Geochemistry of solid effluents and phosphate ore washed from Metlaoui-Gafsa Basin, Tunisia

International audienceThe effluent and washed ore show that treatment of ore enrichment is not aggressive. The results are supported by the projection factor, which clearly show the relationships between different elements and mineralogical composition of the effluents and washed ore.The results are a high concentration of 26-35% P2O5 (fluorapatite), but it remains carbonates (calcite anddolomite) in low quantity. The apatite show significant REE contents that can be by-product of phosphoric acid. Silicates and carbonates are the major part of effluents. The sulphate and fluoride contents are of the order of 3%, and the Na2O content varies between 1 and 1.5%, we observed a good correlation between F-P2O5-Na2O-P2O5 and P2O5-SO3.The levels of Cd, Zn, Cr, V, Ni, Sc, Nb and Cu are from the laundry reject. The maximum values of these elements are in the effluent from the M'DHILLA laundry.The Cd and Zn are found in high concentrations in the solid effluent. The high Cr content is linked with hydrocyclones in chromed steel. The washed phosphate ore was strongly depleted in heavy metals, which were concentrated in the fine fraction released into the hydric network and are thus the main cause of pollution in the region