Isolation of Cellulosic Nano Fibers from Delonix Regia Fruits by Mechano-chemical Route

Abstract

Lignocellulosic fibres have acquired prominence over past few years among researchers due to its prevalence in nature, biodegradability and high specific strength, among other factors. In this paper, mechanochemical route is used to obtain cellulosic nano fibres (CNF) from raw Delonix Regia fruits. CNFs are extracted with chemical treatments including alkali treatment, bleaching, acid hydrolysis and mechanical treatment including ball milling, centrifugation and high speed homogenization. Characterization of the material produced is carried out using X-Ray Diffraction (XRD), Thermo-Gravimetric Analysis (TGA), Fourier Transform Infrared Spectroscopy (FTIR) and Nano Particle Size Analyzer (NPA). XRD results showed that the crystallinity index (CrI) improved from 52.24% to 73.59% for extracted cellulose whereas it got reduced slightly to 68.31% for CNF samples and the crystallite size extracted cellulose and CNF was estimated to be 6.9 nm and 5.1 nm respectively. TGA results proved that the extracted cellulose and CNF are thermally stable compared to raw DRFF samples. First degradation in TGA started near 70-80C which represents moisture loss. Second degradation temperature improved for cellulose and CNF from 173.6C for DRFF to 223.4C and 246.1C which showed improvement in thermal stability. Major weight loss in second degradation shifted from 298.3C to 346.8C and 348.5C for cellulose and CNF respectively. Ash content was slightly decreased for CNF and cellulose samples compared to DRFF. Typical characteristic IR bands of cellulose were observed at 3400 cm-1, 2800-2900 cm-1, 1643.6 cm-1,1447 cm-1, 1084.6 cm-1 and 673.8 cm-1 of O-H stretching vibrations, C-H stretching, O-H bending, CH2 bending of pyranose ring, C-O-C pyranose ring vibration and O-H out-of-plane bending respectively in extracted cellulose and CNF samples. Improvement in cellulose content was observed from FTIR results and found suitable for application in composite materials. The average particle size of CNF measured by NPA was 247.3 nm proving the abundance of material at nanoscale. The average zeta potential of CNF was estimated at -50 mV with negative sign representing hydroxyl group. From the results of zeta potential measurement, material was found to be electro-statically stable and can be utilized for nanocomposite fabrication.