Does DI resin only remove charged ions?
- Thread starter Raul-7
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Assuming the feedwater is permeate (aka RO water), then yes. The cation and anion beads are referred to as "ion exchange media." That exchange happens only with charged ions.
That's what I thought, but wanted to make sure.
But wasn't their an earlier water filter that had a carbon filter, then a separate cation and anion resin [no RO]? I could've sworn it made 0 TDS water.
I run a similar recirculating system at work which produces 11000 litres per day. However it is expensive to run because it treats all of the water. Using a membrane is more wasteful in regards to water, but more efficient generally for us as 95% of the contaminants have already been thrown down the drain.
Randy Holmes-Farley
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A DI resin can bind charged most any compounds, and can also bind some uncharged organic materials.
There are some grey areas, such as particulates, which may bind when very small, and may get caught physically if larger, but middling sized particulates won't likely get caught.
There are some grey areas, such as particulates, which may bind when very small, and may get caught physically if larger, but middling sized particulates won't likely get caught.
Randy Holmes-Farley
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I'm not sure what you are actually asking about.
A DI resin where the counterions are H_+ and OH- will make 0 ppm TDS water. No RO membrane is needed.
An ion exchange resin, where the counterions are anything else (such as Cl- and Na+) cannot make 0 ppm TDS water, and will not appreciably lower the TDS of the incoming water, except in special circumstances, such as the incoming water containing only HCl or NaOH.
TDS meters are really just conductivity meters calibrated for typical charged ions. Different ions contribute different levels of conductance, so it is an average at best - but a good inexpensive measure. Conductivity meters are not going to measure non-conductive organic compounds unless they strongly disassociate hydrogen ions and so they will not register on your TDS meter. These are generally removed by the activated carbon and/or RO membranes depending on the species.
