Valorização do biossorvente de bagaço de cana-de-açúcar pós adsorção: dessorção e potencial energético

Abstract

Aiming at the valorization of agro-industrial residues and with the objective of adding value to this industry by-product, the use of chemically treated sugarcane bagasse in the adsorption process of a synthetic effluent contaminated with dye Neolan Black WA was studied. The first process performed was adsorption, which showed satisfactory results, with qe,adsorption of 6.32 (mg.g-1) and percentage of 94.8% of dye removal. Then, the study of the dye's desorption kinetics was carried out, seeking to know its efficiency and percentage of dye removal now contained on the bagasse surface. For this, two tests were carried out with different temperatures, of 25C and 50C. For the procedure performed under a temperature of 25C, a desorption percentage of 6.12% and a qe, desorption of 0.32 (mg.g-1) were obtained. On the other hand, for the other temperature tested, the obtained results were 3.64% of removal efficiency and qe,desorption of 0.19 (mg.g-1). Data obtained after the desorption process were fitted to the pseudo-first order and pseudo-second order kinetic models using the SciDavis© software. The pseudo-second order model was the one with the best fit to the experimental data of the processes performed in both mentioned temperatures, showing correlation coefficients of 0.962 and 0.971, kinetic constants of 0.060 and 0.277 and qe,desorption of 0.329 and 0.211 for temperatures of 25 and 50C, respectively. To study the structure of the biomass used and the functional groups present in it, after the adsorption process, Fourier transform infrared spectroscopy (FTIR) analyzes were performed, where, through the transmittance peaks, it was possible to identify possible changes on the biosorbent structure after the adsorption and desorption tests. For this, the FTIR analysis of the same biosorbent, but raw, were used. To study the energy potential of the bagasse, the proximate analysis and combustion in a thermogravimetric analyzer were performed. The calculation of the high heating value (SCV) was also performed, using correlations found in the literature. From the proximate analysis, the percentages of volatile matter, ash and fixed carbon were found, being these values 83.18%, 1.72% and 15.10%, respectively. The HHV values found were 13.3 (MJ.kg-1) for the correlation of Demirbas (1997), 14.81 for Cordero et al. (2001) and 15.78 for the correlation of Jiménez and González (1991). Using the Universal Analysis© software, the characteristic combustion temperatures were found for the raw and post-adsorption bagasse samples. For the raw sample, an ignition temperature (Tig) of 260.38C, a peak temperature (Tp) of 314.98C and a burnout temperature (Tb) of 505.20C were obtained. The post-desorption sample presented results of 298C for Tig, Tp of 338C and Tb of 520.32C. Comparing the results for the tested samples, it is concluded that the best sample for both the tested analyses, was the raw sample.