Aplicação de hemiceluloses catiônicas sintetizadas a partir de hemiceluloses extraídas de holoceluloses obtidas por diferentes métodos de deslignificação da palha de milho, como coagulante em tratamento de efluente de laticínio

Abstract

The corn straw lignocellulosic biomass biorefinery was investigated in this project. Corn straw is an agribusiness residue with the potential to be used and valued in biorefineries and the circular economy. In this residue, the lignocellulosic biomass contains cellulose, lignin and hemicelluloses, macromolecular structures that can be used and valued using the concept of biorefinery. The hemicelluloses extracted from corn straw can be used, when cationized, as a natural organic coagulant in the treatment of water and effluents. The objective of this project was to investigate two synthesis processes of cationic hemicelluloses (CH), both extracted from corn straw, and to apply them as a primary coagulant in the treatment of synthetic dairy effluent (SDE). The extraction of natural hemicelluloses (NH) occurred by two delignification strategies: oxidation with sodium chlorite (NH CHL) and with hydrogen peroxide (NH PER), with 80% reduction in synthesis time and 86.34% in cost, both methods followed by cationization with 2,3-epoxy-propyl-trimethyl-ammonium chloride (ETA) to obtain CH CHL-ETA and CH PER-ETA, respectively. The FT-IR spectra of the CHs showed an increase in the intensity of the methyl groups band (-CH3), at 1480 cm-1, strongly indicative of cationization. The DS of 0.39 ±0.01 for CH CHL-ETA and 0.34 ±0.01 for CH PER-ETA were sufficient to increase the solubility in water. The efficiency of the coagulants was tested in jar test, for dosages from 6.25 to 50 ppm and coagulation pH from 5 to 11. The coagulation diagrams generated by the spatial interpolation method of the adapted Kriging regression model showed conditions of maximum performance in the treatment physical-chemical with CH CHL-ETA and HC PER-ETA, respectively, of 18.75 ppm at pH 11 and 12.5 ppm at pH 10, with removal of turbidity, true color and COD of 83.74%/ 73.61% 93.33%/ 84.91% and 55.67%/ 64.90%. Both cationic hemicelluloses showed high performance at basic/neutral pH. Obtaining cationic hemicelluloses using hydrogen peroxide as an oxidant was simpler, faster and had proven effectiveness. With an overview of the coagulation diagrams, it could be seen that cationic hemicelluloses perform well at more basic pHs, but can also provide good results at pHs closer to the natural pH of the synthetic dairy efluente (7.92).