Sciencemadness Discussion Board

Getting Celite 545 out of a medium frit?

SuperOxide - 14-3-2022 at 06:49

I have a 100mL Laboy brand medium frit Buchner funnel, and I was going to filter some ferrous chloride through it, but since it would take so many filters (because in my experience, some of the ferric chloride particulate matter makes it through), I put a thick layer of Celite 545 on it.
I was told by a friend that maybe it's not the best idea to do that since it could clog it up, but I was convinced that that wasn't the case based off of some stuff I had read online, for example, this doc actually says to use Celite to prevent it from getting clogged up:
Quote:
- If you are filtering to remove a very fine precipitate and don't want material to clog the pores of your frit, you should first layer a pad of Celite (also known as diatomaceous earth or Kieselguhr ) on the frit. Wet the pad with your solvent and then filter your solution, taking care not to disturb the Celite layer. If your filtration slows down or stops you can simply stir the topmost layer of the Celite pad.
- Avoid filtering charcoal solutions on a frit unless you are using a thick Celite pad. Carbon does not clean out of your frit using acid, base or solvents and can only be removed by heating the frit in a furnace at 480 degrees C in an oxidizing atmosphere. ...

As well as a number of YT videos from various types of accounts (such as this one and this one) which had me feeling reasonably confident that I would be ok. Also, I have used some Celite on it before, but looking back, it does seem to filter slower after using Celite each time.
I eventually wisened up and put a piece of filter paper down first, but I think by that time I think the frit was already pretty clogged.

So does anyone have any way I can unclog it? Is there anything I can use to attack the Celite that won't also attack the frit?

Thanks in advance,
-J

P.S. I am fairly sure it's not ferrous/ferric chloride that's clogging the frit, as I let it sit in a hot solution of oxalic and citric acid overnight. The ferric chloride color went away entirely, but only filters slightly faster.

[Edited on 14-3-2022 by SuperOxide]

macckone - 16-3-2022 at 13:12

Celite and the frit are both silica. So there is no significant difference between the two materials. You can try blowing it out with air or water by a reverse flush.

Putting something like fiberglass filter paper between the frit and the celite is recommended. There are various recommended filter stacks. Example. Fast paper, sand, celite. The paper and sand will prevent celite from reaching the frit but works better than just celite.

Antigua - 16-3-2022 at 13:34

Is this a problem with vacuum filtrations on a frit? In my experience on a G3 frit they're lighting fast and even with celite stuck inside it shouldn't take more than a minute to filter a 1L stock of solution.

SuperOxide - 16-3-2022 at 18:07

Quote: Originally posted by macckone  
Celite and the frit are both silica. So there is no significant difference between the two materials. You can try blowing it out with air or water by a reverse flush.

Putting something like fiberglass filter paper between the frit and the celite is recommended. There are various recommended filter stacks. Example. Fast paper, sand, celite. The paper and sand will prevent celite from reaching the frit but works better than just celite.

Yeah, I did start putting filter paper on it, but only thought to start doing that _after_ I clogged it... lol. fml
Quote: Originally posted by Antigua  
Is this a problem with vacuum filtrations on a frit? In my experience on a G3 frit they're lighting fast and even with celite stuck inside it shouldn't take more than a minute to filter a 1L stock of solution.

That's what I thought. I mean the benefit of celite is that it's very porous, so im surprised that it's so well clogged up. Also, I know I've used celite on frits before and I don't recall it slowing down this much. It takes at least 45 seconds to filter 100 mL through it.

Bmoore55 - 16-3-2022 at 19:54

This might work if you have an ultrasonic bath available. Try inverting the funnel and fill the spout with water. Then submerge the funnel top down in the bath and try to get all the air out of the funnel if possible then turn on the ultrasonic bath. This may take some time to work and you may need to add a surfactant (soap) to get it to work, but I have tried this in the past and had success. Hope this helps.

Sulaiman - 16-3-2022 at 22:44

You could convert your blocked 'medium' frit to a clean 'faster' frit with hot sodium hydroxide solution.
The fine particles should dissolve faster than the frit martix.
I guess :)

SuperOxide - 17-3-2022 at 18:06

Quote: Originally posted by Sulaiman  
You could convert your blocked 'medium' frit to a clean 'faster' frit with hot sodium hydroxide solution.
The fine particles should dissolve faster than the frit martix.
I guess :)

Hmm.... That's not a terrible idea, actually. lol.

Vomaturge - 25-3-2022 at 19:01

What about making some kind of adapter to connect the “output” end of the funnel to an outdoor tap? Basically Macckones’d suggestion of a reverse flush, albeit long lasting and forceful.

Possibly an awful idea because domestic water pressure might br strong enough to crack the thing.

Texium - 25-3-2022 at 19:33

Strange. I use celite in medium porosity frits all the time and never had them clog.

Amos - 26-3-2022 at 04:58

My first thought was would be clamping it upside down while dry, blowing air through, and applying some kind of ultrasonic vibration at the same time. Perhaps with a dilding device. Bmoore and sulaiman also have good ideas, and if you ever get too frustrated to continue with dislodging, I think you should indeed just cycle through hot NaOH solution through a bunch of times. Fritted funnels are not everyday funnels for every compound ever for this kind of reason; A buchner funnel and common filter paper are usually just as good. When you're doing inorganic chemistry, saving your fritted funnel for only the compounds that will react with or destroy filter paper(permanganate, very strong acid solutions, etc.) is generally a good strategy for prolonging its life.

[Edited on 3-26-2022 by Amos]

SuperOxide - 26-3-2022 at 06:49

Quote: Originally posted by Texium  
Strange. I use celite in medium porosity frits all the time and never had them clog.

That's exactly my thought! I know I have too and I never compared the before/after, but I also never remember thinking "crap, I fucked it". I was filtering some ferrous chloride/ferric chloride solution through it which stained it a great deal, but I just soaked it in warm oxalic/citric/hydrochloric acid and ran said acid through it and its now 100% white, but very slow. So perhaps you're right, maybe I did mess it up with something else.
Quote: Originally posted by Amos  
My first thought was would be clamping it upside down while dry, blowing air through, and applying some kind of ultrasonic vibration at the same time. Perhaps with a dilding device.

Ahh yes, the old "dilding device" trick.

Quote: Originally posted by Amos  
Bmoore and sulaiman also have good ideas, and if you ever get too frustrated to continue with dislodging, I think you should indeed just cycle through hot NaOH solution through a bunch of times.
Yeah, that was going to be what I tried next. I figure even if it eats away at the frit a bit, that should be fine.
Quote: Originally posted by Amos  
Fritted funnels are not everyday funnels for every compound ever for this kind of reason; A buchner funnel and common filter paper are usually just as good. When you're doing inorganic chemistry, saving your fritted funnel for only the compounds that will react with or destroy filter paper(permanganate, very strong acid solutions, etc.) is generally a good strategy for prolonging its life.
Yeah, and I have a buchner funnel that uses paper filters as well. I do use it, but I just prefer my ground glass fitted frits for convenience.

macckone - 27-3-2022 at 23:16

I have a buchner funnel with paper and 1.5um fiberglass filters.
I can use the very fine fiberglass for filtering strong acids and bases and oxidizers.
I can use paper for anything that won't react with paper.
I find it more convenient than a frit as I can pull out the paper and often just chunk the cake in a beaker.
The 1.5um is for dissolved solids and is very slow but I use a 90mm funnel to compensate.
There are also polypropylene papers with a 10um filter size but they are about US$100 for a 25 pack.
You can use face masks that are also polypropylene/polyethylene that usually have a 0.3um pore size for n95 and about 10um for good surgical masks.
And synthetic vacuum cleaner bags go from 25um to 0.3um pore size.
Using other types of polypropylene means cutting to fit but it is a hell of a lot cheaper.
The downside of polypropylene filters is an upper temperature limit of around 65C for hot filtration.

SWIM - 28-3-2022 at 08:55

This is why I like those ceramic Buchners that just have holes in them and need a filter paper disk.

They're not as convenient, but they're easy to clean.

The only downside is that most of them in the USA are named after my least favorite beer, Coors.

Dr.Bob - 29-3-2022 at 17:14

I like the filter paper before the celite idea, but if you wash it enough, it will likely eventually remove some of the celite and the crap holding it in place. Sonication, soapy water, acid, weak base, and acetone are all good places to try. I also sometimes use Buchners, but they often can leak some solids through. The best solution can be to prefilter with a Buchner then use a frit for the final polish filtration, if you want the filtrate. If you want the solid, a frit can be good, as you don't have to have paper, which can leave fibers in the solids.

But frits can be a pain, I figure most will be used about 20-100 times before being fouled. If I can, I try to use a dedicated frit for each compound or task, like filtering Pd/C, K2CO3, or resins, as then I can pick the best porosity and type, then wash them with the same solvents, and keep them from contaminating other reactions.