Preparation And Characterization Of Cellulose Nanocrystals Extracted From Oil Palm Trunk Using Deep Eutectic Solvents

Agriculture waste have metamorphosed and valorised into new cellulosic materials named cellulose nanocrystal (CNC) with the appreciation of the "Waste-to-wealth" concept. Oil palm biomass is the major contributor of agricultural waste in Malaysia and the trunk is one of the significant wastes from the replantation events which has low economical value and recyclability. Deep Eutectic Solvent (DES) is employed in CNC extraction due to its low toxicity, biodegradability, cheap and ease of preparation. This study investigates CNC extraction from Oil Palm Trunk (OPT) by using DES. The DES formulated of choline chloride and oxalic acid is employed to extract CNC with the duration of 1hr, associated with the chemical pretreatment. The resulting CNC was characterized on its per cent yields, physical, morphology, chemical and thermal properties and was compared to the commercial CNC. DES has successfully isolated CNC with the yields of 20.83 % and improved the crystallinity from 26.2% to 49.5% by removing the hemicellulose and lignin, which has been confirmed by X-ray Diffraction (XRD) and Fourier-Transform Infrared Spectroscopy-Attenuated Total Reflectance (FTIR-ATR). The DES extracted CNC showed positive results in Tyndall effects with commercial CNC in similar colloids and light-scattering properties. Aside from that, both CNCs confirmed their liquid crystalline behaviour by the chiral nematic structure and birefringence behaviour through Optical Polarized microscope (OPM). The morphology of cellulose microcrystalline (CMCs) and CNCs were observed under Scanning Electron Microscopy (SEM) and Field-Emission Scanning Electron Microscopy (FESEM). However, DES extracted CNC showed larger particles size and propensity to agglomerate than commercial CNC, which has been confirmed by Zetasizer analysis with a higher polydispersity index (HI) and zeta potential. Meanwhile, DES extracted CNC shown greater thermal stability than both commercial and acid hydrolysed CNC, which has been confirmed by the Thermogravimetric analysis (TGA) and Differential Scanning Calorimetry (DSC).
Keywords: Deep Eutectic Solvent (DES), Cellulose nanocrystals (CNC), Biomass conversion, Properties of CNC, Thermal stability of CNC