Fig. 1 shows the SEM image of the CaO catalyst obtained from the calcination–hydration–dehydration treatment of egg shells (i.e.) Egg shell-CaO-900-600. It indicates a honey comb like porous surface as observed by Hu et al. for the treated mussel shell. However in the case of the Egg shell-CaO-900, regular micro morphology of rod like particles with size ranging from 1.29 to 2.0 lm of width was observed (Fig. 2).