The charcoals were activated at 850 C with CO2 over different
time intervals of 0.5e4.0 h. The evolution of burn-off grade and
activated carbon yield as a function of activation time is shown in
Fig. 3. An increasing activation time progressively increases the
burn-off grade and reduces the yield of activated carbon; this was
expected, since an increase in burn-off represents an increase in the
weight losses due to the activation process, thereby resulting in a
decreasing yield. It was observed that the relationship between
burn-off and activation time was linear.
Pendyal et al. [14] verified that an activation time of 6.0 h was
necessary for the production of granular activated carbon from
sugarcane bagasse/molasses (1:0.5 ratio) with a burn-off grade of
26%; however, the researchers used a 13% CO2 and 87% N2 gas
mixture for pyrolyzed carbon activation. In our case, the carbon
materials were activated with pure CO2, with a burn-off of 25%
obtained in 2.0 h.