High Surface Area Activated Carbon from Sugar Cane Straw

Abstract

Activated carbon from sugarcane residues, bagasse and straw was obtained with phosphoric acid activation. All samples were characterized by N2 adsorption–desorption isotherm, scanning electron microscopy, coupled with energy dispersive microscopy, X-ray photoelectron spectroscopy and thermal analysis. The advantages of using a ball or hammer milling process were investigated, together with the effect of the impregnation ratio and its influence on the final activated carbon porosity. The results show that all samples exhibit a high surface area and well developed porosity, but those which were ball-milled have a greater gas adsorbed amount, especially those which had straw (1415 m2/g) as precursor material. Furthermore, the results suggest that the process may have an optimum impregnation ratio, which should be around 2 or 3, irrespectively of the lignocellulosic source material. The mechanochemical process seems to be more relevant than the percentage of cellulose in the raw material. According with spectroscopy results, the homogeneous distribution of phosphorus throughout the sample was verified, even after repeated washing steps. Surface phosphate linkages like C–O–PO3 and C–PO3 were also detected.