DI Resins

[AnotherGoldenTeapot]

For some time I've had a DIY DI water filter that seems to work well. I extracted the original resins from a "Tap Water Purifier" and then built my own chambers to house everything.

I've been pondering upgrading this and want to get things right in the DI filter mark two. A more compact design is a must!

My chemistry related questions are:

1. Should I have the cation resin or the anion resin first? Does it even make a difference?

2. Do I really need a carbon pre-filter? The person I spoke to locally send I don't really - I will just marginally reduce the life of the resins.

3. Are industrial-grade resins entirely adequate for my purpose?

4. Does it matter if my recharging solutions are too strong? For example, I'm currently making my caustic soda soulution by mixing one cup of crystals in 1.5 litres of water. Is this okay?

5. Anything else I need to think of?

Thanks :)

[Randy Holmes-Farley]

Should I have the cation resin or the anion resin first? Does it even make a difference?

No.

Do I really need a carbon pre-filter? The person I spoke to locally send I don't really - I will just marginally reduce the life of the resins.

Carbon will taker out some things that DI doesn't, such as uncharged organics. Beyone that, I agree with the person you spoke to.

Are industrial-grade resins entirely adequate for my purpose?

Yes, but I'd run a bit of water through them before collecting for the tank. This will flush out any impurities.

Does it matter if my recharging solutions are too strong? For example, I'm currently making my caustic soda soulution by mixing one cup of crystals in 1.5 litres of water. Is this okay?

Without knowing exactly what the resins are, that's hard to say, but I expect it to not be a problem as long as you don't leave excess acid or base on the resins for too long (and don't heat it).

Anything else I need to think of?

Probably, but I can't tell what it might be:D

[andy-hipkiss]

Should I have the cation resin or the anion resin first? Does it even make a difference?

No.


I'm not sure how important this is but AFAIK, the cation resin goes first in order to acidify the water, IOW, the cation resin releases H+ whilst removing the cation. The removal of anions is more efficient (e.g. silicate is better removed in an acidic environment).

I have hunted around a bit and came up with this link ... FWIW http://www.remco.com/ix.htm

[Randy Holmes-Farley]

Andy:

Why would silicate be absorbed better from an acidic environment?

In a basic environment it will be an anion:

Si(OH)4 ----> Si(OH)3O- + H+

In an acidic environment it will be uncharged Si(OH)4, won't it (unless it is very, very acidic)?

[andy-hipkiss]

Randy,

Dunno .... all I can tell you is that all the references I can find refer to this property ... very curious :confused: One thing, what exactly is the silicate ion, I previously thought it was (Si04)4-.

I've tried searching through all the water treatment websites and they all refer to the cation resin being before the anion bed. Any ideas why?

[Randy Holmes-Farley]

Andy:

I've tried searching through all the water treatment websites and they all refer to the cation resin being before the anion bed. Any ideas why?

Spectrapure, which I have, uses a mixed bed, so they don't use one before the other.

I can only guess why people would want to remove the cations first. Maybe they are worried out precipitation of things like iron oxide etc, if the metals were to get into a high pH solution when they passed through an anion exchanger. These solids might clog up the unit or not be removed, causing dirty looking water????