Isolation and characterization of cellulose nanocrystals (CNCs) from industrial denim waste using ammonium persulfate

Abstract

This research focuses on extraction of cellulose nanocrystals (CNCs) from industrial denim waste using oxidation method in a batch reactor by varying pretreatment methods, ammonium persulfate (APS) concentrations, and reaction times. This oxidation method shows beneficial when compared to the conventional hydrolysis methods in term of less corrosive and shorter extraction time. Two-step method was developed instead of using one-step only to judge the beneficial of alkali pretreatment. The raw material of industrial denim waste was prepared in the form of powder with particle size range of 80–120 mesh. This raw material was characterized using Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), and Thermogravimetric analysis (TGA). The CNCs products were characterized using Dynamic Light Scattering (DLS), Transmission Electron Microscopy (TEM), and X-ray Diffraction (XRD) for confirming the particle size distribution, morphology, and crystallinity, respectively. The results showed that increasing the reaction time from 5 h to 15 h decreased the particle size of CNCs and increased the crystallinity of CNCs, while increasing the APS concentration from 1 to 1.5 M decreased the particle size of CNCs and the crystallinity of CNCs. The optimum operating conditions were obtained that the reaction time was 15 h at 60 °C and 1.5 M APS concentration, which produced the rod like morphology of CNCs with 76.14 ± 8.56 nm length, 18.10 ± 3.54 diameter and the crystallinity of 83 %. From the DLS and XRD characterizations, it was confirmed that the CNCs from denim waste could be produced through the oxidation method using APS.