Closer Approach towards the Preparation of Cellulose and Microcrystalline Cellulose from Corn Husks

Abstract

In this work, cellulose was effectively produced from corn husks by a simple and eco-friendly method. Major influencing variables for cellulose extraction were examined, and the highest yield of lignin and hemicellulose cleavage was achieved after corn husks were treated in 12.5 wt % NaOH solution at solid/liquid ratio (S/L) of 1:10 g mL⁻¹, 70 °C for 90 min. Subsequent bleaching conducted in 10 wt % H₂O₂ solution at 80 °C for 90 min produced cellulose with a lightness value (L^*) of ∼87, chromaticity indexes a^* = −1.85, b^* = 2.94 with high purity, 90.86 %, and crystallinity, 64.94 %. Fourier transform infrared, scanning electron microscopy, and x-ray diffraction analysis showed a clear transition in morphology, structure modification, and crystallinity consistent with the alteration of the chemical composition from raw material to delignified residue and the bleached one. To synthesize microcrystalline cellulose (MCC), the hydrolysis was investigated in H₂SO₄ solutions of different concentrations and durations via monitoring particle size distribution by laser diffraction spectroscopy. At the most efficient conditions (30 wt % H₂SO₄, 18 h, 45 °C, 1:10 S/L ratio), the obtained MCC reached an average particle size of 42.68 µm, crystallinity degree of 61.6 %, and cellulose purity of 92.5 %. Meanwhile, similar parameters with 4 N HCl solution produced MCC with the same purity but higher crystallinity (65.6 %), higher mean size, 67.62 µm, and higher aspect ratio. SEM images showed that 4 N HCl caused less detrimental and erosive action, and less fragmentation on cellulose microfibrils compared to 30 wt % H₂SO₄. The study's outcome supports the feasibility of corn husks to produce cellulose and MCC for further applications.