A novel process for the treatment of steelmaking converter dust: Selective leaching and recovery of zinc sulfate and synthesis of iron oxides@HTCC photocatalysts by carbonizing carbohydrates

A large amount of converter dust (CD) is generated annually, posing serious environmental problems due to its zinc content. Moreover, zinc mainly exists in the form of inert ZnFe2O4 in CD, which negatively affects the leaching efficiency of zinc. On the other hand, the photocatalytic activity of hydrothermal carbonation carbon (HTCC) is restricted by its wide bandgap, poor charge-transfer ability, and inconvenience of recycling. This work presents an oxygen pressure leaching method to selectively leach Zn from CD. In this process, not only the decomposition of ZnFe2O4 is effectively promoted to increase zinc recovery, but also Fe2+ in the solution is skillfully oxidized and hydrolyzed to solid Fe(OH)SO4. Under the optimum conditions, the leaching efficiency of zinc reached 98.8%, and 86.3% of iron remained in the leach residue, realizing the one-step separation of zinc and iron. Furthermore, the leach residue was successfully applied to synthesize a magnetically recyclable iron oxides@HTCC composite photocatalyst.