The Beneficiation Processes of Low-Grade Sedimentary Phosphates of Tozeur-Nefta Deposit (Gafsa-Metlaoui Basin: South of Tunisia)

The enrichment of the low-grade-phosphate ore of the Tozeur-Nefta deposit was investigated using scrubbing-attrition, ball grinding and anionic/cationic reverse flotation in order to separate phosphate-rich particles from their gangue. The choice of the beneficiation process was based on the petrographic, mineralogical and chemical analyses. The petrographic and mineralogical studies have revealed the abundance of phosphatic (carbonate-fluorapatite-CFA) particles) coupled with carbonates (calcite, dolomite,) and silicates (quartz, illite, kaolonite) that constitute the (endo/exo) gangue of these ores. Chemical analysis has demonstrated that the raw phosphate sample contains low amounts of P2O5 (12.0%) and MgO (4.9%) and high amounts of CaO (40.7%) and SiO2 (20.5%). Microscopic observation/counting has shown that the release mesh occurs in the 71-315 mu m size. Scrubbing-attrition, grinding and reverse flotation methods were applied to the +71 mu m fraction. Scrubbing-attrition tests of the 71-315 mu m fraction have helped to improve the P2O5 grade to 15.5%. Ball-grinding tests were used to reduce the coarse fraction +315 mu m. Grounded materials were sieved to 71-315 mu m and combined with the scrubbed fraction in the flotation feed. Reverse-flotation tests of the phosphate-rich fraction (71-315 mu m) have helped to improve the P2O5 grade to 27.1%, with a recovery rate of 92.4%.