Adsorption characteristics of activated carbon obtained from rice husks by treatment with phosphoric acid

Ground rice husks were impregnated with phosphoric acid (30-70 wt.%) followed by carbonization at 673 or 773 K. Analysis of the nitrogen adsorption isotherms was achieved by applying the BET, DR, t- and alpha(s)-methods so as to assess the contribution of micropores and mesopores in the products. The washed products showed reasonable surface areas with dimensions in the micropore range. Adsorption of methylene blue from aqueous solution indicated high affinity and high dye removal capacity. Low iodine numbers and methylene blue values were ascribed to the high ash content extending up to 50% of the activated carbon. Pre-impregnation with 50% H3PO4 and carbonization at 400 degrees C proved to be most effective in producing an activated carbon with the highest adsorption capacity from the gas or solution.