Development and characterization of microwave-assisted activated carbons from Parkinsonea aculeata wood

Activated carbons from invasive Parkinsonia aculeata wood sawdust were developed by microwave assisted H3PO4 acid activation varying the radiation time (2-10 min). Their main physicochemical characteristics were determined, and compared with those of a sample previously obtained by conventional heating using the same precursor, chemical agent, and impregnation ratio. The activated carbons developed for radiation times of 5 and 10 min showed higher BET surface areas (similar to 1300 m(2)/g) and total pore volume (1 cm(3)/g) than those obtained at 2 min (similar to 710 m(2)/g) or by conventional heating (similar to 970 m(2)/g). Microwave assisted activation also led to activated carbons with higher total amounts of acidic oxygen and basic functionalities in comparison with the sample arising from conventional heating. Phenol adsorption capacity for all the samples was also evaluated from determination of the adsorption isotherms and their proper description by the Freundlich model. The adsorption capacity for the activated carbons obtained at 5 and 10 min was almost twice that measured for the samples prepared at 2 min and by conventional heating, in agreement with the higher BET surface areas characterizing the former. Compared with conventional heating, the process assistance by microwave energy not only reduced operation time, but also improved the characteristics of the resulting activated carbons.