How to dissolve iron powder? I know iron can react with many solutions, but when I tried to mix iron powder together with permanganate or dilute sulphuric acid, the iron powder would not react and instead, it just float on the surface of the solution. I tried to stir it for several minutes but it seems doesn't work.

It is pure iron powder, can be attracted by magnet

How can I dissolve iron powder and let it become $\ce{Fe^2+}$ or $\ce{Fe^3+}$ ? (Just dissolve it is ok)
I did some brief research and I saw that sulfuric acid can dissolve iron:

Fe(s) + H$_2$SO$_4$(aq) → Fe$^{2+}$(aq) + SO$_4$$^{2-}$(aq) + H$_2$(g)

Of course, this would leave sulfate ions and perhaps some precautions would need to be taken because of hydrogen gas production. If you absolutely cant have any sulfate ions, you could precipitate them out by adding barium or silver ions to the solution, but that would require extra work and introduce new ions to the solution. Also note, the iron ions should be aqueous in +2 state but I read that if there is oxygen in the system (which there naturally would be), some iron(II) can oxidize to iron(III).