The present work aims to degrade the RB21 dye from synthetic wastewater using semiconductors TiO2 and ZnO. The activity of photocatalytic degradation process of dye was carried out using different light sources of 900 W/m 2 intensity in natural sunlight from 02:00 to 04:00 pm with 48°C temperature in Ahmedabad city in the month of May, 600 Watt microwave oven and high pressure UV-light photocatalytic reactor of wavelength 200-450 nm. All the experiments were performed with dye concentration 50 mg/L, catalyst dosage 0.8 g, pH 7, room temperature, irradiation time 240 min followed by 30 min in dark. All the samples were collected at different time intervals of 30, 60, 90, 120, 150, 180, 210, 240 min for the analysis of COD degradation and color removal. The best performances was achieved using high pressure UVphotocatalytic reactor using TiO2. The successful result obtained using TiO2is 80% COD degradation and 99% color removal followed by 75% COD and 99% color removal with ZnO. Chemical kinetics was found to follow first order mechanism. The formation of intermediate compounds and identification of the final products were carried out using LCMS/MS analysis and FT-IR techniques.

1. http://www.iaeme.com/IJARET/index.asp 8 editor@iaeme.com
International Journal of Advanced Research in Engineering and Technology (IJARET)
Volume 8, Issue 1, January- February 2017, pp. 8–16, Article ID: IJARET_08_01_002
Available online at http://www.iaeme.com/IJARET/issues.asp?JType=IJARET&VType=8&IType=1
ISSN Print: 0976-6480 and ISSN Online: 0976-6499
© IAEME Publication
PHOTOCATALYTIC DEGRADATION OF RB21 DYE BY
TIO2 AND ZNO UNDER NATURAL SUNLIGHT,
MICROWAVE IRRADIATION AND UV-REACTOR
Julie M Pardiwala, Femina J Patel and Sanjay S Patel
Department of Chemical Engineering, Institute of Technology
Nirma University, Ahmedabad, 382481, Gujarat, INDIA
ABSTRACT
The present work aims to degrade the RB21 dye from synthetic wastewater using
semiconductors TiO2 and ZnO. The activity of photocatalytic degradation process of dye was
carried out using different light sources of 900 W/m2
intensity in natural sunlight from 02:00 to
04:00 pm with 48°C temperature in Ahmedabad city in the month of May, 600 Watt microwave
oven and high pressure UV-light photocatalytic reactor of wavelength 200-450 nm. All the
experiments were performed with dye concentration 50 mg/L, catalyst dosage 0.8 g, pH 7, room
temperature, irradiation time 240 min followed by 30 min in dark. All the samples were collected at
different time intervals of 30, 60, 90, 120, 150, 180, 210, 240 min for the analysis of COD
degradation and color removal. The best performances was achieved using high pressure UV-
photocatalytic reactor using TiO2. The successful result obtained using TiO2is 80% COD
degradation and 99% color removal followed by 75% COD and 99% color removal with ZnO.
Chemical kinetics was found to follow first order mechanism. The formation of intermediate
compounds and identification of the final products were carried out using LCMS/MS analysis and
FT-IR techniques.
Key words: Chemical Oxygen Demand, Microwave, Natural Sunlight, Photocatalytic Reactor,
Reactive Turquoise Blue.
Cite this Article: Julie M Pardiwala, Femina J Patel and Sanjay S Patel, Photocatalytic
Degradation of Rb21 Dye By Tio2 And Znounder Natural Sunlight, Microwave Irradiation and
UV-Reactor. International Journal of Advanced Research in Engineering and Technology, 8(1),
2017, pp 01–07.
http://www.iaeme.com/IJARET/issues.asp?JType=IJARET&VType=8&IType=1
1. INTRODUCTION
Huge amount of industrial effluent being discharged into the environment have made the environment
legislation stringent [1]. Industries such as plastics, paper, dyestuffs, textile use dyes to color their products
consuming large amount of the water [2]. Effluent from the textile industry comprises of complex mixture
of many polluting dyes [3]. Characteristics of this wastewater depend on high values of COD, BOD, color
and pH etc[4].The Ecological and Toxicological Association of the Dyestuff Manufacturing Industry
(ETAD) have reported that the highest rates of toxicity (LD50) among all dyes were found inazo dyes [5].
The presence of acute and chronic color of dye obstructs the absorption of solar radiation decreasing
photosynthetic activity and cause changes in ecosystem [6]. Dyes having chromophores and auxochromes

2. Photocatalytic Degradation of Rb21 Dye By Tio2 And Znounder Natural Sunlight, Microwave Irradiation and UV-
Reactor
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groups and classified as reactive, metal complex, acid, direct, basic, disperse, pigment, mordant, vat,
sulphur, anionic etc[7]. Reactive dyes present beyond discharge limits waste streams is one of the issues
for textile industries [1]. Important reactive dye used in textile are copper phtalocyanine dyes with metallic
complexes used to produce blue-green shades having toxicity of metal Cu content [6]. For oxidation and
reduction of water the photocatalystTiO2 is widely used compared to the other semiconductor due to its
stability, nontoxic and inexpensive,[8, 9]. This TiO2 in (anatase, rutile or brookite phase) doped, loaded
with transition or rare earth metal species is used for various treatment of dyes [10, 11]. The band-gap
analysis of TiO2 under visible light occupies <50% of the irradiation coming from the sun while ultraviolet
occupies <10% with band gap (3.03 eV rutile, 3.18 eV anatase) and ZnO (3.2 eV) [12,1 3].The TiO2 as
photocatalysis has received more attention in the environmental sector due to its excellent chemical and
good photoelectron chemical properties such as TiO2/UV [5]. Whereas azo reactive dyes is decoloured
using advanced oxidation processes like O3/UV, H2O2/UV, TiO2/UV etc been described by many authors
[14].The different methods used for wastewater treatment are chemical oxidation, advanced oxidation
processes, hydrogen peroxide, ozone/UV, hydrogen peroxide/UV, Fenton reagent, sonolysis, precipitation,
flotation, ion exchange, adsorption, photocatalytic and biological treatment etc[15, 7, 5]. The
photocatalytic activity lowers the expected attribution to enhance an unknown “recombination sites” but
when the activity is higher suppressed recombination of e-
and h+
for experimental results [16]. An interest
in photocatalysis has increased using semiconductor materials for the removal of organic and inorganic
species from environment [17]. This paper discuss about the performance of semiconductor under different
light sources for the degradation of RB21 dye. The TiO2giving promising results have been characterized
and also kinetic study was carried out in terms of %COD degradation.
EXPERIMENTAL STUDY
2.1. Chemicals and instruments
The chemicals used in the experiments were of analytical grade. The commercial grade reactive turquoise
blue dye (RB21) with molecular weight=1390 g/mol, was generously provided by International Welspun
India Ltd. All the chemicals and dye used as-it-was purchased in the experiments without any purification.
The UV-photocatalytic reactor for degradation of RB21 dye was designed and purchased from Lelesil
innovative system India Ltd, Mumbai.
2.1.1.Characterization
Characterizations were carried out using Fourier transform infrared spectroscopy (FTIR) recorded spectra
with Perkin Elmer (G-FTIR). To find out the intermediate products formed after degradation and to
identify the compound LCMSMS analysis of degraded samples was carried out using LC Waters. For
LCMS/MS both treated and untreated samples were characterized. The (APHA, 2005) Hach (DBR 200,
USA) COD test kit was used with standard method 5220B in APHA, 2005 for COD measurement. For
color removal UV-visible Spectrophotometer (UV-1800, Shimadzu, Japan) with the wavelength range of
200-800 nm was used. All the collected samples after specific time intervals were characterized using
COD analyser for COD degradation in wastewater and color removal in the form of absorbancesin UV-
visible spectro photometer atλmax= 620nm wavelength. The absorbance obtained by UV-visible
spectrophotometer were in the form of concentration of dye which further calculated with the help of
standard calibration curve prepared using different concentration of dye.
2.2. Photocatalytic activity
Under different light sources semiconductor under gophotoexcitation due TiO2 surface attack from the
holes generate the favourable electrostatic interactions with electron transfer or by formation of free
radicals especially •OH oxidize the organic molecules in solution [11]. As shown in Fig. 1. experiments
were conducted to know the activity of TiO2 and ZnO for the degradation of RB21 dye. All the
experiments were carried out at room temperature with operating parameters such as pH=neutral, catalyst

3. Julie M Pardiwala, Femina J Patel and Sanjay S Patel
http://www.iaeme.com/IJARET/index.asp 10 editor@iaeme.com
dosage 0.8 g, dye concentration 50 mg/L, 500 mL solution, irradiation time of 240 min followed by 30 min
in dark, continuous stirring, speed of stirrer was kept 550 rpm. The solutions were drawn with constant
time intervals of 30, 60, 90, 120, 150, 180, 210, 240 min. The collected samples were monitored using UV-
visible spectrophotometer and COD analyser. The color removal of RB21 dye was carried out at λmax=620
nm wavelength by full scanning from 200-800 nm range which is in terms of absorbances. Fig. 2. shows
the decrease in the absorbances of dye from initial, dark and finally to 240 min shows -N=N- bond of dye
gets disappeared. The blue color of RB21 dye at initial stage is dark then gradually decreases as
absorbances decreases by giving irradiation of UV light in the experiment. The percentage color removal
calculated by A0-At/A0 *100, where A0=initial absorbances of dye, At= final absorbances of dye with
respect to time. In order to determine COD the standard close reflux method of APHA is followed also
revealed by Balamurugan B et al., 2012. The percentage COD degradation calculated by COD0-
CODt/COD0 *100, where COD0=initial COD of dye, CODt= final COD of dye with respect to time. The
catalyst also plays terminator role for the radicles to form but increase in catalyst loading leds to
destruction of radicles so the catalyst dosage is the important parameter [1]. The same procedure was
followed using ZnOunder high pressure UV-Photocatalytic reactor. The sample was also tested in natural
sunlight under 900 W/m2
intensity under natural sunlight from 02:00 to 04:00 pm with 48 °C temperature
in Ahmedabad city in the month of May. Table 1 shows color removal and COD degradation of RB21 dye
using TiO2 and ZnO under different light sources.
Figure 1Experimental set-up of photocatalytic degradation of RB21 dye using different light sources: (a) UV-light
photocatalytic reactor, (b) natural sunlight, (c) microwave oven
Figure 2Change in absorbances of 50 mg/L of RB21 dye in 0.8 g TiO2 under UV-Photocatalytic reactor

4. Photocatalytic Degradation of Rb21 Dye By Tio2 And Znounder Natural Sunlight, Microwave Irradiation and UV-
Reactor
http://www.iaeme.com/IJARET/index.asp 11 editor@iaeme.com
Table 1Comparison of RB21dye degradation using different light sources
Catalyst Light source
%COD
degradation
%Color
removal
TiO2 UV-light reactor 80 99
TiO2 Natural sunlight 50 96
TiO2 Microwave No effect No effect
ZnO UV-light reactor 75 99
ZnO Natural sunlight 70 90
ZnO Microwave No effect No effect
Figure 3COD degradation from RB21 dye using TiO2 and ZnO under different light sources

5. Julie M Pardiwala, Femina J Patel and Sanjay S Patel
http://www.iaeme.com/IJARET/index.asp 12 editor@iaeme.com
Figure 4Color removal from RB21 dye using TiO2 and ZnO under different light sources
3. RESULTS AND DISCUSSION
3.1. Fourier transform infrared (FT-IR)
Fig. 5.shows FTIR spectra which recorded in the range of 4000-400 cm-1
. The RB21 initial dye without
any treatment with large number of functional groups present can be seen. After degradation of RB21 dye
using TiO2 and ZnO almost all strong functional groups disappears leaving weak bonds. Dye gets degraded
under high pressure UV-light photocatalytic reactor completely compared to other light sources. The band
at 450-500 cm-1
is due to the TiO2 and ZnO presences. The amine group falling in the range of 1639-1612
cm-1
. The slight banding of the band 3400 cm-1
is due to presences of free hydroxyl group [1, 7]. The band
1085 cm-1
supports the metals present in dye. Rest all the bends shows some small intermediate functional
groups yet to be degraded.

6. Photocatalytic Degradation of Rb21 Dye By Tio2 And Znounder Natural Sunlight, Microwave Irradiation and UV-
Reactor
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Figure 5FTIR spectrum of RB21 dye without treatment and with treatment using TiO2 and ZnO
3.2. Liquid chromatogram and mass analysis (LCMS/MS)
Fig. 6. (a) shows liquid chromatogram without degradation and with degraded samples. Before degradation
the chromatogram shows peak at RT=0.21, 0.52, 2.54 which gets degraded completely. In the Fig. 6 (a)
after 240 min dye gets degraded completely and disappearance of the main peak can be observed. This leds
to conclusion that harmless intermediates are formed after breaking the main bonds of the dye which can
be identified by mass. Fig. 6. (b) shows liquid chromatograph and formation of mass of RB21 without
treatment and with treatment samples. In the fresh sample of fresh dye which is without treatment gave a
main signal peak m/z= 229.3, 231.0, 233.6, 351.3, 563.3, 752.3 etc of RB21 dye increasing the COD level
of the wastewater. After 240 min of dye degradation the signals at m/z=651.2, 545.2 are the only mass
obtained, this result can be compared with80% COD degradation in the activity part. The disappearances
of the main signals and appearances of new signal leds to breakdown of the RB21 dye compounds and
formation of new intermediate products. Reactive RB21 dye having Copper phthalocyanine ring present in
the dye which is metal having strong bond and very stable compound and difficult to degrade. Some bonds
are still remaining after degradation were identified. In break-down of dye according to literature dye gets
degraded and forms the new intermediate products conforms the degradation of dye [15].From the Scheme
1 the intermediate compounds formed and was identified after degradation under UV-light photocatalytic
reactor are shown. The compound identified at the main signal peak m/z= 651.2 is 5-[2-({3-[2-(4-
chlorophenyl) acetamido] phenyl} sulfanyl)-2-phenylacetamido]-4-cyano-3-methyl-N-phenylthiophene-2-
carboxamide and some other harmless compounds in very small proportion. In RB21 dye with metal
complex Cu2+
the major product formed after degradation involving cleavage of nitrogen bonds of dye as
stated by Maria Cristina Silva et al., 2012 was not observed in our result as dye is completely degraded.

7. Julie M Pardiwala, Femina J Patel and Sanjay S Patel
http://www.iaeme.com/IJARET
Figure 6 (a) Liquid chromatogram,
Scheme
3.3. Kinetic study
From Fig. 7. kinetic study data shows the first order reaction mechanism
straight line with value of R2
=0.9662 in
photocatalytic reactor.The value of
concentration, t=0, Ct =concentration of RB21 at reaction time (t) [12].
Figure 7First order
Julie M Pardiwala, Femina J Patel and Sanjay S Patel
IJARET/index.asp 14
Liquid chromatogram, (b) Liquid chromatograph and formation of mass
Scheme 1 Intermediate products identification
From Fig. 7. kinetic study data shows the first order reaction mechanism which is infered
=0.9662 in terms of COD degradation of dye using TiO
value of k= 0.0075 –lnC/C0, where k=reaction rate constant, C
=concentration of RB21 at reaction time (t) [12].
First order kinetic study using TiO2 in UV-Photocatalytic reactor
editor@iaeme.com
Liquid chromatograph and formation of mass
which is infered by fitting the
of dye using TiO2 under UV-light
here k=reaction rate constant, C0=initial
Photocatalytic reactor

8. Photocatalytic Degradation of Rb21 Dye By Tio2 And Znounder Natural Sunlight, Microwave Irradiation and UV-
Reactor
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4. CONCLUSION
Photocatalytic degradation activity were successfully carried out using semiconductors as a photocatalyst.
The efforts to obtain valid light source for semiconductors TiO2 that degrade RB21 dye from wastewater.
The successful result obtained using TiO2 is 80% COD degradation and 99% color removal. The TiO2
having some drawbacks like small amount of photons absorbed in the visible region and electron–hole
recombination rate, thus it works in UV range only. The kinetic study shows the first order reaction
mechanism.
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