Produção de biocarvão por diferentes rotas a partir do resíduo lignocelulósico industrial visando a adsorção de poluentes emergentes

Abstract

Lignocellulosic waste is obtained from the production of second-generation ethanol (2G). This material is rich in lignin, and its main application is in energy production through combustion in boilers. In this study, pyrolysis, biochar activation, and catalytic pyrolysis of this residue were conducted to obtain biochar for its application in the adsorption process of methylene blue dye and the hormone 17β-stradiol. The preparation of the biomass and its characterization were performed using proximate analysis, thermogravimetric analysis (TGA) of the biomass and biomass impregnated with the K2CO3 catalyst (3:1). The produced biochars were characterized using scanning electron microscopy (SEM), pH at the point of zero charge (pHzpc), N2 adsorption/desorption isotherms using the BET method, Fourier-transform infrared spectroscopy (FT-IR), and energy-dispersive X-ray fluorescence spectroscopy (EDX). Finally, batch adsorption studies were conducted with biochar, activated biochar, and catalytic biochar, analyzing the kinetic, isotherm, and thermodynamic parameters. Catalytic pyrolysis showed a higher yield of solid product compared to conventional pyrolysis. The characterization techniques indicated that both catalytic pyrolysis and biochar activation resulted in pore opening in the biochar, leading to an adsorbent with greater surface area and pore volume (261, 736, and 600 m²/g for biochar, activated biochar, and catalytic biochar, respectively). The biochars exhibited behavior according to the pseudo-second-order model, with similar percentages of methylene blue removal for activated biochar and catalytic biochar (85.8 – 99.1% and 95.7 – 99.3% for activated and catalytic biochar, respectively). In the removal of 17β-stradiol, activated biochar showed significantly higher removal percentages than catalytic biochar (73.9 – 76.7% and 37.6 – 65.3%). The Sips model was most suitable for the adsorption data of 17β estradiol for all biochars, while for methylene blue dye, the Freundlich model was applicable to biochar and activated biochar, and the Langmuir model for catalytic biochar. The process was feasible and spontaneous in all cases, being endothermic and accompanied by an increase in entropy, except for the adsorption of 17β-stradiol by catalytic biochar. It was concluded that activation and catalytic pyrolysis increased the adsorptive potential of biochar, and that, for some adsorbates, catalytic biochar shows results similar to those of activated biochar, which is advantageous considering the reduction in the number of steps required for preparing catalytic biochar and consequently a reduction in process costs.