Eco-friendly conversion of corn husk agro-waste into microcrystalline cellulose and cellulose nanofibers

Abstract

Efficient use of bioresources is essential in order to achieve sustainable development goals, and plays an important role in the reduction of any environmental impact and the improvement of resource efficiency. To this end, the present study investigates the process of obtaining microcrystalline cellulose (MCC) and cellulose nanofibers (CNFs) from corn husks (CHs), which are agricultural waste, under “mild” conditions by employing the organosolvent oxidation method using peroxyacetic acid (PAA). The results obtained at an effective hydromodule of CH:PAA 1:18 g/mL, were: MCC yield – 51.60 %, α-cellulose content – 58.73 ± 3 %, residual lignin – 12.92 ± 0.5 %, hemicellulose – 13.8 ± 0.5 %, ash content (SiO₂) – 10.73 ± 0.5 %, and moisture content – 3.57 ± 0.5 %. Furthermore, the effective MCC:FA ratio that was used to obtain CNFs from MCC_CH using formic acid (FA) was found to be 1/30 g/mL. The CNF yield achieved with this ratio was 68.67 %, and the average particle size was reduced by 177 times in length and 33 times in width, as compared to the initial MCC_CH size. The ζ-potential of the resulting MCC was −19.3 mV and the crystallinity index was 80.9 %. The effectiveness of the PAA/FA approach arises from mild oxidation that selectively removes amorphous cellulose, while preserving crystalline regions, thereby maintaining high crystallinity and contributing to favorable material yields. The physicochemical properties of the resulting high-quality cellulose micro- and nanofibers were compared, and found to have been obtained at good efficiency. The MCC and CNFs obtained have excellent potential for use in the medical field as essential components, and in the development of bioplastics and biocomposites, among other applications.