Developing flotation reagents for niobium oxide recovery from carbonatite Nb ores

Anionic collectors (phosphonic acid and hydroxamic acid) and flotation depressants were tested in a modified small-scale flotation tube on high purity single minerals in order to find a suitable reagent combination for niobium oxide mineral flotation from its ores. High purity calcite and quartz were used to represent carbonate and silicate gangue minerals and pyrochlore was used to represent the niobium oxide mineral. Only hydroxamic acid could float pyrochlore at natural pH, with recoveries over 90%. However, it floated calcite as well. To separate the pyrochlore from the carbonate gangue, sodium metaphosphate was used. Single mineral and mineral mixture tests indicated that the calcite could be selectively depressed by the sodium metaphosphate. Bench-scale flotation tests were carried out on a carbonatite niobium ore sample, and they showed that the reagent combination, at less than 2 kg/t Aero 6493 (hydroxamic acid) and 1.0 kg/t sodium metaphosphate, could recover over 90% of niobium oxide from the ore feed at about 30% mass pull. The results indicated that the combination of hydroxamic acid and sodium metaphosphate is a possible reagent scheme for pyrochlore recovery from niobium oxide ores.