Sciencemadness Discussion Board
Not logged in [Login ]
Go To Bottom

Printable Version  
Author: Subject: Filtering the impossible to filter: calcium sulfate and similar
macckone
International Hazard
*****




Posts: 2159
Registered: 1-3-2013
Location: Over a mile high
Member Is Offline

Mood: Electrical

[*] posted on 26-8-2022 at 11:50
Filtering the impossible to filter: calcium sulfate and similar


This isn't exactly a beginner question.
More of a how do you do it question.

We have all had to deal with the almost impossible to filter precipiate of a double displacement with calcium sulfate as the waste product.

I have tried vaccum cleaner bags, nylons, even a french press.

Problems
1) a lot of liquid is entrained in the solid
2) the filter either lets through a lot of calcium sulfate or it clogs or both

so how do you deal with it?

I hate it is an acceptable answer.
View user's profile View All Posts By User
karolus28
Hazard to Self
**




Posts: 51
Registered: 14-4-2019
Location: EU's Brazil
Member Is Offline

Mood: zgrzyt

[*] posted on 26-8-2022 at 12:22


I've heard of people putting "sand, coarse silica, alumina, even shredded paper" into the suspension and then filtering, not sure how it works.



Hi, please read about exif data.
View user's profile View All Posts By User
B(a)P
International Hazard
*****




Posts: 1100
Registered: 29-9-2019
Member Is Offline

Mood: Festive

[*] posted on 26-8-2022 at 12:24


I typically use standard filter paper and the biggest funnel I have. Then it is down to the passage of a lot of time and the acceptance that I will loose yield because as you point out a lot of liquid remains entrained in the solid. Vacuum filtration with a buchner in my experience takes only slightly less time if you have a lot of very fine solid material and I don't like running my pump for extended periods. Decanting off as much liquid as possible after the solid has settled for a period of time (sometimes days) is generally the best way to go IMHO. If I am not concerned about yield I will often not even bother with the remaining liquid and solid after initial decanting.

I have tried the following, but with little success:
- using a kitchen sieve lined with paper towel to try and increasing filtration surface area.
- making vessels from inverted 2 L milk containers with holes in an inverted screwed on lid lined with filter paper. The idea here was to build up some head to drive the liquid through.

Great topic! I look forward to hearing the solution to removing barium sulfate from acids that attack organic material while preserving yield.
View user's profile View All Posts By User
Rainwater
National Hazard
****




Posts: 770
Registered: 22-12-2021
Member Is Offline

Mood: indisposition to activity

[*] posted on 26-8-2022 at 13:17


In industry, a belt filter is used in combination with heat. Basicly providing unlimited surface area



"You can't do that" - challenge accepted
View user's profile View All Posts By User
UC235
National Hazard
****




Posts: 562
Registered: 28-12-2014
Member Is Offline

Mood: No Mood

[*] posted on 26-8-2022 at 17:24


Add a whole bunch of celite/diatomaceous earth (acid washed if maintaining pH is important. The cheap (pool) stuff is alkaline). Flip initial filtrate until clear. Wash cake out thoroughly.

Mostly I filter lots of horrible sticky, tarry protein glop.

[Edited on 27-8-2022 by UC235]
View user's profile View All Posts By User
PirateDocBrown
National Hazard
****




Posts: 570
Registered: 27-11-2016
Location: Minnesota
Member Is Offline

Mood: No Mood

[*] posted on 26-8-2022 at 19:35


Start out with as dilute solutions as is practical.



Phlogiston manufacturer/supplier.

For all your phlogiston needs.
View user's profile View All Posts By User
draculic acid69
International Hazard
*****




Posts: 1371
Registered: 2-8-2018
Member Is Offline


[*] posted on 26-8-2022 at 20:45


This may or may not help but a cotton t-shirt (preferably white) can act as a quick coarse filter if solution is not too far from neutral pH and it can be twisted and squished to recover solutions

[Edited on 27-8-2022 by draculic acid69]
View user's profile View All Posts By User
Metacelsus
International Hazard
*****




Posts: 2530
Registered: 26-12-2012
Location: Boston, MA
Member Is Offline

Mood: Double, double, toil and trouble

[*] posted on 27-8-2022 at 04:38


Perhaps you could centrifuge instead of filtering?



As below, so above.

My blog: https://denovo.substack.com
View user's profile View All Posts By User
Gammatron
Hazard to Others
***




Posts: 125
Registered: 30-8-2022
Location: Abandoned Uranium Mines
Member Is Offline


[*] posted on 2-9-2022 at 13:51


I wonder if you could use a large sep funnel. Since the particles are so small and always remain somewhat suspended even after settling I don't expect it would clog. I've also had success using a pump or siphon too.



View user's profile Visit user's homepage View All Posts By User
WGTR
National Hazard
****




Posts: 971
Registered: 29-9-2013
Location: Online
Member Is Offline

Mood: Outline

[*] posted on 2-9-2022 at 15:04


When I made graphene oxide (this is completely impossible to bulk filter), I loaded the suspended samples into dialysis tubing and stirred them for several days in a large beaker until the rinse water was neutral. I did the same thing when successfully producing amorphous titania, that did not separate out in the centrifuge even.

Of course, that was when I was trying to keep the precipitate, not discard it…but a little DE does help on filter paper in those cases. A little is just enough. A bit more is way too much.

The counterintuitive thing is that fine particles will clog coarse filter paper. For fine precipitates you need the finest filter paper. Things like a thin layer of DE keeps these fine particles from getting into the pores of the filter.

[Edited on 22-09-02 by WGTR]




View user's profile View All Posts By User

  Go To Top