Compósitos de carvão ósseo disperso em quitosana: alternativas ambientalmente amigáveis aplicadas na remoção de cromo e ferro

Abstract

The demand for food production has favored the increase in the generation of solid residues in the meat industries, which leads the scientific community to aim at the development of products, synthesized from residues. From this context, the main objective was based on synthesizing bone char composites dispersed in chitosan, indicating the composition and physicochemical properties, through vibrational spectroscopy techniques in the infrared region (FTIR), total carbon content, thermogravimetric analysis (TGA), differential thermal analysis (DTA), Raman spectroscopy and zero charge point (PZC), as well as evaluating the ability to remove chromium and iron species in aqueous media. From the proposed bone char synthesis, it was possible to obtain a yield of 55% (m/m). The synthesis of composites of bone char dispersed in chitosan resulted in an increase in the total carbon content after the dispersion of char in chitosan when compared to pure bone char. The FTIR spectra revealed that the bands described for pure char, mainly in relation to the phosphate group bands, become evident with the increase in the proportion of char in the chitosan matrix. Likewise, the characteristic bands of the polymer decrease in intensity with the increase in the amount of char introduced into the dispersion matrix. As a complementary analysis to FTIR, the Raman spectrum revealed a higher index to amorphous carbonic structures and the presence of structural defects present in pure char. From the profile of the TGA and DTA curves in an inert atmosphere and in an oxidizing atmosphere, it was possible to identify that bone char has greater thermal stability when compared to chitosan, indicating that the greater dispersion of bones in chitosan contributed to the increase in the thermal stability of the materials composites. The PZC results revealed that the zero charge point is within the range of pH considered neutral ~ pH 7. The chromium removal tests revealed that chitosan is the component that significantly contributes to the chromium removal in the proposed system, with removal capacity ranging from 25.4–57.6 mg g-1. The tests performed for iron revealed a symbiotic contribution between bone char and chitosan, with a removal capacity between 2.2–146.4 mg g-1. The results revealed the incorporation of specific and complementary functional groups in the synthesized composites, due to its formulation composed of bone char (mineral component) and chitosan (organic component), offering new binding sites for potentially polluting species that otherwise would not have been removed in large proportions.