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ILMIY METODIK JURNAL
Majidov Hayotjon Bakhtiyor ugli
E-mail:
Pardayev Ulugbek Khairullo ugli
E-mail:
A student of the Chemistry program at the Faculty of
Natural Sciences, Uzbekistan-Finland Pedagogical Institute.
Buranova Nigora Ikrom kizi
A student of the Chemistry program at the Faculty of
Natural Sciences, Uzbekistan-Finland Pedagogical Institute.
Khusanov Eldor Safariddinovich
Doctor of Philosophy (PhD) in Technical Sciences,
Senior Lecturer at the Department of Chemistry,
Faculty of Natural Sciences, Uzbekistan-Finland Pedagogical Institute.
UDK: 661.631:628.4:543.4
DEVELOPMENT OF A DEFOLIANT PRODUCTION TECHNOLOGY BASED ON
CARBONATE RESIDUES UNDER SEMI-INDUSTRIAL CONDITIONS AND THEIR
COMPOSITIONAL ANALYSIS
ANNOTATION:
This article presents the development of a defoliant production technology
based on carbonate residues derived from the soda industry under semi-industrial conditions. The
study focuses on utilizing environmentally problematic by-products as a valuable raw material
for the synthesis of agrochemically effective defoliants. A process flow was designed and
optimized to ensure technological feasibility, chemical efficiency, and cost-effectiveness. The
semi-industrial synthesis was carried out under controlled conditions, and the resulting products
were subjected to detailed compositional analysis using instrumental methods such as FTIR
spectroscopy. The results confirmed the formation of active components with defoliating
properties, meeting the agrochemical standards for use in cotton cultivation. The proposed
approach contributes to the circular economy by converting industrial waste into high-value
agricultural inputs while reducing the environmental burden. The research findings demonstrate
the potential for scaling up the technology for industrial applications.
KEY WORDS:
Defoliant synthesis, carbonate residues, soda industry by-products, semi-
industrial process, compositional analysis, circular economy, FTIR, agrochemical application.
INTRODUCTION:
Defoliants are chemical agents used to accelerate the natural abscission of
leaves, primarily in the cultivation of cotton, to facilitate mechanical harvesting and improve
fiber quality. The widespread use of defoliants in agriculture necessitates the development of
efficient, cost-effective, and environmentally sustainable production technologies. Traditional
defoliant formulations are often based on imported or chemically intensive components, which
increase production costs and pose environmental concerns due to their persistence in soil and
water systems.
In recent years, the concept of industrial symbiosis has gained prominence, particularly in
chemical technology, where secondary raw materials and industrial by-products are repurposed
for value-added applications. The soda industry, which plays a significant role in the production
of sodium carbonate through the Solvay process, generates large volumes of carbonate-rich
residues. These residues, mainly composed of calcium carbonate and other inorganic salts,
present both an environmental challenge and a technological opportunity. This research aims to
JOURNAL OF IQRO – ЖУРНАЛ ИҚРО – IQRO JURNALI – volume 16, issue 02, 2025
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develop a defoliant production technology that utilizes carbonate residues as the primary raw
material under semi-industrial conditions. By converting these by-products into agriculturally
beneficial formulations, the study aligns with the principles of green chemistry and the circular
economy. Additionally, comprehensive compositional analysis of the synthesized defoliants is
conducted to ensure their effectiveness and compliance with agrochemical standards.
The novelty of this work lies in the integration of waste valorization with agrochemical
production, offering a dual benefit of environmental management and economic efficiency. The
developed technology has the potential to reduce production costs, lower environmental impact,
and contribute to sustainable agricultural practices.
LITERATURE REVIEW
: The growing demand for efficient defoliants in cotton production
has spurred significant research into the synthesis of novel compounds and the improvement of
existing technologies. Defoliants play a crucial role in improving harvesting efficiency and fiber
purity by promoting leaf abscission prior to mechanical picking. However, the chemical
composition of conventional defoliants often includes compounds with limited biodegradability
and potential environmental toxicity.
The integration of industrial by-products, particularly carbonate residues from the soda industry,
into defoliant synthesis is a promising direction in sustainable agrochemical development. Soda
ash production via the Solvay process generates large amounts of calcium carbonate-based waste,
which often remains underutilized or discarded. Several studies have emphasized the potential of
using such waste materials in the formulation of fertilizers and plant growth regulators. Previous
research has demonstrated that carbonate-rich residues possess physical and chemical properties
suitable for modification and incorporation into agrochemical formulations. Their compatibility
with other reactive agents in defoliant mixtures has also been experimentally verified in
controlled settings.
Moreover, the application of green chemistry principles in the reuse of industrial waste aligns
with the broader goals of circular economy and zero-waste production models. In particular,
calcium and magnesium carbonates have shown promise as carriers or base materials in slow-
release formulations for agricultural purposes. Recent advancements in semi-industrial synthesis
processes have enabled researchers to simulate large-scale production of defoliants using pilot-
scale reactors, providing critical insights into process scalability and reaction kinetics.
Furthermore, analytical techniques such as Fourier-transform infrared spectroscopy (FTIR) have
been widely used to characterize the compositional structure and functionality of defoliant
compounds.
Despite notable progress, there remains a gap in the systematic development of defoliant
production technologies based on carbonate residues specifically under semi-industrial
conditions. This study seeks to bridge that gap by designing and evaluating a scalable defoliant
synthesis process while conducting comprehensive compositional analysis to ensure product
efficacy and environmental safety.
METHODOLOGY:
The primary raw material used in this study was industrial-grade carbonate
residue obtained from a soda production facility utilizing the Solvay process. The residue
predominantly consisted of calcium carbonate (CaCO₃), with minor amounts of sodium
carbonate (Na₂CO₃), magnesium carbonate (MgCO₃), and insoluble silicate impurities. Prior to
use, the residues were dried at 105°C for 4 hours and sieved to obtain a uniform particle size
fraction below 250 µm.
Chemical reagents including acetic acid, hydrogen peroxide (30%), ammonium salts, and organic
additives were procured from certified chemical suppliers and used without further purification.
A semi-industrial scale reactor system with a working volume of 25 liters was employed to
simulate scaled-up production conditions. The process involved the following key steps:
The dried carbonate material was treated with dilute acetic acid (10%) under continuous
stirring to partially solubilize the carbonates and release reactive cations.
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A mixture of hydrogen peroxide and selected organic additives was introduced to enhance
oxidation potential and modify the surface chemistry of the residue. This step was conducted at
50–60°C for 2 hours under controlled pH conditions (6.5–7.5).
The modified residue was neutralized and stabilized using ammonium-based compounds to
form the final defoliant formulation. The slurry was filtered, and the solid product was dried at
80°C for 6 hours to obtain a free-flowing powder.
In the final stage, the dried defoliant material was granulated to improve handling and
applied characteristics. The product was stored in air-tight containers for further analysis.
A preliminary field test was conducted on a controlled cotton cultivation plot to evaluate the
defoliant’s effectiveness under real agricultural conditions. Parameters such as leaf drop
percentage, time to effect, and plant safety were recorded and compared with a commercial
defoliant control.
RESULTS AND DISCUSSION:
The initial activation of the industrial carbonate residue with dilute acetic acid (10%) resulted in
visible effervescence, indicating partial dissolution of calcium and magnesium carbonates.
Titrimetric analysis showed that approximately 38–42% of total carbonate content was
solubilized under the selected conditions (pH 6.5–7.0, 60 minutes stirring at room temperature).
The resulting slurry exhibited a pH drop from 8.2 to 6.7, confirming acid–base interaction and
ion exchange activity. (Table 1)
Table 1. Activation Parameters and Results for Carbonate Residue Treated with 10%
Acetic Acid.
№
Parameter
Value / Observation
1
Concentration of Acetic
Acid
10% (v/v)
2
Reaction Time
60 minutes
3
Reaction Temperature
Room
temperature
(~25°C)
4
Initial pH of Slurry
8.2
5
Final pH after Activation
6.7
6
Carbonate
Solubilization
(by Titration)
38–42%
7
Visual Observation
Vigorous
effervescence
(CO₂
evolution)
8
Main Chemical Effect
Partial dissolution of
CaCO₃ and MgCO₃
9
Mechanism Indicated
Acid–base
neutralization and ion
exchange
The addition of hydrogen peroxide (H₂O₂, 30%) in combination with selected organic activators
under controlled thermal conditions (50–60°C) led to surface oxidation and modification of the
solid phase. The reaction was exothermic and completed within 2 hours. (Figure 1)
Figure 1. Kinetics of Surface Oxidation During H₂O₂ (30%) Treatment of Carbonate
Residue at 50–60 °C.
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The graph illustrates the oxidation kinetics of industrial carbonate residue treated with 30%
hydrogen peroxide under controlled thermal conditions (50–60 °C). The oxidation index, which
reflects the relative extent of surface modification, increases sharply during the initial phase of
the reaction. Within the first 40 minutes, approximately 75% of the maximum oxidation potential
is achieved, indicating rapid surface reactivity between the carbonate material and H₂O₂. This
rapid increase is attributed to the availability of reactive carbonate and metal sites on the surface,
which readily participate in redox and ligand exchange reactions. As the reaction progresses
beyond 60 minutes, the oxidation index curve begins to plateau, suggesting that most reactive
sites are saturated or passivated, and the rate-limiting step transitions to diffusion or adsorption-
limited kinetics. These results confirm the effectiveness of H₂O₂ as a surface activator and
functional group introducer, thereby enhancing the physicochemical properties of the carbonate
residue for subsequent use in defoliant formulation.
FTIR spectra of the oxidized sample showed the emergence of new absorption bands at ~1715
cm⁻¹ (C=O stretching) and 1250 cm⁻¹ (peroxide fragments), indicating successful incorporation
of oxygen-rich functional groups. This chemical activation step enhanced the wettability and
reactivity of the carbonate surface for defoliant formulation. (Figure 2)
JOURNAL OF IQRO – ЖУРНАЛ ИҚРО – IQRO JURNALI – volume 16, issue 02, 2025
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Figure 2. Full FTIR Spectrum of Oxidized Carbonate Residue.
The full FTIR spectrum of the oxidized carbonate residue displays a combination of native
carbonate and newly introduced oxidized functional groups. A broad absorption band at ~3420
cm⁻¹ corresponds to O–H stretching, indicating adsorbed moisture or hydroxyl groups on the
surface. A weaker band near 2920 cm⁻¹ is attributed to C–H stretching, likely from organic
modifiers used during oxidative treatment.
Most notably, the spectrum features a strong C=O stretching peak at ~1715 cm⁻¹, confirming the
presence of carbonyl groups resulting from oxidation reactions. The prominent band near 1250
cm⁻¹ is associated with peroxide (–O–O) fragments, providing further evidence of successful
surface functionalization with oxidizing agents.
Characteristic carbonate vibrations are observed at ~1450 cm⁻¹ (asymmetric stretching of CO₃²⁻)
and ~870 cm⁻¹ (out-of-plane bending), which are typical of calcite or modified carbonate phases.
The coexistence of original carbonate signals and new oxidative features confirms partial
modification of the residue rather than complete decomposition, preserving the material's
structural integrity while enhancing its reactivity for defoliant applications.
The post-oxidation neutralization with ammonium salts yielded a stable, homogenous semi-
liquid formulation. The pH was adjusted to 6.8–7.2 to optimize agrochemical stability.
Precipitation of modified carbonate particles was observed upon neutralization, resulting in fine,
evenly distributed defoliant precursors. The filtration yield was 87–91%, and the solid content of
the product after drying exceeded 78%, indicating efficient synthesis. (Table 2)
Table 2. Key Parameters Observed During Post-Oxidation Neutralization and Product
Recovery
.
№
Parameter
Observed Value /
Range
1
Formulation appearance
Stable,
homogenous
semi-liquid
2
Neutralization pH
6.8 – 7.2
3
Visual observation
Fine,
evenly
distributed precipitate
4
Filtration yield
87 – 91 %
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5
Solid content after drying
>78 %
The filtered material was dried at 80°C for 6 hours, resulting in a free-flowing powder with a
residual moisture content of 4.2%, as confirmed by gravimetric analysis. No visible clumping or
thermal degradation was observed during drying. The granulated final product exhibited good
mechanical stability, uniform texture, and optimal particle size distribution (mean ~0.9 mm),
making it suitable for agricultural application via conventional sprayers. (Figure 3)
Figure 3. Drying Curve of Filtered Defoliant Material at 80°C.
The drying curve illustrates the reduction in moisture content of the filtered defoliant precursor
over a 6-hour period at 80°C. The initial moisture content (~25%) decreased rapidly within the
first 3 hours, dropping to approximately 7.2%, indicating the removal of free and loosely bound
water. Beyond this point, the drying rate slowed, approaching a final residual moisture level of
4.2%, as determined by gravimetric analysis.
This two-phase drying behavior—rapid initial water loss followed by a slower diffusion-
controlled phase—is typical for semi-porous granular materials. The absence of clumping or
thermal degradation during the process confirms the thermal stability of the material under the
selected drying conditions. The resulting powder demonstrated excellent flowability and
mechanical integrity, with a mean particle size of approximately 0.9 mm, making it well-suited
for distribution through conventional agricultural spraying equipment. These properties validate
the effectiveness of the drying protocol and the material’s readiness for field application.
A preliminary field trial was conducted in the Samarqand region of Uzbekistan to assess the
agrochemical performance of the synthesized defoliant under real cultivation conditions. The
experiment was carried out on a controlled cotton plot (Gossypium hirsutum L.), where the
synthesized defoliant was applied at a standard dosage and compared to a commercially
available defoliant used as a control.
The application of the synthesized defoliant led to an average leaf drop of 86.5% within 5 days
post-application. In comparison, the commercial defoliant achieved a slightly higher leaf drop
rate of 90.3% within the same period. The marginal difference (3.8%) is within an acceptable
range for field performance and indicates that the test product is agriculturally viable. (Figure 4
and Table 3)
Figure 5. Daily Leaf Drop Percentage After Defoliant Application.
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Table 3. Comparative Leaf Drop Performance of Synthesized and Commercial Defoliants.
Day
Synthesized
Defoliant
(%)
Commercial
Defoliant
(%)
Difference
(%)
1
12.0
15.0
-3.0
2
34.0
39.0
-5.0
3
58.0
62.0
-4.0
4
76.0
82.0
-6.0
5
86.5
90.3
-3.8
The graph illustrates the leaf drop kinetics of cotton plants treated with the synthesized defoliant
compared to a commercial defoliant over a five-day period. On Day 1, both products initiated
moderate foliar senescence (12% vs. 15%), with a gradual increase observed in subsequent days.
By Day 3, the synthesized defoliant reached 58% leaf drop, while the commercial standard
reached 62%.
By Day 5, the synthesized defoliant achieved 86.5% leaf drop, closely approaching the 90.3%
effectiveness of the commercial variant. The performance gap remained consistently under 5%,
indicating that the synthesized product demonstrates comparable efficacy. These results validate
the product's potential as a cost-effective, environmentally derived alternative.
CONCLUSION:
The present study successfully demonstrated the feasibility of developing an
effective defoliant production technology using carbonate residues generated by the soda
industry under semi-industrial conditions. The multi-stage synthesis process—including acid
activation, oxidative modification with hydrogen peroxide, ammonium-based neutralization, and
controlled drying—resulted in a stable, free-flowing defoliant formulation with favorable
physicochemical characteristics.
Compositional analysis using FTIR spectroscopy confirmed the incorporation of oxygen-rich
functional groups, including carbonyl and peroxide moieties, that enhanced the surface reactivity
of the carbonate matrix. Gravimetric analyses further supported the structural transformation and
stability of the synthesized material. The final product exhibited good mechanical integrity and a
consistent particle size (~0.9 mm), making it compatible with conventional agricultural
application systems.
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The semi-industrial trials conducted in the Samarqand region revealed a defoliation efficiency of
86.5% within five days, which is comparable to commercial defoliants (90.3%) and within
acceptable agronomic performance margins. Moreover, the synthesized product showed no
phytotoxic effects and maintained plant safety. This research validates the potential of industrial
carbonate waste valorization into agrochemically active defoliants. The proposed approach not
only addresses environmental challenges related to waste disposal but also contributes to the
development of sustainable and cost-effective agricultural inputs. Future work may focus on
scaling the process to industrial levels, conducting broader agronomic field trials, and evaluating
long-term environmental impacts.
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