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How to Recharge DI Resin

After six years of hoarding used de-ionizing (DI) resin, i figured it was finally time I did something with it.  After reading several DIY tutorials out there, I thought I was up for the challenge.  Since there are several very good DIY tutorials out there (especially David Sander’s), I won’t pretend to know more than I do.  Basically, I just want to show that this is possible for everyday reefkeepers with a bit of common sense.

So, six years of saving equates to about 15 pounds of DI resin for me.  Recharging all of that would save me $165 minus the supplies I had to buy to recharge it all (about $20).  So, for a long afternoon, I saved $145 and kept 15 pounds out of the landfill.  Not too bad.  And, now I have a new skill.

Words of Caution: the chemicals used are…well…just plain nasty.  They can burn skin (including eyes), create toxic fumes, and a whole host of other dangers to people, pets, and property.  If you aren’t an overly cautious person with common sense, please do not attempt this.  Please wear personal protective equipment, to include (but not limited to) chemical eye protection (that seals all the way around the eyes) and long chemical gloves rated for the chemicals used.  I’d also recommend a chemical apron, but it’s not necessary with good caution.  Since these chemicals produce toxic fumes, please do this in a well ventilated area (outside preferably.)  Follow the manufacturer’s instructions on the bottle.  Just…don’t be stupid.  Read all the instructions first before you begin.

Supplies:

  • 1 Container 100% Sodium Hydroxide Crystals (Lye) – I used Roebic brand from Lowe’s found in the plumbing section
  • 1 Container Hydrochloric Acid (Muriatic Acid) – I used KleanStrip brand from Lowe’s found in the cleaning aisle
  • 5 lbs DI resin – about 4 DI chambers full (this “recipe” can be scaled up or down based on your needs)
  • 1 Container Vinegar (this is just in case of emergency)
  • 2 x 3 QT thick plastic containers with lids (purchased mine at Dollar Tree)
  • 2 x 1 QT mixing cups (purchased mine in the paint department at Lowe’s) – best to have a spare on hand as well
  • 1 5g bucket of cool tap water
  • 1 5g jug of RO/DI water
  • Turkey baster or 2-liter bottle with valve fitting (don’t recommend the turkey baster method)
  • Stir stick (used a leftover piece of acrylic…wood stir sticks are fine…no metal!!)
  • Collander (also purchased from Dollar Tree)
  • Muslin or fine material (such as a curtain sheer, etc.)
  • Office clips
  • Ziploc bags (Vacuum-sealed bags preferred)
  • Scale (not required, but very handy)
  • Protective gear (as mentioned above…gloves, goggles, etc.)

Roebic Sodium Hydroxide

Roebic Sodium Hydroxide

Muriatic Acid

Muriatic Acid

Instructions:

1.  Inspect your DI resin.  You’ll lose some along the way, so don’t get too attached to it all.  Scale the recipe to your needs.  Make sure to use larger containers if scaling up the recipe!  Don all protective gear.

My DI Resin Hoarding

My DI Resin Hoarding

2.  Pour 22 ounces of RO/DI water into a 3QT container.

22 oz. RO/DI Water

22 oz. RO/DI Water

 3.  Pour 6 fluid ounces of lye crystals into the 1 QT container.

6 oz. Lye Crystals

6 oz. Lye Crystals

4.  Carefully pour the 6 fl. oz. of lye crystals into the 22 oz. RO/DI water.  This did not splatter or bubble for me, but use caution anyway.

5.  Tightly cap the 3QT container, and place it into the 5g bucket of tap water.  The lye solution will become very hot, so this water bath will help cool it down.  You may notice the 3QT plastic container starting to warp from the heat.  This is why a thick sturdy container is recommended.

Lye Solution in Water Bath

Lye Solution in Water Bath

6.  Carefully and gently shake the 3QT container in the bucket to keep the lye from clumping.

7.  Place the DI resin into the empty 3QT container.

8.  Carefully open the lye solution and pour it into the DI resin.

Lye and Resin Solution

Lye and Resin Solution

9.  Carefully stir the DI resin and lye solution.  Within a few minutes the DI resin starts to separate.  The anion will float to the top, and the cation will sink.  A boundary of lye is in the center.

Anion Floats, Cation Sinks

Anion Floats, Cation Sinks

10.  If you have nothing better to do with your time, you can use a turkey baster to remove the anion (floating resin) and put it into the now-empty (and rinsed!!) 3QT container.  If you find the gap between the anion and cation is too thin, and you’re starting to pick up some cation, then use the turkey baster to suck some lye up from the anion container and put it back in the cation container.  Allow it to settle again before continuing.  I hated that I chose this method.  It’s painful.  If you enjoy having a life, skip this step and go to #11.

Anion on left, Cation on Right

Anion on left, Cation on Right

11.  Instead of the turkey baster method, I’ll use a brine shrimp hatchery from Brine Shrimp Direct from now on.  It’s basically an upside-down 2-liter bottle with a valve (like a transmission fluid valve fitting) on the end.  Just pour the resin-lye solution into the container, let it separate, then open the valve.  The cation (sinking resin) will drain out.  Keep track of which is which!

12.  Place the muslin inside the collander and secure it with the office clips.  Place it over the 5g bucket of tap water.  Pour some tap water out of the bucket if there isn’t enough room for rinse water to be added.  This just helps dilute the lye.

13.  Pour the cation through the muslin collander.  Rinse about 2 gallons RO/DI water through it.  This removes the lye.

Rinsed Cation

Rinsed Cation

14.  Once the cation is sufficiently rinsed, pour it back into a clean 3 QT container.  There will be some resin stuck to the muslin.

15.  Pour 12 ounces of RO/DI into a clean 1 QT container.

16.  Carefully pour 12 ounces muriatic acid into the RO/DI water in the 1 QT container.  Never pour water into an acid!

17.  Carefully add the acid-water mix to the cation resin in the 3 QT container.  This negates the lye and charges the resin.  Some of the resin should change color almost instantaneously.

18.  Stir the cation resin.  Most of it should change color.

Gold Resin Turned Purple!

Gold Resin Turned Purple!

19.  Let the cation and anion sit for about an hour. 

Sitting...Just Sitting

Sitting…Just Sitting

20.  After an hour, place the collander back over the 5g bucket (make sure it has enough space to add rinse water).  Rinse the cation in the collander with RO/DI water (at least 2 gallons).  The diluted lye and muriatic acid will combine to make a rather harmless salt water (don’t use this in your aquarium!!)

21.  Pour the cation into a Ziploc bag or other clean container.

22.  Rinse the anion in the collander with RO/DI water (at least 2 gallons) over the 5g bucket.  Again, combining the diluted lye and acid will make a rather harmless salt water that can be easily disposed of.

 

Cat's in the Bag...I mean...Cation

Cat’s in the Bag…I mean…Cation

23.  Pour the anion into the container with the cation (don’t do this if you have separate anion/cation cartridges).  You did it!

Beautiful Recharged DI Resin

Beautiful Recharged DI Resin

24.  Mix well.  Don’t have too much fun mixing…or it’ll end up in a mess like I did.  Spouses tend to frown on this.

Ooops...

Ooops…

25.  For longer life in storage, separate the resin into 1.25 lb vacuum-sealed bags.

Not Quite Enough

Not Quite Enough

 

Sealed for Storage

Sealed for Storage

 26.  Replace the DI resin with the new recharged resin.  Allow the RO/DI system to run for a few minutes until the TDS meter reads 0 in case the previous rinsing did not remove all the lye/acid.  Do not use the water that does not register a 0 on the TDS meter. 

All Done!

All Done!

This resin should be able to be recharged indefinitely.  However, there is some loss during recharging, so you may need to buy more to make up for the lost resin eventually.

Hope this helped you save some money and keep some resin out of the landfills!

10 comments

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  1. Kevin

    Very nice. Thanks for doing all the science for us.

  2. Waaahsabi

    Wow, didn’t know that you could DIY-regenerate mixed DI raisin. Learning new stuff every day. In Europe we use separate reactors for each resin for easier regeneration. But those are usually stand-alone DI systems. Most people buy the mixed raisin cartridges for their osmosis systems, and dispose of them when depleted (the cartridge, not the RO). Turns out, a lot of money could be saved here too. Provided one is willing to do the NaOH / HCl handling…

    1. admin

      I think this would definitely be *much* easier on separate bed cartridges. In all honesty, I didn’t think handling the NaOH / HCL was that bad. I wore goggles and gloves, and then I kept plenty of water on hand for dilution. I also think this would be best for a club to do – have everyone donate their used DI, and then the club could do a DIY project and redistribute the charged DI resin. It doesn’t make much sense for someone with a 25 gallon tank, but in bulk it sure does!

  3. Martin

    Nice write up! Muslin fabric is made of cotton, I wonder how the muslin resistance to the strong chemical, did you replace it regulary?

    1. admin

      So far I’ve had no need to replace the fabric since it seems to hold up well. Fabric bleaching with lye can take up to several hours, and recharging DI resin takes no where near that time (plus the lye gets diluted quickly.) Worst case, thankfully muslin is fairly inexpensive. 🙂

  4. Martin

    Just today, I tried to recharge my DI resin. It is my first time. I followed exactly your tutorial. My tap water is around 400 ppm, my mix bed resin total volume is 3 litre. Based on my calculation I should get at least 400 liter (105 gal) of DI water. But instead, I only got around 10 galons of DI water, before the TDS started to increase. I check with my hardness test kit, the result is zero hardness (soft water) – my tap water is very hard, around 300 ppm of calcium carbonate. So I am guessing one of the resin is still working, and the other one is exhausted already. But I dont know which resin. Do you have information about the concentration of the regenerant?

  5. admin

    Hi Martin,

    Somehow I missed your post! I’m so sorry. The concentration of the regenerant shouldn’t matter since the particles won’t float/sink until they are recharged. As long as you waited, then they should’ve recharged. An increase in TDS could be from a few different things. My guess is that the chambers weren’t fully packed with resin. Newly recharged DI resin contains quite a bit of moisture, so it’s hard to pack completely. The gaps in the resin allow water to channel through, and that will show a high TDS. I would reopen your chambers, and tap them lightly on a table to get the DI resin to settle. If there is still space, then add a bit more until the chambers are very tightly packed.

    Please let me know if this worked for you. I experienced the same issue, and it took me a while to figure out. In the future, you can let the DI resin dry out a bit (not completely, but just let some of the excess moisture run off) so it will be easier to pack.

    Nikki

  6. Brian

    Thanks for the writeup! great pics too… that really helps the reader follow along.

    Questions: I have a 1 gallon bag (packed) of old resin. I don’t know how much it weighs (hard to measure since it’s still wet). Will the containers you have listed be large enough to recharge all my resin at once?

    Also, can I used gallons of distilled water instead of DI water for the rinsing? I don’t have any DI water, as my resin is exhausted. Next time I’ll remember to fill & store a 5 gallon bucket of the DI water for the recharging!

    Lastly, can I ask where you get old resin? I’d love to not have to pay for something that people are gonna throw out!

    1. admin

      Hi! Thanks for the good questions!

      Questions: I have a 1 gallon bag (packed) of old resin. I don’t know how much it weighs (hard to measure since it’s still wet). Will the containers you have listed be large enough to recharge all my resin at once?

      A: Hm, off the top of my head, you’ll probably need to do two batches with the 1 gallon bag. The lye and muriatic acid quantities are more than sufficient, but the limiting factor will be the container sizes. If you can find large enough containers, then it won’t be an issue.

      Also, can I used gallons of distilled water instead of DI water for the rinsing? I don’t have any DI water, as my resin is exhausted. Next time I’ll remember to fill & store a 5 gallon bucket of the DI water for the recharging!

      A: I would not recommend this. Distilled water still has some total dissolved solids, so your DI resin would not recharge fully. If you’re in a pinch (which it sounds like you are since you’re out of DI resin), it would probably work well enough as long as you accepted that this new batch of DI resin will exhaust quickly. Instead, I would find a friend or a local fish store that sells RO/DI water. You’ll only need a 5 gallon jug, which shouldn’t cost you much (it is usually around $0.50 USD per gallon around where I live.)

      Lastly, can I ask where you get old resin? I’d love to not have to pay for something that people are gonna throw out!

      A: To start, I actually saved six years worth before I tried recharging the resin myself. Now, local friends and fish stores know I collect it and will often donate it to me. Usually for every few pounds they give me, I give them a recharged pound back. It makes everyone happy!

      Thanks for reading! Let me know how it goes!

      1. brian

        Thanks!

        I’m gonna look for 1.5 to 2 gallon containers, as I really dont want to do multiple batches ;.)

        Distilled water, from what I’ve read recently, purfies the water the same but just uses a different process to get there. I bought a TDS meter, and checked some distilled water. Sure enough, 0. However, DI water may be cheaper to buy, so I may go that route anyways. Thanks for the tip on where to get it!

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