Preparation of nano zinc oxide by alkaline treatment of industrial zinc oxide dust

A new method for the preparation of nano-zinc oxide was proposed for the effective use of zinc oxide dust (ZOD) containing complex impurities recycled and processed from local plants. Fe2+, Fe3+, Ca2+, Mg2+, Mn2+, Cu2+, and Pb2+, Sn4+, Al3+, Si4+, Bi3+ were selectively extracted from ZOD by alkaline leaching combined with precursor firing process. The effects of thermodynamic analysis of ZOD, Sodium hydroxide(NaOH) concentration(2–8 mol/L), leaching time (15–75 min), autothermal temperature of leaching reaction (43–70 °C), leaching liquid/solid ratio (L/S:5–25 mL/g), and pH were investigated during leaching process. Thermogravimetry-differential thermogravimetry (TG-DTG) analyses were carried out on Zinc carbonate hydroxide (Zn5(CO3)2(OH)6) precursor. In addition, the effects of calcination temperature(400–700 °C) and holding time (1.5–4.0 h) of precursors on average particle size of nano-ZnO were also studied. The results showed the leaching rate of Zn2+ reached 98.35% under the optimum conditions as: NaOH concentration of 6 mol/L, L/S of 20 mL/g, and leaching time of 60 min. Separation rates of Pb2+, Sn4+, Al3+, Si4+ reached 94.63%, 85.08%, 98.03%, 91.48%, respectively at pH = 5.5. Zn5 (CO3)2(OH)6 nano precursors were obtained at pH = 7–8. After the precursor of zinc carbonate was calcined at 400–600 °C for 2 h, high purity (99.53%) nano-zinc oxide was obtained with a particle size of 20 nm, a specific surface area of 23.84 m2/g, a porosity of 32.66%, and a zeta potential of −13.2 mV. This article provides an alternative new idea for the green and comprehensive utilization of industrial ZOD dusts with complex compositions.