During a reaction I use sodium hydroxide and create sodium silicate as a by-product.

I am curious if there is a way to recycle that sodium silicate into sodium hydroxide?

I am not a chemist, just have to use chemistry and I love it.

My best guess is to use Hydrogen Peroxide and Heat.

or Hydrogen gas.

or maybe even Aqua Ammonia...

For any reaction I have abundant electricity available, to create heat.

I have thought about this for months and stuck in the do-nothing phase until I can get some help from experts and see the reaction on paper.

Any help would be greatly appreciated.

  • 2
    $\begingroup$ The reduction to Si needs extreme reduction conditions at which H2O2 is not available. Neither ozone neither oxygen can be produced at these conditions. By CH2 you probably mean H2. I suppose very high temperature would be needed for the 2nd reaction and it would end up as Na2O. Si would probably and up as sodium silicide. $\endgroup$
    – Poutnik
    Commented Dec 16, 2019 at 8:16

2 Answers 2


The reactions you proposed are pure fantasy. They will never happen. Na2SiO3 does not react with either H2O2 or Hydrogen gas or CH2 (which does not exist, by the way).

The only possibility would be to have silica precipitate by bubbling CO2 in the solution. This will produce a precipitate of Si(OH)4. But this precipitate is so gelatinous that it cannot be easily filtrated. If you are able to filtrate (under pressure), the remaining clear solution contains Na2CO3. $$\ce{Na2SiO3 +CO2 + 2 H2O -> Na2CO3 + Si(OH)4}$$

which could be transformed into NaOH by adding calcium hydroxide (or chalk) Ca(OH)2. This addition creates a new precipitate, CaCO3, which can be filtrated, and the residual solution contains NaOH. $$\ce{Na2CO3 + Ca(OH)2 -> CaCO3 + 2NaOH}$$

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    $\begingroup$ Methylene is a thing, just not very stable or isolable. See here. $\endgroup$ Commented Dec 16, 2019 at 10:52
  • $\begingroup$ Methylene exists as an intermediate of rection, I know. But you cannot store it in a flask, or make it react with a solution of sodium silicate. $\endgroup$
    – Maurice
    Commented Dec 16, 2019 at 17:23
  • $\begingroup$ Noted "not isolable". $\endgroup$ Commented Dec 16, 2019 at 17:34

The one simple chemical reaction that could work is with calcium hydroxide (limewater):

$\ce{Na2SiO3 +Ca(OH)2 -> 2 NaOH + CaSiO3(s)}$

This reaction is used to seal concrete and so is chemically a thing. Now the bad news: the reason the sealing process works is the calcium silicate comes out as a hydrated gel. It would be hard to separate for your purposes, like the silicic acid mentioned in Maurice's answer. Silicates in general are messy in aqueous systems.

Sodium hydroxide is cheap, the silicate not very hazardous with respect to disposal. Buying the sodium hydroxide new seems more feasible than either of our reaction schemes.


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