Bamboo/ lignite-based activated carbons produced by steam activation with and without ammonia for SO ₂ adsorption

A columnarbamboo/ lignite material was prepared by briquetting a mixture of bamboo carbon and lignite. Activated carbons were obtained by carbonizing the material at 500 °C for 30 min, followed by activation at 850 °C for 2 h using either steam or a gaseous mixture of ammonia in water with an ammonia concentration of 2. 42 mass%. The ammonia-activated carbon was soaked in 21. 91% ammonia water for 5 h and dried at 200 °C to modify its surface chemical properties. The pore structure and surface chemical states of the activated carbons were investigated by physical adsorption and XPS. Their desulfurization performance was  evaluated in a simulated flue gas (SO ₂ 0. 1439%, O ₂ 8. 02% and water vapor 10. 11%) at 100°C. Results show that the activated carbons produced with and without ammonia have similar pore size distributions in the range 1-2. 5 nm. Sulfur adsorption capacity of the ammonia-activated one (106. 1 mg/ g) is significantly higher than those of the steam-activated one (69. 8 mg/ g). Surface modification of the ammonia-activated carbon further improves its sulfur adsorption capacity to 155. 9 mg/ g. The surfaces of the two kinds of activated carbons contain the same type of carbon groups. The ammonia-activated carbon and its surface modified derivative have similar nitrogen contents with a similar proportion of pyridine or nitrile groups (398. 3-398. 9 eV), amine, amide, imide and pyrrole class groups (400. 2-400. 8 eV).