Golden Deeps Limited reported outstanding vanadium extraction rates of up to 95% vanadium recovery in Phase 1 hydrometallurgical testwork on gravity concentrate from the Abenab high-grade Vanadium-Lead-Zinc Project1 in the Otavi Mountain Land (OML) of Namibia. This Phase 1 hydrometallurgical test work on the Abenab concentrate sample was carried out by metallurgical consultants and processing engineers, Core Resources ("Core") in Brisbane. The Phase 1 testwork produced a preliminary processing flowsheet to process vanadium-lead-zinc gravity concentrate from the Abenab deposit and produce down-stream high-value products such as vanadium electrolyte for Vanadium Redox Flow Batteries (VRFBs), as well as lead, zinc and potentially copper by-products.

Previous gravity concentration testwork on high-grade underground resource material by Avonlea Minerals Ltd. in 2012, produced high concentrate grades of up to 21% V2O5, 14% Zn and 53% Pb2. Subsequent gravity concentration test work for Golden Deeps, by Mintek - South Africa, used low-grade surface stockpiles and tailings material from historical Abenab production, grading 0.30% V2O5, 1.29% Pb and 1.14% Zn (much lower grade than the Abenab resource) to generate a concentrate with an overall grade of up to 8.9 % V2O5, 30.5% Pb, 8.95% Zn, representing a 30 times upgrade of Vanadium. A representative sample of this gravity concentrate grading 6% V2O5, 20% Pb, 6.5% Zn and weighing approximately five kilograms (5 kg) was provided to Core to carry out the Phase 1 downstream hydrometallurgical leaching testwork.

This work included a series of sulphuric acid leach tests at different conditions, including varied pH, acid addition rates and temperature. The first test (Test 1) was controlled to PH 1 at 45°C, with a relatively high acid addition rate and produced vanadium recovery into solution of 95.4% V. Similar recovery of zinc was achieved and the lead almost entirely precipitated into the residue, for later recovery. Further testwork was carried out to determine the best method for separating vanadium (V) from zinc (Zn) and iron (Fe) to produce saleable down-stream products.

Direct ion exchange (IX) recovery of vanadium from the leach solution was shown to be the most attractive processing option as vanadium can be stripped and processed to multiple high-value end products, including vanadium electrolyte precursors for VRFBs used in the renewable energy industry.