| Studies have shown that selective flocculation process can realize the separation between diaspore and aluminosilicates.But this process can be affected heavily by calcium and magnesium ions in hard water. In this thesis, the sedimentation test, zeta potential measurement and adsorption measurement of calcium ions were used to find out the influences of calcium and magnesium ions on the dispersion of diaspore and silicates.The experiments and mechanism for regulators to eliminate the influence of calcium and magnesium ions on the dispersion of diaspore and silicates had also carried out.The results indicated that the influences of calcium ions on the dispersion of diaspore and aluminosilicates are similar to that of magnesium ions.In acidic conditions,calcium and magnesium ions show little effects on the dispersion of minerals.However, there are strong coagulations for disspore,kaolinite and pyrophylite in alkaline conditions in the present of calcium and magnesium ions.In the present of calcium ions,comparing the influences of several regulators on the dispersion of minerals and the selectivity of flocculation separation, the best regulator is sodium tripolyphosphate, and followed by sodium carbonate,sodium pyrophosphate and hexametaphosphate.The flocculation separation of artificial mixed minerals and bauxite ore show that sodium tripolyphosphate is the best regulator for the selective flocculation separation in presence of calcium ions.For the artificial mixed minerals of A/S 5.64,the sediment with A/S 8.5 and above 90% recovery of Al2O3 was obtained in presence of calcium ions. For bauxite ore, the concentrate with A/S 7.14 and the recovery of Al2O3 89.97% was also produced after the selective flocculation separation while using sodium tripolyphosphate as regulator and sodium polycrylate as flocculation in the presence of calcium ions.These results are closed to the results obtained in Changsha water.The mechanism researches show that the effect of calcium ions on the dispersion of minerals is mainly that the compression of the electric double layer on the surface of mineral particles, and then it causes the attraction and aggregation between mineral particles.A quantity of calcium ions adsorbed on diaspore and kaolinite in alkaline condition, and the adsorption density of calcium on the diaspore is bigger than that of kaolinite under the same condition. The main adsorbing components of calcium on the minerals is hydroxyl calcium.Both of sodium tripolyphosphate and sodium carbonate can improve the dispersion of minerals in the hard water. Sodium carbonate reacts with calcium ions to produce the precipitation of calcium carbonate, and calcium carbonate can also decrease the flocculation selectivity. The reaction between sodium tripolyphosphate and calcium ions contains muti-chemical reactions.At the beginning, Ca3(PO4)2 is mainly reaction product, with the dosage increase of sodium tripolyphosphate,CaNa2P2O7 is gradually generated, and the final reaction products is the soluble complex of Na[Na2Ca(P3O10)]. |
