Selective Depression And Depression Mechanism Of Fluorine-bearing Minerals And Calcium-bearing Carbonate Minerals

Fluorine-bearing minerals resources faced with shortage. Fluorine-bearing minerals such as fluorite and fluorapatite are abundant in Guizhou Procince of China. These minerals often associated with calcium-bearing carbonate minerals such as calcite, dolomite. It was difficult to separate them with froth flotation because physical and chemical properties of these mineral surface are similar. Two kinds of representative fluorite ore and low grade phosphate rock were selected as the research object. Fluorspar, fluorapatite, calcite, dolomite, four kinds of pure mineral floatability were studied. And the effects of selective depression on their flotation have also been studied too. On the basis of this, the research on the actual ore flotation and the mechanism of the depressant is studied.According to high calcium carbonate content characteristics of Guizhou refractory fluorite ore and low grade phosphate rock, fluorspar, fluorapatite, calcite, dolomite, four kinds of pure mineral floatability were studied. And the effects of selective depression on their flotation have also been studied too. On the basis of this, the research on the actual ore flotation and the mechanism of the depressant is studied.The results of pure mineral flotation show that the collect capacity of sodium oleate for the four minerals is more than that of oleic acid, their floatability order is fluorite>calcite>>dolomite>fluorapatite. Under acidic conditions, flotation of fluorapatite is impossible, while calcium-bearing carbonate minerals are floated readily. Under neutral or weak alkaline conditions, fluorite floatability is better than calcium-bearing carbonate minerals. The existence of calcium and magnesium ions is harmful to the flotation separation of the two kinds of mineral. Under the condition of less than 6 of pH, the fluorine ion can improve the flotation gap between dolomite and fluoride. Calcium-bearing carbonate minerals were activated by low concentrations of phosphate ion; fluorine-bearing minerals were less affected. At about pH 7, the depression with water glass or tannins on calcium-bearing carbonate minerals is obvious. Humic acid on calcium carbonate has a strong selective depressing effect.Actual ore flotation results show, under weakly alkaline condition flotation refractory fluorite, better flotation index is obtained, using water glass and tannins, humic acid composition to depression calcium-bearing carbonate minerals. By flotation calcite - quartz type fluorite ore,95.52% CaF2 grade and recovery 91.20% of fluorite concentrate was obtained. Concentrate containing 0.61% CaCO3 was obtained by flotation barite-fluorite ore containing 15.22% calcium carbonate. Under acidic conditions, reverse flotation process is used, qualified phosphorus concentrate with MgO content less than 1% was obtained using sodium fluoride and phosphoric acid as depressant to flotation calcareous phosphate rock or using phosphate as depressant to flotation rare earth-containing phosphate rock.Mechanism research results show that, under alkaline conditions, due to fluoride added, fluorite is generated in the calcite, dolomite surfaces, which is conducive to calcium-bearing carbonate minerals flotation, while there is no carbonate formation in the surface of the fluorapatite, and it also has a certain inhibition effect on the apatite. In flotation process, there is no phosphate formation on the surface of dolomite, and the phosphoric acid has no inhibition effect on dolomite, phosphoric acid added decreased the calcium and magnesium ion concentration in the solution, reduce the activation of calcium and magnesium ions on fluorapatite. At the same time, the phosphate and oleic acid root produce competitive adsorption in the surface of the fluorapatite, thus the flotation of fluorapatite was inhibited. Calcite has a greater adsorption capacity of humic acid and tannin than that of fluorite. And this adsorption is a chemical adsorption. The reaction product produced by humic acid, tannin and the calcium ion in ore pulp, adsorption on the surface of the mineral, it make the mineral surface hydrophilic.