# Trial by fire: Safely heating sand without it agglomerating?

Wikipidia quotes a melting point of 1713C for sand.

I went on the beach to get some sand. I assume it's a mix of all kinds of stuff.

The finality is to prepare a big pile of clean sand to use as filtering aid above paper filter (among other uses).

I'd like to get rid of plastics & organics by heating it up.

What temperature can I bring it up to before the smallest particles start to agglomerate? What temperature would you recommend for pyrolysing as much of everything in there that is not SiO2 such that it either degrades or later more easily disssolves in water?

• Assuming you only need a couple of kilos or so, any reason to not buy clean washed sand from one of the chemical supply houses? Also, that melting point is probably for pure silica (quartz) sand. Real beach sand is all sorts of stuff.
– Ed V
May 15 '21 at 16:59
• I don't know that sand would be perfectly clean anyways, so, since tons of sand is available for free where I'm at I'm thinking why not clean it myself.
– Hans
May 15 '21 at 17:57
• Perfectly clean is not reasonable, but have you priced silica, such as chromatographers might functionalize and use as column packing? Anyway, enough said: best of success and avoid steam explosions from unexpectedly wet sand!
– Ed V
May 15 '21 at 19:18

Sand is not available as a reagent grade chemical, but rather is mineral origin particles of a size between 0.074 and 4.75 millimeters. Gravel is bigger, silt is smaller.

Pure silica (SiO$$_2$$) may melt at 1713$$^o$$, but the melting point of real sand is given as 1500 to 1610, and you can probably find some numbers outside that range.

Perhaps more of an issue than the exact melting point is how much are you preparing to treat? And with what heat source? And what sort of vessel are you going to contain the sand in while you heat it up and cool it down? And for what purpose?

Thin layers of sand (small overall quantity) may burn off organics relatively easily, say in a stainless steel measuring cup, with a propane torch - although, the handle will get hot, so arrange some sort of apparatus to hold the vessel.

Different materials will need different temperatures and times to burn off completely; perhaps you can heat till smoke stops coming off and the sand looks like it is a bright red or orange color. I doubt that you would have to get to a yellow.

• Thank you for this great answer! So around 1000C should do fine for this purpose and it should be low enough that it doesn't stick together (assuming >95% Quartz)?
– Hans
May 15 '21 at 17:24
• If you heat in a sturdy pan, heating to 1000 C with some shaking should keep sand particles separate. Beach sand may contain some salts which could melt and bind sand grains together, but water would dissolve that and free up the sand. The best way to find out is to try it - just be safe: wear protective gloves, keep away from other burnable material, etc, etc. May 15 '21 at 21:59
• I love answering questions that have a significant downvote. The downvote points to very different viewpoints, which is the basic source of the question/issue/problem. The interesting question only exists because someone is thinking outside the box, or because some instructor has described either an incomplete or perhaps imaginary box. May 16 '21 at 13:21
• It is the mark of a noble mind to, at times, intinctively go against the natural reflex of the masses/majority.
– Hans
May 16 '21 at 20:39
• @Hans above 500C is good enough, hydrocarbons break down at that temperature, so typical open flame without anything extreame will do. If oxidiser(air) can access the stuff it more than enough, if not then 600-700C is more than enough. May 16 '21 at 23:37