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DETERMINATION OF THE ADSORPTION AND PHYSICOCHEMICAL
PROPERTIES OF ACTIVATED CARBON DERIVED FROM PEACH PITS.
Isakov Yusuf Khoriddinovich
E-mail:
Doctor of Philosophy (PhD) in Technical Sciences,
Senior Lecturer at the Department of Chemistry,
Faculty of Natural Sciences, Uzbekistan-Finland Pedagogical Institute.
Elmurodova Mahliyo Berdimurod kizi
E-mail:
A student of the Chemistry program at the Faculty of
Natural Sciences, Uzbekistan-Finland Pedagogical Institute.
Pardayev Ulug‘bek Xayrullo ugli
E-mail:
A student of the Chemistry program at the Faculty of
Natural Sciences, Uzbekistan-Finland Pedagogical Institute.
Bobojonov Jamshid Shermatovich
Doctor of Philosophy (PhD) in Technical Sciences,
associate professor at the Department of Chemistry,
Faculty of Natural Sciences, Uzbekistan-Finland Pedagogical Institute.
Annotation:
This study investigates the adsorption efficiency and physicochemical properties of
activated carbon synthesized from peach pit shells (ShFK) through pyrolysis and steam
activation at 850°C. The surface area, pore volume, iodine number, and benzene adsorption
capacity of the prepared carbon were comprehensively analyzed and compared with those of the
industrially known AG-3 grade activated carbon. Experimental data indicate that ShFK activated
carbon exhibits a high adsorption capacity (up to 1.85 g/100 g for benzene), low ash content, and
significant surface functionality, including –OH, –CHO, and –COOH groups, confirmed via IR
and SEM analyses.
Furthermore, ShFK was successfully employed to purify monoethanolamine (MDEA) solutions,
achieving an increase in amine concentration from 40% to 52%, while reducing mechanical
impurities below the permissible level. The presence of thermostable salts was also effectively
lowered, demonstrating ShFK's superior performance over AG-3 in MDEA regeneration. The
results validate the potential of peach pit-derived carbon as a cost-effective, sustainable, and
high-performance adsorbent for industrial applications.
Key words:
Activated carbon, peach pits, adsorption capacity, physicochemical properties,
MDEA purification, surface area, SEM analysis.
Introduction:
Until now, activated carbon has been imported into Uzbekistan from abroad. It
has been widely used in the process of extracting metals from hydrometallurgical solutions, as
well as in the purification of lubricating oils and fuels from sulfur-containing compounds, in the
removal of mercaptans from aviation kerosene, in the purification of water from various heavy
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406
salts, and as a filter in protective gases. Moreover, activated carbon finds extensive applications
in the pharmaceutical industry.
Activated carbon obtained from the shell of fruit tree pits was tested in experimental trials for its
effectiveness in extracting metals from hydrometallurgical solutions. The results of the research
were compared with the properties of the well-known AG-3 grade activated carbon [7, 8]. Since
the activated carbon was derived specifically from peach pits, it was designated as
ShFK
. Its
physicochemical properties were studied in accordance with the requirements of the existing
technical standards.
Literature review
: Activated carbon is a widely used adsorbent due to its high surface area,
porous structure, and ability to remove a variety of pollutants from liquids and gases. Traditional
sources of activated carbon include coal, wood, and coconut shells; however, recent research has
increasingly focused on the valorization of agricultural waste such as fruit pits as cost-effective
and sustainable alternatives [1,2].
Several studies have demonstrated that activated carbon derived from fruit-based biomass—such
as apricot, peach, and olive pits—can possess comparable or even superior adsorption properties
compared to commercial adsorbents [3,4]. Pyrolysis followed by chemical or steam activation
has been shown to yield materials with high surface area and well-developed pore networks,
which are critical for effective adsorption processes [5].
In particular, the regeneration and purification of amine solutions like monoethanolamine
(MDEA) used in gas treatment and chemical processing require efficient adsorbents to remove
heat-stable salts and mechanical impurities [6]. Conventional AG-3 activated carbon is widely
used for such purposes; however, alternative materials derived from local biomass may offer
economic and environmental advantages.
Recent comparative analyses suggest that peach pit-based activated carbon not only exhibits
favorable physical characteristics such as pore volume and surface functionality, but also
achieves high adsorption capacity for organic and inorganic impurities [7]. Infrared (IR)
spectroscopy and scanning electron microscopy (SEM) have further confirmed the presence of
oxygen-containing functional groups and microstructural integrity in these materials [8].
Therefore, the current study builds upon previous works to further investigate the adsorption
behavior and physicochemical performance of activated carbon synthesized from peach pits,
particularly in the context of MDEA purification and its comparison with AG-3 commercial
carbon.
Methodology:
The adsorption capacity of ShFK was determined using the cryoscopic method
[9,10]. This method allows for the evaluation of both the selectivity and the dynamic capacity of
the adsorbents by analyzing the change in concentration of the chromatographic solution passing
through the adsorbent and the corresponding decrease in the crystallization temperature of the
solution.
The analysis is conducted as follows: a 2% standard organic solution is passed through a glass
column filled with 10 g of the adsorbent (particle size 0.25–0.50 mm, pre-dehydrated) in
cyclohexane until saturation is achieved, that is, until the crystallization temperature of the
filtrate (t₃) equals that of the initial standard solution (t₂). The filtration rate is set at 1 drop per
second, which corresponds to a flow rate of 0.4 volumes per hour. The crystallization
temperatures of the pure cyclohexane (t₁) and the standard solution (t₂) are measured in advance.
Then the crystallization temperature of the filtrate (t₃) is determined.
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The filtrate is collected in 12.85 mL portions (equivalent to 10 g of solution). In each portion, the
crystallization temperature (t₃) is measured. The amount of adsorbed substance (in mol.%) is
then calculated using the following formula:
The molar percentage of the adsorbed substance is calculated using the following formula:
M – the molecular weight of the substance;
84.16 – the molecular weight of cyclohexane.
The amount of adsorbed substance is calculated in grams for each portion and then normalized to
100 grams of adsorbent. This method is both fast and accurate. It is designed for the preparation
of model sorbent solutions using cyclohexane as a highly pure solvent [7].
Activated carbon is obtained by carbonizing the shell of fruit pits at a temperature range of 400–
500°C. The raw material is heated at various temperatures, and in each case, a constant mass of
1000 g is used. The yield of the product obtained at each temperature is shown in Table 1.
The carbonized raw material is then impregnated with a 4% ZnCl₂ solution for 20 hours. After
saturation with ZnCl₂, it is dried until approximately 15% moisture remains. The material is
subsequently activated with steam at 800–850°C. The final product is shaped into granules
according to the requirements for its intended application.
The experimental results are presented in Tables.
Results:
The experimental results are presented in Tables 1 and 2.
Table 1. Conditions of the Carbon Production Process and Its Properties:
Temperature, °
C
Weight After
Carboniza-
tion, g
Hardness,
g/dm³
Surface
Area,
m²/g
Ash
Content, %
Benzene
Adsorption
Capacity, g/100 g
400
613
524
211
4,8
0,24
500
521
557
225
5,0
0,46
600
405
562
234
5,1
0,52
700
276
596
475
5,2
0,87
800
253
623
513
5,5
1,18
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Table 2. Adsorption Properties of Activated Carbon Derived from Fruit Pits:
Temperature, °C
Carbonizati
on
Time,
minutes
Burn-off
Rate, %
Hardness
, g/dm³
Surface Area,
m²/g
Ash
Content, %
Benzene
Adsorption
Capacity, g/100
g
800
60
29
577
805
9,5
1,45
850
120
27
570
890
8,5
1,87
According to the experimental results presented in Table 2, activated carbon obtained from fruit
pit shells, carbonized under an oxygen-free environment at 450–550°C and activated with steam
at an average temperature of 850°C for 2 hours, demonstrated an increase in benzene adsorption
capacity up to 1.85 g. Simultaneously, an expansion in the pore structure was observed. The data
in the table clearly show that an increase in adsorption capacity is associated with a decrease in
ash content. It is well known that the expansion of pores contributes to enhanced adsorption
efficiency.
Certain properties of the activated carbon derived from fruit pits — designated as ShFK — were
compared with those of the well-known AG-3 grade activated carbon. These comparative results
are presented in Table 3.
Table 3. Comparative Analysis of the Properties of Activated Carbon and AG-3:
Parameter
Activated Carbon
AG-3
ShFK
Hardness, g/dm³
450
512
Pore Volume, cm³/g
0,8-1,0
0,87-1,03
Micropore Volume, cm³/g
0,24-0,28
0,30-0,35
Adsorption Activity for C₆H₆, g/100 g 1,23
1,87
Iodine Adsorption Capacity, %
43
75
Hardness, %
75
75-78
Ash Content, %
14-16
4-5
Surface Area, m²/g
1016,8
1025,8
Table 3 presents a comparison of the main properties of ShFK activated carbon with those of
AG-3 activated carbon. According to the obtained results, the newly synthesized activated
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carbon (ShFK) demonstrated improved adsorption capacity, a higher amount of retained ash,
greater pore volume and surface area, as well as increased bulk density.
The effectiveness of the prepared ShFK carbon in purifying MDEA (methyldiethanolamine),
used in production, from toxic components was also investigated. In the purification experiment,
when monoethanolamine solution was treated with ShFK activated carbon, its concentration
increased from 40% to 52%. In contrast, purification with AG-3 activated carbon showed a slight
decrease in the carbon efficiency indicator.
Figure 1. Changes in CO and CO₂ Content in Saturated MDEA over Time:
During the purification of MDEA using activated carbon prepared at 850°C, the saturation
behavior of CO and CO₂ adsorption over time was observed. Within 70 minutes, 200 g of ShFK
activated carbon was able to purify approximately 8–9 liters of MDEA solution. Although the
adsorption efficiency gradually decreased, the carbon remained effective for purifying up to 10–
15 liters of solution.
In the purified MDEA solution, the amount of thermostable salts was found to be 2.80 wt%,
which exceeds the permissible concentration by 1%. However, in solutions purified with AG-3
and ShFK activated carbons, the concentrations were 0.83% and 0.81%, respectively—within the
acceptable limits.
The initial, unpurified amine solution contained a high level of mechanical impurities—1068
mg/L, while the maximum permissible concentration is 500 mg/L. After purification with AG-3,
the level dropped to 488 mg/L, and with ShFK it was further reduced to 479 mg/L, indicating
that ShFK performed even better than AG-3. A high level of mechanical impurities can lead to
excessive foaming and operational instability during processing.
Table 4. Physicochemical Properties of MDEA Purified with ShFK Activated Carbon:
№ Properties
Sample
of
Used MDEA
Purified with AG-3
Activated Carbon
Purified with ShFK
Activated Carbon
1
Amine
Concentration, wt.%
40
39
52
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2
рН
10,80
10,40
10,40
3
Density, g/cm³
1,092
1,085
1,122
4
Salt Content, %
2,80
0,83
0,81
5
Content
of
Mechanical
Impurities, mg/L
1068
488
479
6
Foam Height, mm
16
16
15
7
Foaming Time, sec
20
8
8
Figure 2. IR Spectrum Analysis of the Fruit Pit:
400
600
800
1 000
1 200
1 400
1 600
1 800
2000
2200
2400
2600
2800
3000
3200
3400
3600
3800
4000
cm-1
55
58
60
63
65
68
70
73
75
78
80
83
85
88
90
93
95
98
1 00
%T
33
88
,93
30
86
,11
30
28
,24
29
33
,73
28
66
,22
27
29
,27
23
24
,22
21
60
,27
20
38
,76
18
69
,02
17
32
,08
16
81
,93
16
06
,70
14
54
,33
13
67
,53
12
44
,09
11
57
,29
10
45
,42
90
8,4
7
83
1,3
2
74
6,4
5
69
8,2
3
60
9,5
1
46
2,9
2
41
6,6
2
YoAU-KAU-1
MIRacle1 0 (Dia/ZnSe)
The elemental composition and internal structure of ShFK activated carbon adsorbents obtained
by pyrolyzing the shell of fruit pits are shown in Figure 3 using scanning electron microscopy
(SEM). Based on the SEM images of the carbon samples derived from the fruit pit shells, it was
observed that the elemental composition remained almost unchanged. However, the sample
carbonized at 850°C exhibited the presence of surface functional groups such as –OH, –CHO,
and –COOH, indicating chemical activation on the surface.
Figure 3. Microscopic Image of Carbon Obtained from Fruit Pits:
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Figure 4. Elemental Analysis of the Carbon Sample:
Table 5. Quantitative Elemental Composition of the Carbon Sample:
Element
Weight %
Capacity, wt.%
C
85.19
1.26
O
8.27
1.11
Si
1.84
0.23
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K
0.74
0.20
Ca
1.75
0.26
Zn
2.21
0.46
Total:
100.00
Discussion:
The experimental results clearly demonstrate the high potential of peach pit-derived
activated carbon (ShFK) as an effective adsorbent for various industrial applications. The
material exhibited a well-developed porous structure with a high surface area (m²/g) and
significant micropore volume (cm³/g), comparable or even superior to that of commercial AG-3
activated carbon. The benzene adsorption capacity reached up to 1.85 g/100 g, indicating strong
interaction with organic molecules and confirming the effectiveness of the activation process at
850°C.
Infrared spectroscopy (IR) and scanning electron microscopy (SEM) analyses provided further
insight into the surface chemistry and microstructure of the synthesized carbon. The presence of
functional groups such as –OH, –CHO, and –COOH on the carbon surface suggests enhanced
chemical reactivity and affinity toward polar compounds, which likely contributed to the
observed adsorption efficiency.
The application of ShFK in the purification of monoethanolamine (MDEA) demonstrated its
practical relevance. When used in the regeneration process, ShFK increased the concentration of
MDEA from 40% to 52%, outperforming AG-3 in terms of adsorption of contaminants.
Furthermore, the amount of thermostable salts in the treated solution decreased to 0.81 wt%,
remaining within the permissible limits and indicating effective decontamination. Mechanical
impurities were reduced from 1068 mg/L to 479 mg/L, which is below the threshold value of 500
mg/L and slightly better than the result obtained with AG-3 (488 mg/L).
Additionally, the lower ash content and improved foam behavior (lower foam height and
foaming time) in MDEA solutions treated with ShFK suggest that the carbon is not only
effective in adsorption but also contributes to process stability by reducing foaming tendencies.
Overall, these findings confirm that activated carbon synthesized from peach pit shells is a viable
and sustainable alternative to commercial adsorbents. Its performance in both adsorption
capacity and chemical regeneration highlights its potential for broader application in industrial
separation and purification processes.
Conclusion:
The research has demonstrated that activated carbon synthesized from peach pit
shells (ShFK) possesses promising adsorption and physicochemical properties, making it a
strong candidate for industrial purification applications. The carbonization and steam activation
process at 850°C resulted in a material with high surface area, well-developed pore structure, and
functional surface groups essential for effective adsorption.
Comparative analysis with commercial AG-3 activated carbon revealed that ShFK not only
matches but in some aspects exceeds AG-3's performance. Specifically, ShFK achieved higher
benzene adsorption capacity, lower ash content, and better removal efficiency of mechanical
impurities and thermostable salts in MDEA solutions. The increase of amine concentration from
40% to 52% and the reduction of mechanical impurities to 479 mg/L highlight its operational
effectiveness in real-world applications.
The findings support the use of agricultural waste—such as fruit pit shells—as an economically
and environmentally sustainable raw material for producing high-quality activated carbon. The
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successful regeneration of MDEA using ShFK also points to its potential role in chemical
processing industries, offering both cost and performance advantages over conventional
materials.
Future studies should further explore the regeneration cycles, scaling possibilities, and broader
applicability of ShFK-based carbons across other chemical systems and wastewater treatment
processes.
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