Interactions of Cationic and Anionic Dyes with Activated Carbons

Abstract

Five kinds of activated carbon (AC1, AC2, AC3, AC4, and AC5) were prepared, and the characteristics (scanning electron microscopy images, specific surface area, pore-volume, pH_pzc, surface functional groups, and surface hydroxyl groups) of each activated carbon were investigated. Additionally, the adsorption capability of activated carbons and adsorption mechanisms involved in adsorption of cationic and anionic dyes from the aqueous solution were evaluated. The results suggested that the treatment of activated carbon with silver (AC3), titanium oxide (AC4), or magnetic field (AC5) was not useful for increasing specific surface area and micropore volume. Moreover, the amount of cationic and anionic dyes adsorbed using activated carbon prepared from coconut shells (AC1 and AC2) were higher than that adsorbed using AC3, AC4, and AC5. Subsequently, the adsorption mechanism involved in adsorption of cationic and anionic dyes was also assessed. It was found that the amount of cationic and anionic dyes adsorbed was related to the specific surface area, micropore volume, and acidic or basic functional groups. Finally, the interactions between dyes and AC1 were elucidated in this study. Adsorption of dyes onto the AC1 surface was confirmed by the elemental distribution and X-ray photoelectron spectroscopy analysis. These results provide useful information on the surface interactions between the activated carbon and dyes (high molecular organic compounds).