Enhanced SO2 adsorption and desorption on chemically and physically activated biochar made from wood residues

摘要

SO2, one of the most harmful gases, is generated when oxygen in air combines with sulfur species from anthropogenic sources (e.g., the smelting of mineral ores). Thus, the objectives of this study are to assess the potential use of activated biochar for the removal of SO2, and to compare the impact of the activation process on the development of porosity and surface chemistry for SO2 adsorption. Results show that activated biochars develop porosity (with narrow and wide pores) and functional groups connected to their surface, which makes these materials suitable for adsorption of SO2. However, no linear relationship between textural properties and the amount of SO2 adsorbed by activated biochars from dynamic adsorption tests were noticed. In addition, the highest SO2 adsorption capacity was not reached for materials with the highest surface area, or micropore or ultramicropore volume. Specifically, steam-activated biochar had the best performance for the removal of SO2 due to its optimal surface area (590 m(2) g(-1)); volume of ultra- (0.22 cm(3) g(-1)), micro- (0.23 cm(3) g(-1)), and mesopores (0.11 cm(3) g(-1)); its basic character (not from nitrogenated groups); and the low percentage of acid-oxygenated functional groups connected to its surface. After six thermal regeneration cycles, activated biochar exhibited high SO2 removal capacity and high regenerability. Based on these findings, activated biochar made from forest wood residues has promising potential for the removal of gas contaminants.