Effect of pyrolysis temperature and hydrothermal activation on structure, physicochemical, thermal and dye adsorption characteristics of the biocarbons.

Abstract

In this study, the possibility of using sawdust from mixed woods to obtain biocarbons in the pyrolysis and steam activation using microwave radiation as an energy source was investigated. Biocarbons were characterized based on the results of N2 adsorption, thermogravimetric analysis (TGA), Fourier spectroscopy (ATR-FTIR), and Raman spectroscopy. Surface characterization was performed by Boehm titration and pHpzc determination. The adsorption capacity of methylene blue (MB) and methyl orange (MO) was studied. It was proved that the pyrolysis temperature and hydrothermal activation increased the biocarbons structural, surface and adsorption parameters of the obtained biocarbons. The amorphous materials of small specific surface area with a significant share of micropores were obtained. The steam activation resulted in significant development of the porous structure (to SBET =729.2 m2 /g and Vp =0.36 cm3 /g). The presence of functional groups, mainly phenolic ones, and pHpzc values indicating a potential for adsorption applications regarding MO and MB were found. The highest sorption capacity concerning MB (qe =122.8 mg/g) and MO (qe =99.1 mg/g) was observed for the steam-activated biocarbon BC-800MW . Using microwave energy hydrothermal activation proved very efficient, resulting in significant surface area and porosity development with a small loss of carbon matter.