Geochemical Assessment and Mobility of Undesired Elements in the Sludge of the Phosphate Industry of Gafsa-Metlaoui Basin, (Southern Tunisia)

Abstract

The raw phosphates in the Gafsa-Metlaoui phosphate basin are valorized by wet processes that are performed in the laundries of the Gafsa Phosphates Company (CPG, Gafsa, Tunisia) to reach market grades (>28% P2O5). This enrichment process allows the increase of P2O5 content by the elimination of the coarse (>2 mm) and fine (<71 µm) fractions. Mineralogical analysis has shown that all the investigated materials (raw phosphate, marketable phosphate, coarse waste, and fine waste) from the laundries of M’Dhilla-Zone L and Redeyef are both composed of carbonate fluorapatite, carbonates, quartz, gypsum, clays, and clinoptilolite. Chemical analysis shows that Cr, Cd, Zn, Pb, and U are concentrated in the fine wastes and associated with the clay–phosphate fraction. The rare earth elements are more concentrated in both raw and marketable phosphates. Drilling and sludge-water analysis, along with leaching tests conducted on the fine wastes, showed that, due to phosphate industry, cadmium, fluorine, and sulfate contributing to the pollution of water resources in the region, pollution is more conspicuous at M’Dhilla.

Environmental Geochemistry of Potentially Toxic Metals in Phosphate Rocks, Products, and Their Wastes in the Algerian Phosphate Mining Area (Tébessa, NE Algeria)

“…The CaO/P 2 O 5 ratios show that the values for raw and commercial phosphates vary from 1.60 to 1.65, which are relatively similar to those reported in pure CFA (1.57-1.62 [58,59]). In comparison to Morocco and Tunisia phosphorites, the CaO/P 2 O 5 ratio in raw phosphate is higher than those of Moroccan phosphorites [60] and slightly lower than those of Tunisian phosphorites [10].…”

“…The oxides Al 2 O 3 , SiO 2 and Fe 2 O 3 mainly mirror the fine wastes, which are indicative of the abundance of aluminosilicates in fine wastes (1.87 wt %, 8.78 wt %, and 0.66 wt %, respectively). Similarly, MgO (3.27%) is generally known to be a component derived from dolomite and magnesian clay [58]. The LOI values range between 14.30 and 17.27 wt%.…”

Comparison of Sensitivity of Autotrophic and Heterotrophic Microorganisms to the Pollution of Natural Water with Rare Earth Elements (Lanthanum and Cerium)

“…In the areas of ore production which are rich in REE, specific pollution occurs, including the pollution of groundwaters and surface waters. The extraction of many minerals, for example, phosphates, also leads to the release of REE into the environment, since they begin to actively leach out of the waste rock, together with heavy metals [Smida et al, 2021]. Even electronic waste, such as motherboards, is becoming a real source of rare earth element pollution [Dang and Zhang, 2021].…”