ADSORPTION OF AMMONIA BY SEPIOLITE IN AMBIENT AIR
1991 年 8 巻 2 号 p. 87-100
詳細
1991 年 8 巻 2 号 p. 87-100
The adsorption of ammonia by sepiolite containing water previously adsorbed, was studied in ambient atmosphere.
The ammonia-adsorbing capacity of sepiolite grains, treated with water vapor, increased as the relative humidity in the air was lowered. The apparent ammonia adsorption isohume on sepiolite follows Freundlich's one. The amount of ammonia adsorbed on sepiolite grains was about 1.68 mg/g at 9.0% relative humidity in the air containing 10 ppm ammonia at 25°C, and it was about 0.32mg/g in the relative humidity range of 60 to 80010. It may be concluded that ammonia is adsorbed on the unoccupied pores in the channel inherent in the sepiolite structure and also on the water molecular layer covering the pore in the channel as well as on the outer surface of sepiolite. The former adsorption is remarkable when the relative humidity is below or equal to 9.0%, and the latter above 9.0%. The difference of ammonia adsorption between these cases, reflects the above-mentioned adsorption mechanisms.
The ammonia-adsorbing capacity of sepiolite powders, dried at 110°Cfor three days, decreased with the temperature in the air with the dew point of-9.0°C (PH2O=285 Pa). The apparent ammonia adsorption isotherm on sepiolite powders in the air also follows Freundlich's one. The amounts of ammonia, adsorbed on sepiolite powder were about 1.55 and 0.88 mg/g at 10 and 25°C, respectively, in the air with 285 Pa water vapor containing 10 ppm ammonia. It decreased gradually in the temperature range of 10 to 50°C, and reached about 0.65mg/g at 50°C. The amounts of ammonia adsorbed by coconut-shell active carbon was about 0.15 and 0.12mg/g at 10 and 25°C, respectively, in the same atmosphere. Therefore, those by the sepiolite were about ten and seven times higher than those of the carbon at 10 and 25°C, respectively.
