Mass-production of ZnO nanoparticles by precipitation in a rotating packed bed: effect of zinc salt

The effect of three zinc salts (Zn(CH₃COO)₂, ZnSO₄, and Zn(NO₃)₂) on the size of the precursors of the ZnO nanoparticles that were mass-produced by precipitation in a rotating packed bed was studied. The precursors were formed at a rotational speed of 2000 rpm and flow rates of 0.5 L/min by precipitation using various zinc salts and NaOH as the precipitant. When zinc salts were Zn(CH₃COO)₂ and ZnSO₄, the smallest precursors were obtained at a Zn²⁺/OH⁻ molar ratio of 1/2. However, when the zinc salt was Zn(NO₃)₂, the smallest precursors were obtained at a Zn²⁺/OH⁻ molar ratio of 1/1. Additionally, various zinc salts yielded different effects of the concentrations of Zn²⁺ and OH⁻ on the size of the precursors. Experimental results indicate that the smallest precursors for various zinc salts were obtained at a Zn(CH₃COO)₂ concentration of 0.4 mol/L and an NaOH concentration of 0.8 mol/L, a ZnSO₄ concentration of 0.1 mol/L and an NaOH concentration of 0.2 mol/L, and a Zn(NO₃)₂ concentration of 0.2 mol/L and an NaOH concentration of 0.2 mol/L. ZnO nanoparticles were mass-produced by calcining these precursors at sufficient temperatures for 1 h. In this way, the average sizes of the ZnO nanoparticles that were mass-produced using Zn(NO₃)₂, Zn(CH₃COO)₂, and ZnSO₄ as zinc salts were 98, 136, and 186 nm, respectively.