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

Printable Version  
Author: Subject: PTFE filters? What are they for?
fusso
International Hazard
*****




Posts: 1726
Registered: 23-6-2017
Location: Whimsy
Member Is Offline

Mood: Retreated into whimsy

[*] posted on 30-8-2019 at 15:23
PTFE filters? What are they for?


I saw PTFE filter "paper" on ebay, thin like paper. Anyone knows what they're for?



View user's profile View All Posts By User
unionised
International Hazard
*****




Posts: 4124
Registered: 1-11-2003
Location: UK
Member Is Offline

Mood: No Mood

[*] posted on 30-8-2019 at 15:41


"What are they for?"
Anything you like; that's the point.
Want to filter sulphuric acid?- no problem. Strong solvents like ethyl acetate?- sure.
Weird stuff like concentrated solutions of zinc chloride or cuprammonium sulphate? go right ahead.

Don't try those with cellulose based filters, or nitrocellulose ones.
View user's profile View All Posts By User
Dr.Bob
International Hazard
*****




Posts: 2003
Registered: 26-1-2011
Location: USA - NC
Member Is Offline

Mood: No Mood

[*] posted on 21-10-2019 at 09:14


They are membrane filters, often used to micro filter a solution. They are ideal for removing almost any particle, even most bacteria, if the pore size is right. They work well for organic solvents, not so well for water, which does not wet them. There are other materials in membrane form for aqueous solutions. Most are used with Whatman type 47 mm filter apparati.
View user's profile View All Posts By User
TheMrbunGee
National Hazard
****




Posts: 279
Registered: 13-7-2016
Location: EU
Member Is Offline

Mood: Phosphorising

[*] posted on 21-10-2019 at 11:44


I accidentally ordered MCE (mixed cellulose ester) filter papers, cut out and everything, sadly they dissolve in methanol, most used solvent in my lab. There are quite a lot of filter paper materials, as I researched after my "paper" filter dissolved away with everything, each better for some specific application.



View user's profile Visit user's homepage View All Posts By User
RogueRose
International Hazard
*****




Posts: 1353
Registered: 16-6-2014
Member Is Offline


[*] posted on 21-10-2019 at 14:50


Quote: Originally posted by fusso  
I saw PTFE filter "paper" on ebay, thin like paper. Anyone knows what they're for?


Would you want to share the links? I'm looking for some PTFE filters, especially sheets that are cuttable to proper size if possible.

I'm looking at making a PTFE filter housing that can take square sheets of PTFE filter membrane where I can replace the filters. The only thing I'm wondering about is if there is a problem using a square filter. The filter would be held down very tightly (near 2500-5000 PSI holding down filter material using bolts/screws on outside of housing - it's amazing the pressure that can be obtained from bolts!).

The round filter papers are pretty expensive and I'm trying to find a place where I can buy uncut sheets. If you find anywhere, please let me know. I'm thinking maybe alibaba might be a place to find these.

Also, here is a PTFE chemical compatability chart and you will see why it is such a great material for filtration membrane! It even is great with things like aqua regia, fuming HCl or nitric acid and even 100% HF (scary!!)!

https://www.calpaclab.com/teflon-ptfe-compatibility/

I thought I'd look through and see what PTFE didn't have "A-Excellent" resistivity to and here's the list, which is less than 1% of the listed chemicals

"B - Good"
Fuel Oils
Gallic Acid
Gasoline (high-aromatic)
Lead Sulfamate
Mercuric Cyanide
Naphtha


"C - Fair"
Iodoform
Petrolatum


" D - Severe"
Diethylamine
Fluorine
Gold Monocyanide


[Edited on 10-21-2019 by RogueRose]

[Edited on 10-21-2019 by RogueRose]
View user's profile View All Posts By User
Metacelsus
International Hazard
*****




Posts: 2334
Registered: 26-12-2012
Location: Cambridge, MA
Member Is Offline

Mood: Double, double, toil and trouble

[*] posted on 21-10-2019 at 15:13


Quote: Originally posted by RogueRose  


" D - Severe"
Diethylamine
Fluorine
Gold Monocyanide


Hmm, I've used PTFE-coated stir bars with diethylamine solutions and I've never had a problem.




As below, so above.
View user's profile View All Posts By User
BromicAcid
International Hazard
*****




Posts: 3010
Registered: 13-7-2003
Location: Wisconsin
Member Is Offline

Mood: Legitimate

[*] posted on 21-10-2019 at 15:26


Pulling aqueous through a PTFE filter is very difficult. Just a voice of experience.



Shamelessly plugging my attempts at writing fiction: http://www.robvincent.org
View user's profile Visit user's homepage View All Posts By User
RogueRose
International Hazard
*****




Posts: 1353
Registered: 16-6-2014
Member Is Offline


[*] posted on 21-10-2019 at 16:15


Quote: Originally posted by Metacelsus  
Quote: Originally posted by RogueRose  


" D - Severe"
Diethylamine
Fluorine
Gold Monocyanide


Hmm, I've used PTFE-coated stir bars with diethylamine solutions and I've never had a problem.


Well maybe pressure, time and temp can effect how reactive it is. Filters will probably be higher pressure and maybe higher temp. IDK though, I was just listing what was on the page - not personal experience. It's good to know your experience.

I'd be intersted to know the weight of the stirrer before and after the stirring. Maybe it dissolved some PTFE and it wasn't very noticeable?
View user's profile View All Posts By User
Herr Haber
International Hazard
*****




Posts: 636
Registered: 29-1-2016
Member Is Offline

Mood: No Mood

[*] posted on 22-10-2019 at 03:18


Quote: Originally posted by BromicAcid  
Pulling aqueous through a PTFE filter is very difficult. Just a voice of experience.


You said it wrong:
IT IS VERY DIFFICULT !

You guys remember when you didnt have a vacuum pump and had to filter superfine particles clogging the filter and adding to the funnel every few hours ?
Well, it's almost that bad.

But hey, in my case I didnt think much before proceeding and chose the most inefficient solution so I'm the only one to blame.




The spirit of adventure was upon me. Having nitric acid and copper, I had only to learn what the words 'act upon' meant. - Ira Remsen
View user's profile View All Posts By User
RogueRose
International Hazard
*****




Posts: 1353
Registered: 16-6-2014
Member Is Offline


[*] posted on 22-10-2019 at 13:47


Quote: Originally posted by Herr Haber  
Quote: Originally posted by BromicAcid  
Pulling aqueous through a PTFE filter is very difficult. Just a voice of experience.


You said it wrong:
IT IS VERY DIFFICULT !

You guys remember when you didnt have a vacuum pump and had to filter superfine particles clogging the filter and adding to the funnel every few hours ?
Well, it's almost that bad.

But hey, in my case I didnt think much before proceeding and chose the most inefficient solution so I'm the only one to blame.


I'm wondering if it was slow filtering b/c you used a really small pore size or is it b/c of PTFE is hydrophobic maybe?

I've used .45um and .22um filters but I used a 3ml syringe and about 50-70 syringes worth for the 200ml and it seemed pretty easy until the last ~10 or so and it got progressively harder until it was impossible. I started off with a 60ml syringe and it was near impossible after about 8ml worth, then tried 20ml, then moved to 3ml.

IDK if the smaller syringe allows for more pressure or what, but it made a huge difference.
View user's profile View All Posts By User
fusso
International Hazard
*****




Posts: 1726
Registered: 23-6-2017
Location: Whimsy
Member Is Offline

Mood: Retreated into whimsy

[*] posted on 22-10-2019 at 15:26


Quote: Originally posted by RogueRose  
Would you want to share the links? I'm looking for some PTFE filters, especially sheets that are cuttable to proper size if possible.

I'm looking at making a PTFE filter housing that can take square sheets of PTFE filter membrane where I can replace the filters. The only thing I'm wondering about is if there is a problem using a square filter. The filter would be held down very tightly (near 2500-5000 PSI holding down filter material using bolts/screws on outside of housing - it's amazing the pressure that can be obtained from bolts!).

The round filter papers are pretty expensive and I'm trying to find a place where I can buy uncut sheets. If you find anywhere, please let me know. I'm thinking maybe alibaba might be a place to find these.
I just searched ptfe filter on ebay.com. There are literally tons of it. Unfortunately the links I copied are monstrously long.



View user's profile View All Posts By User
G-Coupled
Hazard to Others
***




Posts: 192
Registered: 9-3-2017
Member Is Offline

Mood: Slightly triturated

cool.gif posted on 22-10-2019 at 20:56


You can shorten the links by using the 'URL Tool' on the formatting bar above the post box - it looks like a low rez blue/green globe with a paperclip (?) next to it.

Like this


[Edited on 23-10-2019 by G-Coupled]
View user's profile View All Posts By User
Herr Haber
International Hazard
*****




Posts: 636
Registered: 29-1-2016
Member Is Offline

Mood: No Mood

[*] posted on 23-10-2019 at 03:51


Quote: Originally posted by RogueRose  

I'm wondering if it was slow filtering b/c you used a really small pore size or is it b/c of PTFE is hydrophobic maybe?


Maybe a bit of both but I'm certain I clogged the filter.

Also, since you are looking for sheets / plates be careful not to get fabric impregnated with PTFE. I'm not sure this would be useful as the distribution is uneven.




The spirit of adventure was upon me. Having nitric acid and copper, I had only to learn what the words 'act upon' meant. - Ira Remsen
View user's profile View All Posts By User
unionised
International Hazard
*****




Posts: 4124
Registered: 1-11-2003
Location: UK
Member Is Offline

Mood: No Mood

[*] posted on 23-10-2019 at 10:01


You can make life easier by pre-wetting the filter with a little methanol or acetone before trying to draw water through it.
View user's profile View All Posts By User
DavidJR
International Hazard
*****




Posts: 777
Registered: 1-1-2018
Location: Scotland
Member Is Offline

Mood: Anxious

[*] posted on 23-10-2019 at 14:49


I was just about to write that! Yes, pre-wetting PTFE membrane filters with organic solvent before trying to filter aqueous solutions helps a lot.
View user's profile View All Posts By User
fusso
International Hazard
*****




Posts: 1726
Registered: 23-6-2017
Location: Whimsy
Member Is Offline

Mood: Retreated into whimsy

[*] posted on 23-10-2019 at 15:50


Must the wetting solvent be water-miscible?



View user's profile View All Posts By User
Tellurium
Hazard to Self
**




Posts: 54
Registered: 12-7-2017
Location: Group 16, Chalcogen City
Member Is Offline

Mood: smelly

[*] posted on 9-12-2019 at 08:13


Quote: Originally posted by fusso  
Must the wetting solvent be water-miscible?

I tested it out a few minutes ago.
For comparison I took a unwetted filter, a acetone wetted filter and a DCM wetted filter. "Competitor" for the 0,45um syringe filter was a freshly prepared suspension of precipitated lead sulfate in water.

Through both the Acetone and DCM wetted filter the suspension was a lot more easy to filter, than with the unwetted filter. But I feel, like the acetone wetted filter was a little bit easier to push, but only a very minor difference;)

[Edited on 9-12-2019 by Tellurium]
View user's profile View All Posts By User
DavidJR
International Hazard
*****




Posts: 777
Registered: 1-1-2018
Location: Scotland
Member Is Offline

Mood: Anxious

[*] posted on 9-12-2019 at 15:27


Interesting, I would not have expected that.
View user's profile View All Posts By User

  Go To Top