Desenvolvimento de materiais carbonáceos funcionalizados com nitrogênio a partir de biomassa Quitina e Quitosana para a adsorção de compostos voláteis

Abstract

The emission of volatile organic compounds is a major concern worldwide, and on the part of the researchers, increasing attention is being paid to indoor air quality and associated health problems. Because it is harmful to health and the environment, the effort by researchers to search for new materials that help to combat the exposure of these compounds has been constant. Formaldehyde, in particular, is classified by IARC in group 1 - carcinogenic to humans, is present in several industrial sectors and the fight against its exposure has gained a lot of space. Carbonaceous compounds, such as activated carbon, have been widely used in adsorptive processes involving volatile compounds. The purpose of this work is to explore new sources of production of carbonaceous material, based on renewable raw material abundant in nature, such as chitin and chitosan, and which has characteristics applicable to the adsorption of volatile compounds. Using the pyrolysis process, the precursor material is transformed into a porous carbonaceous material, which has a good physical adsorption capacity. In addition, these materials have significant nitrogen content in their composition, even after the pyrolysis process, which results in an increase in the affinity between adsorbent and adsorbate, given the additional possibility of chemical adsorption. The samples of chitin and chitosan used in this work, of commercial origin, were pyrolysed at temperatures 500, 600, 700 and 800 ° C. The elementary analysis (CNHS) indicated that pyrolysis in the 700 ° C range results in a sample with adsorptive potential because it presents percentages of carbon and nitrogen required for this application. The Fourier transform infrared (FTIR) analysis indicated that, after pyrolysis, the functional groups that were present in the raw material are no longer observed. Analysis by Raman spectroscopy and X-ray diffraction revealed that the samples may have a mixed structure, containing amorphous, crystalline and nanocrystalline structures. The analysis by scanning electron microscopy (SEM) added information about the surface of the thermally treated materials at a temperature of 700 ° C. The evaluation of the porosity through the method of multimolecular adsorption (BET) showed that the pyrolyzed samples at 700 ° C have pores with size between 2 - 50 nm. Finally, preliminary tests using carbonaceous materials derived from pyrolyzed chitin and chitosan, when exposed to an atmosphere of 25 ppm formaldehyde for 1 h, revealed that pyrolyzed chitin had an adsorption capacity of around 71%, while for pyrolysed chitosan this value was 58%.