Shipnibbles
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Any secrets to keeping a frit from getting clogged?
I'm trying to filter a large quantity of water with very fine particles suspended in it. I've tried covering the frit with a filter paper (that either
fits perfectly or almost perfectly) but that doesn't seem to stay unclogged for any longer periods of time. I've read about celine (diatomaceous
earth? ) can help but does it actually stay unclogged for any smaller periods of time? Are there any weird tips or do I just need to filter smaller
amounts at a time and replace filter paper often?
Some more info: I used Liptakovs "polarization method) to make fine NC powder. I also don't know the specs on my frit as where I purchased it did not
include that in the description (the price was very very right).
I know this is a basic question, but I appreciate answers all the same
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hissingnoise
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| Quote: | | Any secrets to keeping a frit from getting clogged? |
Yeah, only use it for stuff that paper won't handle!
But seriously, you could try running strong nitric and/or sulphuric acid (no phosphoric acids or alkalis!) through from the underside.
...And wait...or use mild pressure to speed it up...
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Deathunter88
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Quote: Originally posted by hissingnoise  | | Quote: | | Any secrets to keeping a frit from getting clogged? |
Yeah, only use it for stuff that paper won't handle!
But seriously, you could try running strong nitric and/or sulphuric acid (no phosphoric acids or alkalis!) through from the underside.
...And wait...or use mild pressure to speed it up...
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In addition to that, you really only want to use a frit to filter something where you intend you keep the solid portion. And preferably, the solid is
one that is soluble in at least one solvent. (So for instance, don't try to filter a clay solution)
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Assured Fish
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And never, ever, EVER filter Cr2O3 through it.
Sufficiently advanced science is indistinguishable from madness.
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macckone
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Assured Fish:
Not sure why you wouldn't filter chromium trioxide with a frit.
Frit is going to be immune to oxidation and chromium forms a nice soluble sulfate and it is soluble in acetone.
You may have to soak to hydrate it but it comes out and the stuff eats filter paper so frit is the only way to filter it.
If it isn't a ceramic frit, yeah but who sells non-ceramic frit?
Deathhunter:
The reason to use a frit is something that will react with paper filters. As hissing noise said.
Shipnibbles:
if you don't need the solids then diatomaceous earth over paper in a normal buchner funnel will work much better.
Unless the substance reacts with filter paper, paper is the way to go.
Save the frit for filtering crud that will react with filter paper.
And always make sure you know how to get the solids out of the frit before using it.
Popular methods are different solvent, dissolving with acids like sulfuric or nitric acid, mild bases to strip sulfates.
Insoluble sulfates are the worst.
My current method is leaching with sodium carbonate solution.
sodium sulfate is soluble and for many metals this will result in carbonate on the frit.
Please note that leaching means soaking and changing the solution repeatedly.
This is a metathesis reaction converting one insoluble to another.
Then treat with acetic acid which will convert the carbonate to acetate.
Almost all acetates are soluble (basic iron acetate being the exception).
Citric acid also works but acetic acid is easier/cheaper.
Citric acid will remove iron.
Another method is leaching with sodium acetate or mono-sodium citrate.
And of course for organics, good old piranha solution.
It is better not to get insolubles that you can't deal with easily from becoming lodged in frit.
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Swinfi2
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Filtering graphite out of sulphuric acid is also a bad idea, seems all good until you realise the colour still won't go away from the acid and the
graphite settles constantly clogging the frit and making it black for ever after. Btw does piranah work for this? (I don't currently have a peroxide
source or i would have tried it.)
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beerwiz
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If you want to filter something that you will later dispose, then you can use celite, put 3cm of celite on the frit, then you can filter almost
anything without clogging the frit. I've filtered clays, activated carbon, and very fine zinc using this method with 100% success.
If you have a very fine powder that you must filter and you want to KEEP, then celite won't help you because it will get stuck in the celite. For this
you must use a centrifuge.
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macckone
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Swinfi2:
Yes, piranha solution will oxidize carbon.
Someone recently posted about it oxidizing diamond as well.
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DavidJR
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| Quote: Originally posted by beerwiz | If you want to filter something that you will later dispose, then you can use celite, put 3cm of celite on the frit, then you can filter almost
anything without clogging the frit. I've filtered clays, activated carbon, and very fine zinc using this method with 100% success.
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3cm is a bit excessive, did you mean 3mm?
Note that you will get particles of the celite/diatomaceous earth stuck in the frit permanently, however they are pretty inert and porous so they do
not block the frit. I know this happens because I did it with a diatomaceous earth filter aid (not Celite, but a competing product, Celatom FP3) which
was not white but a yellow colour.
It does work pretty well though.
| Quote: Originally posted by beerwiz |
If you have a very fine powder that you must filter and you want to KEEP, then celite won't help you because it will get stuck in the celite. For this
you must use a centrifuge. |
Not necessarily - in some cases it may be acceptable to just scrape it off and accept small contamination with celite, or, if there is another solvent
that your solid will dissolve in, you can use that to separate it of course.
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Shipnibbles
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| Quote: Originally posted by Deathunter88 | | Quote: Originally posted by hissingnoise | | Quote: | | Any secrets to keeping a frit from getting clogged? |
Yeah, only use it for stuff that paper won't handle!
But seriously, you could try running strong nitric and/or sulphuric acid (no phosphoric acids or alkalis!) through from the underside.
...And wait...or use mild pressure to speed it up...
|
In addition to that, you really only want to use a frit to filter something where you intend you keep the solid portion. And preferably, the solid is
one that is soluble in at least one solvent. (So for instance, don't try to filter a clay solution) |
I do want to keep the solid portion and it's not something that will eat through filter paper (very fine nitrocellulose). So it sounds like perhaps I
should use a just a regular buchner with filter paper? Lol I bought this because in my carelessness I dropped my buchner/knocked it over. Not
once..but twice. The first time it was only a small crack in the side..2nd time it shattered into bits. I really need to finish my workbench so I have
a better working space.
And I've had no problems cleaning the clogged frit.. a bit of pirahna solution allowed to filter through with gravity has seemed to do the trick thus
far ( I know not to use strong alkalis, didn't really know about the phosphoric, but that's not something I have anyway)
Anyway, thanks for the responses everyone, I guess I'll be in the market for a buchner funnel.
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nimgoldman
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I use Celite, even thin layer usually prevents clogging in my applications.
For cleanup, I use sulfuric acid or even Piranha, but only with great care and when I am sure the mixture won't crack the sinter by reacting too
strongly with the organic impurities.
So before applying acid, I thoroughly wash the sinter with water and of course after the application as well, then with basic water and then with
distilled water.
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macckone
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I would use purified acetic acid instead of basic water then test that the water is reading 7 after going through the filter and no acetic odor on the
filter. Sometimes the chemistry matters. Any soluble sulfates that haven't been washed off could become solids with a base. Using acetic acid, it
has a smell that is detectable down to a very low range and gives you a chemical check with the filter is clean. Ie. the water isn't acid.
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Heptylene
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Could EDTA be used to unclog the filter from calcium sulfate, etc. and other typically insoluble minerals? I don't have EDTA on hand to test this but
it is apparently used to chelate limescale to make it soluble.
In general I use a toothbrush and mild waterjet (coming from the output of my water aspirator) to get rid of the bulk of the material.
Then if the material is organic I use a solvent such as ethanol. If this doesn't work I use conc. sulfuric acid, sometimes with a dash of H2O2 if
necessary.
To mitigate the problem I use a filter paper on my frit if I can anticipate that it will clog.
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macckone
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Using my leaching method has removed calcium sulfate pretty effectively.
Calcium carbonate and sodium sulfate are favored products.
Then some acetic acid to get rid of the resulting calcium carbonate.
Of course other methods may work but lime scale is calcium carbonate which
reacts just fine with acetic acid.
Running enough water through calcium sulfate will also work as it has a non-zero solubility.
A liter of water will dissolve 2g. Repeatedly replacing the water will speed the process.
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AJKOER
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To remove/clean a deposit of fine carbon chemically, try this approach. First, a warning to quote a source (see https://www.jstor.org/stable/3430376?seq=1#page_scan_tab_con... ):
"It is possible that these products pose more of a health hazard than either the starting phenols or the unhydroxylated polychlorinated biphenyl
derivatives."
My suggestion prepare HOCl by adding NaHCO3 and CaCl2 to NaOCl (or perhaps vinegar to NaOCl bleach). Reactions:
NaOCl + NaHCO3 = Na2CO3 + HOCl
In the presence of CaCl2, the reaction forms a suspension of CaCO3 which settles on cooling of the mix.
An extract from 'Hypochlorous acid-activated carbon: An oxidizing agent capable of producing hydroxylated polychlorinated biphenyls', by by Evangelos
A. Voudrias,, Richard A. Larson, Vernon L. Snoeyink, Abraham S. C. Chen and Pat L. Stapletont. To quote:
"The mechanisms of these redox reactions are not well understood; however, they may involve one-electron pathways, since the existence of free
radicals in carbons has been establlshed by several techniques. Using electron spin resonance (ESR) and indirect chemical methods, Donnet and Henrich
(2) have estimated that about 1 to 9% of the carbon atoms on carbon black surfaces are free radicals."
The suggested procedure should take place outdoors or in a fume hood. Add the HOCl/NaOCl mix at pH>5 to the fine carbon in the presence of aluminum
metal and injected air. My take on a possible radical based path is, in effect, a bleach battery cell (generates e- in solution) with added oxygen
from an air pump:
HOCl + e- = .ClOH- (see Table 1.2a: Chlorine at https://www.bnl.gov/isd/documents/92710.pdf )
For pH>5, .ClOH- --> Cl- + .OH (k = 6.1x10^9 Source: Supplement Table S1 at: http://www.mdpi.com/1420-3049/22/10/1684 and click on Supplement F1 to download)
At pH < 5, .ClOH- + H+ --> H2O + .Cl (k = 2.1×10^10 Source: Supplement Table S1)
In the presence of carbon radical compounds, possible addition products with .OH (or less safe products with .Cl) are created and can be stripped away
by air. There is also a report of the creation of CO and CO2 from the action of the hydroxyl radical on graphite. See https://www.sciencedirect.com/science/article/pii/0008622375... to quote:
"The reaction of free OH radicals with graphite was studied in a flow system by mass spectrometry,..... The OH radicals react rapidly at 298 K to
produce approximately equal amounts of CO and CO2."
Likely via: .OH + C = .H + CO
And: .OH + CO = .H + CO2 (see https://pubs.acs.org/doi/abs/10.1021/j100149a027 )
Also, O2 + e- --> .O2- (see Eq. R2 at https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/200... )
And, .O2- + HOCl --> O2 + .OH + Cl- (see, for example, https://books.google.com/books?id=8vopDgAAQBAJ&pg=PA18&a... )
Further with select nano carbon structures per a source (see http://www.pnas.org/content/112/8/2343 ) to quote:
"Mechanistic studies of nontoxic hydrophilic carbon cluster nanoparticles show that they are able to accomplish the direct conversion of superoxide to
dioxygen and hydrogen peroxide."
which I depict differently as follows:
2 .O2- + .C + H+ (from water) --> HO2- (takes H+ from water to form H2O2 and OH-) + O2 + .C
being based on Reaction A8 at https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/200... with k = 9.6 x 10^7:
.HO2 + .O2− + H2O --> H2O2 + O2 + OH− (A8)
where the reaction of either e- or HOCl with any formed H2O2 could be an added source of radicals including .OH.
There are also non-radical paths, to quote a source, 'The reactions of hypochlorous acid, the reactive oxygen species
produced by myeloperoxidase, with lipids-' by Corinne M. Spickett:
"The Cl+ ion of HOCl serves as an electrophilic
species; it polarises the double bond and is
added to one of the carbon atoms. The other
carbon atom then bears a positive charge
(carbenium ion)"
Possibly an interesting experiment that may remove problematic carbon.
[Edited on 28-10-2018 by AJKOER]
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macckone
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ajkoer is literally suggesting chlorine gas as a method of removing carbon from frit.
Wow, just wow. vinegar and bleach, wow. I guess it could be worse. the vinegar will react with some of the chlorine and sodium hydroxide.
The other method of adding sodium bicarbonate will not work either as bleach has sodium hydroxide in solution.
Calcium chloride will just lead to precipitation of calcium hypochlorite.
straight bleach will attack some carbon deposits. hydrogen peroxide will as well.
A toluene soak will also remove a good bit of carbon depending on how it was formed.
Better method, just use piranha solution.
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AJKOER
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| Quote: Originally posted by macckone | ajkoer is literally suggesting chlorine gas as a method of removing carbon from frit.
Wow, just wow. vinegar and bleach, wow. I guess it could be worse. the vinegar will react with some of the chlorine and sodium hydroxide.
The other method of adding sodium bicarbonate will not work either as bleach has sodium hydroxide in solution.
Calcium chloride will just lead to precipitation of calcium hypochlorite.
straight bleach will attack some carbon deposits. hydrogen peroxide will as well.
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Wrong.
First, at pH>5, expect the very powerful hydroxyl radicals and not .Cl (which does lead to chlorine and possibly associated chloro-organic products
as a more unsafe option).
Second, I recommend the addition of NaHCO3/CaCl2 to aqueous NaOCl as a path to HOCl, again avoiding a possibly less safe mix.
[Edited on 31-10-2018 by AJKOER]
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DavidJR
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| Quote: Originally posted by Heptylene | Could EDTA be used to unclog the filter from calcium sulfate, etc. and other typically insoluble minerals? I don't have EDTA on hand to test this but
it is apparently used to chelate limescale to make it soluble.
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Yes actually, I did this recently. I needed to prepare some copper (II) chloride and decided to do it by mixing solutions of copper (II) sulphate and
calcium chloride. Filtering off the calcium sulphate left a clogged frit. After a quick google I found some mention of using EDTA salts plus soluble
carbonates - so I tossed some disodium EDTA and sodium carbonate in the wash water and left it to soak. Seemed to work perfectly fine.
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Heptylene
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DavidJR great to know! I'll get some EDTA for sure now.
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beerwiz
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Piranha solution works well. You pour 98% sulfuric acid on the frit then add 30% Hydrogen Peroxide slowly, drop by drop, otherwise it will blow up in
your face and you will die, it will heat up and boil, wear eye protection and gloves.
I make the 30% Hydrogen Peroxide by buying 1 quart of 3% Hydrogen Peroxide and boiling it down 10 times to 95ml on the gas stove, it's quick.
[Edited on 14-11-2018 by beerwiz]
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hissingnoise
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| Quote: | | I make the 30% Hydrogen Peroxide by buying 1 quart of 3% Hydrogen Peroxide and boiling it down 10 times to 95ml on the gas stove, it's quick.
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Boiling the solution doesn't lead to higher HP concentration and heat will partially decompose HP which will actually lower the strength of what you
have...
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DavidJR
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| Quote: Originally posted by hissingnoise | | Quote: | | I make the 30% Hydrogen Peroxide by buying 1 quart of 3% Hydrogen Peroxide and boiling it down 10 times to 95ml on the gas stove, it's quick.
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Boiling the solution doesn't lead to higher HP concentration and heat will partially decompose HP which will actually lower the strength of what you
have...
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It works to some extent but there is a lot of decomposition. Not sure you could get 30%...
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hissingnoise
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Boiling under vacuum works pretty well, though...
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DavidJR
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And when produced industrially via the anthraquinone process, it is indeed vacuum distilled.
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