Efficient flotation of smithsonite using sulfidation reconstruction based on fluidization roasting†

There is an urgent and unprecedented demand for the selective separation of zinc oxide minerals from refractory zinc oxide ores due to declining reserves of zinc sulfide ores. Smithsonite, as a typical zinc oxide resource, requires sulfidation to enhance its hydrophobicity prior to flotation pre-enrichment. In this paper, a sulfidation reconstruction based on fluidization roasting is proposed to treat smithsonite. Flotation experiments were conducted to demonstrate the feasibility of sulfidation roasting. By optimizing the roasting and flotation conditions, a remarkable flotation recovery of 89% was achieved using butyl xanthate (BX) as the collector, following a 20 minute roasting at 450 °C under a 25 vol% H₂ atmosphere. Characterization of the surface properties of the roasted products revealed that the roasting temperature plays a pivotal role in determining the mineral phase composition of the sulfide products. Specifically, a hydrophobic layer of sphalerite coats the surface of smithsonite at a roasting temperature of 450 °C, while the sulfide products primarily consist of hydrophilic wurtzite at a roasting temperature of 750 °C. Additionally, when compared to conventional Na₂S treatment or sulfidation roasting, fluidization sulfidation roasting conducted under a 25 vol% H₂ atmosphere significantly lowers the roasting temperature. This innovative process not only reduces the generation of toxic SO₂ gas but also produces more hydrophobic smithsonite, thereby reducing the dosage of collectors. Our study suggests that the sulfidation reconstruction based on fluidization roasting is a promising process for treating zinc oxide ores, offering a highly effective and environmentally benign alternative to the conventional process.