Optimization of synthesis method for carboxymethylcellulose (CMC) from agro-food wastes by response surface methodology (RSM) using D-Optimal algorithm

Abstract

Carboxymethylcellulose (CMC) has wide commercial applicability for oil drilling fluids, cosmetics, food, and pharmaceutical industries, but the current industrial process for its synthesis from eucalyptus wood has low sustainability and efficiency. This work reports the statistical optimization for the synthesis of CMC from waste biomass celluloses with special reactivity, extracted from sugarcane bagasse (SB) and corn cob (CC). The combined mild acid/peroxide-alkali (APA) treatment, followed by bleaching, was efficient for the extraction of low-crystallinity pulps, which were further converted into CMC. A set of carboxymethylation tests with variable reaction conditions determined by a D-Optimal design of experiments (DoE) were carried out by assessing the factors Activation Time (AT), Reaction Time (RT), NaOH concentration (NaOH%) and Cellulose (SBCel or CCel). Characteristic CMC absorption features were observed via FTIR and Raman spectra, and the deconvolution of X-ray diffractograms showed that the mild APA treatment is able to produce pulps with significant content of amorphous and type II celluloses, whose have higher reactivity and reflects in the optimal results of the DoE. Analysis of variance (ANOVA) and response surface methodology (RSM) results from DoE data proved with high precision (F=184.81; p-value<0.0001; R2=0.9911; SD<1.0×10–5) and accuracy (low regression residuals) that the waste celluloses extracted are promising to produce CMC under milder conditions in comparison to literature, yielding up to 227 % (w CMC/w cellulose) of water-soluble CMC at lower AT and RT. The optimized process is more sustainable, low-cost, and efficient for producing this high valued-added cellulose derivative in the concept of biorefinery.