The American Journal of Applied Sciences
51
https://www.theamericanjournals.com/index.php/tajas
TYPE
Original Research
PAGE NO.
51-56
10.37547/tajas/Volume07Issue05-05
OPEN ACCESS
SUBMITED
18 March 2025
ACCEPTED
14 April 2025
PUBLISHED
16 May 2025
VOLUME
Vol.07 Issue05 2025
CITATION
Sulaymanov Javlon Juraboyevich, Tukhtamuradova Zilola Khamidjon kizi,
Jumanov Yusuf Qurbonovich, & Eminov Aziz Ashrapovich. (2025). Chemical
and mineralogical composition of karnab kaolin raw material and its
leaching methods. The American Journal of Applied Sciences, 7(05), 51
–
56.
https://doi.org/10.37547/tajas/Volume07Issue05-05
COPYRIGHT
© 2025 Original content from this work may be used under the terms
of the creative commons attributes 4.0 License.
Chemical and
mineralogical composition
of karnab kaolin raw
material and its leaching
methods
Sulaymanov Javlon Juraboyevich
PhD student, Institute of General and Inorganic Chemistry of Academy of
Sciences of the Republic of Uzbekistan
Tukhtamuradova Zilola Khamidjon kizi
PhD student, Institute of General and Inorganic Chemistry of Academy of
Sciences of the Republic of Uzbekistan
Jumanov Yusuf Qurbonovich
DSc student, Institute of General and Inorganic Chemistry of Academy of
Sciences of the Republic of Uzbekistan
Eminov Aziz Ashrapovich
Doctor of technical Sciences. Institute of General and Inorganic Chemistry
of Academy of Sciences of the Republic of Uzbekistan
Abstract:
This article provides an in-depth study of the
chemical and mineralogical composition of kaolin raw
material from the Karnab deposit, its industrial
applications, and beneficiation methods. The article
describes effective techniques for removing harmful
impurities present in Karnab kaolin, such as iron and
titanium oxides, as well as alkali and alkaline earth metal
oxides. The kaolin is bleached and its physical and
optical properties are improved through the use of
various chemical reagents (e.g., sulfuric, hydrochloric,
and organic acids), flotation, hydrothermal, and
autoclave processing technologies.
Keywords:
Sanitary ceramics, kaolin, element, chemical,
mineralogical, composition, beneficiation methods,
oxalic acid.
Introduction:
The issue of kaolin raw material quality
remains a pressing problem, primarily due to the
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The American Journal of Applied Sciences
depletion or complete exhaustion of high-quality
kaolin deposits. This situation directly affects the
quality of the products manufactured from it. In recent
years, a noticeable disparity has emerged between the
increasing
quality
requirements
for
ceramic
products
—
particularly sanitary ceramics
—
and the
declining quality of available kaolin.
The term "kaolin" originates from the name of the Kao-
Lin mountain in China and refers to a product of long-
term weathering of rocks. Its chemical formula is
Al
₂
O
₃
·2SiO
₂
·2H
₂
O
, and in its natural form, it occurs
as a mineral raw material containing various impurities
such as feldspars, mica, iron and titanium oxides, and
other minerals. In the composition of kaolin raw
material, the kaolinite mineral dominates significantly
in the mixture with quartz. It also contains remnants of
unweathered primary rocks, alkali metal minerals, and
iron oxide impurities [1].
The development of compositions for refractory
materials requires the use of both primary and
secondary kaolin. Kaolin serves as a key raw material in
the production of fine ceramics, including porcelain
and faience, as well as in the manufacture of white
cement. In the chemical industry, kaolin is used for
producing aluminum sulfate, aluminum oxide, and
ultramarine pigment. It also functions as a carrier and
filler for pesticides and fertilizers, and as a core
material in catalysts for chemical reactions. Globally, a
significant portion of kaolin is consumed in the paper
industry, where it is used as a filler and brightening
agent in paper production. Additionally, kaolin is
widely applied as a filler in the manufacture of paints
and coatings, rubber, plastics, adhesives, and perfumery
products [2].
The Karnab kaolin deposit, located in the Samarkand
region of the Pakhtachi district, 30 km southwest of the
Ziyovuddin railway station and northeast of the Karnab
village, is considered a promising kaolin source [3].
However, despite the large kaolin reserves, it is not
widely utilized. The reason for this is that the kaolin raw
materials are not sufficiently pure, leading several
plants that use kaolin to rely on importing high-quality
kaolin. As a result, the price of the final products
significantly increases, and they struggle to find a place
in the global market. For this reason, the study of kaolin
beneficiation has always been a relevant area of
research.
The low content of coloring oxides (Fe
₂
O
₃
, TiO
₂
), alkali
oxides (K
₂
O, Na
₂
O), and alkaline earth metal oxides
(CaO, MgO) in kaolin, along with the effective methods
for removing them during the beneficiation process,
indicates the potential for improving the quality of
kaolin raw material. The crystal structure of kaolin
consists of infinite layers based on SiO
₄⁴⁻
tetrahedra.
The kaolin crystal structure is composed of two layers:
one is a silicon-oxygen tetrahedral layer, and the other
is an alumino-oxygen hydroxyl octahedral layer. Kaolin
has a hardness of 2-3 on the Mohs scale, a density of
2.58-2.63 g/cm³, and when touched, it forms a greasy,
clay-like mass. Under electron microscopy, fine
hexagonal crystals are observed when highly magnified
[5-6].
Chemical composition of the initial kaolin raw material from the Karnab deposit (mass. %)
Table-1
Mineralogical composition of the initial kaolin raw
material from the Karnab deposit: Kaolinite
(Al
2
O
3
·2SiO
2
·H
2
O) d=0,566; 0,394; 0,255; 0,252; 0,237;
0,233;
0,198;
0,166;
0,148
nm;
Pyrophyllite
(Al(OH)Si
2
O
5
) d=0,102; 0,443; 0,333; 0,200; 0,185; 0,165
Samp
le
s
Oxide content (mass. %)
LOI,
mass.%
SiO
2
Al
2
O
3
Fe
2
O
3
TiO
2
CaO
MgO
SO
3
ZrO
2
FeO
K
2
O
KK-1 48,6
25,2 2,45 0,86 0,67 0,54 0,18 1,52
1,48 1,94
9,02
KK-2 51,3
27,6 1,95 0,78 0,36 0,75 0,36 1,16
1,89 1,75
8,73
KK-3 50,2
18,8 1,82 1,08 0,45 0,46 0,48 1,98
1,93 1,83
9,76
KK-4 49,7 28,3 2,16 1,12 0,78 0,89 0,56 2,08 1,65 1,98
8,44
KK
midl
49.9 24,9 2,09 0,96 0,56 0,66 0,39 1,68 1,73 1,87
8.98
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nm; Quartz (SiO
2
) d=0,310; 0,283; 0,249; 0,245; 0,223
nm; Illite K< (Al,Fe)
2
[OH]
2
(AlSi
3
O
10
)nH
2
O
d=0,370;
0,343; 0,320 nm; Muscovite (KAl
2
(OH)
2
Si
3
AlO
10
)
d=0,198;
0,181;
nm;
Biotite
K(Fe,Mg)
3
[OH]
2
(Al,Fe)Si
3
O
10
) d=0,658; 0,265; 0,551
nm; Bementite (Al
2
O
3
·H
2
O) d=0,619; 0,233; 0,205;
0,166;
0,161;
0,153;
0,145
nm;
Leucite
(К
2
O·Al
2
O
4
·4SiO
2
)
d=0,534; 0,431; 0,413; nm; Orthoclase
(К
2
О·Al
2
O
3
·6SiO
2
) d=0,380; 0,185; 0,153; nm; Anorthite
(СаО·Al
2
O
3
·2SiO
2
) d=0,934; 0,443; 0,320; 0,315; 0,283;
0,255; nm; Gallozaite (Al
2
O
3
·2SiO
2
·4 H
2
O)
d=0,980;
0,708; 0,601; 0,310 nm [4].
Figure 1. Mineralogical composition of the initial kaolin raw material from the Karnab deposit
Methods of purifying kaolin from harmful impurities
1. When thiomelamine is applied in a sulfuric acid
environment (KHSO
₄
, H
₂
SO
₄
), kaolin products with a
whiteness level of 90-94.2% are obtained.
2. In various types of foamy flotation, CaCO
₃
(US patent
No. 2990958) is used as a carrier for the particles.
3. In the formation of flocculation, half-valent cationic
compounds are activated by processing in NH
₄⁺
salts
(US patents No. 3371988; 3701417; 3837482; and
3862027).Dispersants such as Na
₂
SiO
₃
, PAN, and
sodium hexametaphosphate are used. As a dispersing
agent, Na
₂
SiO
₃
should be applied at 1.0 kg/t and 0.25
kg/t NaOH with a pH range of 8.5-9.5. The clay is mixed
with water for 6 hours. The disadvantage of this
method is the low separation efficiency and yield.
4. In addition to Ca(OH)
₂
, 10% CH
₃
COOH acid, 0.05%
polyacrylamide
solution,
potassium-aluminum
bitterstones, and HCl-chloride acid mixtures are
considered somewhat better as coagulants because
the storage of lime slurry in warehouses for 1-2 months
to fully convert to CaCO
₃
is considered a weakness.
5. In the method of bleaching kaolin for use in the
paper industry in Germany, a two-valent iron phosphate
compound is formed in kaolin slurry, and the process is
based on the effect of Na
₂
S
₂
O
₄
solution
in an acidic environment. The main disadvantages of
chemical treatment are the complexity of the
technological scheme and the reduction in kaolin quality
at high temperatures.
6. In the reduction of Fe
3
⁺
to Fe
2
⁺
to remove iron oxides,
a kaolin suspension is first prepared in an HCl-chloride
acid environment. It is then vigorously mixed with
periodically added HCl-chloride acid, followed by the
addition of sodium hydrosulfite (Na
₂
S
₂
O
₄
·2H
₂
O) to the
suspension.
7. In the reduction of Fe
3
⁺
to Fe
2
⁺
, a suspension of
cationic compounds and sodium hydrosulfite is
obtained in a sulfuric acid environment, and they make
up 15% of the total solution. The disadvantage of this
method is that the iron transitions into an isomorphic
state and becomes incorporated into the clay lattice or
the composition of silicate minerals.
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Figure 2. Methods of Kaolin Purification
8.
The kaolin flotation chamber has a volume of 1 liter
and operates in a mechanical machine with an impeller
frequency of 2000 gr. The optimal flotation conditions
are as follows: h:l = 1:4, sulfuric acid consumption is 0.8
kg/t, and collector ANP consumption is 0.9 kg/t. The
concentrate yield is 63.2%. The concentrate
composition contains high-quality Al
₂
O
₃
at 36.12%. The
clay product is dewatered in an autoclave at 2 atm
pressure for 2 hours. Autoclave treatment reduces the
iron content to 0.57%. The brightness level increases
to 68-80%. The sulfuric acid consumption is 50 kg/t [7].
An easy and effective method of kaolin enrichment is
the wet method, which involves the removal of
harmful oxides in a hydrochloric acid medium. Two
approaches using hydrochloric acid were studied:
thermal boiling and autoclave hydrothermal methods.
THE EXPERIMENTAL PART
This article presents a method for removing iron from
kaolin clays using oxalic acid, and the results obtained
indicate the potential for its diverse industrial
applications.
The raw kaolin (average particle size of 35 microns)
from the Karnab deposit contained 2.09% iron oxide
and had a whiteness level of 65.7%. The experiments
were carried out in a 500 ml round-bottom flask
equipped with a central heating and stirring system.
For each experiment, 400 ml of oxalic acid solution
(C
₂
H
₂
O
₄
, reagent grade) at various concentrations
(0.01, 0.10, and 0.50 M) was added to the flask, and
the desired temperature was set. Then, 40.0 g of clay
was added under low-speed magnetic stirring (up to
600 rpm). At specific time intervals (5, 15, 30, 60, 90,
and 120 minutes), 10 ml of solution was sampled and
immediately centrifuged at 300 g for 15 minutes. A 5
ml aliquot of the centrifuged solution was taken to
determine the total iron content. All washing tests
were performed under atmospheric pressure. In
general, a solid-to-liquid ratio of 10 g of kaolin to 100 ml
of washing solution was used. Each experiment was
conducted twice. The studied variables included oxalic
acid concentrations (0.01, 0.10, and 0.50 M) and
temperatures ranging from 25°C to 100°C.
In the solution, oxalic acid (H
₂
C
₂
O
₄
) dissociates to
release a hydrogen ion and a hydrogen oxalate ion
(HC
₂
O
₄⁻
):
H
₂
C
₂
O
₄
→ H⁺
+ HC
₂
O
₄⁻
Subsequently, the formed hydrogen oxalate ion further
dissociates to release an oxalate ion (C
₂
O
₄
²
⁻
):
HC
₂
O
₄⁻
→ H⁺
+ C
₂
O
₄
²
⁻
Among these species, hydrogen oxalate (bi-oxalate) is
the main compound responsible for the dissolution of
iron:
Fe
₂
O
₃
+ H
⁺
+ 5HC
₂
O
₄⁻
→ 2Fe(C₂
O
₄
)
₂
²
⁻
+ 3H
₂
O + 2CO
₂
Therefore, the conditions of the medium must support
the generation of HC
₂
O
₄⁻
ions to serve as an effective
leaching agent. For this reason, evaluating the
temperature and concentration of oxalic acid is
essential.
The dissolution of iron (%) over time at 100°C was
observed using different concentrations of oxalic acid
(0.01, 0.10, and 0.50 M). An increase in iron dissolution
was noted with increasing oxalic acid concentration.
Within a period of 0 to 120 minutes (2 hours), a
maximum dissolution rate of 98% was achieved. This
behavior is attributed to the increased concentrations
of oxalate and hydrogen ions associated with higher
acid concentrations, which in turn promote the
formation of hydrogen oxalate ions (HC
₂
O
₄⁻
)
The increase in hydrogen ions, which directly affects
iron dissolution and pH, is consistent with the findings
reported by Ambikadevi and Lalithambika in 2000. They
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The American Journal of Applied Sciences
identified oxalic acid as the most effective acid for
dissolving iron (in the form of goethite and hematite,
unlike in this study) from kaolin minerals, and
concluded that increasing the acid concentration (from
0.05 to 0.15 M) significantly improves the efficiency of
iron dissolution.
Kaolin concentrates obtained using these methods
meet the requirements of the second-grade GOST
21286
–
82 standard, making them suitable for
porcelain materials and sanitary-ceramic products. To
obtain first-grade kaolins, 300 ml of water is added to
100 grams of raw kaolin. Then, 4 grams of various
acids, such as tartaric, citric, oxalic, and ascorbic acids,
are added depending on the process, forming different
complex compounds, and sulfuric acid (H
₂
SO
₄
) is added
until the pH reaches 2.5. After calcination, the
whiteness of the ceramic div is 89-92%. The sulfuric
acid treatment follows the reactions below [8].
2FeS
2
+14H
2
SO
4(k)
→Fe
2
(SO
4
)
3
+15SO
2
↑+14H
2
O
Mn
2
O
3
+6H
2
SO
4(50%-li sov.)
→2Mn
2
(SO
4
)
3
+3H
2
O
MnO
2
+6H
2
SO
4(k)
→2Mn
2
(SO
4
)
3
+O
2
↑+6H
2
O (t≤110ºC)
2NaHSO
3
+2Fe
2
O
3
+3H
2
SO
4
→Na
2
SO
4
+2FeSO
4
+4H
2
O
Na
2
S
2
O
4
+3Fe
2
O
3
+5H
2
SO
4
→Na
2
SO
4
+6FeSO
4
+5H
2
O
TiO
2
+2H
2
SO
4
→ Ti(SO
4
)
2
+2H
2
O
Chemical composition (mass %) of the kaolin from the Karnab deposit after leaching
Table-2
Samp
le
s
Oxide content (mass. %)
LOI,
%
SiO
2
Al
2
O
3
Fe
2
O
3
TiO
2
CaO
MgO
SO
3
ZrO
2
FeO
K
2
O
KK-1 54,2 35,4 0,36 0,32 0,37 0,15 0,09 0,68
0,76 0,65
7,13
KK-2 52,3 37,2 0,72 0,28 0,34 0,18 0,12 0,52
0,54 0,72
7,68
KK-3 55,5 36,3 0,63 0,36 0,29 0,25 0,11 0,80
0,68 0,82
8,14
KK-4 53,7 35,8 0,56 0,41 0,27 0,19 0,07 0,47
0,59 0,59
7,83
KK
midl
53,9 36,1 0,56 0,34 0,31 0,19 0,09 0,61 0,64 0,69
7,69
CONCLUSİON
In conclusion, a deep analysis of the composition of
kaolin ore from the Karnab deposit and its enrichment
reveals the potential for producing high-quality
ceramic products. The research shows that the raw
kaolin contains iron, titanium, potassium, magnesium,
and other impurities, which limit its industrial use.
Therefore, the article extensively analyzes various
effective cleaning and enrichment methods, including
chemical treatment in sulfate and chloride acid media,
flotation, and autoclave hydrothermal processes.
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Author(s) of the patent: Bruno Passarello. "Method for
iron and its compounds removal from kaolin or quartz
Sand."
Source:
http://www.findpatent.ru/patent/204/2042654.html
