Sciencemadness Discussion Board

Ion Exchange resin use in chemistry - making acids or salts

RogueRose - 17-11-2017 at 17:10

I started reading about ion exchange resins and had limited knowledge of them that they were used in water softening where a salt brine "charges" (saturates) the resins with a desired ion such as Na or K from a salt like NaCl or KCl and it is used to remove the CaCO3 from the water where the carbonate turns into a more soluble K/Na carbonate and the salt turns to CaCl2.

These resins are usually made of sulfanated polystyrene (which I find very interesting!) and I've been told that they are a major PITA if you ever spill them on a hard floor (like millions of spilled bb's or air-soft beads). They must remain moist/wet as if they dry out they could be totally useless in absorbing any ions in the future.

From what I read it looks like the standard ion resin used in water softeners (it says they are "strong acid resins" and it will work with nitrates, carbonates, chromates, ammonium, (phosphates and sulphates I'm guessing but it doesn't list this)

here are some cations that are reported to work in the system
• A monovalent atomic cation: the sodium ion Na+
• A divalent atomic cation: the calcium ion Ca++
• A monovalent molecular cation: the ammonium ion NH4+
• A monovalent atomic anion: the chloride ion Cl—
• A monovalent molecular anion: the nitrate ion NO3—
• A divalent molecular anion: the carbonate ion CO3=
• A divalent complex anion: the chromate ion CrO4=
• The trivalent aluminium cation Al+++ exists only in very acidic solution, not in normal

It also looks like acids and hydroxides can be used to charge the system or can be the product of the process, which seems very interesting indeed! It looks like there may be a way to make ammonium hydroxide with this process, possibly with Ca(OH)2 but I'm not certain on this ATM. From what I read, it looks like it is very possible to make HNO3 and HCl with this system and probably in very high purity although I'm still not certain about how the concentrations are going to be with this setup.

If anyone has used this or know a little more about how it works, i'd appreciate any insight you may have and what may be necessary to use this. I've seen home water softening systems that use this but they would function differently than trying to produce a concentrated solution as it is trying to remove the dissolved CaCO3 from a large amount of water vs converting a more highly saturated solution.

I'm wondering if there are any other possibilities for this application which I didn't mention.

If anyone is curious of cost, I found the "premier brand" of the resin beads in 1 cubic ft for about $90 (though some list for almost $240 and as low as $55 per 1.5cu ft but that was an off-brand with questionable attributes).

It seems that a simple home-made setup could be made to make use of these beads if all they need to do is be covered in a solution, drained, then covered in the next solution giving the end product. No need for the expensive professional water softening setup for this use - though I may be mistaken.

i've also seen these used in glassware that holds the beads and a solution is dripped through them allowing them to perform their magic.

This seems like it could be a very interesting and efficient way to make some acids, salts, etc in possibly for a very pure result.

I'm wondering if there is a way to incorperate reverse osmosis type setup in conjunction with this to maybe concentrate some of the acids/salts so that it extracts the product allowing the water to pass through for re-use to produce the next batch. IDK if there are different size RO membranes which would discriminate which ions/salts could pass through which would give many more options in this type of setup!!

Here is a good link to a PDF that describes ion exchange resins basics:

Attachment: Ion-Exchange-for-Dummies-RH (1).pdf (454kB)
This file has been downloaded 32 times

NEMO-Chemistry - 17-11-2017 at 18:19

Search for water treatment and water membranes, stuff like that in the journal of chemical education. I cant remember the title or much about it but, there is a paper for a classroom experiment that makes a kind of RO membrane.

I found it while digging around for magnetic biochar, i read it really quick a while back, so not much has stuck. But i can tell you thats its definitely in that journal, its definitely to do with making water cleaning membranes..... And i remember thinking that it didnt look that difficult to do (famous last words).

I did a quick search on the journal using water membrane as the search term, some useful stuff popped up, i think this is the one i remember, but TBH i am not 100% sure now.

Rapid Production of a Porous Cellulose Acetate Membrane for Water Filtration using Readily Available Chemicals
Adrian Kaiser, Wendelin J. Stark, and Robert N. Grass
J. Chem. Educ., 2017, 94 (4), pp 483–487
Publication Date (Web): March 30, 2017 (Laboratory Experiment)
DOI: 10.1021/acs.jchemed.6b00776

[Edited on 18-11-2017 by NEMO-Chemistry]

wg48 - 17-11-2017 at 22:11

You can get about one litre of free beads from an old dish washer. The beads are in a container attached to the a salt container as shown below.

aasoftner.jpg - 11kB

Melgar - 20-11-2017 at 13:00

I have a few pounds of the stuff if any is needed. It's hard to purchase in units smaller than cubic feet, although it's used in certain types of aquariums. Ion-exchange resins work especially well with dilute solutions, hence their use in removing calcium and magnesium ions from groundwater. They do not work very well with concentrated solutions, though.