Study On The Separation Of Limonite From Gangues By Flotation And Its Mechanisms

The separation of limonite from calcite, quartz and kaolinite by flotation were investigated in the flotation tests of single mineral and artificial mixed minerals. The flotation behaviors of different collectors, frothers, depressants and multivalent cationics for four minerals were studied, and the best flotation separation scheme for different artificial mixed minerals was also obtained. The mechanisms between reagents and minerals were studied by mineral crystal structure analysis, flotation solution chemistry analysis, Zeta potentials tests and FTIR analysis.The results of single mineral flotation tests show that sodium oleate, sodium dodecyl sulfonate, benzyl hydroxamic acid, salicylic hydroxamic acid are the effective collectors for separation of limonite from other three gangues by flotation. In sodium oleate system and an appropriate pH range, both sodium hexametaphosphate (SHP) and Rosa spp tannin extract depress calcite strongly, but they have little effects on the floatability of limonite, quartz and kaolinite;sodium pyrophosphate depress limonite strongly, but shows little effects on the floatability of calcite, quartz and kaolinite. Ca2+ depress limonite sharply, active quartz strongely at pH 12, but it has no effects on the floatability of calcite and kaolinite. Fe3+ actives quartz sharply but has a little effect on the floatability of limonite and kaolinite. SHP deactivates the effects of Fe3+ on quartz.Based on the results of single mineral flotation tests, sodium oleate and benzyl hydroxamic acid were used as collector and sodium hexametaphosphate and sodium pyrophosphate were used as depressants, different flotation separation schemes for different type of mixed minerals were finally determined. The results show that good flotation indexes were obtained in sodium oleate flotation system:using reverse flotation for the separation of limonite-calcite mixed minerals, and the TFe grade of concentrate increases from 28.45% to 49.5%, the TFe recovery is above 91%; using direct flotation for the separation of limonite-quartz mixed minerals, and the TFe grade of concentrate increases from 28.64% to52.0%, the TFe recovery is above 90%; using direct flotation for the separation of limonite-kaolinite mixed minerals, and the TFe grade of concentrate increases from 29.65% to 45.0%, the TFe recovery is above 90%; using direct flotation for the separation of limonite-quartz-kaolinite mixed minerals, and the TFe grade of concentrate increases from 23.05% to 43.0%, the TFe recovery is above 86.5%. In benzyl hydroxamic acid flotation system, the TFe grade of concentrate can also reach 47%-49%, but its TFe recovery is low (<70%), the separation is not satisfied.The mechanism researches show that the pH of maximum concentration of HOl-Ol- association complex is 8.55 when the sodium oleate concentration is 3×10-4mol/L, this association complex adsorbed on the surface of limonite in the form of chemical adsorption, and in the form of hydrogen bonding adsorption and chemical adsorption on kaolinite surface, but in the form of physical adsorption on quartz.The key cause of Ca2+ has strongly depress effects on limonite flotation but show little effects on calcite is Ca2+ consumed Ol-, lead to the Ol- which absorbed on limonite surface reduced, then the recovery of limonite decreased. Fe(OH)3 adsorbed on quartz and changed the zeta potential of quartz surface from positive to negative, and then it promoted the adsorption of Ol- on quartz surface and caused the activation effects of Fe3+ on quartz.