Dissolve Silica

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stmonte

New member
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Jul 29, 2018
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I am working on a concentrate with 9% Silica and 7% Au encapsulated inside of the Silica, according to ICP-MS.

The gold is nano sized gold.

What would you use to dissolve the Silica? I am looking at Alkali-washing but don't have a great way to bench test it.

What can be used to leach the nano Au following that treatment and precipitate it?

Does anyone know of any refineries that would be interested in processing this type of material in bulk?
 
Welcome to the forum.
A quick google search revealed that plain old simple aspirin dissolved in water should dissolve silica, I’m not sure how effective it will be but for the cost of a bottle of aspirin and a glass of water it’s worth a try on a sample.
 
nickvc said:
A quick google search revealed that plain old simple aspirin dissolved in water should dissolve silica, I’m not sure how effective it will be but for the cost of a bottle of aspirin and a glass of water it’s worth a try on a sample.
I really doubt that. Silica = quartz is really inert or we wouldn't use it in lab glass or fused silica melting dishes.

Silica is really inert and hard to dissolve and the methods to dissolve it is usually very dangerous and either contains high heat, toxic chemicals or both.
For example silica can be dissolved with hydrofluoric acid (a really scary acid), molten sodium hydroxide (also scary) or reacting with fluxes to form a molten slag in a furnace. Silica can also be dissolved in pure water at 450 degrees C, at a very scary pressure.
I don't know if any of these methods would make it possible to collect the gold or if it would just be dispersed in a new media as a colloid.

This is nothing I have any experience with.

Göran
 
I was a little skeptical but it was on sciencing under the geology heading, Göran google how to dissolve silica and it’s there, it could still be complete rubbish but I’m not a chemist :shock: :D
 
I was a little dubious as well, but as Nick suggested, I googled it. What I read was more on an experimental level. I doubt it could be scaled economically. I also don't know that it would be effective on all forms of silica, but as a test, who knows.

Dave
 
Well at least it’s safer than hydrofluoric and hot lye if it has any effect, I agree with Dave it’s worth a small scale test if nothing else.
 
As a 1st shot I would try AR and if it does not work I would add cautiously a little concentrated
Sulfuric acid to heat it and initialize reaction
 
If this is the article you are talking about then I would say it's highly unlikely it would work.
https://sciencing.com/dissolve-silicate-8547322.html

They have a reference at the end of the page and downloading the article it discusses dissolving silicates (not silica) in organic acids. The samples tested were sitting in the acid for three weeks, it dissolved the rocks between 120 to 3000 angstrom in that time. That's between 0.012 to 0.3 um, way less than standard flash gold plating.

Where I live it's easy to just walk out into the nature and study rocks that were grounded flat in the last ice age. Any quartz at the surface is still flat on the top while the surrounding rock have weathered away a couple of millimeters in 10.000 years.

But do a test if you like, at least the solution isn't scary.

Göran
 
I’ve tried to be helpful and I must admit it sounds dubious so if anyone has a better idea please step forward and supply it, I’m happy to admit I’m not a chemist and have very little to no knowledge about ores but I’m sure someone can be more helpful than I can be.
 
Why not just melt with flourospar in a rotary converter?

If it's low yielding, add silver as a collector.


Sent from my iPhone using Tapatalk
 
A boiling, concentrated solution of sodium hydroxide in a steel pan will dissolve silica. Like Goran said, the dangers of boiling sodium hydroxide can be great if you have little to no experience with it's use. It will dissolve flesh and muscle and blind you instantly if it splashes into your eyes. Eye protection, face shield, long sleeves, pants, boots, rubber gloves should all be worn when working with it. Harmful vapor are not likely but at a boil, a mist of solution can damage your lungs permanently, so a respirator is also recommended. When the solution gets hot enough to react to the silica, you will see the reaction start and if you do not leave enough room in the container, a boil over will occur. When the reaction starts, it will get violent very quickly.
 
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