH
4
9
.
 
Many 
other
 
uses
 
are
 
known
 
example
 
is
 
found
 
i
n
 
catalysis
10
.
 
Titanium 
dioxide (TiO
2
) shows its unique photo catalytic activity at an 
excellent choice of photo catalysis application
11
-
16
. TiO
2
 
are also 
using full self cleaning
13
, self sterilizing
17
.
 
Titanium dioxide 
work effectively under low UV light 
intensities and also 
applicable to indoor and outdoor environments. Titanium 
dioxide having band gap (3.23eV) semiconductor, is transport to 
visible light.
 
However, production of synthetic dyes in India 
about 25000 metric tons every
 
year
18
, which are
 
indus
trial
 
health
 
hazards to people
19
. Dye
 
stuff industries have occupied a 
prominent place in the industrial organization of the modern 
world. One of the major routes to incorporate dyestuffs in our 
biological system is by absorption through skin. Some dyes 
ha
ve different degrees of binding ability with protein, collagen 
and lipid
20
-
21
. Study shows that toxic effects of these synthetic 
dyes are observed in the presence of the ultraviolet component 
of sunlight (285
-
400nm)
22
.
 
Photosensitization reactions in 
vario
us analysis is oxygen dependent in which a photo excited 
dye transfers energy  to molecular oxygen to produce activated 
oxygen species
 
like
 
singlet
 
oxygen
 
(1O
2
), peroxide.
 
The
 
activated oxygen
 
species contribute
 
to
 
oxidative degradation of 
proteins, enzyme
s, lipids and other target
 
molecules
 
of cellular   
systems
23
-
25
 
and are also responsible to act as
 
tumor promoters 
in
 
the
 
development
 
of
 
cancer
26
.
 
Although, photosensitization 
studies and chemical property of singlet oxygen and super oxide 
radical was anal
yzed in recent years by the author
27
-
28
.
 
 
Material and Methods
 
Experimental
 
Reagents:
 
Titanium dioxide (TiO
2
) and Zinc 
oxide (ZnO) were used to as 1.0 g/lit suspension.   Methyl   blue   
was   supplied   by   Merck   and   used   in   a concentration of 
10
-
4 M.
 
 
Instrumentation:
 
Ultraviolet  and  visible  spectra  were  
recorded on
 
 
a
 
 
Shimadzu
 
 
450 UV/visible
 
spectrophotometer   
using quartz
 
cells
 
of
 
5cm path length.
 
Irradiation experiments 
were done as follow: 10
-
ml solution was taken in a Petri dish 
(6cm
 
diameter) and irradiated with direct sunlight. The 
temperature was maintained at 20+20C by using a constant 
temperature water bath. Irradiation experiments were done in 
Kanpur, U.P. on sunny days preferably between 9:00 and 11.00 
am.  The  irradiance  of 
 
emitted light   was   measured   by   an 
International
 
Light
 
IL
-
730
 
UV
 
Actinic Radiometer 
(International Light Company, Newburyport, Mass., U.S.A.) 
equipped with a calibrated
 
and
 
cosine
–
corrected ultraviolet 
radiation detecting probe. Sunlight produced an
 
average 
ultraviolet radiation of approx.
 
 
Research Journal of 
Recent 
Sciences 
______
_
_
_______________________________
______________
_
________
 
ISSN 2277
-
2502
 
Vol. 
2
 
(
ISC
-
2012
), 
29
-
31
 
(201
3
)
 
 
 
Res.J.Recent.Sci
 
  
 
International Science Congress Association
 
 
30
 
Result
s
 
a
nd Discussion
 
Effect of sensitizers
: 
Certain  dye  complexes  shows  the  
tendency  to  increase  the  rate  of degradation  by  sensitization  
The  sensitization  route  are  follows  from equation no 1 
to 4.
 
 
The photochemical route proceeds as follows, where sense 
represents the photo sensitizer
 
1Sens
     
hv
 
1sens *
 
(1)
 
 
1Sens*
  
 
3sens *
 
(2)
 
 
3Sens*
 
+  3 O
2
 
1sens + 1
 
 
O
2
 
  
(3)
 
 
1O
2
 
+ substrate
 
products
 
(4) 
 
 
Energy transfer  from  triplet  excited  
3sens*  to  3O
2
  
to  give  
1O
2
  
is  a  spin allowed  process.
 
A  representative  example  is  
the  use  of  excited  azo alkane with O
2
.
 
 
Effect of band gap of semiconductor:
 
The usual exited 
semiconductor has separated the hole and electron pairs that 
ind
uced the photo catalytic reaction and hence the band gap 
energy has important role to play. The band gaps of different 
photo catalysts are summarized in 
t
able 1.
 
ZnO + hv
 
→
 
h+ (VB) + e 
-
 
(CB)
 
 
The hole generated is capable of oxidizing the substrate and th
e 
electron of CB is capable of reducing the substrate. 
Furthermore
, the solution contains species 
e.g
.
 
OH, H
+
, .O
2
-
, 
HO
2
, H
2
O
2
, O
2
, which are due to the semiconductor light
-
water
-
oxygen interactions. These species are also capable of carrying 
out redox rea
ctions. The generation of super oxide radical anion 
.O2
-
 
and .OH radical can be shown as under.
 
h+ (VB) + H
2
O  → . OH ads + H+
 
e
-
 
(CB) + O
2
  
ads
 
→. O2
-
 
 
Subscript
 
“
ads” refers to species
 
adsorbed 
on
 
the
 
surface
 
of 
semiconductor.
 
Table
-
1
 
Band gap of different photo catalysts
 
S. No.
 
Semiconductor
 
Band gap
 
1.
 
PbS
 
0.30
 
2.
 
CdS
 
2.50
 
3.
 
ZnO
 
3.20
 
4.
 
ZnS
 
3.80
 
5.
 
TiO
2
 
3.23
 
 
Photo catalytic activity of TiO
2
 
and ZnO: 
To evolve the TiO
2
 
and ZnO photo catalytic activity six Petri dishes (10 cm 
diameter) each containing 25 ml of a 10
-
4 M solution of methyl 
blue were used. To four of them (two of TiO
2
 
and ZnO); 1.25 
gram o
f TiO
2
 
and ZnO were added.
 
One of these suspension put 
was wrapped in a black plastic bag before experiment to the sun. 
In this way two types of controlled were used .One Petri dishes 
of each photo catalyst with just the MB solution were used 
balance MB is
 
a sensitizers.  Some degradation caused by UV
-
visible light
-
absorption
 
was
 
observed.
 
A second suspension of 
TiO
2
 
and ZnO in the MB solution left in the dark acted as 
control to capture adsorption losses of MB on to TiO
2
 
and ZnO.
 
Under the experimental con
dition it was observed that 
evaporation losses can reach  up  to  12  %  in  just  one  
hour
.
 
In 
order to correct the data obtained in the
 
MB photometric
 
reading, the petri
 
dishes were weight immediately before and 
after exposure. The suspensions were filt
ered using 0.22� m 
membranes and measured absorbances at 555
 
nm.
 
The results 
obtained are shown in the 
t
able 1 and 2.
 
 
The results shows as in 
f
ig
ure 
1 and 2 that the photo catalytic 
activity of TiO
2
 
can be seen more than ZnO by the fact that 
extent of deg
radation reaches  98.3  %  in  just  one  hour  while  
extent  of  degradation  of  ZnO reaches 96.9 % in one hour.
 
As 
shown from both the 
t
able 1 and 2 the net values of degradation 
includes the contribution of some adsorption as well as direct 
destructio
n of organic dyes. When plotting In C/Co to as a 
function of time a structural line yield K=0.0799 min
-
1 (slope) 
and t � 8.67 min for TiO
2
 
and K= 0.0732 min
-
1(slope) and t 
�9.
 
47 min for ZnO.  These
 
values
 
are
 
in
 
good
 
agreement
 
to
 
the
 
same
 
parameter determ
ined by 0.070min
-
1and t� 9.90 min to 
the same concentration MB used in this experiment
29
.
 
 
Conclusion
 
The present study proves Methylene blue degradation by solar 
light in the presence of TiO
2
 
and ZnO as photo catalyst. Study 
proves that degradation of met
hylene blue is higher in presence 
of TiO
2
. The effect of various parameters likes sensitizers and 
band gap of semiconductor were also studied in the present 
investigation. The study is also very helpful in the field of 
industrial research.
 
 
Kinetics of Met
hylene blue photo degradation:
 
C
16
H
18
N
3
SCL + 5 � O
2
→ HCl+ H
2
SO
4
 
+ 3HNO
3
+ 16 CO
2
 
+ 6 H
2
O
 
 
Table
-
2
 
Photo degrading of methyl blue exposed to Sunlight in 
presence of TiO
2
 
Condition 
 
Co mM
 
C
60
 
mM
 
losses
 
MB solution 
 
1.0
 
0.0823
 
17.7
 
MB solution + TiO
2
 
solution [Light]
 
1.0
 
0.00174
 
98.3
 
MB solution + TiO
2
 
solu
tion[ Dark]
 
1.0
 
0.0832
 
16.8
 
 
Table
-
3
 
Photo degrading of methyl blue exposed to Sunlight in 
presence of ZnO
 
Condition
 
Co mM
 
C
60
 
mM
 
losses
 
MB solution 
 
1.0
 
0.0823
 
17.7
 
MB solution + TiO
2
 
solution [Light]
 
1.0
 
0.0031
 
96.9
 
MB solution + TiO
2
 
solution[Dark]
 
1.0
 
0.081
 
15.9
 
Research Journal of 
Recent 
Sciences 
______
_
_
_______________________________
______________
_
________
 
ISSN 2277
-
2502
 
Vol. 
2
 
(
ISC
-
2012
), 
29
-
31
 
(201
3
)
 
 
 
Res.J.Recent.Sci
 
  
 
International Science Congress Association
 
 
31
 
 
Fig
ure
-
1
 
Methylene blue degradation by solar light and TiO
2
 
as photo 
catalyst
 
  
 
F
igure
-
2
 
Methylene blue degradation by solar light and ZnO as photo 
catalyst
 
 
  
 
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