Synthesis and Characteristic of Carboxymethyl Cellulose from Baobab (Adansonia Digitata L.) Fruit Shell

Ahmed A. A. Youssif, Taiseer Hassan M.

Baobab (Adansonia digitata L.) fruit shell was used as the raw material to produce cellulose. A 37.67 % of cellulose was successfully extracted from baobab fruit shell through sodium hydroxide (NaOH) pre-treatment and acidified sodium chlorite delignification. Cellulose was then converted to carboxymethyl cellulose (CMC) by etherification process using monochloroacetic acid (MCA), and various sodium hydroxide concentrations (20, 25, 30, 35 and 40 g/100 ml), in isopropyl alcohol (IPA) medium. The synthesized CMC yield increased with increasing amounts of sodium hydroxide (NaOH) concentration for the alkalization step.  Structural information of cellulose and CMC was obtained using Fourier Transform Infrared spectroscopy (FT-IR), and the surface morphology was studied using scanning electron microscopy (SEM). The carboxymethylation process of cellulose was confirmed by FT-IR spectroscopy. The presence of a new and strong absorption band at 1600.92 cm-1 for all CMCs samples is due to the COO‾ group, which substitutes OH groups at anhydroglucose unit (AGU). The degree of crystallinity for BFS cellulose was calculated to be 60.6% while the crystal size was calculated to be 31.12 nm. XRD analysis confirmed that CMC crystallinity was reduced remarkably compared with cellulose. The viscosity average molecular weight (Mη) of baobab fruit shell cellulose obtained by Mark-Houwink equation using intrinsic viscosity data is 51,024 g mol-1. The optimum condition for carboxymethylation was found to be 35 g/100 ml NaOH, which provided the highest viscosity average molecular weight (Mη=39,241 g mol-1) and degree of substitution (DS = 0.94). The characteristic features of synthesized CMC suggest the possibilities of utilization as food additive.

https://dx.doi.org/10.31873/IJEAS.5.12.02