To remove aluminum oxide from powder, a common method is acid leaching. This process typically involves mixing the powder with a strong acid like hydrochloric or sulfuric acid, then heating and stirring the mixture to dissolve the aluminum oxide. After leaching, the solution is filtered to separate the solid residue from the liquid. The residue is then washed with distilled water to remove any remaining acid and dried to eliminate moisture. Depending on the required purity, additional purification steps such as recrystallization might be employed. It's important to note that this process requires careful handling of strong acids and appropriate safety measures. The exact procedure and its effectiveness can vary based on the specific composition of the powder and the desired level of purity.

The problem with dissolving aluminum oxide using acids is that the metallic components of the mixture are dissolved in these acids before the aluminum oxide.

The only solution to the problem of Al2O3 contamination, in my opinion, is to reduce the formation of this contamination during powder synthesis. Two things help with this: the best possible vacuum or the purest argon (better than 99.999%). Adding hydrogen is counterproductive because it cannot reduce Al2O3 and is usually not as clean as argon (hydrogen with a purity of over 99.999% is very expensive and is rarely available). In contrast, "normal" hydrogen with a purity of 99.5% brings with it far too much oxygen, which causes additional Al2O3 formation.

I agree with Vadim Verlotski. While chemical methods like acid washing are ineffective because aluminum could be more reactive than the acids, a mechanical approach like ball milling offers an alternative. However, you should consider the initial size of your aluminum powder. I used the ball milling method on aluminum powders with an average particle size of 80µm. However, as the particle size decreases, there is a negative effect on the aluminum powder's particle size and morphology.