Obtenção de biocarvão a partir da mistura entre leucena (Leucaena leucocephala) e licor preto industrial para remoção de corantes têxteis

Abstract

Considering that the textile industry is one of the industries that produces the most water and pollutes it, awareness of the environmental impact of these effluents has led to the search for alternative processes and materials to treat these residues. In this context, this study aimed to develop materials from the mixture of parts of leucaena (Leucaena leucocephala) with black liquor , aiming at their application in adsorptive processes for the removal of textile dyes. For this purpose, parts of leucaena (pod and/or seed) were mixed with black liquor . The solids were carbonized in a muffle furnace under an inert atmosphere. Charcoals from the precursor biomass was also obtained for comparison purposes. The solids (precursors and coals) were characterized by thermogravimetric analysis, Fourier transform infrared spectrum, X-ray diffraction, scanning electron microscopy , zero-charge point and Raman spectroscopy analysis with confocal microscopy , and evaluated as adsorbents, using methylene blue as a model molecule. The thermogravimetric analysis of the biomasses indicated low variation in the mass loss for the precursors, in the range of 400 to 1000 ºC, with residual mass ranging from 25-54% up to 600 ºC. The infrared spectra confirmed the presence of several lignocellulosic functional groups in the biomass, as well as their elimination after pyrolysis. The diffractograms and Raman spectra confirm the predominance of amorphous carbon and disorganized structure in the coals. The adsorbents obtained from the mixture were efficient in removing methylene blue dye in solutions with pH values above the zero charge point (7.0-9.0), with removal between 87% and 94% for the seed and pod samples, respectively . The kinetic experiments best fit the pseudo-second-order kinetic model, with the materials presenting an adsorptive capacity of 3.64 mg.g-1 for the seed sample with liquor and 4.40 mg.g-1 for the pod sample with liquor.