Nanocellulose extraction from date palm waste using 1-butyl-3-methylimidazolium hydrogen sulphate

This study provides insights into nanocellulose production using 1-butyl-3-methylimidazolium hydrogen sulphate ([Bmim]HSO₄) as a green solvent, utilizing cellulose derived from date palm waste. Critical hydrolysis parameters were optimized through analysis of variance and response surface methodology. The predicted nanocellulose yield (Y) followed a quadric equation represented by Y=55.48-0.57pH-0.478ST+0.997T-0.006721T²+0.0681pH×ST-0.0681pH×T+0.003833ST×T. The developed empirical model showed excellent predictive accuracy (R²>0.95). The optimized hydrolysis parameters were pH 1, a temperature of 80 °C, and a stirring time of 45 min, resulting in an 80.5 % yield of nanocellulose. Scanning electron microscopy showed the nanocellulose's needle like morphology, while transmission electron microscopy indicated an average particle size ranging from 50 to 60 nm. Fourier transform infrared spectroscopy confirmed the purity of the nanocellulose by indicating the removal of non-cellulosic components. X-ray diffraction analysis showed a crystallinity index (C_rl) of 72.22 %, representing a 67.5 % increase compared to the C_rl raw date waste. Dynamic light scattering showed a hydrodynamic diameter of approximately 100 nm. Thermal stability performed using thermogravimetric analysis indicated a high initial degradation temperature (T_onset) of 233 °C, while differential scanning calorimetry confirmed the absence of melting transitions up to 250 °C, underscoring the material's exceptional thermal stability. This study highlights the robust capability of [Bmim]HSO₄ to produce high quality nanocellulose from lignocellulose-derived cellulose, broadening its application beyond the previously reported use with microcrystalline cellulose to produce nanocellulose.