Application of Fly Ash and Activated Carbon in the Removal of Cu²⁺ and Ni²⁺ Ions from Aqueous Solutions

Abstract

The main objective of this study was to remove Cu²⁺ and Ni²⁺ 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°C and at metal concentrations of 1–10 × 1⁻⁴ M using different amounts of adsorbent (1–12 g/L). The equilibrium time was fixed at 60 min in the case of Cu²⁺ and Ni²⁺, 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 Cu²⁺ and Ni²⁺ ions, respectively. For AC, on the other hand, maximum removal was obtained at 4.0 for Cu²⁺ and 6.0 for Ni²⁺ with 95.0% and 63.0% removal, respectively. The adsorption capacities are 7.0 mg/g for Cu²⁺, 5.9 mg/g for Ni²⁺ for fly ash, and 6.9 mg/g for Cu²⁺, 5.4 mg/g for Ni²⁺ for activated carbon. The orders of adsorption of heavy metal ions for fly ash and activated carbon change in the order of Cu²⁺ > Ni²⁺ and Cu²⁺ > Ni²⁺, respectively. The fly ash was found to be a metal adsorbent as effective as commercial activated carbon.

Keywords:

• activated carbon
• adsorption
• copper and nickel
• fly ash
• solid waste utilization
• sorption isotherms

Acknowledgment

This study was supported by the Scientific Research Foundation (BAP in Turkish initials) of Selçuk University (Project No. 2003/028).

Notes

^a mmol/g adsorbent;

^b 1/mmol.