Making carbon powder using fireplace and weak acid

I am doing a little home experiment trying to make as pure carbon powder as I can. I plan to then used it to eat up oxygen from a container where I want to try to melt aluminum.

My process was following:

1. I have put some sawdust in an iron can.
2. I covered the opening of the can with clay, leaving only a small opening.
3. I put the can in a fireplace and let it heat to about $$\pu{800 ^\circ C}$$.
4. After removing, I ended up with about 1/3 volume of black powder.
5. I washed the powder with water and filtered the water out.
6. I placed the wet powder in a beaker and added more water.
7. I added about 12% hydrochloric acid to dissolve calcium and metal oxides and hydroxides.
8. The solution started bubbling slightly, so I left it for several hours with occasional mixing.
9. I washed the resultant powder with water twice and left it to dry.

Did I manage to purify the carbon in the powder somewhat? Did the use of acid bring any benefit?

• 2x yes, obviously. I don't understand what you're asking for here. Your sequence sounds like you know what you're doing.
– Karl
Mar 18 at 21:38
• Only that wood ash also contains carbonates. Hence the bubbling. Hydroxides don't survive at 800°C.
– Karl
Mar 18 at 21:41
• @Karl I don't know if I know what I'm doing. I followed what I thought would work, and wanted to check if this is the right approach to remove impurities and leave relatively pure carbon. Mar 18 at 22:02

The result of your first pyrolysis must be charcoal plus the mineral constituants that are present in wood ashes. Now the wood ashes are usually a mixture of : $$40 - 70$$ % $$\ce{CaCO3}$$, $$5 - 10$$ % $$\ce{Na2CO3}$$, $$5 - 10$$ % $$\ce{K2CO3}$$, $$2 - 3$$ % $$\ce{K2SO4}$$, $$2 - 5$$ % $$\ce{Ca3(PO4)2}$$, $$5 - 10$$ % $$\ce{MgCO3}$$, $$2 - 10$$ % $$\ce{SiO2}$$, < $$1$$ % $$\ce{FePO4}$$. Washing your charcoal with water and hydrochloric acid must remove all these substances, except $$\ce{SiO2}$$. This impurity cannot be removed.