Abstract: Three types of ammonia modification was carried out in 300-1 000 ℃ using nitric acid oxidized activated carbon obtained commercially from steam activation using coconut shell as raw materials. The formation and evolution of surface nitrogen functional groups of the activated carbon were investigated. Element analysis, Boehm titration and X-ray photoelectric spectroscopy (XPS) were employed to determine the element contents, acid and basic functional groups contents and the types of nitrogen-containing functional groups of activated carbons. The results showed that when the activated carbon were treated at the temperature below 700 ℃, nitrogen functional groups were mostly nitrogen oxides(N-X, such as amides, imides and lactams) generated mainly by combining ammonia and surface oxygen-containing functional groups, and some pyridinic(N-6) and pyrrolic(N-5) groups by the reaction of ammonia and carbon atoms in the carbon matrix. when the temperature increased to 800 ℃, the formation of nitrogen functional groups were contributed to the combination of ammonia and carbon atoms and pyridinic, pyrrolic and quaternary(N-Q) groups were predominantly generated. With the temperature increasing, amides, lactams and imides were progressively converted into pyridinic, pyrrolic groups and eventually into quaternary groups. Besides, there was no quaternary surface group below 800 ℃.

Key words: activated carbon, ammonia modification, nitrogen functional groups, evolution