Study On The Flotation Desilication Of Low Grade Bauxite Ore With High Content Of Pyrophyllite

Abstract:A low grade bauxite ore with high content of pyrophyllite from Xiaoguan in Henan province was used for the study in this paper. To slove the problem of difficult inhibiting of pyrophyllite and improving of the concentrate grade, a reasonable flotation process and reagent regime were determined based on the mineralogy investigations and laboratory flotation experiments. The reasons why it is difficult to inhibit the flotation of pyrophyllite and to improve the grade of concentrate were also studied and analyzed by the single mineral flotation tests, solution chemistry calculation and infrared spectrum analysis.The result of mineralogy investigation shows that the main valuable mineral and gangue mineral in bauxite ore are diaspore and pyrophyllite, respectively. The content of other clay minerals, including illite, kaolinite and chlorite, are less than that of pyrophyllite in ore. Finely disseminated diaspore needs fine grinding to produce high libration of diaspore from gangue minerals.For bauxite flotation,high consumption of sodium carbonate was adopted as regulator, industrial oleic acid131and sodium hexametaphosphate were used as collector and inhibitor, respectively. A flotation flowsheet with twice roughing, triple cleaning and twice scavenging was used. Finally, a concentrate with the alumina-silica ratio of5.33and alumina recovery of85.56%was produced from the feed with the alumina-silica ratio of3.39.Sigle mineral flotation tests show that sodium hexametaphosphate has better suppression effect on pyrophyllite than sodium silicate and sodium fluorosilicate. However, the dosage of sodium hexametaphosphate should not be too high, otherwise, the recovery of diaspore could be significantly decreased. The iodine value of industrial oleic acid has some effects on the bauxite flotation seperation.The higher the iodine value of industrial oleic acid, the better selectivity of industrial oleic acid on the flotation separation of diaspore from pyrophyllite under the condition of using the same amount of sodium hexametaphosphate.Zeta potential studies show that diaspore, pyrophyllite and kaolinite are negatively charged under the alkaline condition. According to the results of infrared spectrophotometric analysis, sodium hexametaphosphate can be adsorbed chemically by A1on the surface of the three minerals. Industrial oleic acid makes zeta potentials of the three minerals decrease further, and the competitive adsorption occours between sodium hexametaphosphate and industrial oleic acid on the surface of the minerals. As the iodine value of industrial oleic acid increases, the content of linoleic acid increases, that is beneficial to separating diaspore from pyrophyllite. Linoleic acid has higher solubility than oleic acid, which makes linoleic acid dispersing and dissolving more easily in pulp.The more curved steric structure of linoleic acid has stronger steric hindrance effect on the reagent that tend to adsorb on mineral surface than oleic acid. Because the quantity of Al-O bonds on the surface of diaspore is much higher than that of pyrophyllite, so the linoleic acid increases the surface activity difference between diaspore and pyrophyllite which is beneficial to the flotation separation of both minerals.