Flotation Mechanisms in Zinc Mineral Processing

Flotation of zinc ores relies on the transformation of naturally hydrophilic zinc oxides and carbonates into hydrophobic sulphide surfaces that can be selectively separated from gangue. Central to this process is sulfidization, in which reagents or in-situ generated sulphur react at the mineral interface to form a thin layer of zinc sulphide. This hydrophobic layer permits adsorption of collector molecules—such as xanthates, hydroxamates or phosphonic acids—which further enhance surface wettability contrasts. Key factors include temperature, pH, sulfidizing agent dosage, presence of activators (for example metal ions) or depressants, and the mineralogy of target ores (smithsonite, hemimorphite, sphalerite). Modern research combines thermodynamic and kinetic analyses with advanced surface-sensitive techniques (XPS, AFM, UV–Vis DRS) and theoretical modelling (DFT) to elucidate phase transformations, interfacial adsorption, nucleation of sulphide nuclei and growth of zinc sulphide crystals. Optimisation of sulfidization and collector adsorption delivers improved recovery, lower reagent consumption and reduced environmental impact, supporting global zinc production from both primary and secondary resources.

Research from Nature Portfolio

Studies of roasting ZnO with pyrite have shown that gaseous sulphur released by pyrite decomposition drives surface sulfidization at temperatures around 450–600 °C, yielding ZnS nuclei that grow more rapidly in the presence of iron-bearing phases. Subsequent formation of mixed (Zn,Fe)S compounds accelerates crystal growth and improves flotation response. Addition of carbon suppresses SO₂ emissions and lowers the decomposition temperature of pyrite, while inclusion of alkali fluxes (for example Na₂CO₃) promotes sulphidization at reduced temperatures. Detailed thermogravimetric, XRD and SEM-EDS analyses indicate that sulphidation is controlled by surface chemical reactions and oxygen migration within ZnO particles, offering pathways to tailor roasting–flotation schedules for diverse zinc oxide feeds.

Flotation Mechanisms in Zinc Mineral Processing publication trend

The graph below shows the total number of articles in flotation mechanisms in zinc mineral processing across all publications each year (not limited to Nature Index journals).

Technical terms

Sulfidization: Chemical reaction converting oxide or carbonate mineral surface into a sulphide layer.

Collector: Organic reagent that adsorbs on mineral surfaces to increase hydrophobicity.

Zeta potential: Electrical potential at the slipping plane of a particle, indicating surface charge and stability.

Hydrophobicity: Tendency of a surface to repel water, enabling attachment to air bubbles in flotation.

XPS (X-ray photoelectron spectroscopy): Technique for analysing elemental composition and chemical states at surfaces.

DFT (Density functional theory): Quantum mechanical modelling method to predict electronic structure and adsorption energies.

Nucleation: Initial formation of a new phase (for example ZnS) at specific surface sites before growth.

References

1. Formation of zinc sulfide species during roasting of ZnO with pyrite and its contribution on flotation. Scientific Reports (2018).
2. Sulfidation mechanism of ZnO roasted with pyrite. Scientific Reports (2018).
3. DFT simulation of S-species interaction with smithsonite (0 0 1) surface: Effect of water molecule adsorption position. Results in Physics (2019).
4. Density Functional Theory Study on the Surface Properties and Floatability of Hemimorphite and Smithsonite. Minerals (2018).
5. Improved Understanding of the Sulfidization Mechanism in Amine Flotation of Smithsonite: An XPS, AFM and UV–Vis DRS Study. Minerals (2020).