Leftover water in DI chamber

[smellslikeTUNA]

Should I manually empty the extra water that is left in DI chamber when the unit is not in use since I don't have a flush kit?

[disc1]

It should probably stay full of water.

The flush kit won't have anything to do with the DI stage. All the flush kit does is bypass the flow restrictor so all the water comes out the waste line (none into the DI) to flush off the outside of the RO membrane.

[Palting]

Once wet, you don't want the filters to go dry again. Don't really know why but maybe someone can fill that in, but that's whats recommended. As Disc said, the flush valve just allows water to flush out and clean the membrane by bypassing the restrictor, and has nothing to do with emptying out the DI.

[smellslikeTUNA]

Thanks for the info guys! much appreciated

[dzhuo]

Originally Posted by Palting

Don't really know why but maybe someone can fill that in, but that's whats recommended.

DI resin works by ion exchange. When it dry up and in direct contact with air, it will pick up a lot of free floating ions from the air thus quickly exhaust it. Both membrane and DI resin must stay wet.

[disc1]

Originally Posted by dzhuo

it will pick up a lot of free floating ions from the air

Like what? What ions floating around in the air?

[smellslikeTUNA]

Originally Posted by dzhuo

DI resin works by ion exchange. When it dry up and in direct contact with air, it will pick up a lot of free floating ions from the air thus quickly exhaust it. Both membrane and DI resin must stay wet.

Makes sense, and considering both the resin and DI were shipped 'wet'
Thanks!

[dzhuo]

Originally Posted by disc1

Like what? What ions floating around in the air?

That's the exact reason why you use a RO/DI in the first place because it's not the water that's problematic, it's the pollutants in it that matters. Air is another medium that's full of pollutants so lots of stuff can be picked up with a little of moisture. The other reason to avoid resin to be in direct contact of air is obvious: Carbon dioxide which air is full of.

[dzhuo]

Originally Posted by smellslikeTUNA

Makes sense, and considering both the resin and DI were shipped 'wet'

Yes you need to leave both membrane and DI resin moist or seal them in a vacuum. You also need to make sure they don't over heat. For example, most membrane will simply "melt" at roughly ~110F (but that's kind of rare).

[disc1]

Free ions floating in air requires a lot of energy. That's not something that is really an issue.

The reason the media has to stay wet has to do with hydration. The little beads have lots of holes and channels and tunnels through them. That increases their surface area to a point that they become useful. When you let them dry out, the water leaves those little channels and tunnels and nooks and crannies.

Those beads are made of a resin. You ever see how water beads up on a freshly waxed car? Same kind of idea. The water "beads up" on the beads. It's a surface tension thing. But long story short, the media never fully re-hydrates. All those nooks and crannies and channels stay dry. So the effective surface area of the media, the amount of media that is in contact with the water, is much much smaller.

In the world of HPLC, we say the media has de-wetted. The fix, and how they got it wetted in the first place is to mix with something to get the surface tension down to a point that the water will wick up into all those little places. Not something you can necessarily do on your own. Even in the lab, we get those kinds of resins wet and throw them away if they de-wet.


BTW, CO2 is not ionic until it dissolves in water and reacts to make carbonic acid. Will not attach to dry media at all.

[dzhuo]

Originally Posted by disc1

The reason the media has to stay wet has to do with hydration.

Possible. A complete dry up DI resin properly won't be much use anyway.

Originally Posted by disc1

Even in the lab, we get those kinds of resins wet and throw them away if they de-wet.

You don't necessary need to throw them away. A dry up DI resin (assuming it's still capable of ion exchange) can be regenerated with acid and alkaline but the process involve separating the cation and anion resins which is a PITA.

Originally Posted by disc1

BTW, CO2 is not ionic until it dissolves in water and reacts to make carbonic acid. Will not attach to dry media at all.

I don't know how much this really matter. CO2 can quickly exhaust your DI resin so it's one of the reason why you don't want that to happen.

I am curious, in what scale you work with DI resin?

[disc1]

Originally Posted by dzhuo

Possible. A complete dry up DI resin properly won't be much use anyway.



You don't necessary need to throw them away. A dry up DI resin (assuming it's still capable of ion exchange) can be regenerated with acid and alkaline but the process involve separating the cation and anion resins which is a PITA.

I'm talking about the ion exchange resins we use in the lab. Once they de-wet, they are useless. They can still do some small amount of ion exchange on the outer surface, but the overall capacity goes to nothing.

The re-wetting process is complex and time consuming and in many cases a trade secret. So we throw that away when it de-wets.

DI resin in your RODI that gets dry doesn't necessarily mean it de-wetted. The water stays trapped inside and slowly evaporates away. If it's been dry for days or weeks, it's no good any more.

Originally Posted by dzhuo

I don't know how much this really matter. CO2 can quickly exhaust your DI resin so it's one of the reason why you don't want that to happen.

But only if it is dissolved in water. In air it is definitely not an ion.

Originally Posted by dzhuo

I am curious, in what scale you work with DI resin?

I do analytical chemistry for a living. So mostly on small scales for LC work.

[dzhuo]

Originally Posted by disc1

But only if it is dissolved in water. In air it is definitely not an ion.

No. It isn't. I mentioned 2 cases (there might be others) why you don't want your DI resin to dry out:

1. Air is a medium full of polluants similar to water. Whatever it picks up along with moisture will affect the DI because that's how a DI works.

2. CO2 (regardless whether it's dissolved in water or not) will quickly exhaust your DI resin. It doesn't need to be an ion to do that.

I am not sure about your de-wett statement since I am not in the field. When I said regeneration, I really mean a typical dry out DI resin which can be generated with acid (or sodium) and alkaline but the process is involved since it requires separating the cation and anion. The cost and process of doing that is more than just buying a new one so if the DI dries out, it's probably easier to replace it.

[smellslikeTUNA]

This simple yes/no question has turned into quite the chemistry debate :P

[disc1]

Regeneration is for media that has been exhausted. That is, all of the ionic binding sites have bound an ion other than H+ or OH- and can no longer take up anything more. So you use strong acid solution for cation resins or strong base for anion resins to displace the ions that are bound. Now, in a weaker solution like DI water, new ions can come in and replace the H+ and OH- and be removed from the water.

In the case of a dried out resin this won't help much. I don't mean a resin that got dry for a bit, I mean something that has dried completely out. In that case the resin can be regenerated, but it may or may not last for very long, depending on what the resin is made from.

Please show me a chemical reaction where CO2 binds to any ion exchange resin without a water molecule in the equation. I'm sorry to disagree, but only ionic (charged) species will bind to the resin. CO2 when not dissolved will not. It will dissolve into the water in wet resin and then carbonic acid binds to the anion resin. It does nothing to the cation resin.

[dzhuo]

Originally Posted by disc1

Please show me a chemical reaction where CO2 binds to any ion exchange resin without a water molecule in the equation.

If you are really interested in why, I suggest you can do a little research on your own. I mention earlier that I am not in the field so I am not interested in how the chemical reaction works in the molecule level. You mention earlier that you have access to lab equipment,etc so you should be able to easily test this out. Take a DI resin out and subject it to CO2 in air (with or without water) to see how it affects it's ability or performance. Russ (Buckeye Field Supply) and Jim (The Filter Guys) has mentioned multiple times over the years that one of the reason you don't want to left your DI resin in direct contact with air is to avoid CO3 exposure. Here is one quote from Jim:

Storage life on DI resin?

You have exhausted your DI resin only and it needs to be changed. Our DI resin packages are sealed in special bags and will keep if you do not open the package until your ready to use it. DI resin needs to be protected for CO2 in the air.

Billy it needs to be protected from CO2 in the air. The best way is to seal opened resin in a glass jar. Our unopened resin pouches will stay fresh until your ready to use them just keep them in a cool place.

Your other info is also easily accessible from the RO/DI article Randy wrote. Like I mention earlier, the re-generation process is somewhat involved and generally not cost effective.

Sorry for the OT smellslikeTUNA. I will leave this thread alone without continue to spam everyone else from more important things to read.

[PurdueWaterGuy]

As to shelf life of ion exchange resin, the guys at ResinTech found some barrels of IX resin that had been sealed and stored for years with no appreciable degredation. Gotta keep that air out!

Me? I have 90 cubic feet of high-purity low-TOC IX resin in my system at work. Costs about $200/cubic foot.

Originally Posted by dzhuo

If you are really interested in why, I suggest you can do a little research on your own. I mention earlier that I am not in the field so I am not interested in how the chemical reaction works in the molecule level. You mention earlier that you have access to lab equipment,etc so you should be able to easily test this out. Take a DI resin out and subject it to CO2 in air (with or without water) to see how it affects it's ability or performance. Russ (Buckeye Field Supply) and Jim (The Filter Guys) has mentioned multiple times over the years that one of the reason you don't want to left your DI resin in direct contact with air is to avoid CO3 exposure. Here is one quote from Jim:

Storage life on DI resin?



Your other info is also easily accessible from the RO/DI article Randy wrote. Like I mention earlier, the re-generation process is somewhat involved and generally not cost effective.

Sorry for the OT smellslikeTUNA. I will leave this thread alone without continue to spam everyone else from more important things to read.

[disc1]

Originally Posted by dzhuo

If you are really interested in why, I suggest you can do a little research on your own. I mention earlier that I am not in the field so I am not interested in how the chemical reaction works in the molecule level. You mention earlier that you have access to lab equipment,etc so you should be able to easily test this out. Take a DI resin out and subject it to CO2 in air (with or without water) to see how it affects it's ability or performance. Russ (Buckeye Field Supply) and Jim (The Filter Guys) has mentioned multiple times over the years that one of the reason you don't want to left your DI resin in direct contact with air is to avoid CO3 exposure. Here is one quote from Jim:

Storage life on DI resin?




Your other info is also easily accessible from the RO/DI article Randy wrote. Like I mention earlier, the re-generation process is somewhat involved and generally not cost effective.

Sorry for the OT smellslikeTUNA. I will leave this thread alone without continue to spam everyone else from more important things to read.

Exactly. They are both talking about wet resin. I forgot how we got onto this. Oh yeah. CO2 isn't an ion. Really doesn't matter.