Preparation of Nano-ZnO Powders from Zinc Slag Oxidation Dust Using a Deep Eutectic Solvent

Herein, a novel solvent-assisted approach is being proposed to recover Zn as nano-ZnO.powders from zinc slag oxidation dust (ZSOD). Choline chloride–urea–butyl alcohol deep eutectic solvent (ChCl–urea–BA DES) was used as an efficient solvent for selective leaching of Zn from the ZSOD, coupled with water precipitation and calcination, to produce highly porous nano-ZnO powders. The ChCl–urea–BA DES exhibits a high selectivity for Zn and Pb from ZSOD, achieving extraction efficiencies of 78.2% and 91.6%, respectively, after leaching at 80°C for 36 h under a liquid/solid ratio of 50 mL g −1 . Afterward, the dissolved Pb was efficiently removed with a residual concentration of 8.6 mg L −1 by cementation with Zn powders at an optimal Zn/Pb 2+ molar ratio of 2:1 at 75°C for 2 h. A mixture of ZnO and Zn 4 (OH) 6 (CO 3 )⋅H 2 O was obtained by adding deionized water to precipitate the purified leaching solvent. The resulting mixtures were then calcined at high temperature to produce nano-ZnO powders, the purity of which was greater than 99.71 wt%. As a novel synthesis method of high value-added functional materials, the ZnO powders exhibited a flower spherical structure packed with ultrathin mesoporous nanosheets, having a thickness of around 10 nm and pore size of 20–40 nm.