Interaction Mechanism of Ferric Ions with Celestite Surface and Implications for Flotation Recovery

In practical celestite flotation, iron contamination is commonly found on celestite surfaces. The effect of ferric ions on celestite flotation was assessed by a combination of ion release experiments, DFT calculation, X-ray photoelectron spectroscopy (XPS) analysis, adsorption isotherm study, and flotation experiments in this work. The ion release experiments showed that the associated limonite released ferric ions to solution. According to DFT calculation and surface complexation theory, we found that equivalent to SrOH0 and equivalent to SO4H0 are primary functional groups on celestite surface in aqueous environments. The XPS analysis and adsorption isotherm study revealed that ferric ions mainly adsorbed on celestite surface by complexing with two oxygen atoms of surface equivalent to SrOH0 groups to form equivalent to Sr-O-Fe-OH precipitates. Flotation results showed that ferric ions strongly depressed celestite flotation. Combined with the change in surface properties determined by XPS, it can be concluded that the adsorption of ferric ions on celestite surface decreased adsorption sites for the collector, and hence, led to depression on celestite flotation.