<b>СРАВНИТЕЛЬНЫЙ АНАЛИЗ МЕТОДОВ ВЫДЕЛЕНИЯ ЛИГНИНА ИЗ ОТХОДОВ ХЛОПКОВОЙ ШЕЛУХИ ДЛЯ ПРОИЗВОДСТВА БУРОВЫХ РЕАГЕНТОВ</b>

Cotton processing waste (husks and stalks) in Uzbekistan represents a significant renewable raw material for lignin production, the basis of thermo- and salt-resistant drilling fluid reagents. The choice of lignin extraction method affects its purity, molecular weight, functional group content and, consequently, the efficiency of subsequent modification. Three methods of lignin extraction from cotton husk were compared: alkaline extraction, acid hydrolysis and the organosolv method. Alkaline extraction (1% NaOH, 80°C, 2 h), acid hydrolysis (3% , 120°C, 1 h), organosolv method (ethanol-water 1:1, 180°C, 2 h). The obtained lignins were characterised by yield, ash content, elemental composition, hydroxyl group content (acetylation method), molecular weight (GPC), structure (FTIR, NMR) and thermal stability (TGA). The alkaline method gives the maximum yield (18.5±0.5%), but high ash content (3.2%). Acid hydrolysis gives a low yield (8.2%) and sulfur contamination. The organosolv method gives an intermediate yield (12.4%), low ash content (0.8%), higher molecular weight ( = 4.1 kDa) and the highest content of phenolic OH (4.1 mmol/g). In terms of thermal stability, all samples are similar (Tonset 200-210°C). For the production of drilling fluid reagents, the alkaline method is optimal due to its high yield and simplicity, despite its higher ash content. The organosolv method is preferable for fundamental research where high lignin purity is required.

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