Characterization and applicability of fly ash carbons in the removal of organo-metallic dye effluents

Fly ash carbons have been structurally altered while passing through the combustor by breaking and opening of aromatic structures, forming of condensed aromatic ring systems, interaction of C=C bonds with binding of oxygen, formation of C-oxygen functional groups, and bridging hydrogen bonds among other mechanisms Hence, fly ash carbons are characterized by a unique porosity, surface area, and surface chemistry and may constitute a precursor for the production of distinctive adsorbents. Both BET and high resolution SEM studies indicate that fly ash carbons have a concentration of mesopores which provide easy access to macro-molecular structures such as those encountered by dye molecules and other macro-molecular organic species. It was demonstrated in two different ways, by using reagent grade dyes and using residue dye effluents, that fly ash carbons (with the majority of the pores being in the macro and meso size range, >50 A), play a key role in removing macro-molecules with fast adsorption kinetics unlike active carbons and do so without the need for expensive activation steps. Characterization studies including high resolution HRSEM, XPS as well as in situ visualization of bacteria associated with the dye-effluents and their physical adsorption on the fly ash carbon surfaces are discussed.