Arundo donax cane as a precursor for activated carbons preparation by phosphoric acid activation

Canes from Arundo donax, a herbaceous rapid-growing plant, were used as precursor for activated carbon preparation by phosphoric acid activation under a self-generated atmosphere. The influence of the carbonization temperature in the range 400–550 °C and of the weight ratio phosphoric acid to precursor (R=1.5–2.5) on the developed porous structure of the resulting carbons was studied for 1 h of carbonization time. Surface properties of the activated carbons were dependent on a combined effect of the conditions employed. Carbons developed either with R=1.5 over the range 400–500 °C, or with R=2 at 500 °C exhibited surface areas of around 1100 m2/g, the latter conditions promoting a larger pore volume and enhanced mesoporous character. For both ratios, temperature above 500 °C led to reduction in porosity development. A similar effect was found for the highest ratio (R=2.5) and 500 °C. The influence of carrying out the carbonization either for times shorter than 1 h or under flowing N2 was also examined at selected conditions (R=2, 500 °C). Shorter times induced increase in the surface area ( 1300 m2/g), yielding carbons with smaller mean pore radius. Activated carbons obtained under flowing N2 possessed predominant microporous structures and larger ash contents than the samples derived in the self-generated atmosphere.