Sodium slicate (water glass)

[SweetGold]

Does anyone know if sodium silicate (aka sodium metasilicate aka water glass) can aggregate colloidal gold or silver in water or an aqueous solution? How effective is this and what is the micron size threshold for this effect to take place?

To quote from wikipedia:

Water glass is used as flocculant in waste water treatment plants. Waterglass binds to colloidal molecules, creating flocs of denser particles sinking to the bottom of the water. The microscopic negatively charged particles suspended in water interact with sodium silicate. Their electrical double layer collapses due to the increase of ionic strength caused by the addition of sodium silicate (doubly negatively charged anion accompanied by two sodium cations) and they subsequently aggregate. This process is called flocculation

--> http://en.wikipedia.org/wiki/Sodium_silicate

If this can be applied to precious metals, what would be the best SiO2:Na2O ratio from commercially available sodium silicate? Wiki says the ratios vary between 2:1 and 3.75:1. Thanks!

 

[SweetGold]

So does anyone know or have any experience with sodium silicate? I found a video that talks about it, from a gold panning perspective. Sure would like to know how this really works and how big the clusters could get.
http://www.youtube.com/user/goldrushgang#p/a/u/1/fuejIDMgnrQ

 

[Lino1406]

The list of flocculants and coagulants is long...

 

[SweetGold]

The list of flocculants and coagulants is long...

Whats the cheapest one you know? 500ml of Sodium Silicate seems to run between 8 and 12 bucks...though Im not sure of the concentration.

 

[Platdigger]

Here is a little diddy on making some.

http://chemistry.about.com/od/makechemicalsyourself/a/make-sodium-silicate.htm

 

[goldsilverpro]

The choice of flocculents are often specific to the solution. Probably the cheapest and most common is alum but, in my experience, it only works with certain solutions.
https://encrypted.google.com/search?hl=&q=flocculent+alum&sourceid=navclient-ff&rlz=1B3MOZA_enUS408US409&ie=UTF-8&lr=all

 

[Arrowood]

I just did some research on Sodium Silicate. I saw micron sizes in the 5-10 size range mentioned often. If you do a Google Scholar search for "Sodium Silicate and Metal recovery" you will find hundreds of interesting patents. There is one patent on selective precipitation of clays as I remember. It might have some information on ratios.

On the subject of making Sodium Silicate, the easiest way I have seen was to dissolve some sand in hot sodium hydroxide. The products are sodium silicate and water. Very similar to the method platdigger mentioned using silicon beads.

 

[lazersteve]

I looked into this subject several years ago and determined that it may be useful for cleaning base metals out of solutions. I never did any experiments, just a lot of studying.

Steve