Can the IPT process going to produce 4N HPA? Remembering that...

Can the IPT process going to produce 4N HPA? Remembering that the IPT Lake Hope deposit contains around 2% iron. Yes, they have dissolved aluminium using sulphuric acid, but the next stage is step 4, purification and details of this are to be worked out. See the IPT 18 October 2023 Metallurgical Test Work Update.
ASX:IPT - Lake Hope HPA Project WA PFS and Metallurgical Test Work Up (impactminerals.com.au)
Page 3 says: The samples of intermediate salt have been submitted for purification in Stage 4 purification by hydrochloric acid- gas sparging with subsequent calcining in Stage 5 to produce HPA.

Purification is the costly part of HPA, otherwise HPA would be much cheaper. If you can settle for a lower purity you would buy metalurgical grade alumina which is the 2N grade for US32cents per kg in Australia.

The current 4N HPA price of US$20,000 is attractive, but with such a high price on offer will the price remain so high, or will others find a cheaper process?

The company Alpha HPA Ltd ASX: A4N is aiming to producing 4N HPA and have an impressive sounding solvent extraction process. See: Products - Alpha HPA

Also, the article from Aluminium International Today is worth reading:
AIT-High-Purity-Alumina-–-Another-way-aluminium-is-part-of-the-clean-energy-revolution-Scanned.pdf

Regards