Laboratory Comparison of Dense Medium Separation and Acid Leaching for Preconcentration of Coarse Rejects from Phosphate Washing Plant

Reverse flotation is a commonly used method for separating carbonate minerals from apatite, but its application to phosphate beneficiation coarse rejects, which are low in P2O5, is often costly due to the high collector dosages used. This study aimed to explore alternative techniques for preconcentration before flotation to improve recovery rates and reduce costs. Our investigation focused on dense medium separation and acid leaching. Dense medium separation, conducted at a cut-off density of 2.76, yielded a preconcentrate with 27% P2O5 and a recovery rate of 90%. The feed material had an initial P2O5 content of 20.52% and a particle size range of +40 µm to −4 mm. In contrast, acid leaching, employing an 8% acetic acid solution over 35 min, yielded a concentrate with 29.11% P2O5, an LOI of 8.99%, and a recovery rate of 100% from an ore fraction [400–200 µm] with an initial P2O5 content of 22.82% and an LOI of 15.78%. Furthermore, integrating flotation and leaching resulted in a concentrate with 32.27% P2O5 and a recovery rate of 98.38%. These findings suggest that combining acid leaching with flotation can enhance P2O5 recovery and reduce processing costs for low-grade phosphate ores.