Phosphoric acid activation of agricultural residues and bagasse from sugar cane: Influence of the experimental conditions on adsorption characteristics of activated carbons

Activated carbons from two different types of sugar cane wastes, agricultural residues and bagasse, were prepared by phosphoric acid activation varying the carbonization temperature (300-600 degreesC), the weight ratio of phosphoric acid to precursor (R = 1-2.5), and carbonization time (0-3 h). Surface properties of the resulting carbons were markedly dependent on the precursor and a combined effect of the conditions employed. Bagasse carbons showed higher surface area and pore volume than those from agricultural residues. Maximum surface areas of around 1100 and 780 m(2)/g were respectively attained. Temperature above 500 degreesC, impregnation ratio higher than 2, or prolonged carbonization beyond Ih led to reduction in porosity development. Selected carbons from both wastes with relatively large mean pore radius showed good ability to decolorize a diluted solution of synthetic melanoidin, used as a model of molasses wastewater. Iodine number between 608 and 746 and methylene blue uptake of 213-261 (mg/g) were determined for the selected samples.