Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: scientizscht on 07/02/2021 13:07:26
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Hello
Can you explain in simple words what is ion exchange?
I cannot figure out from wikipedia, is it resins that are conductive to specific ions under voltage or that contain specific ions which can adsorb other ions under specific (what?) conditions?
After use, do ion exchange materials get saturated and need regeneration?
Thanks!
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They are resins with charged groups in their structure- typically quaternary ammonium groups which are positively charged or sulphate groups which are negatively charged.
If you put them in water containing ions those ions stick to the charged groups on the resins.
How well depends on the nature of the resin and the ion.
And yes, they need to be regenerated (or disposed of) after use.
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Ion exchange is a reversible chemical reaction in which ions are exchanged between a solid (ion exchanger) and an electrolyte solution.understandably?
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lon exchange is a powerful chemical technoloav through a reversible chemical reaction where dissolved ions are removed from solution and replaced with other ions of the same or similar electrical charae. lon exchange resin facilitates ion exchange reactions The resin itself is composed of organic polymers that forms a network of hvdrocarbons. and ion exchange sites. called"functional qroup" throughout the matrix The ion exchange sites attract ions of an opposina charge.
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I read about this a while back. They didn't work the way I expected.
Basically, an ion exchange column used for water softening has beads which are weakly attracted to basically all metal ions. To charge them up, you just saturate them with sodium ions using a sodium chloride salt solution. Potassium chloride would also work but it's more expensive.
Then when you run water containing calcium over it, the ions get picked up by the ion exchange beads, and some of the sodium ions fall out of the beads into the water.
But because there's so many sodium ions in the beads and relatively few calcium ions the net effect is to remove calcium ions and replace them with sodium.
Eventually though the beads will have lost some sodium and picked up many calcium ions. But you can then regenerate them by soaking them back in a strong salt solution and it will remove most of the calcium again by simple overwhelming numbers. The calcium ions will leach out into the water and get replaced by sodium just because you have (say) 8 times the number of sodium ions.
That's also why they're not very efficient. You have to soak them in a very strong salt solution to overwhelm the calcium ions, so the running costs with so much salt are relatively high. Salt's reasonably cheap, but not stupidly cheap.
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That's one way they are used- for "softening" water.
But they are also used for deionising water which is a bit more complex.