Magnetite precipitation approach for zinc hydrometallurgy: a microfluidic strategy

Abstract

Magnetite (Fe₃O₄) possesses the highest theoretical Fe content (72.4%) and magnetic properties among various iron oxides. Magnetite precipitation is a novel approach for Fe–Zn separation from pregnant leach solution (PLS) in zinc hydrometallurgy, which is beneficial for the minimization of Fe-bearing wastes and iron resource recycling. However, insufficient mixing in stirred reactors results in complex intermediates, such as goethite, lepidocrocite, akaganeite, during magnetite formation, leading to the increased undesired co-precipitation of zinc. To address this issue, microfluidic technology can be used to optimize magnetite precipitation and Fe–Zn separation, as it offers the advantage of enhanced mixing and mass transfer. Magnetite rapidly forms in a helical microchannel reactor and exhibits favorable magnetic properties. The magnetite precipitates obtained by the microfluidic method have higher Fe–Zn separation efficiency (Fe/Zn = 32.51) compared to those formed by traditional stirring (Fe/Zn = 7.81 and 8.97). It is speculated that the effect of microfluidic technology may involve a reduction in the amount of intermediates and the accelerated transformation of intermediates to magnetite. This study proposed a strategy for the microfluidic enhancement of magnetite precipitation and Fe–Zn separation in PLS, which offers new insights for the advancement of iron removal technologies and the optimization of iron resource recycling.