blogfast25
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Filtration nightmare! (help!)
Yesterday I was filtering a suspension of fine-particle organics (mostly solids but maybe some liquids too) with dissolved Al, Zr and HCl, with GREAT
difficulty.
I used a grade 1 'medium speed' filter on a Buchner with decent (but unmeasured) vacuum. After 1 - 2 minutes the filtration stalled completely and the
bit of collected filtrate wasn't very clear at all.
A slightly larger pores (more general purpose) paper just blew through.
A 'Pyrex C4' glass (or ceramic) frit didn't allow anything through at all, a coffee filter didn't either.
Then I had the intuitive idea to boil the suspension for some minutes and that helped a bit. Hot filtering was relatively quick but the filtrate was
far from clear.  
Any decent suggestions welcome...
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Texium
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Are you after the solids or the filtrate? If you only care about the filtrate, try putting a layer of diatomaceous earth in the Büchner funnel.
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AvBaeyer
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As follow on to Texium's suggestion, I have found that in situations similar to what you describe adding some filter aid (eg, diatomaceous earth)
directly to the material to be filtered and then filtering through a diatomaceous earth pad per Texium will often work well. Of course, this holds
only if you do not want the solids.
AvB
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Sulaiman
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Many suspensions precipitate out eventually.
Maybe just observe the precipitation rate for a day or two with a view to decanting?
CAUTION : Hobby Chemist, not Professional or even Amateur
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blogfast25
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Quote: Originally posted by Texium  | | Are you after the solids or the filtrate? If you only care about the filtrate, try putting a layer of diatomaceous earth in the Büchner funnel.
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Yes, I'm only after the filtrate.
So I'll definitely try that.
@AvBaeyer: Ta.
@Sulaiman: tried. Didn't work here. Ta.
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Sulaiman
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Side note :Tyndal effect if you have a laser pen handy it is interesting to see.
eg https://m.youtube.com/watch?v=OXoKZPLb6Qo
CAUTION : Hobby Chemist, not Professional or even Amateur
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Jenks
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I'm very familiar with filtration nightmares. You can keep pouring the contents of the stopped filter into a new filter, and it may eventually all go
through. Someone else on my project found success using successively smaller pored filters to get the organic suspension filtered. If there is any
settling, you can gauge if it is a better use of time to wait for some settling, then filter the clearer liquid on top before filtering the thicker
liquid below to delay the inevitable clogging of the filter. It could be worth a shot to try the cooking technique, I think it might be called a
"consomme", where a protein like gelatin is added to the liquid and it is frozen, then thawed in a strainer. Apparently, for things like beef broth
and carrot juice, the gelatin binds the particulates, enabling them to be strained out, giving a clear liquid melt. Good luck!
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blogfast25
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| Quote: Originally posted by Jenks | | I'm very familiar with filtration nightmares. You can keep pouring the contents of the stopped filter into a new filter, and it may eventually all go
through. Someone else on my project found success using successively smaller pored filters to get the organic suspension filtered. If there is any
settling, you can gauge if it is a better use of time to wait for some settling, then filter the clearer liquid on top before filtering the thicker
liquid below to delay the inevitable clogging of the filter. It could be worth a shot to try the cooking technique, I think it might be called a
"consomme", where a protein like gelatin is added to the liquid and it is frozen, then thawed in a strainer. Apparently, for things like beef broth
and carrot juice, the gelatin binds the particulates, enabling them to be strained out, giving a clear liquid melt. Good luck! |
Thanks Jenks. Like the consomme idea! There are several versions of it, also used by winemakers (Bentonite)
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