CHAPTER-3
MATERIAL AND METHODOLOGY3.1.
Material
All the chemicals used in this study were of analytical grade and used without further
purification. Zinc nitrate hexahydrated [Zn(NO3)2.6H2O], sodium hydroxide NaOH, sodium
tungstate hexahydrated Na2(WO4).6H2O, ethanol, methyl orange dye all were provided by
department of basic sciences, chemistry research lab at Shoolini University Solan, which
were used in this study. All aqueous solutions were prepared in double distilled water.
3.2. Apparatus
Beakers (50 ml and 200 ml), test tubes (10 ml), flasks (250 ml), filter paper, discs, micro
pipette, measuring cylinder, glass rod, Centrifuge machine, muffle furnace and u.v visible
spectrophotometer
3.3. Preparation of solution
Methyl orange 5×10-3 M: Stock solution of methyl orange was prepared by adding 0.16 g of
methyl orange in 250 ml of double distilled water. Working solutions were prepared
appropriate dilution of the stock solution.
3.4. Preparation of reagent solutions
HCl, 1 M: The solution was prepared by dissolving 4.3 ml HCl in distilled water and the
final volume was made to 50 ml.
NaOH, 1 M: The solution was prepared by dissolving 2 g NaOH in distilled water and the
final volume was made to 50 ml.
3.5. Preparation of (ZnO/ZnWO4/AC) nanocomposite
Synthesis of ZnO/ZnWO4/AC nanocomposite
In a typical procedure, 0.1 M aqueous solution of zinc nitrate [Zn(NO3)2.6H2O] was prepared
by dissolving 1.4 g of [Zn(NO3)2.6H2O] in 50 ml double distilled water. Then in another
beaker 50 ml of 0.5 M solution of NaOH was also prepared. To the zinc nitrate solution, 0.5
M sodium hydroxide was added dropwise with continuous stirring. The obtained solution was
lablled as solution A.
In the next step 0.1 M aqueous solution of zinc nitrate [Zn(NO3)2.6H2O] was prepared. Then
0.1 M aqueous solution of [Na2(WO4)2H2O] was also prepared by dissolving 1.6 g in 50 ml
water in an another beaker. To the solution, zinc nitrate was added dropwise and stirred
continuously for about 45 min, the obtained solution was lablled as solution B.
Now solutions A and B were mixed and stirred for 30 min. To the mixture, 1.5 g activated
carbon was added and the obtained solution was continued with stirring for next 30 min.
Then the mixture was sonicated for 20 min and precipitates were filtered and washed with
absolute ethanol and distilled water. The obtained precipitates were heated in muffle furnace
at 200 0C for 1 h and then preserved for further use.
3.6. Photocatalytic experiment
The photocatalytic activity of synthesized ZnO/ZnWO4/AC composite was explored for
degradation of methyl orange dye. Photocatalytic experiments were carried in a set of five
borosilicate beakers. Total volume of the reaction mixture was always kept to 50 ml. Prior to
photocatalytic studies, suspension composed of dye and ZnO/ZnWO4/AC composite was
stirred. Then suspension was exposed to solar light. At specific time intervals, aliquot (2 ml)
was withdrawn. The concentration of methyl orange dye in suspension was determined on
uv-vis spectrophotometer at 460 nm. The degradation percentage was calculated by equation1
A0-At
Degradation (%) =
x 100
(1)
A0
Where A0 is the initial absorbance of methyl orange dye and A t is absorbance of dye after
time t (min).
3.7. Characterization techniques
3.7.1. X-ray diffraction analysis (XRD)
It is a rapid analytical technique that tells us about the crystallinity of the material and its
quantitative analysis. It reveals detailed information about the chemical composition of the
natural and manufactured materials and is primarily used for phase identification of a
crystalline material. The phase compositions of the nanoparticles were determined by using
x-ray diffractometer using CuKα radiation. Particle size analysis of synthesized nanoparticles
was done using Debye-Scherer relation (Klug et al., 1974 and B.D Cullity 1956).
D=
Kλ
β Cos θ
(2)
Where D is the crystallite size, λ is wavelength, K is constant having value 0.9 and β is the
full width at half maximum (FWHM) and θ is the Bragg’s angle of diffraction.
3.7.2. Fourier transform infrared spectroscopy (FTIR)
FTIR analysis was carried in the wave number range 400 cm-1 to 4000 cm-1 using infrared
spectrophotometer. FTIR spectroscopy can be used to identify the structure of unknown
composition or its chemical group and intensity of the absorption spectra associated with
molecular composition or content of the chemical group.
3.7.3. Transmission electron microscopy (TEM)
TEM produces a high resolution, black and white image from the interaction that takes place
between prepared samples and energetic electrons in the vacuum chamber. TEM provide
topographical, morphological, compositional and crystalline information. TEM images are
able to yield information of surface features, shape, size and structure.
3.7.4. Scanning electron microscopy (SEM)
The scanning electron microscopy studies were made on scanning electron microscope with
an accelerating voltage of 20 Kv to determine the morphology of particles. It is a technique
which images a sample by scanning it using a high- energy electron beam. The electrons then
interact with atoms of the sample, thus producing signals which reveal information about the
samples composition, surface topography and other properties such as electrical conductivity.
3.7.5. Energy dispersive x-ray analysis (EDX)
EDX is an analytical technique used for the elemental analysis of a sample which utilizes Xrays that are emitted from the specimen when bombarded by the electron beam.