E-045 (P)
The 2nd Joint International Conference on “Sustainable Energy and Environment (SEE 2006)”
21-23 November 2006, Bangkok, Thailand
Synthesis of Zeolite A from Aluminium Etching By-product
Supaporn Douglas1,*, Noppadon Cheamsawat2 and Kanokorn Hussaro3
1
Department of Chemical Engineering, King Mongkut’t University of Technology Thonburi, Bangkok, Thailand
Department of Chemical Engineering, King Mongkut’t University of Technology Thonburi, Bangkok, Thailand
3
Department of The Joint Graduate School of Energy and Environment, King Mongkut’t University of Technology Thonburi,
Bangkok, Thailand
2
Abstract: Zeolites are generally synthesized from sodium aluminosilicate gel prepared from various silica and alumina compounds.
The By-product of aluminium etching process is used in this research for producing zeolite by hydrogel process. Analysis of the
chemical composition of the raw materials and the products demonstrates that the By-product can be used to produce the high quality
of zeolite. It carries a large amount of Al2O3 content which is usable as raw materials for zeolites synthesis. Synthetic zeolites are
prepared using hydrogel process at 60-90°C for 1 h and mole ratio of reactants about 2.
Keywords: Etching Process, Aluminium Hydroxide, Zeolite
1. INTRODUCTION
Zeolites are crystalline microporous solids containing regularity of cavities, channels of molecular dimensions between 3 to 10
°A and the diverse framework Chemical compositions allow “tailoring” [1] of structure and properties, synonymously call molecular
sieves. They are different is dimensions from other adsorbent such as activated carbon, activated alumina and silica gel. The
difference is that the latter materials do not have crystal structure. Irregularity cavities and channels of other adsorbent dimensions
may be between 20 °A to 50 °A or 20 °A to 1000 °A. Zeolites also help protect the environment by reducing automobile exhaust
and other emissions, cleaning up hazardous wastes; for example; extraction of nitric oxide and nitrogen dioxide from an oxygen
carrier using molecular sieve 5A [2]. Zeolites are crystalline hydrous aluminiumsilicate of alkali and alkali earth metals i.e. sodium,
potassium, magnesium, calcium, strontium and barium, etc. The chemical formula of zeolite is Mx/n[(AlO2)x(SiO2)y] wH2O [3], where
the charge-balancing non framework cation M (alkali or alkali earth cation) has valence n, y/x ratio is 1 to 5, w is amount of molecule
water in the void. Some zeolite properties that are determined during synthesis include: structure; silica-to-alumina ratio; pore size
[4]. The principal synthetic (aluminosilicate) zeolites in commercial use are Linde Type A (LTA), Linde Types X. The unique
properties of low silica zeolites (zeolite NaA, zeolite NaX with SiO2/Al2O3 ratios ~ 2 and ~ 3 respectively) such as ion exchange
capacity, sorption and catalytic activity, make them ideal for various industrial applications [5].
Zeolite are generally synthesized from sodium aluminosilicate gel prepared from various silica and alumina [5] and some of the
factors that determine the type of synthetic zeolite produed are time of reaction, temperature, pressure, and synthesis conditions (like
the order of mixing, gel aging, and stirring) [4]. Accordingly, the by-product of aluminium etching process shall be used in this
research for producing zeolite. The etching process in the aluminium profile is the first step in aluminium profile surface treatment
prior to anodizing and colourizing. It is etched by sodium hydroxide solution which produces an aluminium hydroxide (Al(OH)3) as
by-product. The precipitate of aluminium hydroxide (Al(OH)3) is separated before the recycle of sodium hydroxide solution back to
the etching tank. It produces a low wholesale price aluminium hydroxide (Al(OH)3) normally further used for producing alum
(Al2(SO4)3). The quality of this aluminium hydroxide (Al(OH)3) is too pure to be used for alum (Al2(SO4)3) production. The process
of zeolites synthesis in this experiment showed high potential of utilizing the by-product from aluminium etching for zeolite A
production.
2. METRODOLOGY
2.1 Zeolite synthesis
The general synthesis procedure consisted of the preparation of gels with an adequate composition mixed in an
experimental stirrer tank reactor. The process involves a reaction between sodium silicate and sodium aluminate in hydrogel process.
By-product from aluminium etching process is composed of 92.17±0.03% aluminium oxide (Al2O3) and 6.03±0.3% sodium oxide
(Na2O). By-product carries a large amount of Al2O3 content which is usable as raw materials for synthesis zeolites. The main
composition of synthetic zeolites are Al and Si (shown in the chemical formula Mx/n[(AlO2)x(SiO2)y] wH2O) and it was found that the
insufficient content of Si and Na in the By-product needed to be compensated by the addition of sodium metasilicate.The by-product
was used for producing zeolite by reacting with sodium silicate and sodium hydroxide in the hydrogel process. The started mole
ratios of SiO2/ Al2O3, Na2O/SiO2, H2O/ Na2O in the mixed reactant were 2, 2 and 82 respectively. The sodiumsilicate solution was
prepared from sodium metasilicate; weight of sodium metasilicate about 42 grams dissolved in water at temperature 50 °C. Sodium
aluminate solution was prepared from By-product of aluminium etching process, with the addition of sodium hydroxide (50 %) and
distilled water. Then, the By-product about 10.4873 grams was weighted to produce the mole ratio of reactance; SiO2/Al2O3, Na2O/
Al2O3 of 2, by dissolving in 50 % NaOH 60 cm3 and diluting with water of 240 cm3 at temperature 60 °C, with 30 minute stirring.
Then, it was filtered to obtain a clear solution. The synthesis of zeolite by hydrogel process; the clear solution was mixed and reacted
with sodiumsilicate solution for 1 hr, with continuous resulting stirring for 60 min at 60-90°C. The solid samples obtained, filtered
and washed thoroughly with distilled water till the leached water pH reach 11 before drying at 110°C.
Corresponding author: [email protected]
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E-045 (P)
The 2nd Joint International Conference on “Sustainable Energy and Environment (SEE 2006)”
21-23 November 2006, Bangkok, Thailand
Table 1 Experimental design
Reactant composition (moles)
Condition
No
SiO2/Al2O3
Na2O/ Al2O3
H2O/SiO2
Time(hr)
Temperature(°C)
1
2
2
85
60
1
2
2
2
85
70
1
3
2
2
85
80
1
4
2
2
85
90
1
2.2 Characterization methods
The samples of the hydrogel process were studied and characterized for the content of elements by X-ray fluorescence
spectrometer (XRF), Philips model PW 2404. The vibration of molecule was measured by X-ray fluorescence (FTIR), Perkin Elmer.
3. RESULTS AND DISCUSSION
The chemical compositions of the synthesized zeolites are presented in Table 2. The comparison of chemical contents of the
synthesized zeolites with standard zeolite A (commercial grade from Thai Silicate Company) was studied. The chemical
compositions of the synthesized zeolites (SiO2/Al2O3 mole ratio and Na2O/ Al2O3 mole ratio) are reduced with increasing reaction
temperature.
Table 2 Chemical contents of synthetic zeolites by XRF
Mole ratio of reactance
Mole of synthetic zeolite
Reaction
SiO2
Al2O3
Na2O
SiO2/Al2O3 Na2O/ Al2O3
temperature °C
ZA∗
90
2
80
2
70
2
60
2
∗ zeolite A from Thai Silicate Company
2
2
2
2
0.6522
0.7650
0.7927
0.7742
0.7812
0.3511
0.3082
0.2975
0.2936
0.2931
0.4040
0.3623
0.3515
0.3776
0.3690
Na2O/Al2O3
SiO2/Al2O3
1.15
1.12
1.18
1.28
1.25
2.0
2.11
2.26
2.63
2.66
The presence of temperature affects the crystallization process, possibly due to higher perfection of reaction accourding to
equation (1) and (2).
Zeo ≡ SiO−Na+ + Al(OH)-4 ↔ [Zeo≡Si-O-Al(OH)3]-Na+ + OHOr
[Zeo≡Al-OH]-Na+ + -O-Si≡ ↔ [Zeo≡Al-O-Si≡]-Na+ + OH-
(1)
(2)
However, at lower temperature such as 60 °C there may be the short chain molecule of [Zeo≡Al-OH]- Na+ or Zeo ≡ SiO-Na+ which
is the molarity of the amorphous zeolite A as shown in equation (3).
Al(OH)3 + Na2SiO3
60°C ↓ NaOH
Sodium aluminosilicate (amorphous)
↓
Zeolite A
(3)
Therefore, the proper temperature required for production of zeolite was 90°C corresponding to the synthesized zeolite A at the
mole ratio of Na2O/Al2O3 of 1.12 and SiO2/Al2O3 of 2.11 which closely agree with the standard zeolite A containing the mole ratio of
Na2O/Al2O3 of 1.15 and SiO2/Al2O3 of 2.00.
The vibrations of molecule analyzed by Infrared spectrophotometer (Perkin Elmer system 2000R), Figs. 1(a-b), Figs. 2(a-c) and
Table 3 shown FT-IR spectra of the zeolite A and FT-IR spectra of the products. The absorption bands of zeolite A at 555 and
464 cm-1 were attributed to double rings and silicon, Al-O bending in the zeolite A, and those at 1003/1050/1150 cm-1 and 666 cm-1
were attributed to asymmetric and symmetric structures of the framework aluminosilicate in the zeolite A, and those at 3434 cm-1 and
1651 cm-1 were attributed to O-H stretching and O-H bending in the zeolite A respectively. The absorption bands of the products at
595/596 and 447 cm-1 were attributed to double rings and silicon, Al-O bending in the products structure, and those at
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E-045 (P)
The 2nd Joint International Conference on “Sustainable Energy and Environment (SEE 2006)”
21-23 November 2006, Bangkok, Thailand
1004/1003/1007 cm-1 and 711/712/718 cm-1 were attributed to asymmetric and symmetric structures of the framework
aluminosilicate in the products, and those at 3433/3434 cm-1 and 1649/1651/1652 cm-1 were attributed to O-H stretching and O-H
bending in the products respectively These results demonstrated that there was very similar to the bands of zeolite A, which agreed
with the XRF results.
a. ZA
b. ZA1
Fig. 1 FTIR spectra of (a) zeolite A, FTIR spectra of products, synthesis SiO2/Al2O3, Na2O/ Al2O3 ratio equal to 2 (b) at 60°C
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E-045 (P)
The 2nd Joint International Conference on “Sustainable Energy and Environment (SEE 2006)”
21-23 November 2006, Bangkok, Thailand
a. ZA2
b. ZA3
c. ZA4
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The 2nd Joint International Conference on “Sustainable Energy and Environment (SEE 2006)”
21-23 November 2006, Bangkok, Thailand
E-045 (P)
Fig. 2 FTIR spectra of products, synthesis SiO2/Al2O3, Na2O/ Al2O3 ratio equal to 2 (a) at 70°C (b) at 80°C and (c) at 90°C
Table 3 FTIR spectroscopy
reactant composition
(moles)
SiO2/
Na2O/
No
Al2O3
Al2O3
ZA
ZA1
ZA2
ZA3
ZA4
2
2
2
2
2
2
2
2
Condition
Temp.
Time
(°C)
(hr)
60
70
80
90
1
Wavenumber (cm-1)
464
447
447
447
447
555
595
596
596
595
666
712
711
718
711
1003 1050 1150
1004
1003
1003
1007
1651
1649
3434
3433
1651
34
1651 34
1652 35
4. CONCLUSION
Based on the present study, it can be concluded that the By-product of aluminium etching process can be used to produce zeolites
in hydrogel process. In the process, the reaction was between the sodiumsilicate solution and sodiumaluminate solution with the mole
ratio of reactance about 2 (SiO2/Al2O3, Na2O/ Al2O3), in the range of temperature from 60-90 ° C. The resultant samples of the
hydrogel process were characterized using XRF and FTIR demonstrates that they were very similar to standard zeolite A. The result
XRF and FTIR analysis confirmed that the main product was zeolite A. The important control parent the synthesis of zeolite from byproduct of aluminium etching was temperature. The proper temperature required for production of zeolite was 90°C. The comparison
of chemical contents of zeolites A. The synthesized zeolite A had the mole ratio of Na2O/Al2O3 of 1.12 and SiO2/Al2O3 of 2.11. The
standard zeolite A had the mole ratio of Na2O/Al2O3 of 1.15 and SiO2/Al2O3 of 2.00.
We conclude that zeolite syntheses of waste product from alkaline etch of the aluminum industry have the major analysis agree well
with those of commercial zeolite A, which intrigues as to further study in it application as molecular sieve.
5. ACKNOWLEDGMENTS
The financial support received from the The Joint Graduate School of Energy and Environment at King’s Mongkut University of
Technology Thonburi was highly appreciative.
6. REFERENCES
[1] John, D. (1999).”Synthetic Zeolites and other Microporous Oxide Molecular Sieve” , Research and Development Department,
96(7), pp. 3471-3472.
[2] Poulton, B.B., Foubert, L. (1996).”Extraction of Nitric Oxide and Nitrogen Dioxide from an Oxygen Carrier Using Molecular
Sieve 5A”, British Journal of Anaesthesia, 77, pp. 534-536.
[3] Rawanyakun, S (1993). “Zeolite”, Journal of Department of Science Service, 131(41), pp. 28-30.
[4] Bonnie, K., William, E. (1999). “Going Green with Zeolites”, American Institute of Chemical Engineers.
[5] Pramada, P.N. (2001). “Sintering Behaviour of Calcium Exchanged Low Silica Zeolites Synthesized from Kaolin”, Ceramics
International, 21, pp. 105-114.
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