ZEOLITES FROM FIREWORKS ASH: SYNTHESIS AND CHARACTERIZATION THROUGH FTIR AND XRD STUDIES by ijsidonlineinfo

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									                                       S.Padmavathy et al., IJSID 2011, 1 (2), 208-215



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Research Article                                                       Available online through www.ijsidonline.info

ZEOLITES FROM FIREWORKS ASH: SYNTHESIS AND CHARACTERIZATION THROUGH
                        FTIR AND XRD STUDIES
            S. Padmavathy1, Venkataramann Sivsankar2*, Thiyagarajan Ramachandramoorthy1

           1Department      of Chemistry, Bishop Heber College (Autonomous), Tiruchirappalli – 620 017
     2Department         of Chemistry, Thiagarajar College of Engineering (Autonomous), Madurai–625 015

 Received: 21.09.2011

 Modified: 15.10.2011
                                                                         ABSTRACT
 Published: 27.10.2011
                                              Zeolites, the largest group of microporous materials, are
                                      crystalline inorganic polymers with a three-dimensional SiO4 and AlO4
 *Corresponding Author
                                      tetrahedral arrangements.           Zeolites are of considerable commercial
                                      importance in the applications ranging from water softening to catalysis
                                      in the petrochemicals industry. In the present work, the synthesis of
                                      zeolite has been attempted using fireworks ash, a waste accumulated
                                      from a fire works industry at Sivakasi in Tamil Nadu, South India. The
                                      prepared synthetic zeolite material has been characterized by FTIR and
                                      X-Ray Diffraction studies. The synthesized zeolites under hydrothermal
                                      condition exhibited about 49% crystallinity whereas those from
 Address:                             microwave irradiation had about 31% crystallinity. Further study is
 Name: Venkataramann Sivasankar
                                      envisaged to increase the crystallinity of these synthetic zeolites and
 Place:   Madurai, Tamil Nadu,
 India                                also to apply these zeolitic materials for industrial benefits.
 E-mail:
 vsivasankar@tce.edu

                                      Keywords:
                                                    INTRODUCTION

                                      Zeolite, Fireworks ash, FTIR, XRD, Crystallinity

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                                                   INTRODUCTION
          Zeolites are crystalline microporous structures with uniformly sized pores of molecular
dimensions. The cavities serve an important role because only molecules that are smaller than the pore
size can pass through the cavities. Numerous 8-ring and 10-ring zeolites with small pores have been
examined as candidates for absorbents that can be used for the separation of small molecules [1-4]. A
number of studies proposed different methods for synthesizing zeolites from flyash by hydrothermal
alkaline conversion [5-14]. The potential industrial application of the zeolitic material obtained varies as
a function of the prevalent zeolite type. The synthesis of zeolites has been improved by introducing an
alkaline fusion stage prior to the conventional synthesis [15] by applying a dry conversion system or by
applying microwaves [16] to reduce the reaction time down to 30 min. Zeolites have their applications in
oil processing and petrochemical industries, as ion exchangers, sorbents and catalysts [17]. The present
study aims at the synthesis of zeolites at a pilot plant scale from the Fireworks ash, procured from the
Fireworks industry at Sivakasi in Tamil Nadu, India.
                                           MATERIALS AND METHODS
Procurement of Fireworks ash (FWA)
          Fireworks ash, an ultimate waste material formed after the complete burning of fireworks wastes,
was procured from the dumping sites located at the proximity of the Fireworks Station at Sivakasi in
Tamil Nadu. The raw FWA was ground and sieved for the particle size of 300 µm. This sieved FWA was
calcined in a muffle furnace at a temperature of about 800 ± 10 ° C for 2 hrs. About 81% of FWA was
obtained after the calcintion process. The calcined FWA was treated with Con.HCl to increase its activity
in zeolite formation. The acid treated FWA was fused with NaOH in the following ratios 1:1(FWAZ-1),
1:3(FWAZ-2) and 1:5(FWAZ-3). Alumina was also fused with FWA and NaOH in the ratio of
0.5:1:1(FWAZ-4). The mixture was kept in a muffle furnace at a temperature between 500 and 650° C
for 1 hr followed by cooling down to room temperature. After cooling, the material was added with
distilled water (10g/100ml) and prepared in the form of slurry.                         Then the slurry was agitated
mechanically in Iodine flasks for several hours. The agitated slurry was heated at a temperature of 90-
110 °C for 6 hrs without disturbance. The resulting zeolitic material was repeatedly washed to remove
the excess NaOH till the pH of the washings reaches between 9 and 11. The material is ultimately dried in
an air oven at about 50 °C for few hours. All the other reagents were of analytical grade, having 99.9%
purity.
          The heating was also carried out in a microwave oven for the ratio of 1:1 FWA-NaOH mixture by
varying the time of irradiation from 1 to 8 min. This microwave irradiation replaces the hydrothermal
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fusion (using muffle furnace) in a view to reduce the time duration of the process. The FWA-NaOH
mixture with a ratio 1:1 after the irradiation for 2, 4, 6 and 8 minutes is shown as FWAZ-5, FWAZ-6,
FWAZ-7 and FWAZ-8 respectively.
Characterisation studies
       The synthetic zeolitic materials were characterized by FTIR and XRD studies. Powder X-ray
diffraction (XRD) patterns were recorded from X’Pert ANAlytical                 X-ray Diffractometer using Cu Kά
radiation (40 kV and 30 mA). FTIR characterization of the zeolitic material was also taken from JASCO
FT-IR 460 Plus Spectrophotometer using KBr pellet.
                                          RESULTS AND DISCUSSION
       The percentage crystallinity of FWAZ samples is ascertained by the comparison of the ratio of
intensity of the peak at 560 cm-1 to that of the peak at 464 cm-1, with the corresponding ratios for
standard zeolite – A samples reported [18]. The basis of this method has already been discussed [19]. The
crystallinity of the FWAZ samples has been proposed using the IR technique in the present study. The
impure phases associated with the synthesized zeolites have negligible influence on their proposed
applications [20]. The characterization of IR bands associated with standard zeolite is shown in Table 1.
IR spectra for the eight FWAZ samples, viz., FWA, FWAZ 1-4 and FWAZ 5-8 are shown in Fig.1 and Fig. 2.




                            Fig. 1 FTIR patterns of FWA and FWAZ 1 – 4
       The IR spectra of FWAZ-1, FWAZ-2 and FWAZ-4 have shown a sharp peak with high intensity at
1000 ± 2 cm-1. This type of strong vibration is assigned to the Si-Al-O asymmetric stretching vibration of
the FWAZ samples. It is mentioned that the wave number of this stretching vibration band decreases
with respect to an increase of Al content in the zeolite structure[21]. Hence, the shift of T-O bands to a
lower wave number indicates the incorporation of Al in the amorphous alumino silicate.

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                                 Fig. 2 FTIR patterns of FWAZ 5 – 8
      The decreasing shift of wave number is observed for FWAZ-4 sample (hydrothermal synthesis)
and the samples synthesized under microwave irradiation have the asymmetric vibrational shift to lower
wave numbers with respect to the time duration of irradiation. For the FWAZ samples (1,2 and 4), the
sharp but less intense band at 467 ± 2 cm-1 can be assigned to the Si-Al-O bending mode of vibration. For
all the FWAZ samples, the IR assignments approve that the asymmetric stretching and bending modes of
vibration is more than that of symmetric stretching mode of vibration occurring at 660 cm-1. Another
intense and sharp band occurring at 565 cm-1 is related to the presence of double ring, D4R in the
framework structure of FWAZ-1, FWAZ-2 and FWAZ-4 samples.                       The O-Si(Al)-O bending mode of
vibration is observed at 436 ± 5 cm-1 for the FWAZ(1-7) samples. The broadband observed at 3440 ± 5
cm-1 is characteristic of OH hydrogen bonded to the oxygen ion of the framework. In addition, an intense
band observed at 1641 ± 1 cm-1, is characteristic of the bending mode in the water molecule. The bands
occur near 3440 cm-1 and 1641 cm-1 for the FWAZ samples correspond to water of hydration and the
sharpness of the peaks indicate a higher percentage of water of hydration. The IR frequencies observed
for various samples are given in Table 2. From Table 2, it is seen that the remaining FWAZ samples show
the characteristic IR bands in the range discussed for FWAZ-1, FWAZ-2 and FWAZ-4 samples. The
percentage crystallinity of FWAZ samples given in Table 3 shows that the maximum crystallinity is
observed to be 49.3% for FWAZ-4 and the crystalline nature is found to increase with respect to the
addition of NaOH and Al2O3. The IR assignments of FWAZ-5, FWAZ-6, FWAZ-7 and FWAZ-8 (synthesized



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under microwave irradiation) shown that these samples were of poorly crystalline, where the
crystallinity could be observed up to about 31%.
                      Table 1 Characterization of IR bands associated with Zeolite – A
                        Type of IR band                          Frequency (cm-1)
                  Assymmetric Stretching of T-O* bond                         1000 - 1500
                   Symmetric Stretching of T-O* bond                             660
                    Bending vibration of T-O* bond                               464
                              D4R rings                                          560
                                                    T = Si or Al

              Table 2 IR frequencies for different FWAZ samples and standard zeolite –A
                                   Frequency reported in Literature (cm-1)
          Sample   Peak -1 Peak – 2 Peak – 3 Peak -4 Peak-5 Peak-6 Peak-7
                     995         465          660       560       3400     1645        437
          FWAZ -1        1002.8       465.7        619.0            563.1     3448.1        1640.1      431.0
          FWAZ -2        1000.8       468.6        729.1            565.0     3447.1        1642.1      441.6
          FWAZ -3        1004.7       465.7        710.6            594.9     3437.5        1646.9      439.7
          FWAZ -4        1003.8       467.6        724.1            558.3     3445.2        1641.1      441.6
          FWAZ -5         999.9       449.3        714.5            591.1     3435.5        1645.9      435.8
          FWAZ -6         997.0       430.1        689.4            567.9     3434.6        1644.9      430.1
          FWAZ -7         997.0       443.6        713.5            583.4     3433.6        1648.8      443.6
          FWAZ -8         996.1       456.1        715.5            597.8     3434.6        1649.8      456.1

                          Table 3 Percent Crystallinty of FWAZ Samples from FTIR
                       560 cm-1                     464 cm-1
                         Peak        Intensity         Peak       Intensity
       Sample                                                                Ratio                   Crystallinity
                       intensity        (A)         intensity        (A)
                                                                                                          %
                          %T                           %T
       Degussa           45.891           0.3383            65.68            0.1826         1.85          ---
       FWAZ -1           80.15            0.0961            42.51            0.3715         0.26         14.0
       FWAZ -2            63.4            0.1979            31.60            0.5003         0.40         21.4
       FWAZ -3           71.98            0.1428            51.83            0.2854         0.50         27.0
       FWAZ -4           69.36            0.1589            66.90            0.1743         0.91         49.3
       FWAZ -5           55.36            0.2568            35.55            0.4492         0.57         30.9
       FWAZ -6           35.19            0.4535            7.33             1.1345         0.40         21.6
       FWAZ -7           58.93            0.2297            36.67            0.4357         0.53         28.5
       FWAZ -8           60.19            0.2204            40.29            0.3947         0.56         30.2


       The XRD pattern for FWAZ, FWAZ-4 and FWAZ-6 samples is shown in Fig. 3-5. The diffraction
peak for the FWAZ-4 sample at 28.9° was exhibited, but the crystalline nature of the sample was not good
as expected. This is also supported by the intensities calculated from IR Spectral data. The FWAZ-6
samples exhibited two distinct peaks at 26.6° and 28.8° but the crystalline nature of the sample is poor
which is also witnessed by the percentage crystallinity calculation based on IR spectral data. The above
observed peaks for the FWAZ-4 and FWAZ-6 samples are in agreement with a work reported by Rayalu et
al. (2005)[19].
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                         Fig. 3 XRD pattern of Fireworks Ash (FWA)




                                Fig. 4 XRD pattern of FWAZ - 4




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                                           Fig. 5 XRD pattern of FWAZ-6

                                                     CONCLUSION
       The present attempt on synthetic zeolites on a pilot plant scale from the fireworks ash is an
opening to exploit the hidden resources of fireworks ash, which is dumped without any use. As the study
is focused to make a preliminary step in the synthesis of zeolite from FWA, some work is done by the
authors so far. The extension of the present work is also seriously envisaged with respect to synthesis
and applicability of FWA zeolites.
                                               ACKNOWLEDGEMENT
       The authors thank the Principal and Management of Thiagarajar College of Engineering
(Autonomous), Madurai – 15 for their support and encouragement.
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