期刊
POLYMERS
卷 15, 期 6, 页码 -出版社
MDPI
DOI: 10.3390/polym15061530
关键词
jute; cellulose nanocrystals; acid hydrolysis; particle size; thermal stability
In this study, cellulose nanocrystals (CNCs) were successfully extracted from waste jute fibers through sulfuric acid hydrolysis and characterized. The CNCs obtained after 45 minutes of acid hydrolysis showed high crystallinity and stability. This easy-to-reproduce method provides an efficient way to produce CNCs from waste jute fibers.
Natural cellulose, a sustainable bioresource, is highly abundant in nature. Cellulosic materials, particularly those that explore and employ such materials for industrial use, have recently attracted significant global attention in the field of material science because of the unique properties of cellulose. The hydroxyl groups enable the formation of intra- and inter-molecular hydrogen bonding and the arrangement of cellulose chains in a highly ordered crystalline zone, with the remaining disordered structure referred to as an amorphous region. The crystalline areas of cellulose are well-known as cellulose nanocrystals (CNCs). In the present study, we extracted CNCs from pure cellulose isolated from waste jute fibers by sulfuric acid hydrolysis, followed by characterization. Pure cellulose was isolated from jute fibers by treating with sodium hydroxide (20% w/w) and anthraquinone (0.5%) solution at 170 degrees C for 2 h, followed by bleaching with chlorine dioxide and hydrogen peroxide solution. CNCs were isolated from pure cellulose by treating with different concentrations (58% to 62%) of sulfuric acid at different time intervals (20 min to 45 min). The FTIR study of the CNCs reveals no peak at 1738 cm(-1), which confirms the absence of hemicellulose in the samples. The CNCs obtained after 45 min of acid hydrolysis are rod-shaped, having an average length of 800 +/- 100 nm and width of 55 +/- 10 nm, with a high crystallinity index (90%). Zeta potential significantly increased due to the attachment of SO42- ions on the surface of CNC from -1.0 mV to about -30 mV, with the increment of the reaction time from 20 min to 45 min, which proved the higher stability of CNC suspension. Crystallinity increased from 80% to 90% when the reaction time was increased from 20 to 45 min, respectively, while a crystallite size from 2.705 to 4.56 nm was obtained with an increment of the acid concentration. Acid hydrolysis enhanced crystallinity but attenuated the temperature corresponding to major decomposition (Tmax) at 260 degrees C and the beginning of degradation (Ti) at 200 degrees C due to the attachment of SO42- ions on the surface, which decreased the thermal stability of CNC. The second degradation at 360 degrees C indicated the stable crystal structure of CNC. The endothermic peak at 255 degrees C in the DTA study provided evidence of sulfated nanocrystal decomposition and the recrystallization of cellulose I to cellulose II, the most stable structure among the other four celluloses. The proposed easy-to-reproduce method can successfully and efficiently produce CNCs from waste jute fibers in a straightforward way.
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