[xx0numb0xx]

How can I purify the silicon dioxide from beach sand? I want relatively large amounts of silicon dioxide for making quartz via the Verneuil process, for making my own glass evaporation dishes, the thermite reaction between silicon dioxide and aluminum, Prince Rupert's drops, etc.. I imagine the most plentiful source of silicon dioxide is sand, but sand has a large amount of impurities.

The two ways of removing impurities that I've thought of are strong heating to burn off organic substances and mixing it with water then filtering out soluble substances. Because calcium carbonate decomposes into carbon dioxide and calcium oxide at 840°C, I would add the water immediately after heating to form calcium hydroxide, which is a bit more soluble than calcium carbonate.

Would this be sufficient enough to purify silicon dioxide from sand? If not, what other methods would I have to use? The sand would be from the eastern coast of southern Florida, if that helps with identifying the material's composition.

[Arkcon]

How can I purify the silicon dioxide from beach sand?

This way:  http://en.wikipedia.org/wiki/Silicon_dioxide#Production

I want relatively large amounts of silicon dioxide

Wouldn't we all.

for making quartz via the Verneuil process,

So you have a flame-fusion furnace? http://en.wikipedia.org/wiki/Verneuil_process OK.  That will help.

for making my own glass evaporation dishes, the thermite reaction between silicon dioxide and aluminum, Prince Rupert's drops, etc..

Shine on you crazy diamond.

I imagine the most plentiful source of silicon dioxide is sand, but sand has a large amount of impurities.

This is true, but ...

The two ways of removing impurities that I've thought of are strong heating to burn off organic substances and mixing it with water then filtering out soluble substances.

Pretty good start.

Because calcium carbonate decomposes into carbon dioxide and calcium oxide at 840°C, I would add the water immediately after heating to form calcium hydroxide, which is a bit more soluble than calcium carbonate.

Gah.  Yikes.  Can you really do this practically?  You see no problems with this plan?

Would this be sufficient enough to purify silicon dioxide from sand? If not, what other methods would I have to use? The sand would be from the eastern coast of southern Florida, if that helps with identifying the material's composition.

No.  You haven't addressed other metals contamination, and other minerals besides silicon dioxide.

[billnotgatez]

I GOOGLE
from sand to glass
and got lots of hits
here is just 1
http://www.wikihow.com/Make-Glass

[xx0numb0xx]

I GOOGLE
from sand to glass
and got lots of hits
here is just 1
http://www.wikihow.com/Make-Glass

I know how to make glass, and sand with a hydrochloric acid wash should be sufficient for that, but I'm interested in processing relatively pure silicon dioxide. The main reason is for making high-quality quartz. It would also make the silicon from silicon dioxide thermite much purer. Purer reagents lead to purer products!

This way:  http://en.wikipedia.org/wiki/Silicon_dioxide#Production

Those methods are for production, not purification.

So you have a flame-fusion furnace? http://en.wikipedia.org/wiki/Verneuil_process OK.  That will help.

I'll be using the principles of the process: melting fine particles onto a support rod that is slowly lowered, keeping the tip of the boule liquid while the lower portion slowly solidifies. I'm not sure exactly how well it will work without an oxyhydrogen flame, but if I just get a glass rod instead of a quartz rod, that would still be useful.

Gah.  Yikes.  Can you really do this practically?  You see no problems with this plan?

The problems I see are boiling solutions splashing everywhere, containers breaking from thermal stress, and the exothermic reaction of calcium oxide with water. I hadn't thought of the splashing when I posted that. I also hadn't thought of using hydrochloric acid to react with the calcium carbonate instead of attempting to decompose it at high temperatures then having it undergo an exothermic reaction with a liquid while still at those high temperatures. That definitely wasn't the most intelligent idea I've come up with.

No.  You haven't addressed other metals contamination, and other minerals besides silicon dioxide.

Hydrochloric acid would react with calcium carbonate, which I imagine will be the primary contamination. It would also react with any non-noble metals, although very slowly for certain metals.

Some other more predominant contaminants could possibly be: calcium sulfate, aluminum oxide, iron oxides, mica, and various silicates and aluminosilicates. Aluminum oxide and iron oxides would react with hydrochloric acid. I'm not sure whether the others will react or not, and I'm also not sure if they will decompose in strong heat.

One other idea that I just thought of is milling what's left over (I would mill beforehand as well, put I imagine the particles would aggregate together when heated and also when soaked) then jerry-rigging some kind of vibration table. Setting the milled mixture into a bucket fixed to the vibration table and leaving it to vibrate for hours, days, or weeks would separate the constituents by density. This would only work, of course, if the particles vary noticeably in appearance.

This last method is not one I would use for large amounts of silicon dioxide and is also just as much of a shot in the dark as the other ideas I've had. Once I've purified the sand as much as I can, I could mix it with molten sodium hydroxide. The resulting sodium silicate would be water soluble. This would only work if the contaminants either react with the sodium hydroxide to form an insoluble hydroxide or do not react at all. The resulting mixture would be dissolved in water and filtered. The filtrate would be reacted with hydrochloric acid to form sodium chloride and silicon dioxide. This would be filtered with water to remove the sodium chloride. I wouldn't do this in large amounts because of the amount of sodium hydroxide it would require.

Those are all the ideas I can come up with. Is there anything else that I'm missing?

[vmelkon]

That's a lot of work and various chemicals you need.
One way to make SiO2 would be to buy some silicone. Let it dry first. Then burn it. The white smoke will be SiO2 and it sticks to things sort of like the carbon from a burning candle.

[billnotgatez]

@vmelkon
From WIKI

Combustion
When silicone is burned in air or oxygen, it forms solid silica (silicon dioxide) as a white powder, char, and various gases. The readily dispersed powder is sometimes called silica fume.

I assumed that char could be carbon soot.
That would make a mixture of silica and carbon soot. 
That makes the result not pure silica.
Am I wrong?
Since I have not done it, I do not know.

In any case, I am guessing that it would be too expensive to get the amount of Silicon dioxide that @xx0numb0xx wants burning silicone.