Síntese de Hemiceluloses catiônicas por indução de micro-ondas para utilização como coagulante em tratamento de efluentes industriais

Abstract

Cationic hemicelluloses (HC) are biopolymers used by the modification of natural hemicelluloses (HN), from peanut shell, with a quaternizing agent. In this paper was used 2,3-epoxypropyltrimethylammonium (ETA). HC can be used as coagulation aids or primary coagulants in wastewater treatment. The purpose of this work consisted of the synthesis of HC assisted by microwave, which has stood out when compared to the conventional mode of synthesis, performed in basic solution, for presenting relevant advantages of energy saving, less reaction time and providing greater degree of substitution (GS) in the chemical structure. Initially, the variables were screened: (B) NaOH volume, (T) reaction time; (W) volume of H2O, and (E) volume of ETA. As a result of the analysis of the variables, the contents of C, H and N were provided, from which the GS calculation was performed, which incorporates a maximum of 50% (compared to the conventional synthesis method) for the B+T+W-E+ sample, which indicates that the reaction time variable was more determinant. The extended infrared spectra that the cationization of hemicelluloses caused intensification of the band in 1624 cm-1 regarding the etherification of the structure and indicators of the presence of amine salts, suggesting efficiency of cationization of the hemicelluloses, showing that these groups were incorporated in the structure of HC . Thermograms indicated greater thermal stability for the HCM sample (B+T+W-E+), showing greater proximity with the HCC thermogram. In the physical-chemical treatment, all HC presented efficiency of turbidity removal greater than 80%, when applied in association with Tannins - both in neutral and acidic media - determining the greatest effect on the coagulation process. The association of HCM + Tannin solubilized in neutral solution, showing greater efficiency (86%) of removing turbidity. And HCM + Tannin solubilized in acid solution showing efficiency (83%) and the lower sludge volume. So, we concluded that the use of microwave irradiation as a heating source for syntheses of Cationic Hemicelluloses coagulants, represented a significant advance for the area of synthesis research. Given the three principles of green chemistry: Decrease in the use of solvents and auxiliaries; Energy efficiency and; Use of substances from renewable sources