Effect of a CA depressant on flotation separation of celestite from fluorite and calcite using SDS as a collector

The effect of depressant citric acid (CA) on flotation separation of celestite from fluorite and calcite using anionic collector sodium dodecyl sulfate (SDS) is investigated. Through a series of micro-flotation tests, solution chemistry and reaction thermodynamic analysis, zeta potential measurements and Fourier transform infrared (FTIR) analyses, the selective flotation performance of the depressant CA and underling adsorption mechanism of the reagents are demonstrated. The micro-flotation tests indicate that the SDS collector has a good flotation performance on celestite and fluorite, while the depressant can selectively inhibit the flotation of fluorite and realize the flotation separation of celestite from fluorite and calcite over a pH range of 9-10. The solution chemistry shows that strontium sulfate transforms to strontium carbonate at a pH of 7.8 on the celestite surface and calcium fluoride transforms to calcium carbonate at a pH of 8.5 on the fluorite surface. The reaction thermodynamic analysis further demonstrates that within the flotation separation pH range 9-10, ΔGm0 is negative for the reaction between fluorite and CA and positive for the reaction with celestite or calcite. The zeta potential measurements and Fourier transform infrared (FTIR) analyses indicate that the depressant CA and collector SDS chemisorb on the mineral surface and that the chemisorption strength of the CA on the mineral surfaces is in the following order: fluorite > calcite > celestite.