Aluminum powder from aluminum sulfate?
Metallic aluminum cannot be obtained from a solution of its salts. It is because pure aluminum reacts with water, a little bit like sodium. Of course a piece or a sheet of aluminum does not usually react with water, because the metal is covered by a thin, colorless and waterproof layer of aluminum oxide, which prevents the contact between aluminum and air. And if you remove this layer with a knife, the oxide layer will immediately be remade by air.
The only way of showing that aluminum reacts with water is to dip the aluminum piece in a solution of Mercury chloride. There will be a surface reaction like $$\ce{2 Al + 3 HgCl2 -&gt;  3 Hg + 2 AlCl3}$$ Then the mercury Hg will make an alloy with aluminum. And this alloy cannot be covered by the alumina shield. So such a piece of amalgamated aluminum will be quickly oxidized in air, and will produce long white filaments of $\ce{Al2O3}$ or $\ce{Al(OH)3}$ if abandoned in air for a couple of minutes due to one of the following reactions $$\ce{4Al + 3 O2  -&gt; 2 Al2O3}$$  $$\ce{4 Al + 3 O2 + 6 H2O -&gt;  4 Al(OH)3}$$ This production of alumina filaments is very interessant to observe. Of course it is not allowed any more today, because of the toxicity of mercury.