Extraction and Characterization of Cellulose Microcrystals from Corn Husk Agrowaste: Study on the Effect of Organosolv Pretreatment and Different Bleaching Agents.

The amount of lignocellulosic waste has increased over the last decades, this biomass has received special attention since it constitutes a promising alternative source of bio-based materials and energy. In addition, cellulose has become an interest of researchers because of its exceptional mechanical properties, as well as versatily in the synthesis of derivative products.

In Peru, corn is the most cultivated cereal nevertheless concerning ways of waste’s disposal are implemented, mainly by open burning, associated with negative impacts on the environment and detrimental effects on people’s health. Addressing this problem, this work focuses on the valorization of these residues into cellulose microcrystals using mechanical treatments combined with bleaching and alkaline extraction processes.

The feedstock was collected from local markets and after washing it several times, the sample was dried, milled and sieved under 850 µm. Afterwards two extraction procedures were conducted, the first one including an Organosolv pretreatment in a high-pressure reactor followed by alkaline treatment and bleaching, and the second one including an alkaline treatment followed by bleaching with 3 different agents. In all cases the alkaline treatment was carried out twice by sodium hydroxide at 4% (w/v), and the bleaching agent’s evaluation was performed with: sodium chlorite, hydrogen peroxide and peracetic acid. Finally, acid hydrolysis was conducted with sulfuric acid at 45°C followed by centrifugation, sonication and dialysis.

In order to identify characteristic functional groups of spectral bands, characterization by FT-IR spectroscopy was carried out, characteristic bands of cellulose were found at 1426 cm^-1, 1325 cm^-1, 1163 cm^-1 and 1110 cm^-1. While the decrease in signals at 1251 cm^-1 and 1736 cm^-1 indicates that hemicellulose and lignin were removed after the chemical treatments. This effect was more evident after bleaching with peracetic acid while the sample bleached with sodium chlorite exhibit the highest yield. Other characterization techniques employed in this work were RAMAN spectroscopy, Atomic Force Microscopy (AFM) and thermogravimetric analysis by TGA/DSC.

Finally, X-RAY diffractograms showed peaks at 22.5° and 34°, characteristics of the crystal polymorphs of cellulose, and lastly the morphology of the microcrystals was investigated by scanning electron microscopy.