beerwiz
Hazard to Others
Posts: 130
Registered: 6-2-2014
Member Is Offline
Mood: No Mood
|
|
Collecting solid from filter paper after filtration - what is the proper technique?
I often filter high value solids with vacuum filtration and very often a lot of solids remain on the filter paper seemingly stuck in the fibers of the
paper and can't really be scraped off.
What is the proper technique for removing all of the filtered product from filter paper?
|
|
|
gdflp
Super Moderator
Posts: 1320
Registered: 14-2-2014
Location: NY, USA
Member Is Offline
Mood: Staring at code
|
|
Two options here which I can think of. Firstly, use a glass frit instead which should trap less of your product, allowing for a better recovery. Be
sure not to use metal objects to scrape the frit though as this can damage it.
Alternatively, if your product isn't heat sensitive, you can buy so "quantitative" filter paper. This type of filter paper is designed to burn with
little or no ash residue, so you can simply place the filter paper in a crucible, and burn it off to recover the adhering product. Quite commonly
used in settings such as inorganic analysis, where the salts such as oxides are not typically heat sensitive, but a near quantitative recovery is
desired.
If neither of these are an option for you, just let the filter paper dry before trying to remove the product, and you should be able to recover the
vast majority of it.
|
|
|
beerwiz
Hazard to Others
Posts: 130
Registered: 6-2-2014
Member Is Offline
Mood: No Mood
|
|
I tried to do that just now with a well dried piece of filter paper with embedded product. Using a metal spatula, I was able to scrape off some of the
product but a lot remains embedded in the filter paper. About 50% of the poduct I scraped off contains paper fibers that came off. There must be
another solution.
Maybe I should use non-paper filter like PTFE membrane disk filters? Recovery of nearly 100% of the product is mandatory due to the high value of the
product.
Another idea that comes to mind is to soak the dried filter paper in a suitable solvent to wash the product out completely. Then evaporate the solvent
and scrape off the product from the glass walls of the beaker or RBF.
[Edited on 27-5-2016 by beerwiz]
|
|
|
JJay
International Hazard
Posts: 3440
Registered: 15-10-2015
Member Is Offline
|
|
I've recovered some pretty valuable products before and have never really had a serious issue with that.... You might also try using a smaller Buchner
with a smaller piece of filter paper. Also, you might try making bigger batches so you experience less mechanical loss (on a percentage basis).
[Edited on 27-5-2016 by JJay]
|
|
|
Sulaiman
International Hazard
Posts: 3698
Registered: 8-2-2015
Location: 3rd rock from the sun
Member Is Online
|
|
I have two different types of paper filter disks from two different suppliers,
and the slow (#1) paper feels smoother and seems to trap less product than the medium (#3) papers.
Scraping the product off of the paper sounds like a bad idea (paper fibers as noted)
let your filter cake get really dry and usually only a stain remains in the paper.
OR
use a MUCH smaller filter, e.g. glass funnel with nail + small filter disc.
|
|
|
DFliyerz
Hazard to Others
Posts: 241
Registered: 22-12-2014
Member Is Offline
Mood: No Mood
|
|
This is a completely wild guess, but are the high value solids gold or PGMs that are to be re-dissolved in aqua regia? If so, just put the paper in
the aqua regia and it will dissolve. If it's not to be re-dissolved, I just burn the filter paper while melting the metal.
|
|
|
confused
Hazard to Others
Posts: 244
Registered: 17-3-2013
Location: Singapore
Member Is Offline
Mood: tired
|
|
possible to redissolve the residue on the filter paper and recrystalise it?
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
