Abstract: Modification of activated carbon could increase the content of surface acid functional groups and NH₃ adsorption capacity, which would strengthen adsorption refrigeration process using activated carbon-NH₃ working pairs. Modification reagents were screened out. The effects of modification conditions on the content of superficial groups were investigated. Superficial microstructure of modified activated carbon was analyzed by FT-IR and SEM. Adsorption capacity of NH₃ on activated carbon was measured. The results show that nitric acid modification can obviously increase surface acid functional groups of activated carbon. The feasible modification conditions are: concentration of nitric acid 4 mol/L, temperature 20℃, modification time 12 h. Compared to the original sample, the acidic functional groups content of activated carbon increased 3.5 times, adsorption capacity for NH₃ increased 36.98% while iodine value decreased 9.20% after nitric acid modification.

Key words: activated carbon, adsorption, NH₃, functional groups