I think I have kept a fairly consistent line here with respect to HPA and I have volunteered that I am working on a similar sulphate route for HPA elsewhere. The fact it has taken 12 months to get to this point is not surprising to me in the least, based on my own experiences.
Regarding the announcement, if you read what they are saying carefully, it is clear;
- the 99.99% product was produced from a batch leach liquor from the non-mag fraction. This is therefore one result out of many attempts. ( n = ? )
- this means that the previous tests (and other tests) on leach liquors produced from other material, didn't work. This is to be expected, otherwise everyone would be leaching random rocks to get HPA.
- this matches what I have been saying, that the process needs to be optimised by presenting the acids with the best possible material with which to work, not just throwing **bro in a bucket and hoping for the best
- the 'reagent' used in the leach is undefined, but almost certainly sulphuric acid, and likely ammonium. Sulphuric acid consumption is a concern previously raised, and this will differ according to the composition of the rock being leached, length of leach, etc.
- a two stage purification process to go from the initial aluminium sulfate precipitate to 99.99% is good, although as said first up, this is one test result out of a series of tests
- the discussion about impurities suggests they have not, at this stage, assayed the calcine product via glow discharge mass spectrometry for a definitive result
- the assay results are not presented in the announcement, which is a little concerning as this suggests the numbers are not sufficiently firm as to put the C on the B over; they may be awaiting the GDMS results which could be a long time coming due to COVID. THe lab is in New York, so, yeah.
Overall, this is what I would consider an encouraging step. These processes can take a long time to work through. For example, when you do each precipitation test, the solution and residue need assaying. Even with a laboratory attached to the met lab, it can still take 1-2 weeks per step in the process to see if your experiment worked. So, best case, front to back from getting the crushed rock through the magnetic separation to the end would have been a minimum of 10-14 weeks, or 3 months. Given the 99.98% result was achieved in December, that's right on schedule, given Dec-Jan is cactus due to Christmas.
But, next step is optimisation, which will take another 3-6 months at least. Not sure the cheer squad is really banking on this, but it is absolutely clear that the vanadium PFS is toast, all hail the HPA PFS!
(20min delay)