| Fluorapatite is slightly soluble salt-type mineral, flotation of fluorapatite is easy to be influenced not only by itself dissolved lattice ions, but also by the dissolved components of other salt-type mineral in the same flotation system. In addition, because of the low selectivity of fatty acid collector, it is sensitive to the dissolved ions in flotation. Therefore, it is important to study the effect of complex ions on the phosphate ore flotation for dressing plant developing targeted wastewater treatment and backwater clean utilization.The two typical phosphate ore in this paper are collected from Guizhou province. The appropriate flotation process was determined by flotation condition experiments. The complex ions on the reverse flotation indexes of phosphate ore were investigated by single-factor experiment and orthogonal-experiment, hence determined the lowest concentration of harmful ions on flotation indexes. The mechanism of unavoidable ions on the reverse flotation indexes were studied by solution chemistry calculation, X-ray diffraction(XRD) analysis, scanning electron microscopy(SEM) analysis and surface tension test.The valuable mineral of the two phosphate ore samples is fluorapatite, and main gangue minerals are dolomite and a small amount of quartz. The grade of P2O5, Mg O and Si O2 of 1# phosphate ore sample are 28.72 %, 5.78 % and 2.11 % respectively, the grade of P2O5, Mg O and Si O2 of 2# phosphate ore sample are 22.67 %, 7.58 % and 4.30 % respectively. For 1# phosphate ore sample, the appropriate grinding fineness is-75 μm accounted for 80.67 %, the dosage of H2SO4 and collector are 14 kg/t and 0.6 kg/t respectively. On this condition, the P2O5 and Mg O grade of the concentrate are 35.82 % and 1.05 % respectively, the P2O5 recovery is 95.43 %. For 2# phosphate ore sample, the appropriate grinding fineness is-75 μm accounted for 70.76 %. The dosage of H2SO4 and collector are 18 kg/t and 0.8 kg/t respectively. On this condition, the P2O5, Mg O, Si O2, Al2O3 and Fe2O3 grade of the concentrate are 33.81 %, 1.20 %, 5.48 %, 0.63 % and 1.10 % respectively, the P2O5 recovery is 87.16 %.After concentrate filtrate returned to flotation, with the increase of the filtrate cycles, the concentrations of Ca2+, Mg2+, SO42-, TP and F- in backwater increased gradually, existing “cumulative effect” of ions. Meanwhile the flotation indexes are affected by use of backwater, especially for P2O5 recovery of the concentrate.In the single-ion system, the P2O5 and Mg O grade of the concentrate can be influenced byCa2+ and Mg2+ in the backwater. SO42- had great influences on the reverse flotation indexes of phosphate ore, especially for the P2O5 recovery of the concentrate. The effect of Ca2+ and SO42- on flotation of 2# phosphate ore sample is greater than 1# phosphate ore sample. PO43- and F- had little influence on flotation indexes, Ca2+, Mg2+, SO42- and PO43- had little influence on Si O2, Fe2O3 and Al2O3 grade. In order to reduce the impact of ions on the flotation indexes, the concentrations of Ca2+, Mg2+ and SO42- should be controlled in 1610 mg/L, 550 mg/L and 5500 mg/L respectively in the flotation backwater for1# phosphate ore sample. Ca2+, Mg2+ and SO42- should be controlled in 1640 mg/L, 600 mg/L and 4800 mg/L respectively for 2# phosphate ore sample.The flotation solution chemistry calculation shows that the existence state of the unavoidable ions in pulp are Ca2+, Mg2+ and H2PO4- at p H ranging from 3 to 4. The collector of GJBW exists mainly in the form of soluble RCOOH molecules and generates molecular adsorption on dolomite surface. Because Ca2+ and Mg2+ can precipitate dissociated RCOO-, the effective concentration of collector is reduced, and the precipitating action of Ca2+ is higher than Mg2+, leading to the influence of Ca2+ on the concentrate grade is greater than Mg2+. SO42- can interact with Ca2+ to generate calcium sulfate precipitation, both XRD analysis and SEM analysis show that calcium sulfate can precipitate on the fluorapatite surface. The flotability of fluorapatite can be enhanced by the adsorption of calcium sulfate, fluorapatite were floted with dolomite, and then reducing the P2O5 recovery of the concentrate. Moreover, the surface tension of GJBW solution increased after adding in SO42-, thereby affecting the flotation indexes. |
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