Effect of Acid/Fiber Ratio on Physical Properties of Cellulose Nanofibers Extracted from Cassava Pulp

Cellulose nanofibers (CeNF) were extracted successfully from cassava pulp (CP) by submitting to alkali, bleaching and acid hydrolysis treatments. The raw CP was mercerized with NaOH solution and then followed by bleaching treatment using a solution made up of equal parts (v:v) of acetate buffer and aqueous chlorite. In order to obtain cellulose nanofibers, the acid hydrolysis treatment of bleached fibers was performed using a mixture of HCl/H2SO4 (1:2 v/v). In this acid treatment reaction, the effects of acid/fiber ratio (ml/g) on physical properties of obtained cellulose nanofibers were investigated. Nanofibers were morphologically characterized by transmission electron microscopy (TEM) revealing the nanofibers with diameter in the range of 12-24 nm and immeasurable length were obtained. An increase in crystallinity of fibers after treatments was revealed by X-ray diffraction (XRD). Due to the introduction of sulfate groups at the outer surfaces of fibers during the hydrolysis, thermal stability of nanofibers, characterized by thermogravimetric analysis (TGA), was lower than that of raw CP. The acid/fiber ratio of 150ml/2g was found to be a proper ratio for thermal stability of obtained nanofibers. The crystallinity of nanofibers increased with the increase of acid/fiber ratio.