THE USA JOURNALS
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VOLUME 06 ISSUE06
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PUBLISHED DATE: - 13-06-2024
https://doi.org/10.37547/tajas/Volume06Issue06-02
PAGE NO.: - 7-11
SOL-GEL SYNTHESIS IN THE CaO-Al
2
O
3
SYSTEM USING ALUMINA-CONTAINING
WASTE
Khomidov Fakhriddin Gafurovich
PhD, Institute of General and Inorganic Chemistry of Academy of Sciences of
the Republic of Uzbekistan Tashkent, Uzbekistan
Orchid:
https://orcid.org/0000-0002-9110-351X
Kadyrova Zulayho Raimovna
Doctor of Chemical Sciences, Prof. Institute of General and Inorganic
Chemistry of Academy of Sciences of the Republic of Uzbekistan
Orcid:
https://orcid.org/0000-0003-3962-0461
Usmanov Khikmatulla Lutpullayevich
Doctor of Sciences, Institute of General and Inorganic Chemistry of
Academy of Sciences of the Republic of Uzbekistan
Orcid:
https://orcid.org/0000-0002-7434-9411
Niyazova Shokhista Mansuraliyevna
PhD, Institute of General and Inorganic Chemistry of Academy of Sciences of
the Republic of Uzbekistan
Orcid:
https://orcid.org/0000-0003-0395-4013
Khonimkulov Jamoliddin Asatulla ugli
PhD student, Institute of General and Inorganic Chemistry of Academy of
Sciences of the Republic of Uzbekistan
RESEARCH ARTICLE
Open Access
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INTRODUCTION
Calcium aluminates are among the most widely
studied refractory compounds, included in a
number of technical products, such as aluminous
cement, Portland cement, some special cements,
abrasives, phosphors, etc. [1-2]. They are also
widely used in ceramics, binders in refractory
castings for the steel industry, detectors,
biomaterials and optical devices [3]. They have
different crystal structures and are formed during
the production of a number of chemical products,
in the manufacture of transparent glasses for
infrared radiation, called cobol glasses . They have
not been found in natural materials, but their
formation as intermediate compounds is possible
during the formation of igneous rocks [4-5].
Over the past few decades, many methods have
been used to synthesize calcium aluminates,
including hydrothermal, combustion, Pechini ,
precipitation, and sol-gel methods [6-10].
In this work, Ca3Al2O4 was synthesized by the sol-
gel method. The sol-gel method allows you to form
the necessary phase compositions and structure of
the material at lower temperatures.
In this regard, the possibility of using the alumina-
containing component of the Shurtan gas-chemical
complex for the synthesis of tricalcium aluminate
by the sol-gel method.
MATERIAL AND METHODS
As the starting component for the study, we used 4-
hydrate calcium nitrate (Ca(NO3)
‧
4H2O
“
pure
grade
”
) and an alumina-containing spent catalyst,
in which the aluminum oxide content is in the range
of 94-96 mass % (Table 1), as well as nitric acid and
polyvinyl alcohol.
The phase composition of the materials used and
the synthesized calcium aluminate powder was
determined on a LABX XRD-6100 SHIMADZU
diffractograph using CuKα radiation, a Ni filter with
a wavelength of 1.5418 Å.
RESULTS AND DISCUSSION
In many gas-chemical industries, the Claus method
is used to purify natural gas from hydrogen sulfide;
in particular, the Shurtan Gas-Chemical Complex
(SGCC) in the Republic of Uzbekistan carries out
catalytic oxidation of the latter with atmospheric
oxygen on the surface of a high-
alumina “bauxite”
catalyst with the associated production of “gas”
sulfur.
In this case, imported highly porous synthetic
granular aluminum hydroxide is used as a catalyst,
which, after expiration of its service life, is
transferred to a dump as waste. The mass content
of Al2O3 in this waste is 82-90 mass %, and after
calcination at a temperature of 900 oC it usually
reaches values of at least 95 mass % ( Table 1) [11].
The mineralogical composition of the alumina-
containing spent catalyst consists of gamma forms
of alumina and gibbsite (Figure 1a).
Table 1
Chemical composition of the original and calcined waste sample
alumina-containing catalyst ShGKhK
Abstract
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Name of samples
Mass content of oxides, %
LOI
wt.%
SiO
2
Al
2
O
3
Fe
2
O
3
TiO
2
MgO
CaO
R
2
O
SO
3
Original
0.46
82.20
0.04
0.09
1.15
1.23
0.43
0.1
14.15
Heated
0.54
96.02
0.05
0.11
1.34
1.44
0.50
-
-
To obtain a single-phase gamma form of alumina
(Figure 1b), the alumina-containing spent catalyst
was heat treated at a temperature of 900 °C for 2
hours. X-ray data showed that after heat treatment
of the original alumina-containing waste, lines of
diffraction maxima with interplanar distances d =
0.455, 0.288, 0.236, 0.226, 0.197, 0.152, 0.139 nm
are observed , related to the gamma form of
alumina γ
-Al2O3 and d = 0, 618, 0.317, 0.241,
0.185, 0.145, 0.143, 0.131 nm related to the
gibbsite mineral γ Al(OH)
3. At a temperature of
900 oC gibbsite is completely transformed into
gamma form of aluminum oxide, resulting in a
single-
phase gamma alumina powder γ
-Al2O3 with
an interplanar distance d = 0.456, 0.280, 0.238,
0.227, 0.197, 0.151, 0.139 nm.
Figure 1. X-ray diffraction patterns of the alumina-containing component
a) original and b) thermally processed at a temperature of 900
℃
The resulting γ
- form of aluminum oxide was
crushed in an agate mortar and dissolved in an
aqueous solution of HNO 3 , and 4-water calcium
nitrate (Ca(NO3) 4H2O) was dissolved in distilled
water at room temperature. After stirring,
polyvinyl alcohol (PVA) was added to the resulting
solution. The precursor solution was stirred on a
magnetic stirrer at a temperature of 70 °C until a
gel-like mass was obtained. The resulting gel-like
mass was dried at a temperature of 130 °C in an
oven to obtain xerogels. To determine the
formation of the crystal structure of tricalcium
aluminate and the effect of exposure time during
heat treatment on the synthesis process and the
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complete completion of phase formation tricalcium
aluminate, the dried gel was fired at a temperature
range from 900 to 1100 °C 120 minutes in a muffle
furnace SNOL 5/1300.
The X-ray diffraction pattern of the synthesized
nanodispersed tricalcium aluminate powder by the
sol-gel method is shown in Figure 2.
The results of X-ray analysis showed that the
calcination process at temperature 900°C revealed
diffraction lines with interference indices - hkl
(231), (422), (342), (440), (462), (800), (844),
(5102), and (1204) corresponding to the tricalcium
phase aluminate and the intermediate mineral
maenite Ca12Al14O33 (Figure 2c). As the firing
temperature increases, 1000 °C the intensity and
diffraction lines of tricalcium aluminate increases,
and in proportion to the intensity of the maenite
lines it decreases (Figure 2b).
However, when the temperature increases to 1100
°C, the presence of a line of diffraction maxima is
observed, corresponding to the tricalcium mineral
phase aluminate In this case, residual diffraction
lines of the mineral maenite are also observed ,
with an insignificant amount (Figure 2a).
Figure 2. X-ray diffraction patterns of tricalcium aluminate synthesized by the sol-gel method.
a) t - 900 °C b) t - 1000 °C c) t - 1100 °C
The experimental results obtained confirm that the
process of formation of the structure of the
crystalline phases of tricalcium aluminate
(Ca3Al2O4) is completely completed.
CONCLUSION
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In the course of experimental studies by the sol-gel
method, the optimal temperatures for the
synthesis of tricalcium aluminate and the
possibility of using alumina- containing SHGCC
waste as an initial component in their synthesis
were determined . It has been established that the
optimal synthesis temperature is 1100 oC , which
corresponds to the most complete formation of
tricalcium aluminate with the smallest particle
dispersion up to a size of 100-700 nm .
REFERENCES
1.
Kyeongsoon P., Joon W., Deshmukh A. Effect
of
alkaline
metal
ions
on
the
photoluminescence properties of Eu 3+ -
doped Ca 3 Al 2 O 6 phosphors. Journal of
rare earths. 2016.
–
Vol. 34.
–
No. 12.
–
P.
1193
–
1197.
2.
Rodr´ıguez MA Aguilar CL Solution
combustion
synthesis
and
sintering
behavior of CaAl 2 O 4 // Ceramics
International.2012.
–
Vol. 38.
–
P. 395
–
399
3.
Feng Ch., Yanruo H., Jialin S..Preparation and
characterization of calcium aluminate by
chemical synthesis //Journal of University of
Science and Technology Beijing. 2006.
–
Vol.13.
–
P.82
–
86.
4.
Lukáš K., Jiří M., Jan K., František Š. XPS
characterization of polymer
–
monocalcium
aluminate interface // Cement and Concrete
Research. 2014.
–
Vol. 66.
–
P. 110
–
114.
5.
Ahmed AA, Hamdy E. Synthesis and
characterization of some calcium aluminate
phases from Nano-size starting materials //
Boletín de la Sociedad Española de cerámica
y Vidrio .
–
2020.
–
Vol.240.
–
P.9
–
15.
6.
Dekkers R., Woensdregt CF Crystal
structural control on surface topology and
crystal morphology of normal spinel
(MgAl2O4) // J. Cryst . Growth.
–
2002.
–
Vol.236.
–
P.441
–
454.
7.
Freeda M., Subash TD Photoluminescence
investigations of Ytterbium doped Calcium
Aluminate nanophosphorus synthesized by
sol-gel technique // Materials Today:
Proceedings.
–
2020.
–
Vol.24.
–
P.2149
–
2156.
8.
Madhukumar
K.
Thermoluminescence
dosimetry of rare earth doped calcium
aluminate phosphors//Bull. Mater. Sci. 2006
.
–
Vol. 29.
–
No. 2.
–
P.119
–
122.
9.
Xiaowu Hu., Limin Wu. E ff ects of co
-
activator species and transition metal ions
doping on structure and fl uorescence
properties
of
strontium
aluminate
phosphors//Journal of Materials Science:
Materials in Electronics.
–
2019.
–
Vol.30.
–
Iss.4.
–
P.3804
–
3810.
10.
Khomidov F.G., Kadyrova Z.R. and others.
Features of aluminum-magnesium spinel
obtained by the sol-gel method // Problems
of geology and subsoil development:
Proceedings of the VII International
Symposium of students, graduate . and
young scientists.
–
Tomsk .
–
20 20 .
–
T.1.
–
P.382
–
383.
11.
EminovAl.A ., Kadyrova ZR, Iskandarova M.
Gas processing waste perspective raw
materials for designing the composition of
ceramic grinding bodies // Glass and
Ceramics. 2021. No.1. P. 43
–
48.
