Aura Energy Limited (AEE: ASX, AURA: AIM) has announced a highly encouraging update on the program of metallurgical leach test work examining vanadium recovery by acid pressure leaching for the Häggån Vanadium Project, Sweden.
The company reported that the test work resulted in vanadium recoveries of up to 96.9% to leach solution, with average recovery of 96.5% V2O5.
It may be noted that the program was carried out on three drill hole composite samples defined as representative of the mineralisation within the Häggån Vanadium High Grade Resource following consultation with the ASX on the Häggån Scoping Study.
Häggån Vanadium project
The Häggån Vanadium Project is located in central Sweden and is one of the largest undeveloped vanadium and Battery Metals projects in the world.
Häggån is a large poly-metallic deposit containing economically significant levels of vanadium (V), nickel (Ni), zinc (Zn) and molybdenum (Mo) as well as other Battery Metals. The project has a resource of 15,100 Mlbs vanadium pentoxide (V2O5).
Aura had completed the initial submission of the Häggån Vanadium Project Scoping Study in early September 2019. However, several technical queries were raised during the ASX review process. These queries related predominantly to assumptions regarding vanadium leach recovery.
The need for metallurgical testwork
To ensure a comprehensive response to the issue and provide additional confidence in the results of the Häggån Vanadium scoping study, Aura commissioned a vanadium targeted metallurgical test work program at ALS Minerals, by acid pressure leaching.
It may be noted that acid pressure leaching is generally considered the most efficient method for extraction of vanadium from Black Shale resources.
Metallurgical test work program at Häggån
The company reported that the metallurgical test work program was undertaken on splits of three samples used in the 2018 beneficiation and flotation program undertaken at ALS Minerals.
These samples were considered representative of mineralisation in the Häggån resource, with a range of vanadium grades. The summary of diamond drill hole composite samples used in oxidative acid pressure leaching test work program is as below.
Acid pressure leach conditions
The company reported that the acid pressure leach conditions were determined based on recommendations from METS Engineering. This includes Grind of P80 of 75μm; Oxygen partial pressure of 1,200 kPa O2; Total acid concentration – H2SO4 of 200 g/L H2SO4; Residence time of 2 hours; and Temperature of 180°C.
High vanadium extraction
The company reported that the results of acid pressure leaching tests targeted at vanadium recovery demonstrated that consistently high vanadium extraction could be achieved across a range of samples.
The tests returned an average vanadium extraction of 96.5%, with only 0.4% deviation from this average between the tests.
The summary of vanadium extraction by acid pressure leaching by sample is as shown below
Previous metallurgical testwork
In October 2018, Aura had announced successful completion of beneficiation and flotation test work for material from the Häggån Vanadium Project.
These results had demonstrated recovery of an average of 85% vanadium to a concentrate with an average of 64% of the feed mass. The concentrate mass reduced to a total of 50% of feed mass with removal of the carbon component.
Scoping study to include recovery
The preferred Häggån Vanadium flow sheet includes beneficiation, acid pressure leaching and solvent extraction of vanadium.
The company said that the overall expected recovery for the Häggån vanadium process, including each of these components will be included in the Häggån Vanadium Scoping Study.