A Simulation-Based Study on Reprocessing of Phosphate Tailings for Recovering Pyrochlore and Monazite

The present study aims to investigate possibilities for improving the recovery of pyrochlore ((Na, Ca)₂Nb₂O₆) and monazite ((Ce, La, Th, Sm)PO4) as by-products from a phosphate mine with current niobium (Nb) production from geometallurgical perspectives. With this purpose, process mineralogy of Nb- and REE-bearing minerals together with operating properties of the concentration plant are examined using respectively mineral liberation analyzer (MLA) and the HSC® Chemistry 9 simulation module. A plant-site sampling campaign was performed and key operating parameters such as throughputs and pulp densities for individual streams were measured. The results obtained by MLA analyses as the base of mineral mass balances were compared and validated by commonly used chemical characterization techniques i.e. X-ray fluorescence spectroscopy (XRF) and inductively coupled plasma–optical emission spectroscopy (ICP-OES). Simulation results showed that the combination of Nb flotation rougher and scavenger cells into one single rougher bank plus the addition of a new scavenger bank (4x1.4 m³ cells) can increase pyrochlore recovery in the silica/niobium flotation circuit from approximately 31% to 44%. This cell configuration improves the ultimate pyrochlore’s plant recovery from 27% to 38% leading to a substantial enhancement in final concentrate throughput from 540 to 740 kg/h. Future studies on this topic include the use of wet high intensity magnetic separation (WHIMS) and froth flotation respectively for the pre-concentration and concentration of monazite.