Recharging De-ionization Resin

As promised, I documented my first hand experience at recharging my spent de-ionization resin that I have been accumulating for the last few years. As mentioned before, it has been said that this is a messy job and because of the time and hassle it takes to recharge the DI resin, it isn’t really worth it. It’s not my intention to prove this statement right or wrong, this is merely a step by step account of how to do it, you may form your own opinion on whether you wish to attempt it or not.

First thing I did was track down everything I needed, which was easier than I thought, I literally went to two places; 99 Cents store and Lowes.

At the 99 Cents store I got:

2 each 38 oz containers
1 each 108 oz container
1 each 20 oz measuring cup
1 each 8 oz measuring cup
1 each plastic colander
1 package of plastic clips (5 each)

And of course they were all $0.99 each.

At Lowes I got:

1 each 2 lb container Roebic drain cleaner (100% sodium hydroxide)
1 gallon Muriatic acid

That came to about $20

I had an old blender that had a crack in the bottom that worked out perfect for me (I’ll explain later). We just bought a new one and this one was sitting in the garage ready to be thrown out next trash day.

I also had two 5 gallon buckets one filled with RO/DI water and the other was filled with cold tap water.

I had some window sheer that was left over from when my wife was making curtains for the house that I used as a fine filter, held onto the colander with the plastic clips (see pictured below).

Of course some safety precautions, I had a couple pairs of rubber gloves and some safety glasses already on hand.



So before I start I’d like to point out that this can become dangerous because you are working with acid as well as a base. There are some fumes that may be harmful if you inhale too much of, I personally didn’t use a respirator but if I were doing this on a daily basis it could become a problem. I did this in my garage with the doors open to promote cross ventilation.

A little insight on what I’m doing, DI consists of 2 types of resin beads the anion and cation. In a RO/DI filter, tap water passes through the reverse osmosis (RO) membrane and a large portion of the total dissolved solids (TDS) are removed then the water travels through the DI resin to trap the last of the TDS. Over time the DI resin becomes depleted and we either replace with new DI resin or we can recharge the resin through a chemical process like the one documented below.

Lets get started, first thing I needed to do was mix 3 (fluid) oz of sodium hydroxide (AKA Lye) into 11 oz of RO/DI water.




I poured the water into the 38 oz containers DO NOT POUR THE LYE IN FIRST:


Then I poured in the lye in slowly while mixing it:


I need to point out that when mixing these together the chemical reaction created a lot of heat, enough heat in fact that it deformed the container I was mixing it in. That’s the reason why I had a bucket of cold tap water handy. I spent too long ensuring that the lye dissolved and I should have put the container into the bucket of cold tap water sooner.

Next, I mixed 6 oz of the acid and 6 oz of RO/DI water together into the other 38 oz containers.



Water first:



Then the acid:



This mixture didn’t create heat but the gases were pretty strong, I wouldn’t advise standing over top of it while mixing.

Set this container aside for later.

I only poured half of my spent DI into the container (I could’ve easily done the hole bag)



I then poured the lye into the spent DI:



It immediately turned bluish/black:



I then mixed it up and the anion and cation separated, anion floated to the top and the cation sank to the bottom:









--------------------------------


Since there was a valve on the bottom of the blender I was able to separate the cation from the anion simply by opening the valve and allowing the cation to flow out. After I removed the cation I put the anion with the lye into the 38 oz containers. At this point the lye is recharging the anion. Set that aside and allow it to sit for an hour.


Then I took the cation and rinsed it with 1 gallon of RO/DI water to remove all the lye:





I then poured the cation into the acid mixture that was set aside earlier:



Placed the cap on and let it sit for an hour as well.

After an hour has passed I emptied the bucket that had the cold tap water in it and poured the anion through the colander and ran 2 gallons of RO/DI water through it to remove the lye:









I emptied the clean anion into the 108 oz container.

I emptied the 5 gallon out again and did the same thing with the cation:







I poured it in with the anion and mixed it up:







And there you have it, recharged DI. I put it in a zip loc bag and stored it for when I need it.

There was some waste in the process, the resin beads stick to everything, and even with my efforts to save as much as possible, I probably wasted a total of a teaspoon or resin.

I probably have enough lye and acid to do this 8-10 more times before I run out of lye.

so did you save the blender for next time?

yes. I kept it but it's not ideal, the valve really needs to be on the bottom. Even after I closed the valve the tiny beads of resins wound get caught in the valve and not allow it to close completely, so the lye continued to trickle out. After I removed the majority of cation I had to hurry up and pour the anoin with lye into the 38 oz container.

SLP,

That's awesome, I may have to try that when and if I ever get a RO/DI. I get my water from an LFS.

Amazing! This saves so much money. Im saving up my di to do the same thing to it so once i have enough you will have to help me out. Great write up by the way

shortbus wrote:SLP,

That's awesome, I may have to try that when and if I ever get a RO/DI. I get my water from an LFS.

I know this is a bit off topic, but there was an informal study done on what it cost to make your own salt water with an RO/DI unit verses buying it from an LFS.

when you factor in the upfront cost of an RO/DI, the preventative maintenance of replacing the filters, De-ionization resin and the membrane, factor in the cost of the water your local municipality charges per gallon. RO/DI it only cost about $0.19 a gallon to make, now you add in mixing salt to the equation (depending on salt brand) you add another $0.25 to the total and for less than $0.50 a gallon you can have better quality and control over the salt water that you put in your tank.

Curious, what does your LFS charge for salt water per gallon?

Kind of makes me wish I didn't throw mine out all those years.

SLP, Have you already started using the recharge stuff yet?

sisterlimonpot wrote:

shortbus wrote:SLP,

That's awesome, I may have to try that when and if I ever get a RO/DI. I get my water from an LFS.

I know this is a bit off topic, but there was an informal study done on what it cost to make your own salt water with an RO/DI unit verses buying it from an LFS.

when you factor in the upfront cost of an RO/DI, the preventative maintenance of replacing the filters, De-ionization resin and the membrane, factor in the cost of the water your local municipality charges per gallon. RO/DI it only cost about $0.19 a gallon to make, now you add in mixing salt to the equation (depending on salt brand) you add another $0.25 to the total and for less than $0.50 a gallon you can have better quality and control over the salt water that you put in your tank.

Curious, what does your LFS charge for salt water per gallon?

also, I don't have to tote buckets to and from the fish store, spilling water all over my car...

TLC wrote:Kind of makes me wish I didn't throw mine out all those years.

SLP, Have you already started using the recharge stuff yet?

No I still have a bag of virgin DI that will take me a good 6 months to go through. Maybe next time I need to replace the DI I will through some of this in there and run a few TDS test to verify it's in fact recharged.

After talking with Paul (our resident chemist), I have decided that leaving the ani and cati separate is a better idea. During the recharge process this allows for the most time consuming part of separating the 2 to be skipped. The only concern was that I had to have 2 separate cartridges for the di in my rodi unit (which I did) the first cartridge after the RO membrane has to be the cati and the second is the ani, once the ani changes color then I replace the entire 2 parts with new.

Now when I recharge I just pour the spent ani in the lye solution and the cati in the acid solution and wait 1 hour, this is going to be so much easier!!! The only problem I see is keeping the spent ani and cati labeled correctly so that I charge them in the right solution.

So is there any way to recharge mine that u have?

of course, come on up and we'll charge it

Oh ok cool ill see when im avaliable

wow, way more complicated than what I have to do! You would be jealous if you watched how I do mine...

haha, is it because you have access to better equipment? Or is there something in this process that is over complicated that can be simplified?

Its because all my resin is already separated and because they are in their own containers. All I have to do is flow the specific solutions through my resin in the container and I am done.

Paul,
Do you use filters before you go through the di? could you post a picture of your set up?

dwolson2 wrote:Paul,
Do you use filters before you go through the di? could you post a picture of your set up?

No filters, and no pictures at the moment. sorry. But the water comes straight out of the tap into the Kati side, then goes into the Ani side. Makes 0-1ppm TDS water.

However, dont make the same mistake as me, I spilled 20gal of basic recharge liquid on my garage floor yesterday. Stupid mistake...

Was that sodium hydroxide or is there a product that you use for that?

sisterlimonpot wrote:Was that sodium hydroxide or is there a product that you use for that?

yep, sodium hydroxide...it was a fun morning.

Wow I didn't see 20gal the first time. Did you have to call in a hazmat team to help?? seriously though, how do you neutralize and dispose of that?

sisterlimonpot wrote:Wow I didn't see 20gal the first time. Did you have to call in a hazmat team to help?? seriously though, how do you neutralize and dispose of that?

A lot of water....