With activation time going on, the
increase of micropores gradually became slow and a slight drop
was observed at 30 min, while the mesopore surface and volume
went up steadily in the whole process. This phenomenon implied
that the formation of new pores became less significant as the activation
proceeded, and the micropores were continuously widened
into larger ones, resulting in the increase of mesopores. Another
possible reason for the loss of micropores was that they might also
be destroyed after long time exposure to the microwave radiation.A
similar tendency has been observed in the preparation of activated
carbon from rice husk (Kennedy et al., 2004).