The beneficiation of mumbwa phosphate deposit by various techniques

The Mumbwa phosphate ore constitutes of Apatite(43.6wt%) as the major mineral, Feldspar(29.0wt%), Iron oxides(14.4wt%), minor quantities of Quartz(8wt%) and the rest being trace minerals. The chemical composition of the ore averages 22.7 % P2O5 with the other constituents being 22.8% SiO2, 19.0% CaO, 7.0% Fe2O3, 4.0 % Al2O3 and 0.2% MgO. Beneficiation studies were performed to investigate methods of concentrating the phosphate values. Preliminary investigations involved detailed identification of mineralogical and chemical properties of the constituents minerals which would form the basis of selective separation of the phosphate values from the gangue. The results of these studies showed that liberation of apatite occurred below the average grain size of 500 μm. On the basis of the identified mineralogical and chemical properties of the minerals, heavy media separation using Bromoform and subsequently flotation were applied in the beneficiation tests. The results indicate that heavy media separation techniques could not be used to give a final phosphate concentrate. It has to be a pre-concentration process prior to another concentration process. Encouraging concentrate grades were obtained after flotation with a cationic collector, petroleum sulphonate. The optimum pH being 9.5 and the concentration of petroleum sulphonate 1200 g/ton. Under these conditions, the grade was 40.8% P2O5 with 1.65% SiO2 while the combined grade was 50.2% P2O5. On the basis of this test, a treatment flow sheet for this deposit has been proposed.