Sulfuric acid leaching of Kab Amiri niobium–tantalum bearing minerals, Central Eastern Desert, Egypt

The ore under study was obtained from the Kab Amiri area located close to the northern boundary of the Central Eastern Desert. The ore is constituted of different kinds of refractory minerals. These are mainly represented by the niobium–tantalum rare earth-bearing minerals namely euxinite, samarsakite and fergusonite, beside the uranium refractory minerals davidite and zircon. Increasing demand for niobium, tantalum, titanium, uranium, thorium and rare earth elements has stressed the importance of developing methods for their recovery and processing into marketable form. In the present work, Kab Amiri ore was subjected to direct agitation leaching with sulfuric acid. Variables such as acid concentration, temperature, time, ore to acid ratio and oxidant effect were studied. When finely ground ore (−74 μm) was reacted upon for 2 h with a mixture of sulfuric acid (10.8 M) and nitric acid (5.3 M) in the ore to acid weight ratio of 1:3 at 200 °C, almost complete recovery of both niobium and tantalum was achieved while the leaching extents of thorium and total rare earths were 86% and 70%, respectively. On the other hand, the recovery of both uranium and titanium did not exceed 60% due to their presence in the refractory mineral davidite.