The company is investigating both vat leach of lump material and agitated tank leach of concentrates using sulphuric acid.
Scoping level capex and opex costings have supported the agitated tank concentrate leach option as the preferred process route to produce vanadium pentoxide (V2O5), titanium dioxide (TiO2) and iron oxide (Fe2O3) products.
In addition, King River has targeted other high value specialty commodities such as high purity alumina (HPA), magnesium oxide and vanadyl sulphate.
A prefeasibility study (PFS) is underway and is examining several process routes to extract these commodities.
Metallurgical refining test work has initially focused on precipitating iron, aluminium and titanium products from the sulphuric acid leach solutions as these metals occur in the highest concentrations.
The Fe2O3 chemical precipitation tests have used a sulphuric acid leach solution from the 5.6mm lump agitated vat leach and column leach tests completed by Nagrom.
These leach solutions contained 32-35g/L iron. The iron reduction method was used to initially precipitate a hydrated ferrous sulphate from the leachate at 81- 82% precipitation efficiencies.
The hydrated ferrous sulphate was washed to help remove entrained contaminants including vanadium and titanium.
The final precipitate was dried and staged calcined up to 1000°C to produce an Fe2O3 product that assayed 67.13% iron, with 1.91% magnesium and 0.21% aluminium.
Further iron reduction, purification and other methods of producing Fe2O3 are under investigation to develop the best Fe2O3 process route and maximise acid recycle or regeneration for the SSM project.
High-purity titanium dioxide products
King River’s TiO2 chemical precipitation tests have used the sulphuric acid leach solution from the 5.6mm lump column leach tests after iron reduction and precipitation of ferrous sulphate.
These leach solutions contained 3.4-3.9g/L titanium. The hydrolysis method has been used successfully to precipitate titanium dioxide from the leachate at 87-92% precipitation efficiencies.
Further hydrolysis and other methods of producing TiO2 are under investigation to produce 98% and high purity 99.5% TiO2 products and develop the best process route for the SSM project.
The King River board continues to be most encouraged by this ongoing test work, and in particular these excellent initial precipitation efficiencies of iron oxide and titanium dioxide products from a pregnant sulphuric acid leach solution.
These ongoing tests of a range of different extraction methods will enable King River Resources to identify the optimal process route to produce high grade, high value vanadium pentoxide, titanium dioxide, iron oxide and alumina products to be incorporated into a PFS for later in 2019.