Removal process and mechanism of lead in Zn-containing rotary hearth furnace dust

To deal with the removal of PbO 2 during the purification process of the Zn-containing rotary hearth furnace (RHF) dust, this study adopts a choline chloride-urea (ChCl-urea) based deep eutectic solvent system and water-washed Zn-containing RHF dust as the main target of investigations, preparing ZnO nanoparticles using a Zn-induced PbO 2 removal and thermal treatment of the precursor. The effects of the mass ratio of Zn particles and Zn dust (maked as Zn particles - Zn dust), reaction temperature, and reaction time on the removal of PbO 2 were also investigated. The ZnO nanoparticles and the PbO 2 -removed products were characterized by X-ray diffractometry, X-ray fluorescence spectroscopy, scanning and transmission electron microscopy. The results showed that the optimal conditions for efficient removal of PbO 2 included the reaction temperature of 80 °C, The Zn particles - Zn dust is 1.6, with a reaction time of 3 h. The final product had a ZnO content of 98.332% with a particle size distribution in the range of 10–100 nm with an average diameter of 39 nm, belonging to the Category-II ZnO nanoparticles. The PbO 2 removal mechanism mainly involved the dissolving of PbO 2 in ChCl-urea, forming [Pb(ClO·urea) 2 ] 2− , and the replacement reaction between Zn particles and [Pb(ClO·urea) 2 ] 2− , producing metallic Pb and [ZnClO·urea] − .