Production of carboxymethylcellulose fibers from waste lignocellulosic sawdust using NaOH/NaClO₂ pretreatment

In this study, waste lignocellulosic sawdust was converted to carboxymethylcellulose (CMC) by the combination process of an inorganic base (NaOH) and a weak acid (monochloroacetic acid, MCA). Optimum conditions for the pretreatment were studied on the basis of lignin and hemicellulose removal. NaOH and MCA concentration, reaction time, and operating temperature were the parameters studied to acquire the optimized conditions for the production of CMC. Degree of substitution (DS) and solubility were greatly influenced by the changes in the experimental conditions. DS increased on increasing the concentration of NaOH and MCA but the effect was more profound during the NaOH loading. A maximum DS of 0.5 was obtained on the treatment with 20 % NaOH and 20 % MCA concentration at 50 °C, 150 rpm for 4 h. 1.28 g CMC/g cellulose was obtained at the optimized set of conditions. Structural information of cellulose and CMC was obtained using IR spectroscopy and the surface morphology was studied using field emission scanning electron microscopy (FESEM). Carboxymethylcellulose showed lower crystallinity than the native cellulose extracted from sawdust which was studied using X-ray diffraction.