CAPTURE OF AMMONIA BY ACTIVE-CARBON FIBERS FURTHER ACTIVATED WITH SULFURIC-ACID

Capture of ammonia (100 ppm) in the atmosphere was studied at room temperature on active carbon fibers (PAN, pitch, and phenol resin based ACFs) and their further activated forms with sulfuric acid. The as-received ACFs absorbed only 0.2% of ammonia until its breakthrough. Activation with sulfuric acid by impregnation and heating at 250-degrees-C for 4-6 h increased remarkably adsorption up to 3% in repeated uses after regeneration at 185-degrees-C. Two kinds of acid sites were found after the activation; the remaining H2SO4 and acidic oxygen containing groups. The latter groups are produced by oxidation through the reduction of SO3 to SO2 to contribute the regenerable adsorption of ammonia. Hence the adsorption capacity of ACFs was linearly correlated with the amount of evolved CO2 at 250-400-degrees-C in their temperature-programmed-decomposition profiles. The regeneration conditions were intended to remove ammonia from the surface of ACF without decomposing the acidic oxygen sites.