Abstract
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 μm size. Scrubbing-attrition, grinding and reverse flotation methods were applied to the +71μm fraction. Scrubbing-attrition tests of the 71–315 μm fraction have helped to improve the P2O5 grade to 15.5%. Ball-grinding tests were used to reduce the coarse fraction +315 μm. Grounded materials were sieved to 71–315 μm and combined with the scrubbed fraction in the flotation feed. Reverse-flotation tests of the phosphate-rich fraction (71–315 μm) have helped to improve the P2O5 grade to 27.1%, with a recovery rate of 92.4%.
Highlights
Tunisia is the second largest phosphate producer in Africa, with an annual production of about8 million tons (Mt) [1,2]
The most abundant phosphatic elements are as rounded to sub‐rounded embedded microsparitic cementby
This study has revealed that this material is a low-grade ore (12.0% P2 O5 ) with siliceous and carbonated gangue
Summary
Tunisia is the second largest phosphate producer in Africa, with an annual production of about8 million tons (Mt) [1,2]. The Tozeur-Nefta deposit, which is the subject of the current study, is located in the Southwest region of the Gafsa-Metlaoui Basin, and has remained untapped. In order to upgrade its phosphate-production capacity, the Compagnie des Phosphates de Gafsa (CPG, Tunisia) has planned to make use of the Tozeur-Nefta deposit before 2020. This deposit, which has been the subject of several studies [7,8,9,10,11], contains about 410 Mt of phosphate, has been considered, to date, as a strategic reserve. The majority of the low-grade phosphate ore is organized either in the form of a single layer or a layer-beam including non-phosphatic intercalations [12]
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