Upgrading silicon-calcareous phosphate ores using sodium polymer [(Naphthalene formaldehyde) sulfonate] (PNFS) as an efficient and eco-friendly depressant

Sodium polymer [(Naphthalene formaldehyde) sulfonate] (PNFS) was selected as an efficient dolomite depressant to upgrade phosphate ores in this work. The depression ability and selectivity were tested through micro-flotation and batch flotation, and the depression mechanism was revealed via Fourier transform infrared spectroscopy (FTIR), Zeta potential, adsorption capacity and X-ray photoelectron spectroscopy (XPS) measurement. Flotation tests proved that PNFS was able to depress dolomite effectively, but hardly influenced the flotation of apatite, which also exhibited high selectivity for raw head ores. FTIR, zeta potential, adsorption capacity and XPS results proved that -SO3- groups of PNFS complexed with Ca and Mg atoms on dolomite by means of single layer, while PNFS physically adsorbed on apatite surface in the form of multilayer. The pre-adsorbed PNFS could be replaced by NaOL for apatite, while it couldn't be substituted by NaOL in the case of dolomite. PNFS had good prospective to be applied as an eco-friendly alternative for apatite depressant with good selectivity and low toxicity.