Leaching of a low-grade niobium–tantalum ore by highly concentrated caustic potash solution

The recovery of niobium and tantalum from a low-grade niobium–tantalum ore by using highly concentrated caustic potash as an alternative to hydrofluoric acid has been investigated. Experiments on the leaching behavior of niobium and tantalum, as well as other associated impurities, such as titanium, iron, manganese, silicon, and aluminum were carried out. The effect of various parameters including leaching temperature, KOH concentration, leaching time, alkali-to-ore mass ratio and particle size on the agitation leaching was examined. When finely ground ore (− 61 μm) reacted with KOH solution (84 wt.%) in a mass ratio of alkali-to-ore of 7 : 1 at 300 °C for 60 min, almost complete extraction of both niobium and tantalum was achieved while the extraction of titanium was 85% and the extraction of other impurities in the ore was less than 35%.