Otimização da síntese de Carboximetilcelulose advinda de biomassas da coroa do abacaxi e do caroço da manga via planejamento experimental

Abstract

Lignocellulosic biomass from agro-industrial residues has stood out in research on its reuse and the conversion of its components, mainly cellulose, for the biorefinery sector. Among the high value-added polymers from cellulose, carboxymethylcellulose (CMC) stands out, with applications in various branches of industry. This work presents contributions to the biorefinery industry, through the use of pineapple (AB) and mango (MA) residues for the production of high reactivity pulps, ABCel and MACel, respectively. for conversion to high-quality CMC. The ABCel and MACel celluloses were extracted through the combined acid/peroxide-alkaline (APA) treatment, and later converted into CMC through the heterogeneous etherification process under different conditions, selected by a D-Optimal experimental design of 28 experiments, where the following factors were varied: Activation Time (TA), Reaction Time (RT), NaOH Concentration (NaOH%), Mass of monochloroacetic acid (Ac. HAcCl) and Cellulose (ABCel or MACel). Analytical techniques such as Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TG/DTG), X-ray diffractometry (XRD), scanning electron microscopy (SEM) and nuclear magnetic resonance (NMR) were used to characterize the materials studied, in order to evaluate the efficiency of the treatments and the reactivity of the celluloses produced. The characterizations proved the efficient extraction of high-purity cellulose, as well as its successful carboxymethylation, especially due to the appearance of the characteristic bands and peaks of CMC in the FTIR and NMR spectra. Models for evaluating the Mass Yield and Solubility responses were constructed through analysis of variance (ANOVA) with high precision (F = 36.36, p-value< 0.0001, R2 = 0.9655); in addition, optimization via response surface methodology (RSM) demonstrated that it is possible to generate products with good water solubility and significant yields (up to 244% w/w) from 135 min of carboxymethylation, with NaOH and monochloroacetic acid concentrations, as well as cellulose type, being the most significant factors in the response variation. These results reaffirm the potential of using agro-industrial waste as a sustainable raw material to produce CMC, with high mass yields and water solubility, in a more environmentally friendly process based on the principles of Green Chemistry.