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

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 P 2 O 5 (12.0%) and MgO (4.9%) and high amounts of CaO (40.7%) and SiO 2 (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 P 2 O 5 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 P 2 O 5 grade to 27.1%, with a recovery rate of 92.4%.Minerals 2019, 9, 2 2 of 15 Currently, phosphate fertilizers are generally produced from primary-phosphate ores. Phosphate material can easily be separated from the gangue and concentrated by conventional beneficiation techniques (i.e. washing process). As a result of the concurrent increase in demand for phosphate products, and the continuous depletion of phosphate reserves, much more focus is made today on opportunities to recover phosphate ores from secondary sources (i.e. tailings and low-grade ore deposits). These new sources are continually investigated, as is happening now at the Hazara deposit in Pakistan (16% P 2 O 5 ) and the Kohe-lar deposit in Iran (5.01% P 2 O 5 ) [13,14]. Upgrading processes of sedimentary-type phosphate ores consist of separating the gangue minerals (silicates and carbonates) from the valuable phosphate material [15][16][17]. New processing techniques are needed to upgrade the low-grade phosphates to commercial-grade products (P 2 O 5 > 28%) [18]. The choice of the suitable beneficiation process requires a good knowledge of the mineral assemblages of the studied ore [19]. Several industrial processes are used worldwide for the enrichment of phosphate ores, ranging from simple mechanical preparation to more complex treatment schemes, which combine several methods such as flotation, magnetic, electrostatic and dense-media separation (DMS). Calcination is applied for the enrichment of phosphates that are rich in organic materials, like those of the Youssoufia deposit in Morocco [12], or that include a carbonated gangue, like those of Akashart's phosphates in Iraq [20]. Electromagnetic separation is used mainly for...

Impact of Recirculating Mining Process Water on the Flotation Performance of a Sedimentary Phosphate Ore

“…The CaO/P2O5 ratio of averaged 1.37 was achieved which is reasonably accepted to industry specification of 1.6 for downstream processing. A high CaO in phosphate concentrate may increase the consumption of sulfuric acid during the production of phosphoric acid [5].…”

Beneficiation of phosphate sludge rejected from Djebel Onk plant (Algeria)

“…On the other hand, the mining industry has been the basis of the industrial sectors development for centuries. Mining activities have expanded and developed an amount of tailings, the deposition and storage of these later became a serious problem for the mining industry and environment threat, particularly over the last 30 years (Boujlel et al, 2018).…”

Phosphate sludge: opportunities for use as a fertilizer in deficient.

“…Morocco, represented by Office Chérifien du Phosphate (OCP), is a worldwide leader in the phosphate-based products industry. Moroccan phosphate ore is processed through a combination of successive enrichment steps involving crushing, screening, washing and flotation (Khasawneh and Doll, 1979;Boujlel et al, 2019). The washing and flotation steps generate large quantities of PS, reaching 28 million metric tons in 2010 (Haouas et al, 2021a).…”