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

Abstract

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.