Hidrólise da casca do coco verde com líquido iônico para extração de nanocelulose

Abstract

Nanocellulose is a plant-based material composed of crystalline and amorphous cellulose, with at least one of its dimensions on the nanometric scale. It exhibits characteristics such as low toxicity, high length-to-diameter ratio, low density, high fracture resistance, among others, which make it beneficial for industrial applications. This study aimed to analyze the routes for obtaining nanocellulose from green coconut using acid hydrolysis and ionic liquid, starting from a biomass treated by the acetosolv process. The characterization of the biomass revealed percentage contents of lignin, cellulose, and hemicellulose in the raw state as 42.23±0.24%, 37.73±0.32%, and 13.80±0.62%, respectively, and after pretreatment as 0.78±0.04%, 72.93±9.56%, and 21.08±8.81%, respectively. FTIR analysis showed the behavior of the raw biomass and after treatments, where peaks in the range of 1701 cm⁻¹ and 1514 cm⁻¹, characteristic of absorbed water and lignin, were eliminated. Peaks at 1375 cm⁻¹, 1035 cm⁻¹, and 898 cm⁻¹ became more evident, indicating the presence of cellulose in the sample. Morphological analysis revealed changes in the cellulose matrix, which became exposed after the bleaching step, suggesting an increase in contact area for hydrolysis. Thermogravimetric analysis indicated more stable behavior at higher temperatures for the pretreated biomass, highlighting the effectiveness of alkalization followed by bleaching in forming a thermodynamically more efficient cellulose. The results of acid hydrolysis were satisfactory, with mass yields of 42.29%, 36.81%, and 24.92% at temperatures of 30, 45, and 60ºC, respectively. The treatment with ionic liquid, followed by acid hydrolysis, was not satisfactory, despite showing mass yields of 89.76% and 89.14% at temperatures of 80 and 100ºC, respectively, due to the low hydrolysis of the biomass under the study conditions.