Sciencemadness Discussion Board - Filtration nightmare! (help!)

Filtration nightmare! (help!)

blogfast25 - 14-2-2023 at 13:16

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. :mad:

Any decent suggestions welcome...

Texium - 14-2-2023 at 13:53

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.

AvBaeyer - 14-2-2023 at 19:14

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

Sulaiman - 14-2-2023 at 19:32

Many suspensions precipitate out eventually.
Maybe just observe the precipitation rate for a day or two with a view to decanting?

blogfast25 - 15-2-2023 at 04:02

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.

Yes, I'm only after the filtrate.

So I'll definitely try that.

@AvBaeyer: Ta.

@Sulaiman: tried. Didn't work here. Ta.

Sulaiman - 15-2-2023 at 06:33

Side note :Tyndal effect if you have a laser pen handy it is interesting to see.
eg https://m.youtube.com/watch?v=OXoKZPLb6Qo

Jenks - 15-2-2023 at 12:12

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!

blogfast25 - 16-2-2023 at 04:01

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)