RU_KLO
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DIATOMACEOUS EARTH 101
I purchase diatomaceus earth (sold as non toxic ant killer)- lets call it DE - to use as filter aid.
Its a creamy beige color fine powder, no lumps
Never used, read some posts, watch some videos.
So I have some questions (or "confirmations" - just say yes or no - if no, how or why) from what I found:
1) Does it need to be acid washed or it is used as bought?
2) It is used on top of a fiterpaper in frited/buchner filters - meaning plain filter surface - no V shaped filter.
3) Only use if you are going after the filtrate, but not after the precipitate.
4) Could be used for coloids?
5) Does it improves speed on difficult filtering solutions, CaSO4 for example?
6) The DE layer should be not thick. for example:1-2 mm
7) Could be used to retrieve the precipitated, but it should be dissolved with a solvent does not attack the DE. (from wikipedia: . It is usually
composed of 80% to 90% silica, 2% to 4% alumina minerals, and 0.5% to 2% iron oxide, although the precise composition of every deposit is different.)
8) It should be used dry.
.
Any other information is appreciated.
Thanks
Go SAFE, because stupidity and bad Luck exist.
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chempyre235
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IIRC, diatomaceous earth is typically 90-95% diatomaceous, with the remainder being either calcium or sodium bentonite clay. I think the bentonite
clay is the reason for the color. Pure diatomaceous earth -- I believe -- is white.
As for the other questions, I couldn't say.
"However beautiful the strategy, you should occasionally look at the results." -Winston Churchill
"I weep at the sight of flaming acetic anhydride." -@Madscientist
"...the elements shall melt with fervent heat..." -2 Peter 3:10
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Boffis
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Products called diatomaceous earth are usually pretty much the raw product and usually contains some detrital matter such as quartz and clays. I use
it extensively "as bought" mixed with decolourising charcoal for clarifying organic solutions. If you are going to use it with acid solutions I would
wash it first. If it is beige coloured it may have been calcined, the raw material is usually light grey. The calcining process removes organic mater
and make the Fe oxides less acid soluble.
If the slurry feels "gritty" wash by decanting. Suspend in water to a thin slurry and after a short standing to allow any sand to settle and decant
the slurry of diatomite. I checked mine with dilute HCl to look for carbonates but they are absent.
I find the use of equal volumes of DE and decolourising charcoal to be much easier to filter then charcoal alone. I find that with charcoal alone some
of the finest charcoal is drawn through the filter paper, DE prevents this. I also find that the haze sometimes found in say copper or ferrous
sulphate solutions are easily removed by adding DE before filtering. It also allow the filtration of barium sulphate suspensions but you need quite a
lot of DE in this case.
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Keras
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I use DE to filter e.g. copper oxalate. NurdRage found copper oxalate would pass through a sintered glass funnel, but it will be retained if you cover
the sintered glass disc in DE. So it definitely works to retain very thin particles (in my experience).
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MrDoctor
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i found raw DE impossible to filter, id load it in the buchner with either fast or slow filter paper, turn on vacuum, and get maybe a few drops before
the filter totally clogs
I havent touched it again though, been meaning to try acid washing and calcining it in my furnace, and was going to say, probably needs decanting.
what i had in mind was loading some into a tall beaker, letting water pump in, swirl around and overflow, to pick up all the light stuff leaving only
larger particulates. otherwise, decanting is probs the way to go, maybe also hitting it with my submersible ultrasound cleaner, the diatoms are silica
and crystaline wheras all the nasties are calcium and, probably soft stuff, so ultrasound should strongly favor non-silica getting much finer. ill
just have to see how that goes what it takes to make it filterable.
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Dr.Bob
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There are brands of washed DE, like Celite, which are carefully washed with acid, pH adjusted, rinsed, and dried to give a more useful material.
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Mateo_swe
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I think there is quite a difference between diatomaceus earth that you buy in a garden store and diatomaceus earth that are found in a lab store.
S3 chemicals sell some diatomaceus earth that i think is used as filter aid.
They also have a specification on their diatomaceus earth what it contains exactly.
https://shop.es-drei.de/laborhilfsmittel/12388/kieselgur-77-...
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macckone
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Prep for DE for the lab is
1) remove large chunks of foreign matter
2) wash with acid (usually acetic or nitric) to remove carbonate
3) rinse thoroughly with distilled water
4) dry
5) filter through a fine mesh
6) treat with sodium bicarbonate rinse (long soak)
7) wash with nitric acid
8) rinse
9) wash with hydrochloric acid
10) rinse
11) dry at high heat
12) analyze for further processing
This process is tedious and expensive hence the high cost of cellite compared to garden grade DE. If there are organic contaminants an acetone wash
and rinse and then pirahna solution is used. Unless you live in a country where it is simply unavailable a commercial product is going to be
cheaper. Having said that, most amateur chemist can get away with a peracetic acid wash and rinse thoroughly. We don't need a usp grade product.
Now the question becomes what contaminants are you worried about. For most of us it is going to be carbonate. Other contaminants are heavy metals
and alkaline earths. As well as alkali salts such as sodium silicate. ACS grade is pure to ppm level. For specific heavy metals that can be ppb
level.
You can buy food grade that meets the heavy metals and toxins limits already without processing. That is a better start than garden or pesticides
grade. Neutralize carbonate with acetic acid (not vinegar) rinse thoroughly, and it is probably good enough for amateur use.
If you need ACS sodium levels, buy a commercial product.
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