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Optik 160 (2018) 371–379

Contents lists available at ScienceDirect

Optik

j ourna l ho me pa ge: www.elsev ier .de / i j leo

riginal research article

hotocatalytic degradation of Alizarin Red dye under visibleight using ZnO & CdO nanomaterial

.B. Bharti a,∗, A.V. Bharatib,∗∗

Shri Ramdeobaba College of Engineering and Management & J D College of Engineering and Management, Nagpur IndiaShri Ramdeobaba College of Engineering and Management, Nagpur India

r t i c l e i n f o

rticle history:eceived 8 January 2018ccepted 30 January 2018

eywords:nO nanoparticlesdO nanoparticlesydrothermal methodicrowave-assisted method

lizarin Red dyeinetic analysis

a b s t r a c t

ZnO, CdO nanomaterial were utilized for the degradation of Alizarin Red dye photocatalyti-cally under visible light illumination. Zno photocatalyst was prepared by the hydrothermalmethod at a temperature of 160 ◦C and CdO synthesized by the microwave-assistedhydrothermal method at a temperature of 140 ◦C.Synthesized nanomaterial was charac-terized by XRD, SEM, TEM, UV–vis spectroscopy and PL. The photocatalytic degradation ofAlizarin Red (AR) dye was carried out utilizing prepared photocatalyst irradiated with 60 WTungsten light source with the fixed dose of catalyst on standard AR dye and studied itsKinetic analysis of photodegradation on Alizarin Red dye and conclude the efficiency of ZnOand CdO nano photocatalyst at the same condition.

© 2018 Elsevier GmbH. All rights reserved.

. Introduction

Over so many decades dyes has been prepared and used. In ancient time dyes are prepared from the natural source andegraded naturally but after industrialization, so many organic dyes synthesized artificially because of much more demand

n textile, leather, paper, paint and other industries. All over world approximately 7 × 105 tons of dye and pigments areroduced and have thousands of varieties. During the process of dyeing 20–25% dye of worldwide production is readilyeleased in the form of industrial effluent and today’s most threatening part due to which environmental pollution occurredn wastewater which was most probably released from textile and other industries. [1,2]. Without dye textile industriesxistence in doubt i.e. dye vs. textile industry. Most worried part of the organic dye is modern dyes are more stable for theuality reason of dyeing i.e. resistant chemically and biological and to light-induced fading. Now this one causes big trouble

n the form wastewater which causes environmental pollution. Therefore, the new method for treatment of dyes, whichhould be easier and cheaper with higher efficiency, is necessary. Recently AOP and photocatalysts which employs suitableemiconductor with visible light as a promising destructive technology leading to complete removal of pollutants basicallyye, pigments etc. [3–5]. Photocatalytic nanomaterial with narrow band gap energy is suitable for photodegradation of dye.

As wide band gap is decreases called as semiconductors and it will absorb energy of certain wavelength due to whichlectrons from valence band promotes to the conduction band, leaves the hole in valence band and electron in conductionand called as the photogenerated electron-hole pair. This electron and hole promotes reduction and oxidation of dyehenever adsorbed at the surface of photocatalyst showing semiconducting behavior and shows oxidative degradation

∗ Corresponding author.∗∗ Corresponding author.

E-mail address: datta bharti@rediffmail.com (D.B. Bharti).

https://doi.org/10.1016/j.ijleo.2018.01.122030-4026/© 2018 Elsevier GmbH. All rights reserved.

372 D.B. Bharti, A.V. Bharati / Optik 160 (2018) 371–379

Fig. 1. Structure of Alizarin Red S(C14H6Na2O7S).

of dye via radical mechanism The absorption of energy of certain wavelengths by a semiconductor [6,7] & Photocatalyticdegradation of Alizarin Red dye using semiconductor such as ZnO and CdO is simple and effective and clean technologyand applied for industrial post production wastewater treatment with minimum dose has attract more attention [8,9]. Thistechnique is popularized because it shows an ability completely degradation of organic dye into the water and carbon dioxideand minimal and or no any harmful by-products i.e. water purifier [10–12]. ZnO and CdO nanomaterials semiconductor ismost favored material in this technique and as particle size decreases surface area increased also shows some interestingresults. This photodegradation technique for removal of Alizarin Red dye and its mechanism shown in many kinds of literature[13–18]. Alizarin Red dye selected as the standard dye for this study for coming to conclusion because it is water soluble andwidely used as a coloring agent in the industry such as leather, fiber, textiles etc. [19–21]. The chemical structure of selectedalizarin red dye Fig. 1.

This study was conducted with the aim and objective of synthesis of ZnO and CdO photocatalysts nanomaterial byhydrothermal and microwave assisted method and estimated the photocatalytic degradation of Alizarin Red dye undervisible light with fixed dose catalysts on same dye concentration to compare.

2. Materials and experiment

2.1. Material for synthesis of ZnO and CdO

a) For ZnO nonmaterial synthesisZinc acetate [Zn(CH3COO)2], Urea ((NH2)2CO), Cyclohexane (C6H12), Tertiary Butyl Alcohol (C4H9OH), cetyl trimethy-

lammonium bromide (CTAB), ethanol and deionised water.b) For CdO nanomaterial synthesisCadmium oxlate [Cd(C2O4), Urea [(NH2)2CO], Cyclohexane (C6H12), Tertiary Butyl Alcohol (C4H9OH), cetyl trimethylam-

monium bromide (CTAB), ethanol and deionised water All reagents used without further purification.

2.2. Synthesis of ZnO naomaterial

Hydrothermal synthesis of ZnO already discuss but it will further analyzed and compaired [22] Firstly, take 3 gcetyltrimethylammonium bromide (CTAB) and 1.8 g of urea and dissolved in 150 ml of deionized water and stirred for15 min to this add 50 ml cyclohexane and 6 ml t-butyl alcohol again stirred for 5 min. After 5 min, 0.5 mmol Zn(OAc)2 wasadded dropwise prepared in 25 ml distilled water. This mixture was transferred to a hydrothermal reactor and heated at180 ◦C for 16 h, then cooled to room temperature and washed several times with distilled water and ethanol and calcinatedat 200 ◦C for 2 h and collected air dried.

2.3. Synthesis of CdO nanomaterial

The nanosize CdO particles were grown using microwave-assisted reactor. Aqueous solutions of cadmium oxalate[CdC2O4] and urea [CO(NH2)2] were used as sources of Cd2+ and O2− ions, respectively. Firstly, prepare 5 ml of 0.5 mmolcadmium sulfate in the beakers. An appropriate amount of 0.104 g CTAB was then added with continuous stirring to the500 ml round bottom flask containing 100 ml millipore water. After stirring for 15 min, 5 ml of 5 mmol urea was addeddropwise to the round bottom flask to this adds 25 ml cyclohexane and 4 ml t-butyl alcohol and again stir for 5 min. After,5ml of 0.5 mmol cadmium sulfate was added dropwise to round bottom flask and stir for 30 min. After half an hour transfer

inside a microwave oven. The deposition was performed at 150 ◦C for 10 min under microwave irradiation. The samples werewashed with deionized water & ethanol to collect cadmium hydroxide [Cd(OH)2] on calcination at 300 ◦C for 2 h, finally,collect Cadmium oxide (CdO) nanoparticles.

D.B. Bharti, A.V. Bharati / Optik 160 (2018) 371–379 373

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Fig. 2. Showing XRD pattern of ZnO and CdO.

.4. Characterization of ZnO and CdO

Synthesized material characterized by X-ray diffraction technique recorded the phase formation of the all the materialsy using Rigaku miniflex II X-Ray diffractometer with CuK� radiation using CuKa radiation with X = 1.54 Å over the rangef 30–90◦. The surface morphology of ZnO and CdO particles were studied by Scanning Electron Microscope (JEOL JSM-600F) at various magnifications. The morphologies of the samples were observed using transmission electron microscopyTEM Model: CM 200) IIT BOMBAY SAIF, Mumbai (India), operating at 200 kV equipped with a field emission source. UV–visbsorption spectra were recorded on Perkin Elmer spectrophotometer (Lambda-25) in the range of 180–800 nm. Photolu-inescence analysis (PL) was carried out on Hitachi F- 7000 fluorescence spectrophotometer over the range of 180–800 nm

rom Amravati University of the synthesized ZnO & CdO nanoparticles.

. Photodegradation process and analysis

The photocatalytic reactions were carried out in a Pyrex glass round bottom flask with tap (250 cm3). This arrangementrovides a Circular irradiation source of tungsten filament lamp 60 W scattered in all direction. At the middle of reactortand with the clamp to hold glass round bottom flask with tap situated upon the magnetic stirrer. The heat generated byhe lamp measured by thermometer at an initial stage to the time of sample collection.

The experiments were carried out with 100 ml Alizarin red dye solutions prepared in appropriate concentrations usingeionized water. Prior illumination of the result might have been obtained after continuous stirring with the help of elec-rically operated magnetic stirrer at 400–600 rpm for 30 min to guarantee adsorption equilibrium between the AR solutionnd catalyst. During the experiments, 5 ml about over result might have been taken out toward separate duration of theime intervals also filtered and the absorbance about response result might have been measured by a UV-1800 (Shimadzu)pectrophotometer in the range wavelength extent from 200 nm to 650 and decolorization, defined as

%Degradation = (C0 − C × 100)/C0 (1)

here C0 is the initial Alizarin Red dye concentration at �max = 424 nm.C is concentration at different interval of time in min.In photocatalytic degradation of Alizarin red dye process analysis, base values of the process are set up as: Catalyst loading:

0 mg, Dye concentration = approx. 10 mg/l, light intensity = 60 W, �max = 424 nm at pH = 7, illumination time = 75 min.

. Result and discussion

.1. ZnO and CdO nanoparticle characterization analysis

The XRD pattern of ZnO and CdO obtained is shown in Fig. 2. XRD pattern shows sharp and well-defined peaks indicatehe crystalline nature of ZnO and CdO. IT shows strong diffraction peaks for ZnO at 2� values of 30.9◦, 33.7◦, 35.48◦, 46.7◦,5.8◦, 62.24◦, 71.68 and 76.26◦ matching the cubic ZnO (JSPDS card No. 75-1533) and for CdO at2� values of 32.69◦, 39.41◦,7.41◦, 67.72◦ & 32.72◦, 39.90◦, 57.66◦, 67.98◦ respectively matching the cubic CdO, (COD CIF File card No. 00-101-1003). No

ther impurity peaks were detected indicating that the obtained CdO was phase pure. The average particle size of ZnO, CdOas calculated using Debye-Scherrer equation (Eq. (2)) (Klug & Alexander, 1974) [23].

d = k�/�Cos� (2)

374 D.B. Bharti, A.V. Bharati / Optik 160 (2018) 371–379

Fig. 3. Showing UV–vis spectra of ZnO and CdO.

Fig. 4. Showing Band gap of ZnO and CdO.

Where d is the average particle size of the bulk material, � is the wavelength in nm, � is the width of the XRD peak athalf maxima, k is the factor which is approximated as 0.89, and � is the diffraction angle. The calculated average particlesize of cadmium oxide nanoparticles was found to be 15.8 & 138.4 nm. UV–vis absorption spectra show absorption atwavelength 390 nm which is in the visible region i.e in the broad region of visible light in Fig. 3. The band gap of ZnO and CdOnanoparticles was estimated by plotting the (�h�])2 versus h� (eV) as shown in the Fig. 4.The band gap energy of ZnO andCdO nanoparticle was found to be 2.49 eV & 2.0 eV respectively. The value of particle size and the band gap of ZnO clearlyshows that this nanomaterial is applied in photocatalytic activities and optical devices.

An SEM and TEM spectroscopic image shows the morphology and structural features of ZnO & CdO nanoparticles. TheSEM image Fig. 5 shows cuboid and spherical nature of ZnO and cuboid structure of CdO shaped morphology. TEM imageFig. 5 of ZnO & CdO shows particles with a spherical and cubic shape. The larger particles present are due to aggregation orthe overlapping of small particles and porous in nature. The average particle diameter of 25 nm for ZnO and 50–130 nm forCdO was determined and the average particle size from TEM is consistent with values obtained by XRD Fig. 2.

PL spectra were measured by using spectrofluorometer with an excitation wavelength of 378 nm and 430 nm at roomtemperature for ZnO and CdO respectively. Shows the room-temperature PL spectra of the synthesized ZnO and CdO nano-material in Fig. 6.The spectra consist of a sharp and strong emission band at around 378 nm and a weak and broad emissionband centered at 430–520 nm for ZnO and sharp and strong emission band at around 488 nm and a weak and broad emis-sion band centered at 606 nm for CdO nanoparticles. The green emission at around 515 nm for ZnO and Orange emission at598–606 nm for CdO are related to the singly ionized oxygen vacancy and this emission results from the recombination ofa photogenerated hole with a singly ionized charge state of the specific defect.

4.2. Photocatalytic degradation of Alizarin Red dye and kinetic study

In this experiment of photodegradation Alizarin Red dye studied with ZnO and CdO nanoparticles with the requisite10 mg dose of the catalyst with approximate 10 mg/l dye concentration at ph = 7. During this analysis first standard dyesolution of 20 mg is used for calibration shown in Fig. 7 at �max = 424 nm and rate constant K = 0.182and 0.114 min−1 andR2 = 0.830 and 0.809 for ZnO and CdO respectively.

Fig. 8 shows the photodegradation of alizarin red dye with small dose so that to find out the trace of pollutants remove

effectively. During this experiment Alizarin red dye, degradation studied over 75 min interval of time with 15 min differenceand it has been observed that at initial stage rapid decolorization take place due to the available active surface area of thecatalyst but as the end, it slows down because degradation of intermediate takes place slowly.

D.B. Bharti, A.V. Bharati / Optik 160 (2018) 371–379 375

Fig. 5. Showing SEM and TEM of ZnO & CdO.

Fig. 6. Showing Photoluminescence spectra of ZnO and CdO.

376 D.B. Bharti, A.V. Bharati / Optik 160 (2018) 371–379

Fig. 7. Absorbance verses wavelength of 20 mg/l Alizarin Red.

Fig. 8. UV–vis absorption spectra of the photocatalytic decolorization of Alizarin Red by ZnO & CdO nanoparticles.

Fig. 9. Degradation vs. time of AR with ZnO & CdO nanoparticles as a catalyst.

Kinetic study of photodegradation of Alizarin in presence of ZnO and CdO nanoparticles shows that ZnO is shown inFig. 12 more better result as compare to CdO because of reduced particle size and spherical morphology and observed %

degradation are 92% and 80% respectively and after completion of reaction catalyst recollected to recycle and that’s whyphotodegradation is the greener pathway. From the Figs. 9–11 it is clear that as time interval increase concentration decreasewith the first-order rate of reaction.

D.B. Bharti, A.V. Bharati / Optik 160 (2018) 371–379 377

Fig. 10. Concentration of AR vs. time with ZnO & CdO nanoparticles as a catalyst.

Fig. 11. Log[AR] vs. time ZnO, CdO nanoparticles as a catalyst.

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Fig. 12. C/Co of AR vs. time (min) with ZnO & CdO nanoparticles as a catalyst.

At an initial stage of analysis few parameters are fixed such as the concentration of dye, dose of catalyst and pH = 7ecause all these three factors play an important role during degradation of dye by hydroxide radical production and it haseen observed that at ph = 7 and 10 mg/l concentration of dye with 10 mg dose of catalyst get the best result [24] shows inigs. 13–15 with the approximate temperature = 40 ± 5 ◦C.

. Conclusion

In this study, Characterisation and photocatalytic decolorization of an Alizarin red dye has been investigated using ZnOnd CdO nanocatalyst. The particle sizes of synthesized material are nano with somewhat porous in nature and sphericalnd cubic shape of ZnO and CdO respectively by SEM & TEM analysis. From band gap study it has been observed that this

378 D.B. Bharti, A.V. Bharati / Optik 160 (2018) 371–379

Fig. 13. Showing the effect of Alizarin Red dye concentration on ZnO & 3CdO = 10 mg/100 ml, pH = 7, Illumination time = 75 min, temperature = 40 ± 5 ◦C.

Fig. 14. Showing the effect of dose of ZnO & 3CdO = 10 mg/100 ml, pH = 7, Illumination time = 75 min, temperature = 40 ± 5 ◦C on Alizarin Red dye.

Fig. 15. Showing the effect of pH on [AR] = 10mg/l, ZnO & 3CdO = 10 mg/100 ml, Illumination time = 75 min, temperature = 40 ± 5 ◦C.

material utilized for visible light irradiation and confirmed by PL. Dye concentration decreases as time increase i.e. inversely

proportional. It has been observed that surface area and morphology play an important role in the degradation of dye asall other parameters are same. �max is 424 nm i.e. in visible region and decolonization is faster in visible light due to themodulated band gap of ZnO and CdO in the degradation process at neutral pH with the minimal dose of the catalyst.

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