Molecular and structural characterization of micronized lignocellulose from date-pits by alcoholic fractionations

Six alcoholic fractionated micronized lignocellulose date-pits fibers (i.e. three fractions from the successive residues, i.e. L₁, L₂ and L₃; and three fractions from supernatants, i.e. S₁, S₂ and S₃) were prepared and their compositions, molecular and structural characteristics were measured. Mass average diameters of these fractions varied from 27 to 47 μm. Residue fractions showed integrated compact structure with trenches or pores, while first two supernatants (i.e. S₁ and S₂) showed lumped particles and S₃ showed individual spherical and rod shaped particles. Differential Scanning Calorimetry (DSC) analysis showed that supernatant S₁ and S₃ contained the highest levels of amorphous fraction, while L₁ and L₃ contained the lowest level of amorphous fraction (i.e. highest crystallinity). X-ray Diffraction (XRD) analysis also showed the highest crystallinity in the cases of residue layers L₁ (i.e. 65 %) and L₃ (i.e. 53 %), while supernatants S₁ (i.e. 4 %) and S₃ (i.e. 27 %) showed the lowest crystallinity. Fourier Transform Infrared (FTIR) spectra showed higher absorption intensities in the selected functional groups when supernatant fibers were compared to the residue layers, thus molecular damage was increased in the supernatants. Overall, alcoholic fractionation could produce mainly two types of fibers, one highly crystalline and another one highly amorphous.