PREPARATION OF ACTIOVATED CARBONS FROM LONGAN SEED BY PHYSICAL AND CHEMICAL ACTIVATION METHOD
Keywords:
Activated carbon, porosity, adsorption, longan seedAbstract
Longan seed is the solid waste that is produced from the fruit cannery in Thailand. This work aims to convert this solid waste into the useful activated carbon adsorbent, the process of which is considered to be a more effective means for waste disposal control. The activated carbons were prepared by two typical methods, physical activation with carbon dioxide and chemical activation by phosphoric acid. The porous properties of the derived activated carbons were characterized using nitrogen adsorption isotherms at -196°C. Activation temperatures in range of 800 - 900°C and activation time 30 - 180 min were studied in the physical method. Chemical activation was limited to study only the carbonization temperature in the range of 400 - 900°C. In physical activation, the increasing in activation temperature or activation time resulted in an increase in the burn-off in the range of 14 - 90%. For increasing burn-off up to 70%, the BET surface area and total pore volume increased and reached a maximum with the values of 1,278 m²/g and 0.81 cm³/g, respectively, then they decreased at higher burn-off levels. The correlation between the porous properties such as the BET surface area, total pore volume and micropore volume with the burn-off level could be described by the third-order of polynomial equation. Chemical activation produced the activated carbons with the BET surface area and total pore volume in the range of 651 - 946 m²/g and 0.33 - 0.49 cm³/g, respectively. These porous properties decreased with increasing in carbonization temperature from 400°C to 700°C, and then tended to increase at higher temperatures.
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