Abstract
Alkaline leaching of secondary fly ash from municipal incineration plants using 3 M NaOH yields an alkaline solution rich in heavy metals such as Zn and Pb. For the purpose of separating and recovering these metals from the solution, the basic solvent extraction characteristics of commercially available Kelex100 the active component of which is 7-(4-ethyl-1-methyloctyl)-8-hydroxyquinoline (HQ) and bis-(2-ethylhexyl)phosphoric acid (D2EHPA) for these metals from alkaline solution and from acetic acid media, respectively, were investigated. It was found that Kelex100 extracted about 98% of Pb and 15% of Zn from the alkaline leach liquor. Stripping of loaded Kelex100 was carried out using acids such as HCl, HNO3 and acetic acid, and it was found that 0.5M acetic acid or 0.1M HCl were suitable for stripping all the Pb and about 50% of the Zn leaving Kelex100 loaded with only zinc. Zinc was further separated from Pb by D2EHPA from the acid solution produced in stripping. The recommended flowsheet was proposed based on the experimental results.