Activated carbon from cotton stalks by impregnation with phosphoric acid

Dried, crushed cotton stalks were impregnated with varying concentrations o f phosphoric acid (20-85 wt.%), dried at 383 K and carbonized at 773 K for 2 h. Porosity was determined by analysis of N-2/77 K adsorption isotherms. High adsorbing carbons with well developed mesoporosity were obtained. Anal ysis for microporosity, by the alpha(S)-method, proved the presence of mino r content in all products. Non-dried impregnated precursor produced a carbo n with much lower adsorption capacity, whereas carbonization at 673 K furni shed a carbon with comparatively lower texture parameters. TG analysis of t he acid-impregnated precursor exhibited considerable modification in the py rolysis characteristics. The effect of activant was associated with its eff ect as dehydrant, shift in decomposition to higher temperatures, suppressio n of volatiles, and space left by its leaching thereafter. (C) 1999 Elsevie r Science B.V. All rights reserved.