New insights of inorganic phosphate inhibitors for flotation separation of calcium-bearing minerals

In this paper, the inhibition ability of tetrasodium pyrophosphate (TSPP), sodium tripolyphosphate (STPP) and sodium hexametaphosphate (SHMP) to scheelite, fluorite and calcite was predicted by performance calculation and further verified by micro-flotation test. The results of hydrophile lipophilic balance (HLB) calculation, group electronegative calculation and micro-flotation test indicated that the inhibition ability of phosphate to the three minerals increases with the increase of the number of phosphate groups and the order of inhibition ability of the three inorganic phosphates was SHMP > STPP > TSPP. STPP had great potential for flotation separation of scheelite from fluorite and calcite. The order of inhibition ability of STPP against the three calcium-bearing minerals is calcite>fluorite>scheelite. The results of contact angle measurement, adsorption amount measurement, X-ray photoelectron spectroscopy (XPS) analysis and atomic force microscope (AFM) imaging presented that the adsorption of STPP on the fluorite and calcite surface was much larger than that on the scheelite surface. The weak adsorption of STPP on the scheelite hardly influenced the collection of sodium oleate (NaOL). STPP could complex with Ca 2+ on the surface of fluorite and calcite, and hinder the subsequent adsorption of NaOL. The results can provide guiding significance for the flotation of scheelite and the screening of inhibitors for calcium-bearing gangue minerals.