ACID TREATMENT OF LIGNITE AND ITS EFFECT ON ACTIVATION

Coal specimens with different contents of inorganic constituents were produced from Greek lignite under various acid treatment conditions. A ctivated carbons were produced with heat treatment of the raw and acid -treated lignites at 900-degrees-C. Characterization of the activated carbons was accomplished by adsorption of N2 at 77 K and CO2 at 298 K. Adsorption isotherms were analysed by the Dubinin-Radushkevich method to give an assessment of the micropore volumes. The ash content of th e lignites depended upon the type of the acid used and the treatment s tages. Removal of the catalytically active inorganic constituents brou ght about a lowering in the reactivity of the acid-treated coals. Comp lete demineralization resulted in activated carbons with a highly deve loped microporosity and very large pore volumes. However, activated ca rbons from lignites with medium ash content presented values of pore v olume lower than the respective values of the above samples, yet excee ded the corresponding volumes of carbons from untreated lignite.