Removal of feldspar from phosphate ore using Gemini quaternary ammonium salt as a novel collector

Feldspar is a typical sesquioxide which is associated with phosphate ore. It can greatly prevent the formation of calcium sulfate crystals during the wet process of phosphoric acid production, resulting in the loss of P2O5, and therefore lowering the phosphoric acid recovery. To achieve the selective separation of feldspar from phosphate ore, we first tried using a new Gemini quaternary ammonium salt as the collector in conjunction with a reverse flotation approach. The flotation tests of single minerals and artificially mixed minerals were employed to investigate the collecting ability and selectivity of the collector, the adsorption mechanism was also evaluated by means of zeta potential measurements and molecular dynamic calculations. The flotation results demonstrate that the collector showed a strong harvesting effect and selectivity on feldspar rather than fluorapatite. When the Gemini concentration was set at 7.5 x 10-6 mol/L, the P2O5 grade could reach 31.69% with a corresponding recovery of 77.57%, indicating that Gemini collector could suitably be used as a potential chemical to achieve the effective removal of feldspar from phosphate ore. The results obtained from zeta potential measurements and molecular dynamics simulations indicate that the adsorption of Gemini collector on feldspar was more pronounced compared to that on fluorapatite surface and the interaction between Gemini and both minerals was mainly ascribed to electrostatic interaction. This work aims to provide a reference for using Gemini as collector combined with reverse flotation approach to achieve the effective removal of sesquioxide from phosphate ore and further enhance the quality of phosphate fertilizers.