Sorption behavior of cationic and anionic dyes from aqueous solution on different types of activated carbons

The effect of dye molecular charges on their adsorption from solution was i nvestigated by using different types of activated carbon adsorbents. Two ty pes of model systems were used representing cationic and anionic dyes. Scre ening investigations using single point tests were used throughout the stud y. Cationic dyes, of which Methylene Blue is an example, showed a higher ad sorption tendency towards activated carbon over anionic dyes represented by an ate-type reactive compound. Of the number of activated carbons tested, only one of the adsorbents showed an exception to this behavior, and a good relation was observed between Methylene Blue capacity and activated carbon performance. The high capacity of cationic dyes in comparison to anionic d yes was also evident in the results obtained by a preliminary kinetic study carried out on the selected systems. Surface net charge of activated carbo n and the nature of attractions between the molecules were suggested to be one of the reasons attributed for this behavior.