Carboxymethyl Cellulose (CMC) Synthesis and Characterization From Invasive Weed Senna didymobotrya Through Response Surface Methodology (RSM)–Guided Alkalization and Etherification Methods

Abstract

In this study, the synthesis of carboxymethyl cellulose (CMC) from nonusable invasive weed Senna didymobotrya cellulose was possible through response surface methodology (RSM)–guided alkalization and etherification methods. The RSM method indicates that the maximum CMC yield obtained, 0.85 gm or 85.6%, was achieved when 1 gm or 6 mol of anhydrous glucose unit (AGU) cellulose reacted with 1 gm or 3.24 mol of KOH/AGU and 1.1 gm or 2.05 mol of monochloroacetic acid (MCA)/AGU at 60°C with a total reaction time of 2 h. This finding opens a new avenue for saving chemicals while producing industrial chemicals. The RSM analysis also indicates that the method was significant and valid. This is because the factors and factor interactions used in this method were significant (p < 0.05) and the method was precise because the adequate precision (30.7) found was much higher than the expected precision value of 4. The factors used were alkalization, etherification, and temperature. The degree of substitution of synthesized CMC was 2.5 and comparable with the commercial CMC (2.9). The viscosity measurement of the synthesized and commercial CMC indicates that both materials showed non-Newtonian pseudoplastic behavior. The viscosity of the synthesized CMC was 331.64 cP and the commercial CMC was 227.08 cP. This indicates that the synthesized CMC was more viscous than the commercial CMC. Hence, the synthesized CMC could be used as a good thickener in different factories. The FTIR, XRD peaks, and SEM images indicate that the CMC was synthesized from the isolated cellulose. The TGA/DTA analysis also indicates the CMC was thermally stable up to 380°C and exhibited heat resistance up to 800°C. Therefore, the two simplest, not time- and energy-taking, methods used and the results of their characterizations with respect to commercial CMC indicate that our synthesized CMC from the weed Senna didymobotrya cellulose can be extended to large-scale production of CMC and marketed locally and worldwide.