Adsorption behavior of ammonia and trimethylamine in pores of oxygen plasma treated activated carbon.

Abstract

The adsorption characteristics of ammonia and trimethylamine into pores of oxygen plasma treated activated carbon (PT-AC) were investigated in terms of adsorption isotherms, desorption isotherms, and isosteric differential heats of adsorption. The acid functional group concentration of PT-AC was increased 4 times as compared with that of raw activated carbon (R-AC). The surface area and pore volume of PT-AC were about the same as those of R-AC, but the adsorption capacity for ammonia was remarkably increased over that of R-AC. The adsorption capacity for trimethylamine was about the same as that of R-AC. The adsorption of ammonia and trimethylamine on PT-AC was found to be physical adsorption from the desorption isotherms. In the initial stage of adsorption, the isosteric differential heat of adsorption of ammonia on PT-AC was approximately twice that on R-AC. It seems that the amount of ammonia adsorbed on activated carbon is greatly increased by oxygen plasma treatment, probably because acid functional groups produced in the pores attract ammonia in the initial stage of adsorption. It is concluded that PT-AC is a characteristic adsorbent having a remarkably increased adsorption capacity for ammonia, which is a small and weakly basic molecule.