Preparation of Cellulose Fiber from Cattail Using Two-Stage Pretreatment and Choline Chloride-Oxalic Acid Deep Eutectic Solvent Extraction for Oil Adsorption

The aim of this study was to produce cellulose fibers from cattails through a sequence of hydrothermal pretreatment (HTP) and alkaline pretreatment, followed by the synthesis of a deep eutectic solvent (DES). The raw cattail was pretreated in two steps: (1) HTP at 180 °C for 2 h; and (2) alkaline pretreatment using 3% sodium hydroxide (NaOH) at 90 °C for 1 h. After that, the pretreated materials were extracted with choline chloride-oxalic acid at temperatures of 50, 70, and 90 °C. The oil adsorption capacity under the optimum conditions was observed for various oil types (palm oil, engine oil, and used cooking oil). The results showed that the optimal temperature for DES synthesis was 70 °C, resulting in microfibers with a composition of 43.13% cellulose, 3.88% hemicellulose, and 8.6% lignin. Adsorbent materials from cattails that have been treated under appropriate conditions can adsorb various oils at a similar rate, approximately 6–7 g/g. Biodegradable natural absorbent materials are environmentally friendly and help reduce the burden of weed management.