Removal of Cu2+ and Zn2+ in aqueous solutions by sorption onto mixed fly ash

Disposal of a growing amount of fly ash creates environmental problems due to the leachability of their heavy metal content. However, fly ash is shown to be efficient in the removal of heavy metallic ions in the aqueous phase , for example, in the polluted wastewater resulting from desulfurization tr eatment in power plants. The objectives of this work were to study the remo val of CU2+ and Zn2+ in water by sorption onto fly ash and fly ash mixture. The stability of the resulting cake was also approached in terms of leachi ng capability. Experimental design methodology was used in order to identif y influential parameters and to evaluate their interactions. Temperature, f ly ash to ion concentration ratio, and ash quality were particularly studie d. Different ashes and a fly ash mixture were investigated. They each have alkaline reaction with water to a different extent, and this allows the con trol of the pH solution without lime addition. Final metal ion concentratio n in solution, sorption capacity and ion leaching were determined. The resu lts are discussed in order to get the optimal operating parameters in terms of ion control to develop industrial techniques to remove and stabilize he avy metal ions present in wastewater. (C) 2001 Elsevier Science Ltd. All ri ghts reserved.