# Removing aluminum oxide from impure silica

We have an assay for a mine. Our goal is to have only silica. Is there a cost effective way to extract the contaminants? The product is a fine powder called diatomaceous earth, or fossil shell flour. Our goal is to use the product to help poor pacific islanders increase their silica uptake and assist in heavy metal detox. Many members of the pacific island nations suffer from heavy metal poisoning. The composition of the powder is:

• > 84.7% $\ce{SiO2}$
• < 4% $\ce{Al2O3}$
• < 2% $\ce{Fe2O3}$
• < 0.33% $\ce{CaO}$
• < 0.36% $\ce{MgO}$
• < 0.5% "other"

We aren't concerned with the calcium, iron or magnesium oxides, just the aluminum oxide.

• Is there a simple process to reduce the aluminum oxide levels?

• Also, what is the easiest process to convert the silica to orthosilicic acid for increased bio-availability?

Treat it with concentrated $\ce{HCl}$, it will react with the aluminium oxide and turn it into aluminium chloride. You can separate it from the silica powder by a simple filtration.

$$\ce{Al2O3 + 6HCl -> 2AlCl3 + 3H2O}$$

• I doubt this will work when the alumina is part of some complex clay mineral (which it is in this context). – matt_black Dec 20 '18 at 12:17

ore or mineral should be treated with some flux like CaO, which react with silica to form Ca-silicate. and which can be separated after filtration process.