Combined Removal of Zinc (II) and Cadmium (II) from Aqueous Solutions by Adsorption onto High-Calcium Turkish Fly Ash

The aim of this work is the investigation of possible use of flyash in the removal of zinc (Zn²⁺) and cadmium (Cd²⁺) contained in aqueous solutions. Batch adsorption experiments wereperformed in order to evaluate the removal efficiency oflignite-based fly ash. The parameters studied include contact time, pH,temperature, initial concentration of the adsorbate and fly ashdosage. The contact time necessary to attain equilibrium was found to be two hours. Maximum adsorption occurred in the pH range of 7.0 to 7.5. The percent adsorption of Zn²⁺ and Cd²⁺ increased with an increase in concentration of Zn²⁺ and Cd²⁺, dosage of fly ash and temperature. Theapplicability of Langmuir isotherm suggests the formation ofmonolayer coverage Zn²⁺ and Cd²⁺ ions at the outer surface of the adsorbent. Thermodynamic parameters suggested the endothermic nature of the adsorption process. The fly ashwas found to be an metal adsorbent as effective as activated carbon.