Speed is the key for carbon
15 Jan 2000
Activated carbon is more active if it is made quickly, according to researchers at the University of Alicante. The researchers found that 'flash-carbonised' material can adsorb more gases than that made slowly, even though it contained the same volume of pores.
The team used olive stones as their raw material, heating them to 850 C in a stream of nitrogen. They prepared three samples: one in a horizontal reactor, raising the temperature at 5degC/min in an 80ml/min flow of nitrogen; another in a vertical reactor, with the same temperature rise rate and a 1275ml/min nitrogen flow; and the third in the same vertical reactor and flow-rate, but with the stones already heated to 850 C when they entered the reactor. Each sample was then 'flash-activated' with CO2.
The activation processes revealed that the flash-carbonised char was more active adsorbed more gas than the slow-made product.
This might be explained by the pore structure, they say. Total pore volume was much the same for all three samples, they say, but the 'fast' samples had a larger proportion of wide pores.
