Application of fly ash and activated carbon in the removal of Cu2+ and Ni2+ ions from aqueous solutions

The main objective of this study was to remove Cu(2+) and Ni(2+) ions from aqueous solution by using fly ash, an industrial solid waste of the sugar industry and commercial activated carbon at equilibrium, which follows Langmuir and Freundlich adsorption isotherms. In order to identify influential parameters and to evaluate their interactions, effects of time, pH, initial metal concentration, and amount of adsorbent were studied, and the results were compared with those of activated carbon under the same experimental conditions. Adsorption studies were performed in a time interval (1-240 min), at various pH values (2.0-8.0) at 25 degrees C and at metal concentrations of 1-10 x 1(-4) M using different amounts of adsorbent (1-12 g/L). The equilibrium time was fixed at 60 min in the case of Cu(2+) and Ni(2+), and 8 g/L of fly ash and 6 g/L activated carbon was sufficient for the optimum removal of both the metal ions. The sorption of metal ions increased with an increase of pH, and maximum removal was obtained at 5.0 for fly ash with 97.2% and 78.2% removal for Cu(2+) and Ni(2+) ions, respectively. For AC, on the other hand, maximum removal was obtained at 4.0 for Cu(2+) and 6.0 for Ni(2+) with 95.0% and 63.0% removal, respectively. The adsorption capacities are 7.0 mg/g for Cu(2+), 5.9 mg/g for Ni(2+) for fly ash, and 6.9 mg/g for Cu(2+), 5.4 mg/g for Ni(2+) for activated carbon. The orders of adsorption of heavy metal ions for fly ash and activated carbon change in the order of Cu(2+) Ni(2+) and Cu(2+) Ni(2+), respectively. The fly ash was found to be a metal adsorbent as effective as commercial activated carbon.