Nanocellulose Extracted from Paraguayan Residual Agro-Industrial Biomass: Extraction Process, Physicochemical and Morphological Characterization

Residual biomasses from agro-industries in Paraguay, including soybean hulls (SBHs) and sugarcane bagasse (SCB), were studied as a source for nanocellulose extraction for the first time. For that purpose, both biomasses were delignified in a semi-pilot stainless-steel reactor, and the cellulose pulp was subjected to a bleaching process with NaClO (2.5%, w/v). The nanocellulose (CNC) was obtained after two-step acid hydrolysis. Firstly, the bleached cellulose was hydrolyzed with HCl (17%, w/w) for two hours at 60 degrees C to obtain microcrystals by removing most of the amorphous fraction. The celluloses were then treated with H2SO4 (65%, w/w) at 45 degrees C for 45 min to obtain nanocellulose. Physicochemical and morphological properties were analyzed using attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), atomic force microscopy (AFM), and X-ray diffraction analysis (XRD). The SBHs nanocellulose had a whisker-like form with a 230 +/- 42 nm diameter and a 12 +/- 2 nm height, and the SCB nanocellulose had a fibril-like form with a 103 +/- 30 nm diameter and a height of 6 +/- 3 nm. The nanocellulose from SBHs and SCB had good thermal stability as its degradation temperature started at 250 degrees C. Furthermore, the nanocellulose obtained was negatively charged and formed stable dispersion in water at 0.1 mg/mL concentration and a pH of around 6.5.

Automated summary

This study investigated the utilization of residual biomasses from agro-industries in Paraguay, such as soybean hulls and sugarcane bagasse, for nanocellulose extraction. The obtained nanocellulose exhibited good thermal stability and formed stable dispersions in water.