High purity alumina (HPA) is a processed, premium non-metallurgical alumina product characterised
by its purity level ie 99.99 per cent (4N) or 99.999 per cent (5N). The market price, application, and
performance of HPA varies widely according to its degree of purity. High purity alumina is a form of
aluminium oxide (Al2O3) with growing use in LED lighting and coating on the ceramic cathode
separator sheets in lithium ion batteries.
This paper describes a study on producing high purity alumina from feldspar to produce HPA and
potash for use as a fertiliser. The project was positive for a number of reasons. High potassium
extraction (>99 per cent) was achieved in the alkali leach using sodium hydroxide as the leaching
agent and full dissolution of the alkali leach residue was achieved using hydrochloric and sulfuric
acid. The potential to produce a high purity alumina product via a complex but promising emerging
process was assessed. The potential to extract potassium as potassium sulfate to add value to the
project was also demonstrated with the test work.