Recovery of lead and zinc from a leach liquor produced from alkaline leaching of secondary fly ash from municipal incineration plants by means of liquid-liquid extraction using Kelex100 and D2EHPA

Alkaline leaching of secondary fly ash from municipal incineration plants u sing 3 M NaOH yields an alkaline solution rich in heavy metals such as Zn a nd Pb. For the purpose of separating and recovering these metals from the s olution, the basic solvent extraction characteristics of commercially avail able Kelex100 the active component of which is 7-(4-ethyl-1-methyloctyl)-8- hydroxyquinoline (HQ) and bis-(2-ethylhexyl)phosphoric acid (D2EHPA) for th ese metals from alkaline solution and from acetic acid media, respectively, were investigated. It was found that Kelex100 extracted about 98% of Pb an d 15% of Zn from the alkaline leach liquor. Stripping of loaded Kelex100 wa s carried out using acids such as HCl, HNO3 and acetic acid, and it was fou nd 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 f urther separated from Pb by D2EHPA from the acid solution produced in strip ping. The recommended flowsheet was proposed based on the experimental resu lts.