PHYSICOCHEMICAL PROPERTIES OF SODA INDUSTRY DISTILLATION SOLUTIONS AND STRUCTURAL ANALYSIS OF PRODUCTS SYNTHESIZED IN THE PRESENCE OF SODIUM HYPOCHLORITE

ABSTRACT

In this study, a secondary product generated during the application of a classical technological process in the calcined soda production unit of JV LLC “Kungrad Soda” was investigated using modern physicochemical analysis methods. The composition and phase state of the distillation liquor were determined by X-ray diffraction (XRD) and X-ray fluorescence (XRF) analyses. The results revealed the predominance of calcium and magnesium compounds in the solution, as well as the presence of chloride and carbonate components. The distillation liquor was subjected to chemical modification with a 16–18 wt.% sodium hypochlorite solution at various reagent ratios, resulting in the synthesis of new inorganic reaction products. The chemical composition and structural characteristics of the obtained products were comprehensively studied using infrared (IR) spectroscopy and X-ray diffraction analysis.

The obtained results demonstrate the feasibility of recycling soda industry waste to produce inorganic products and confirm the prospects for developing environmentally sustainable low-waste technologies, as well as the utilization of these wastes as raw materials for chemical industry applications.

АННОТАЦИЯ

В данной статье с использованием современных физико-химических методов анализа исследован вторичный продукт, образующийся при применении классического технологического метода в цехе производства кальцинированной соды на предприятии СП ООО «Кунград сода». Состав и фазовое состояние дистилляционного раствора были определены методами рентгенофазового дифракционного анализа и рентгенофлуоресцентного анализа. В результате исследований установлено преобладание соединений кальция и магния в составе раствора, а также наличие хлоридных и карбонатных компонентов. Дистилляционный раствор подвергался химической модификации 16–18%-ным раствором гипохлорита натрия при различных соотношениях реагентов, в результате чего были синтезированы новые неорганические продукты реакции. Химический состав и структурные особенности полученных продуктов комплексно изучены методами инфракрасной спектроскопии и рентгенофазового дифракционного анализа.

Полученные результаты демонстрируют возможность переработки отходов содового производства с целью получения неорганических продуктов, а также подтверждают перспективность разработки безотходных и экологически безопасных технологий и использования данных отходов в качестве сырья для производства продукции химической промышленности.

Keywords: distillation liquor, soda industry waste, JV LLC “Kungrad Soda”, X-ray diffraction analysis (XRD), X-ray fluorescence analysis (XRF), infrared spectroscopy (IR), sodium hypochlorite, physicochemical properties, secondary raw materials, environmentally sustainable processing technology.

Ключевые слова: дистилляционный раствор, отходы содовой промышленности, СП ООО «Кунград сода», рентгенофазовый дифракционный анализ (XRD), рентгенофлуоресцентный анализ (XRF), инфракрасная спектроскопия (ИК), гипохлорит натрия, физико-химические свойства, вторичное сырьё, безотходная технология.

Introduction

The effective utilization of secondary products generated during the production of finished goods in the chemical industry contributes to ensuring environmental sustainability, rational use of available resources, and increased production efficiency. In recent years, the development of waste-free technologies and the recycling of secondary raw materials have become among the most important directions of scientific research. In Uzbekistan’s chemical industry, which is led by “Qo‘ng‘irot Soda” JV LLC, the traditional Solvay (ammonia–soda) process is used for soda production; as a result of this process, a large amount of a secondary product in the form of distillation solution is generated [1]. This, in turn, has a negative impact on the environment. The development of scientifically grounded approaches for processing this solution is of great importance, as it not only increases economic efficiency but also offers prospects for obtaining environmentally beneficial products. In 2016, the second production line of “Qo‘ng‘irot Soda Plant” JV LLC was commissioned, increasing its capacity to 200 thousand tons per year. By 2022, with funding attracted by “O‘zkimyosanoat”, a project was approved to expand the plant’s capacity from 200 thousand tons to 450 thousand tons per year. These indicators inevitably lead to an increase in the amount of raw materials required for the production of calcined soda. For example, the supply volumes of salt and limestone from the Barsakelmes and Jamansay deposits were increased accordingly: the capacity of the Barsakelmes salt deposit was expanded from 330 thousand tons/year to 470 thousand tons/year, while the capacity of the Jamansay limestone quarry was increased from 240 thousand tons/year to 400 thousand tons/year [2].

Although calcined soda (NC) is produced as the main product, a significant amount of secondary product (distillation solution) is also formed during the process. In the ADKF (Absorption, Distillation, Carbonation, Filtration) units of the first and second stages of soda production, after the distillation process, the distillation liquid is discharged into sludge storage facilities for liquid waste. Under these conditions, the daily soda production volume is approximately 548 t/day, and an average of 10–11 m³ of distillation solution is generated per 1 ton of calcined soda produced. This ratio reflects the stability of the technological process and the fundamental pattern of secondary product formation.

Considering that the plant’s current production capacity has been increased to 450 thousand tons per year, it can be determined that the annual volume of distillation solution generated as a result of technological processes ranges from 4.5 to 5.0 million m³/year. These results demonstrate that as soda production increases, the amount of secondary product also increases proportionally [3–4].

Research object and methodology. The object of the study was a distillation solution. The research was conducted using samples of the distillation solution generated in the calcined soda production unit of “Qo‘ng‘irot Soda Plant” JV LLC. The research methodology was based on a комплекс of technological process analysis, calculations, and experimental methods. Initially, the technological flow scheme of soda production and the main processes in the ADKF units were studied, and the sources and quantitative indicators of distillation solution formation were determined.

The crystalline phases present in the secondary product of the calcined soda production unit of “Qo‘ng‘irot Soda” JV LLC, namely the distillation solution sample, were investigated by X-ray diffraction phase analysis (XRD). The qualitative and quantitative elemental composition of the sample was studied using X-ray fluorescence (XRF) analysis on a Shimadzu RF-6000 instrument.

The X-ray diffractogram (Cu Kα, λ = 1.5406 Å) of the waste sample obtained from the distillation process was analyzed. The highest-intensity reflection appeared at approximately 29.4°, indicating that calcium carbonate (CaCO₃) is the dominant phase in the sample [5].

Figure 1. X-ray diffractogram of the waste from the ammonia regeneration unit of “Qo‘ng‘irot Soda Plant” JV LLC

Additionally, a distinct reflection at approximately 26.6° confirms the presence of silicon dioxide (SiO₂), indicating the existence of silicate compounds or inert minerals originating from the raw material source. Several peaks observed in the 35–43° range are associated with aluminum- and magnesium-containing phases; the reflections of silicates and certain aluminum oxides are typically located in the 35°–38° range. These phases also correspond to iron oxide impurities. The intensity and positions of these peaks indicate a mixture of phases. Low-intensity reflections and peak broadening suggest the presence of hydrated sulfates or amorphous components.

The sample was further subjected to chemical analysis by X-ray fluorescence (XRF) using a Shimadzu RF-6000 instrument.

Figure 2. X-ray fluorescence spectrum of the waste from the ammonia regeneration unit of “Qo‘ng‘irot Soda Plant” JV LLC

The XRF analysis results show that the main component of the sample is CaO, accounting for 79.9%. This composition indicates that the material is a high-calcium raw material or a technological waste product. In addition, the presence of Cl⁻ at 6.3% and S at 4.67% confirms the existence of chloride and sulfate compounds in the sample. MgO (4.45%), A (2.64%), and Si (1.38%) are present as secondary oxides, while F (0.63%), although in a very small amount, is detected as an impurity.

Furthermore, characteristic peaks of Ca, Cl, S, Mg, Al, Si, and Fe elements were clearly recorded in the spectrum, and their intensities are consistent with the quantitative results presented in the table 1.

Table 1.

XRF Analysis Results of the Chemical Composition of the Sample

The wastewater (distillation liquid) generated during the production of calcined soda contains C, N, and C ions in the form of CaCand NaCl chlorides. The main component is CaO, which indicates the predominance of CaC salt in the distillation solution.

Since a high content of calcium compounds was identified in the purified distillation solution, a processing procedure was carried out in order to convert them into chemically active and practically valuable forms. In this process, a 16–18% aqueous solution of sodium hypochlorite was used as the oxidizing reagent, and experiments were conducted at various ratios between the reagent and the distillation solution.

Under laboratory conditions, sodium hypochlorite (NaClO) does not directly produce chlorate; instead, it first undergoes disproportionation to form chlorate ions (Cl), which subsequently combine with C ions. For this reason, a simple stoichiometric ratio is not sufficient, and an excess amount of NaClO is required.

When sodium hypochlorite was used in a 30–40 % excess relative to calcium ions, the oxidizing environment was intensified, and the formation of chlorate ions as a result of hypochlorite ion disproportionation was observed.

In the IR spectrum of the solid product obtained from the distillation solution reacted with NaClO in a 1:3 molar ratio, the broad, low-intensity absorption band observed at 3347 c corresponds to O–H stretching vibrations of water molecules bound in the crystal lattice. This indicates the presence of Ca(ClO₃)₂ in its hydrated form. Weak absorption bands around 2979 c are associated with structural water or intermolecular hydrogen bonds and do not significantly affect the main structure.

Figure 3. Infrared (IR) spectrum of the solid product obtained from the interaction of the distillation solution with NaClO at a 1:3 molar ratio

One of the most important diagnostic regions of the spectrum is the strong, sharp absorption observed around 1402 c, which corresponds to the symmetric stretching vibrations (ν₃) of the Clanion. This intense maximum serves as a reliable spectral marker confirming the presence of chlorate ions. The high intensity and clarity of this peak indicate that the chlorate form is predominant in the composition of the product.

Additionally, the absorption bands observed at 1224 c and 1055 c correspond to the asymmetric and deformation vibrations of Cl–O bonds, which fully agree with the IR spectral data for Ca(Cl reported in the literature. These peaks indicate that the chlorate ions are stably positioned within the crystal lattice.

In the low-frequency region of the spectrum, specifically at 712 c and 671 c, distinct absorption bands are observed that correspond to the C– Cl ionic interactions and lattice vibrations. This region is characteristic of calcium chlorate compounds and confirms the absence of other calcium salts in the product, such as CaC or Ca(OH.

An important point is that no absorption bands characteristic of hypochlorite (Cl) in the 950–980 c range were detected. This confirms that the excess NaClO underwent disproportionation, converting hypochlorite ions into chlorate ions:

3Cl → Cl​+ 2C

As a result, a stable Ca(Clcompound was formed with C ions.

As a result of processing the purified distillation solution with 16–18% sodium hypochlorite solution at various ratios, the calcium compounds present were converted into chlorate forms.

The results of infrared spectroscopy (IR) and X-ray diffraction analyses confirmed the composition and phase state of the obtained products, demonstrating the effectiveness of this method.

The X-ray phase diffractogram (Cu Kα, λ = 1.5406 Å) of the solid product obtained from the distillation solution reacted with NaClO at a 1:3 ratio was analyzed to determine its phase composition.

Figure 4. Diffractogram of the solid product obtained from the interaction of the distillation solution with NaClO at a 1:3 ratio

The presence of distinct, sharp, and high-intensity diffraction maxima indicates that the obtained product has a crystalline structure. The main intense peaks are observed in the 2θ regions of approximately ≈ 29–30°, 45–46°, 55–56°, and 65–66°. These maxima correspond well with the diffraction data reported in the literature for calcium chlorate (Ca(ClO₃)₂) and confirm that this phase predominates in the product composition.

Conclusion. In this study, the composition, phase state, and processing potential of the distillation solution generated during calcined soda production at “Qo‘ng‘irot Soda” JV LLC were investigated using comprehensive physicochemical methods.

X-ray diffraction (XRD) analysis revealed that calcium compounds are the dominant phase in the solid residue of the distillation solution, along with the presence of silicon dioxide, magnesium, aluminum, and iron oxides, as well as silicate mixtures. X-ray fluorescence (XRF) analysis showed a high content of CaO (79.9%) in the sample, confirming the predominance of calcium compounds in the distillation solution. This indicates that this secondary product can be considered a promising raw material for obtaining valuable calcium-based chemical compounds.

In the next stage of the study, experiments were conducted to convert the C ions in the purified distillation solution into chemically active forms by processing it in an oxidizing medium with 16–18 % aqueous sodium hypochlorite solution.

The research demonstrated that the distillation solution can be processed not as waste but as a secondary raw material for the production of high-value chemical products. The proposed method can contribute to the introduction of waste-free technologies in the soda industry, reduce environmental impact, and improve the economic efficiency of production. The obtained results are also of scientific and practical significance for the future development of technologies for calcium chlorate-based defoliants and other functional products.

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