ISOLATION OF CELLULOSE FROM A NATURAL POLYMER AND INVESTIGATION OF ITS QUALITY INDICATORS

ABSTRACT

This article investigates the technology for producing cellulose from paulownia wood and the main quality indicators of the obtained cellulose. Paulownia wood aged 3 and 5 years was selected as the research object, and the cellulose content was determined for its structural components (trunk, branches, roots, and bark). The cellulose production process was carried out based on hydrolysis and alkaline treatment methods. Optimal technological conditions were established by cooking in NaOH solutions of various concentrations. The yield, whiteness degree, lignin and ash content, viscosity, α-cellulose content, and degree of polymerization of the obtained cellulose were studied. The morphological characteristics of the fibers were analyzed using L&W Fiber Tester and Mettler Toledo instruments. The results demonstrate that paulownia wood is a promising raw material for the pulp and paper industry.

АННОТАЦИЯ

В данной статье исследованы технология получения целлюлозы из древесины павловнии и основные показатели качества полученной целлюлозы. В качестве объекта исследования была выбрана древесина павловнии возрастом 3 и 5 лет, по структурным компонентам которой (ствол, ветви, корни и кора) определено содержание целлюлозы. Процесс получения целлюлозы осуществлялся на основе гидролиза и щелочной обработки. Путём варки в растворах NaOH различной концентрации были установлены оптимальные технологические условия. Изучены выход целлюлозы, степень белизны, содержание лигнина и золы, вязкость, содержание α-целлюлозы и степень полимеризации. Морфологические показатели волокон проанализированы с использованием приборов L&W Fiber Tester и Mettler Toledo. Результаты исследования показали, что древесина павловнии является перспективным сырьём для целлюлозно-бумажной промышленности.

Keywords: Paulownia wood, natural polymer, cellulose production, alkaline treatment, α-cellulose, fiber length, quality indicators, Mettler Toledo.

Ключевые слова: Павловния, природный полимер, получение целлюлозы, щелочная обработка, α-целлюлоза, длина волокна, показатели качества, Mettler Toledo.

Introduction. Cellulose is one of the most widespread natural polymers and plays a key role in the development of the pulp and paper, chemical, and textile industries. Owing to its renewability, biocompatibility, and ability to undergo chemical modification, cellulose is regarded as a promising basis for the production of environmentally friendly and sustainable materials. In the context of the growing interest in “green” technologies and the reduction of dependence on fossil resources, the development of efficient methods for obtaining cellulose from natural plant raw materials is of particular relevance [1–2].

Traditionally, wood from softwood and hardwood species has been the primary source of cellulose. However, the limited availability of forest resources, increasing consumption of pulp and paper products, and stricter environmental regulations have stimulated the search for alternative natural polymers and renewable plant raw materials. In this context, fast-growing plants and non-traditional wood species, characterized by high productivity and relatively low processing costs, are of considerable interest [3–4].

The process of cellulose production from natural polymers involves a complex set of physicochemical stages aimed at removing lignin, hemicelluloses, and mineral impurities while preserving the polymeric structure of cellulose. Hydrolysis and alkaline treatment methods are the most widely applied approaches, allowing control over the degree of purification, product yield, and physicochemical properties. The selection of technological parameters significantly affects the quality indicators of cellulose, such as α-cellulose content, degree of polymerization, viscosity, whiteness, and morphological characteristics of fibers [5].

The investigation of the quality indicators of the obtained cellulose is an important stage in assessing its suitability for further industrial applications. Modern analytical methods and instruments enable a detailed study of fiber structure and properties, thereby contributing to the optimization of technological processes and the expansion of application areas of cellulose-based materials [6].

Research methodology. Pavlovnia tree is a fast-growing tree with large leaves, about 70 cm in diameter and flowers up to 6 cm in diameter, with a beautiful crown. The diameter of the tree is up to 1 meter. The average lifespan is up to 100 years. Depending on the growing environment, trees can reach a maximum of 25 meters and different heights [7].

Pavlovnia wood fibers are not as dense as other dense woods. Paper is a good raw material for the production of products. A 3-year-old Pavlovnia tree with a girth of 50-60 cm and a height of 12-15 m replaces a 35-40-year-old pine [8]. 

Currently, in countries with developed cellulose industry, various researches are being conducted to reduce the participation of factors that cause various destructive conditions in the process of extracting cellulose from various plants containing natural polymers. Because the quality indicators of the obtained cellulose are required to be at a level that allows for its wide use in the future. Taking into account the above points, some simplifications were made in the process of obtaining cellulose from the perennial plant pavlovnia tree. First, the plant stem was separated into small pieces and chemical processing was carried out in special laboratory conditions [9-10].

Propagation of the pavlovnia plant is underway, it is a fast-growing tree that is used as a building material. In order to determine the suitability of pavlovnia plant for chemical processing, individual parts (body, branches, root, bark) were studied and the fractional composition of fibers was determined by the new automatic Fiber Tester [11] method.

Results and discussion. The results of the analysis of the components of pavlovnia (table 1) show that the most important part of wood, cellulose, is present in the largest amount in the trunk of the tree and is 45.5%, while the least amount of cellulose is present in the bark 24,5%.

Table 1.

The amount of cellulose and other components in the components of pavlovnia

Table 1 shows that the branches and roots of pavlovia can be used as secondary raw materials for chemical processing, because they contain up to 37.2 and 39.1 %, respectively, that is, only 6-8% less cellulose than the body. will be available. Lignin, the second chemical component of pavlovnia, increases with decreasing cellulose content. 21.8, 18.7, 19.2 and 17.1% of lignin were found in the trunk, branches, roots and bark, respectively. It is desirable to use pavlovian bark, which has the least amount of lignin, to obtain fibrous semi-products. The remaining components are valuable secondary resources for chemical processing to extract cellulose.

From the Pavlovnia tree, cellulose is obtained by first hydrolysis and then alkali treatment. In order for the chemical treatment to be effective, the pavlovian fiber is cut and crushed in the size of 0.5-1 cm. Then 100 g is taken out, put in a glass and 500 ml of water is poured into it. The mixture is boiled for 4 hours, extracted and filtered, and the pirahe part is separated. After the mass is separated from the liquid, it is hydrolyzed in a 3% nitric acid solution for 60 minutes, then it is washed to pH 6.5...8.5 and boiled with 5% sodium alkali to separate the pulp from lignin, polysaccharides and fatty substances. After washing the obtained cellulose to pH 9...9.5, it is bleached with hydrogen peroxide solution. Then the mass is washed and bleached cellulose is dried in a drying cabinet. To determine the optimal conditions for the extraction of cellulose from Pavlovnia fiber, it is cooked in 5% alkali for different times.

In order to determine the optimal conditions for the extraction of cellulose from the Paulownia fiber, it is cooked in different concentrations of alkali for 6 hours (Table 2).

Table 2.

Quality indicators of cellulose obtained from 3- and 5-year-old paulownia trees

^* DP – Degree of polymerization

In table 2, in order to determine the optimal concentration of alkali solution for extracting cellulose from the composition of 3 and 5-year-old raw materials, it was boiled for 6 hours in its 2.5, 3.5, 5.0, 5.5% solution and the optimal conditions were determined (table 2). It can be observed from the table that certain properties of cellulose produced under the influence of different alkali concentrations have different indicators. At the alkali concentration of 5.0%, the 3-year paulownia cellulose content increased to 43.6%, α-cellulose to 70.1%, whiteness to 87.2%, lignin to 29.1%, ash to 3.51%, viscosity to 11.6 and polymerization degree to In 410 and 5-year-old paulownia cellulose, the amount of cellulose is 46.1%, α-cellulose is 87.1%, whiteness is 89.6%, lignin is 20.7%, ash is 2.51%, viscosity is 23.2, and the degree of polymerization is 1025. it became known in the experiment.

The L&W Fiber Tester, developed by the Yuman company, is used to determine the average fiber size [12-13].

The length of 3- and 5-year-old cellulose fibers of Pavlovnia tree is different, 0.620 mm in 3-year and 0.884 mm in 5-year. (Figure 1).

Figure 1. The average fractional composition of the cellulose obtained from 3- and 5-year-old Pavlovnia trees by fiber length, mm: A – 3-year and B – 5-year

In the data presented in Figure 1, after processing the pavlovian raw material under the same conditions and taking cellulose fibers from it, and determining the length of the fibers on the Fiber Tester device, the cellulose of the pavlovian tree was 0.620 mm in 3 years and 0.884 mm in 5 years, and the difference between them was 0.264 mm. Based on this, it turned out that the older the pavlovian tree, the more cellulose fibers have a positive morphological structure.

Table 3 shows the average measurement length of fibers and their average measurement width.

Table 3.

Average fiber length and average fiber width of 3-year-old Pavlovnia tree pulp

Table 4.

Average fiber length and average fiber width of 5-year-old paulownia pulp

As can be seen in Table 3-4, the average length of cellulose fibers obtained from the 3- and 5-year-old pavlovian tree, when measuring 3807 fibers in the 3-year suspension of pavlovian cellulose in the Fiber Tester apparatus, is 0.620 mm; width - 0.006 mm, and average length - 0.884 mm when measuring 3254 fibers in a 5-year suspension of pavlovian cellulose; width - 0.007 mm.

When the current conductivity of the cellulose obtained from the Pavlovnia tree was checked in the Mettler Toledo apparatus, it was 77.8 mS/m in 3 years and 76.5 mS/m in 5 years, and the difference between them was 1.3.

Conclusions. Experiments were carried out during processing of 3- and 5-year-old Pavlovnia tree, and it was determined that cellulose and its derivatives, as well as paper products, can be produced with high-quality products.

1. Cellulose extraction from Pavlovnia tree raw materials, its optimal conditions were thoroughly studied;

2. All main quality indicators of obtained cellulose were determined and compared with celluloses of other perennial plants;

3. The average length of 3,807 fibers in a 3-year suspension of paulownia cellulose in a 3-year suspension of paulownia tree and a width of 0.006 mm was measured in the Fiber Tester apparatus of 3- and 5-year-old celluloses, and the average length of 3,254 fibers in a 5-year suspension of paulownia cellulose was 0.884 mm; The dimensions of fibers with a width of 0.007 mm were studied.

4. In the Mettler Toledo apparatus, the current conductivity of cellulose obtained from the Pavlovnia tree was 77.8 mS/m in 3 years and 76.5 mS/m in 5 years, and the difference between them was 1.3.

5. It was found that it is possible to obtain simple and complex esters from cellulose obtained from the Pavlovnia tree and it is recommended as a good raw material for various paper production industries.

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