SYNTHESIS AND PHYSICOCHEMICAL PROPERTIES OF COMPLEX-FORMING CORROSION INHIBITORS FROM INDUSTRIAL WASTE

ABSTRACT

This study investigates the modification of hydrolyzed polyacrylonitrile (HYPAN) with sodium bisulfite to obtain polymer products with enhanced properties suitable for industrial applications. HYPAN, known for its multifunctional characteristics and environmental safety, was processed by precipitation in an acidic medium followed by reaction with sodium bisulfite at various temperatures (30–50°C) and reagent ratios. The viscosity of the reaction system was monitored as a key parameter indicating molecular changes and reaction progress. Results demonstrate that increasing the amount of binding agent leads to higher viscosity due to molecular growth and possible structural transitions from linear to branched configurations. Temperature elevation from 30 to 50°C initially reduces viscosity, allowing greater incorporation of sulfo groups, while excessive binder concentrations result in the formation of solid, insoluble viscous masses. Optimal conditions were identified at 50°C with 35 mL of 10% sodium bisulfite solution, enabling maximum complex formation with iron ions.

АННОТАЦИЯ

В данном исследовании изучается модификация гидролизованного полиакрилонитрила (ГИПАН) бисульфитом натрия для получения полимерных продуктов с улучшенными свойствами, пригодных для промышленного применения. ГИПАН, известный своими многофункциональными характеристиками и экологической безопасностью, был обработан путем осаждения в кислой среде с последующей реакцией с бисульфитом натрия при различных температурах (30–50°C) и соотношениях реагентов. Вязкость реакционной системы контролировалась как ключевой параметр, указывающий на молекулярные изменения и ход реакции. Результаты показывают, что увеличение количества связующего агента приводит к повышению вязкости из-за роста молекулярной массы и возможных структурных переходов от линейной к разветвленной конфигурации. Повышение температуры с 30 до 50°C первоначально снижает вязкость, обеспечивая большее включение сульфогрупп, в то время как чрезмерные концентрации связующего приводят к образованию твердых, нерастворимых вязких масс. Оптимальные условия были определены при температуре 50°C с использованием 35 мл 10% раствора бисульфита натрия, что позволяет достичь максимального комплексообразования с ионами железа.

Keywords: HYPAN, Viscosity, IR spectroscopy, hydrolyzed polyacrylonitrile, Solid mass, export.

Ключевые слова: ГИПАН, вязкость, ИК-спектроскопия, гидролизованный полиакрилонитрил, твердая масса, экспорт.

INTRODUCTION

Polyacrylonitrile-based polymers have garnered significant attention in materials science due to their versatile properties and wide-ranging industrial applications. Among these, hydrolyzed polyacrylonitrile (HYPAN) stands out as a particularly promising material, distinguished by its multifunctional characteristics and suitability for various technological fields. HYPAN has attracted considerable research interest not only for its functional versatility but also for its environmental safety profile, which aligns with contemporary demands for sustainable materials development [1-3].

The production and packaging technology of commercial HYPAN variants, such as "HYPAN A+," have been optimized to meet rigorous quality standards, enabling their export to international markets. This industrial maturity provides a solid foundation for further modification and value addition through chemical processing [1-3]. The modification of HYPAN to obtain diverse polymer products represents one of the most widely employed approaches in polymer industry, offering pathways to tailor material properties for specific applications.

Previous studies have established that successful modification of HYPAN typically requires its initial conversion into solution form, as this state facilitates handling and significantly enhances reaction efficiency [4-6]. One fundamental processing route involves precipitation of HYPAN in acidic medium, yielding the polymer in pure powder form. This precipitation process, when conducted under controlled industrial conditions, follows specific reaction mechanisms that not only purify the substance but also create reactive sites amenable to subsequent chemical modification [7-9].

The present study focuses on the modification of HYPAN through reaction with sodium bisulfite, investigating how varying reagent ratios and temperature conditions influence the reaction system's viscosity and the resulting polymer properties. Understanding these relationships is crucial for optimizing processing parameters to achieve desired material characteristics while maintaining process efficiency and product quality. The viscosity of the reaction system serves as a valuable indicator of molecular changes, reflecting polymer chain interactions, molecular weight evolution, and potential structural transitions[10; 11].

This research aims to: (1) elucidate the effects of HYPAN-to-binder ratios on reaction outcomes across different temperatures; (2) establish optimal conditions for controlled modification without excessive crosslinking; (3) characterize the structural features of modified products using spectroscopic methods; and (4) assess the potential of modified HYPAN for applications requiring specific functional properties, particularly complex formation with metal ions.

MATERILAS AND METHODS

When HYPAN is precipitated in an acidic medium, certain changes occur in the molecular structure of hydrolyzed polyacrylonitrile. These changes not only ensure the purification of the substance during the process, but also create the possibility for its further modification. As a result, the process proceeds according to the following reaction mechanism:

1. HYPAN, previously converted into a solution form, is introduced into an acidic medium.
2. In the acidic medium, certain segments of the polymer chains become protonated and undergo hydrolysis.
3. As a result of the process, a pure powder product is formed, which provides a suitable raw material for subsequent production processes.

The reactions were carried out at different ratios of HYPAN to binder: 50:1, 50:2, 50:3, 50:4, 50:5, and higher ratios, under continuous stirring.

The reaction was carried out at various initial reagent ratios (starting from 10:1, with an increasing proportion of HYPAN) at temperatures ranging from 30 to 80 °C. As the temperature and amount of binder increased, a large amount of product formed, resulting in a solid, viscous mass that did not dissolve in solvents. This is likely due to the complete interaction of the reacting substances, which sharply increases the molecular weight.The reduction in solubility and formation of a solid viscous mass is also explained by the transition of HYPAN from a linear to a more branched structure, which decreases the polymer’s solubility. Initially, the carboxyl groups of HYPAN, in their sodium salt form, were converted to the acid form by treatment with hydrochloric acid, resulting in a white mass.

When the resulting white mass is treated with sodium bisulfite, a reaction occurs between the carbonyl groups and the polyfunctional groups of HYPAN. A 10% aqueous solution of sodium bisulfite was used for this reaction.

HYPAN Modification Process:

1. Solution Preparation: HYPAN is dissolved in water to obtain a homogeneous solution, creating favorable conditions for modification.
2. Precipitation in Acidic Medium: The solution is introduced into an acidic medium, where the polyacrylonitrile chains break down, and the substance precipitates in powder form.
3. Purification: The resulting powder is washed several times and separated in a dry form.
4. Final Product: The obtained product can be used as a polymer raw material in subsequent production stages.

RESULTS AND DISCUSSION

As a result of the modification, HYPAN acquires new physicochemical properties. This process plays an important role in creating new materials for the polymer industry and expands the potential applications of the substance. At the same time, the technology is distinguished by being environmentally safe and economically efficient.

The effect of the ratios of the reacting substances and the temperature on the viscosity of the reaction system was selected as a factor determining the course of the reaction. The temperature and component ratios are presented in Tables1.1–1.3.

Table 1.1

Properties of the polymer obtained from hydrolyzed polyacrylonitrile and sodium bisulfite at different ratios and 30 °C

Figure 1.1. Change in viscosity of the polymer obtained from hydrolyzed polyacrylonitrile and sodium bisulfite at 30 °C

As shown in the graph, the increase in the amount of the binding agent leads to growth in molecular size, which in turn causes an increase in the viscosity of the reaction system.

Table 1.2.

Properties of the polymer obtained from hydrolyzed polyacrylonitrile and sodium bisulfite at different ratios and 40 °C

Figure 1.2. Change in viscosity of the polymer obtained from hydrolyzed polyacrylonitrile and sodium bisulfite at 40 °C

As seen from the graph, the viscosity increases with the rising amount of the binding agent, and under the effect of temperature, the growth in molecular size due to increased yield leads to a further increase in the viscosity of the reaction system.

Table 1.3.

Properties of the polymer obtained from hydrolyzed polyacrylonitrile and sodium bisulfite at different ratios and 50 °C

Figure 1.3. Change in viscosity of the polymer obtained from hydrolyzed polyacrylonitrile and sodium bisulfite at 50 °C

As shown in the graph, the viscosity increases with the increasing amount of the binding agent. Unlike the previous two graphs, at higher temperatures, the growth of molecular size due to increased yield leads to a rise in the viscosity of the reaction system.

Table 1.4

Change in viscosity of HYPAN and the reaction product

As seen from the table, the change in viscosity at the final values is not significant. The structure of the synthesized substance was analyzed using IR spectroscopy, which revealed characteristic absorption peaks corresponding to the specific structural features of the compound.

CONCLUSION

This study systematically investigated the modification of hydrolyzed polyacrylonitrile (HYPAN) with sodium bisulfite, examining how reagent ratios and temperature (30–50°C) affect polymer properties. Key findings show that increasing sodium bisulfite concentration consistently raises viscosity due to molecular growth and structural transitions from linear to branched configurations. Higher temperatures initially reduce viscosity, enabling greater sulfo group incorporation. Optimal conditions were identified at 50°C with 35 mL of 10% sodium bisulfite per 50 mL HYPAN, achieving maximum iron ion complexation without premature solidification. Excessive binder concentrations (>30–35 mL) produced insoluble masses, establishing critical processing limits. IR spectroscopy confirmed successful functional group incorporation. The modified polymers exhibit enhanced properties suitable for metal recovery, catalysis, and adsorbent applications, offering an environmentally safe and economically efficient approach to producing functional materials. This work provides a foundation for developing tailored HYPAN-based products for industrial use.

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