Utilization of a Solid Waste Inhibitor for the Clean Flotation Enrichment of Phosphate Ores

The accumulation of phosphogypsum (PG) in the phosphorus chemical industry poses significant environmental challenges. Therefore, developing a harmless utilization method is crucial for alleviating these burdens and promoting sustainable industry practices. In this study, PG was used as a flotation inhibitor, enabling the flotation separation of apatite and dolomite based on the main components and dissolution behavior of PG. A microflotation study revealed that 0.875 g/L PG selectively inhibited dolomite when the sodium oleate (NaOL) concentration was 1.5 × 10^-4 mol/L, reducing dolomite recovery 76% to 10% at pH in the range of 7-11. Conversely, apatite recovery remained above 90% at pH 7-9 and was only slightly inhibited at pH in the range of pH 9-11. When CaSO₄·2H₂O and CaHPO₄·2H₂O were added as flotation inhibitors, they also inhibited dolomite, though their effects were weaker than PG. Measurements of contact angles, zeta potentials, and adsorption capacities indicated that PG enhanced the hydrophilicity of dolomite, hindering NaOL adsorption thereon, while it had little effect on the floatability of apatite. Atomic force and scanning electron microscopy revealed selective PG was adsorbed on the dolomite surface, altering its properties, while PG was weakly adsorbed on the apatite surface and had minimal impact on its properties. The solution chemical composition and microthermal results showed that CaSO₄ and CaHPO₄ are the effective components of PG inhibition. X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry confirmed that CaSO₄ and CaHPO₄ in PG were selectively adsorbed at Ca and Mg ion sites on the dolomite surface. Molecular dynamics simulations showed that CaSO₄ interacts with the surface of dolomite, and CaHPO₄ can promote the adsorption of CaSO₄ on the surface of dolomite. Utilizing PG as a flotation inhibitor provides a novel approach for the environmentally safe use of PG resources.