I know... not the most glamorous thing used in chemistry.
However, I just bought a 10 kg bag of sand for a buck and wanted to use the sand for two things: a sand bath for my hi-temperature experiments, and
for packing a small column.
So I proceeded to "clean" roughly the sand first, by pouring it in an empty bleach bottle , filling it with hot water, shaking it vigorously and
decanting it very rapidly. The first 10 washes went from dark chocolate brown to nearly clear. I went ahead with 2 or 3 more washes to get the last
remaining dust and organic stuff out.
Then I put the sand in a large pan lined with aluminum paper and "cooked" it at increasingly high temperatures. Right now it's been in the oven for 5
hours and i'll let it ride for a couple more hours.
But finally, I want the sand to be truly clean of any organics or reactive compounds, like pyrite dust and stuff, so what should I use to make it
clean enough to put in a reagent without contamining it?
I was thinking of putting it in a large beaker filled with diluted sulphuric acid. Would that do the trick? Or maybe HCl?
Has anyone tried to wash sand for lab use? What are your techniques?
Thanks in advance for your suggestions and recommendations.
Robert
Wizzard - 4-3-2011 at 10:47
I'd imagine some sort of acid bath would scrub out quite a bit of stuff, and turn it into something more soluable than SiO2aonomus - 4-3-2011 at 14:23
What comes to mind is digestion with sulfuric acid, you may want to do some small scale tests to see just how much material is extracted when digested
with varying concentrations.
If you digest with sulfuric acid and you expect there to be any decent amount of pyrite inside the sand, you could end up releasing H2S, and forming
FeSO4 which can end up oxidizing to Fe(III) mixed hydroxides that are just as insoluble.Arthur Dent - 4-3-2011 at 14:46
Good idea, i'll put a bit in a test tube with a dropper-full of H<sub>2</sub>SO<sub>4</sub> to see if there's much reaction
with the dried product. I'll test this tomorrow since it's suppertime and my cashew chicken is calling!
Robert
[Edited on 4-3-2011 by Arthur Dent]aonomus - 4-3-2011 at 16:45
I would do a little more than that, consider how much mass you loose, quality of the sand before and after, etc. Try different concentrations too, and
consider how the heck you are going to work it up. Its not like you have a big ceramic Buchner and conc H2SO4 resistant filter media.Melgar - 4-3-2011 at 17:21
I'd soak it in bleach to oxidize most of the organics, then rinse with water, then rinse with muriatic acid to solubilize any metal salts or oxides.
Sulfuric may end up leaving behind insoluble sulfates, and my instinct is the most likely contaminants are stuff like iron oxides or calcium salts,
both of which would be dissolved by HCl.Elawr - 4-3-2011 at 18:21
One thing you can do is fuse some sand with NaHS04. Do it outdoors or in hood. Combine dry sand and bisulfate prills in non-metallic vessel good for
temps around 400-500C. The salt will melt and dissolve most metal oxides readily. When it's finished, you'll have a greenish or grey mass with some
fuming. Cool the mass, break it up and dissolve in some distilled H2O, The impurities should dissolve and rinse free from the sand, which now will be
as white as snow.DougTheMapper - 4-3-2011 at 20:49
For my sand bath I bought fine white silica sand which was already free of garbage, $5 for 50lb. You might end up spending more on reagents than it's
worth.ldanielrosa - 5-3-2011 at 00:18
DougTheMapper beat me to it. I tried the same with beach sand and all the alumina and magnetite turned into endless silt after I tried to wash it
with acid.
I must say it's nice to have an old crock pot with a sand bath to cook down two or three beakers at once though.Arthur Dent - 5-3-2011 at 07:24
@DougTheMapper: You know what, you're right! Fuggitabout the sand for my column, I think the sand is clean enough for my sand bath right now. I put a
few grains on a microscope slide and it's just absolutely lovely, with transparent quartz crystals and spar of every colour!
I dropped the sand in a plastic bottle and will use it next time I need to setup a sand bath. After pulling the sand from the oven, the damn thing was
still hot for many many hours! That stuff really keeps the heat on for a long time, which does complicate thing when you have to quickly pull-out the
heat from a reaction using complicated sealed joints...
As for the column, I'll check out the silica sand you're suggesting. Thanks!
That stuff really keeps the heat on for a long time, which does complicate thing when you have to quickly pull-out the heat from a reaction using
complicated sealed joints...
Support the hot plate holding the sand bath on a Lab Jack and just lower the jack to remove the sand bath from the flask. This can also be used with an oil bath or heating mantle.hissingnoise - 5-3-2011 at 13:01
There you go again entropy, clouding the issue with plain common sense!
